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Chapter Transport Biology SPM

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Biology Form Five Notes

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Chapter Transport Biology SPM

  1. 1. CHAPTER 1: TRANSPORT CHAPTER 1: TRANSPORT LEARNING OBJECTIVE: 1.1 The importance of having a transport system in some multicellular organisms. Learning outcome : A student is able to :  Identify the problem that could be faced by multicellular organisms in obtaining their cellular requirements and getting rid of their waste product.  Suggest how the problem is overcome in multicellular organisms. Previous knowledge : Unicellular and multicellular organisms. CONTENT: Introduction: Multicellular Unicellular Earth worm Frog Snake hydra  All living organisms constantly need to exchange food, waste materials and gases with their surroundings in order to survive and grow.  Thus Transport System is needed in order to distribute the food and oxygen throughout the body and to remove the waste materials such as carbon dioxide. Biology Form Five Notes © Copyright Maryam Shah 2007 Amoeba sp.. 1 LLiivviinngg oorrggaanniissmmss
  2. 2. CHAPTER 1: TRANSPORT The substance that are required by living things The substance that are needed to be eliminated from living organisms  Oxygen  Nutrients  Water  Mineral salt  Vitamins  Carbon dioxide  Nitrogenous waste How the unicellular obtained their cellular requirements and eliminated their waste products How the multicellular obtained their cellular requirements and eliminated their waste products  Through a process of diffusion  Example : Transportation of oxygen and carbon dioxide in amoeba sp. is through simple diffusion  They need a system  Example :  Blood circulatory system to transport nutrient  Respiratory system to obtain oxygen and to eliminate carbon dioxide O2 The problems that could be faced by multicellular organisms in obtaining their cellular requirements and getting rid of their waste product:  The oxygen and nutrients needed by the cells could not be supplied by simple diffusion through body surface area.  Neither can waste products be removed quickly enough.  This is due to the fact that as organisms become larger, the total surface area to volume ratio becomes smaller. In other words, the cells in multicellular organisms are situated far away from the external environment.  These problems are overcome by having a circulatory system to transport substances throughout the body. Biology Form Five Notes © Copyright Maryam Shah 2007 2 Co2
  3. 3. CHAPTER 1: TRANSPORT LEARNING OBJECTIVE: 1.2 Synthesising the concept of circulatory system. Learning outcome : A student is able to :  State what a circulatory system is  State the three components of circulatory system in humans and animals  State the medium of transport in humans and animals  State the composition of human blood  Explain the function of blood and haemolymph in transport Previous knowledge : Circulatory system (lower form) CIRCULATORY CIRCULATORY SYSTEM OF HUMAN SYSTEM OF HUMAN BBLLOOOODD HHEEAARRTT THE BLOOD WHITE BLOOD CELLS  What is a circulatory system? THE BLOOD VESSELS Perform various functions  Circulatory system is the system of structures consisting of the heart, blood vessels and the blood which is circulated throughout the body.  It is also called as vascular system.  The circulatory system is responsible for the transport of nutrients and oxygen to cells and the removal of waste products from the body as well as protection of the body from infections.  The circulatory system transports oxygen from the lungs and nutrients from the digestive tract to every cell in the body, allowing for the continuation of cell metabolism. Biology Form Five Notes © Copyright Maryam Shah 2007 VESSELS PPLLAASSMMAA BBLLOOOODD CCEELLLLSS Perform various functions RREEDD BBLLOOOODD CCEELLLLSS WHITE BLOOD PPLLAATTEELLEETTSS CELLS 3
  4. 4. CHAPTER 1: TRANSPORT  The circulatory system also transports the waste products of cell metabolism to the lungs and kidneys where they can be expelled from the body. Without this important function toxic substances would quickly build up in the body.  The components of circulatory system in humans and animals are:  Blood  Blood vessels  Heart  The medium of transport in humans and animals in in is called is called Blood Haemolymph protects the body from transports regulates O2 CO2 DIAGRAM 1: Blood and haemolymph as medium of transport in humans and animals as well as their distinctive functions. Biology Form Five Notes © Copyright Maryam Shah 2007 4 has 3 general functions through through important in the Medium of transport Humans and Animals Invertebrates A blood-like nutritive fluid which fills the entire body Transportation Regulation Protection is Transportation of water, inorganic salts, and organic compounds Lungs cells Lungs cells Nutrients, hormones and antibodies throughout the body 1pH of body fluids 2body temperature 3water content of the cells excessive blood loss diseases / infections Body Immune System Blood Clotting
  5. 5. CHAPTER 1: TRANSPORT  The composition of human blood Human Blood comprises 55% Plasma 45% Cellular Components DIAGRAM 2: Composition of human blood DIAGRAM 3: Major functions of constituents in the plasma Photograph Structure Functions Biology Form Five Notes © Copyright Maryam Shah 2007 5 comprises Erythrocytes Leucocytes Platelets ERYTHROCYTES
  6. 6. CHAPTER 1: TRANSPORT  Erythrocytes are tiny biconcave disks, thin in the middle and thicker around the periphery.  Does not have a nucleus.  7.5 μm in diameter.  Each of which contain 250 million molecules of haemoglobin (O2-carrying protein pigment)  Provides a large ratio of TSA/V for gaseous exchange.  Haemoglobin is the material that gives blood its red colour.  The haem group that found in the haemoglobin contains an iron atom that is the site for O2 binding. Blood Cells Structure Functions White blood cells (Leucocytes)  Leucocytes are colourless and contain nucleus and mitochondria.  Irregular in shape and larger than red blood cells.  They are made by the stem cells in the bone marrow.  They are classified as either granular or agranular  Fight infections in various ways.  Most activities take place in the interstitial fluid outside the blood vessels.  They can squeeze through the pores in the blood capillaries and fight the pathogens present in the interstitial fluid. Platelets  Platelets are fragments of large cells from the bone marrow  No nucleus and are about 2-3 μm in diameter.  Important in blood clotting mechanism Biology Form Five Notes © Copyright Maryam Shah 2007 6 LEUCOCYTES Granulocytes Agranulocytes Neutrophils Engulf and digest bacteria and dead cells Eosinophils Release enzymes to combat inflammation in allergic reaction Basophils Involved in combating inflammotary and allergic reactions Lymphocytes Produce the immune response against foreign substances Monocytes Engulf and digest bacteria and dead cells
  7. 7. CHAPTER 1: TRANSPORT LEARNING OBJECTIVE: 1.2 Synthesising the concept of circulatory system. Learning outcome : A student is able to :  Describe the structure of human blood vessels  Explain how blood is propelled through the human circulatory system  Explain briefly how blood pressure is regulated  Compare and contrast the circulatory systems in the following: humans, fish and amphibians.  Conceptualise the circulatory system in humans Previous knowledge : blood as a component of circulatory system in previous lesson. CONTENT:  The structure of human blood vessels (Refer to Diagram 4) Biology Form Five Notes © Copyright Maryam Shah 2007 7
  8. 8. CHAPTER 1: TRANSPORT DIAGRAM 4 Characteristic arteries capillaries veins Wall Thick, muscular, elastic One-cell thick, no muscle or elastic tissue Thin, less muscular, less elastic Lumen Small Very small Large Valve No valve No valve Have valves which maintain the one-way flow of blood Blood pressure high Very low Low Direction of blood From heart to the flow organs (away from the heart) From arteries to veins From all parts of the body to the heart (blood returns to the blood) Blood content Oxygenated blood except the pulmonary artery Oxygenated blood At the arteriole ends and deoxygenated blood at the venule ends Deoxygenated blood except the pulmonary veins Function To transport blood quickly at high pressure from the Allow rapid gaseous exchange between the blood and the Allow blood from the tissues to return to the heart Biology Form Five Notes © Copyright Maryam Shah 2007 8
  9. 9. CHAPTER 1: TRANSPORT heart to the tissue body cells by diffusion The Human Heart The structure and function of the human heart 1The heart is a cone-shaped, muscular organ about the size of a clenched fist. 2The heart pumps the blood which (a) carries vital materials required by the body. (b) removes waste product that the body does not need 3The human heart has 4 muscular chambers: (a) The two upper chambers are the atria and the two lower chambers are the ventricles. (b) The atria receive blood returning to the heart while the ventricles pump blood out of the heart. 4The heart contracts and relaxes in a rhythmic cycle. (a) When it contracts, it pumps blood. (b) When it relaxes, its chambers are filled with blood. 5The atria have relatively thin walls and function as collection chambers. (a) Right atrium receives deoxygenated blood from the vena cava (b) Left atrium receives oxygenated blood from the pulmonary veins. 6 As the atria contract, blood is pumped into the ventricles. The ventricles have thicker walls and stronger contractions than the atria. 7 The muscular wall of the left ventricle is thicker than the wall of the right ventricle. This is because the left ventricles needs to pump blood to all parts of the body while the right ventricle pumps blood to the lungs only. 8 The heart has valves that allow blood to flow in one direction only. (a) Tricuspid valve and Bicuspid valve. (b) These two valves prevent the blood from flowing back into the atria. (c) The Semi-lunar valves which are located at the exits, where the pulmonary artery and aorta leave the heart. (d) These valves prevent blood from flowing back into the ventricles when the ventricles relax. (Refer Diagram 5 for detail) Biology Form Five Notes © Copyright Maryam Shah 2007 9
  10. 10. CHAPTER 1: TRANSPORT Blood flows to the DIAGRAM 5: The flow of blood in the heart 2 1 Oxygenated blood from the lungs enters the left atrium through the pulmonary veins. 2 Deoxygenated blood from the rest of the body enters the right atrium via the vena cava. 3 As blood fills the atria, the atria contract and push the blood through the bicuspid and tricuspid valves into the two ventricles. Blood goes to the 4 When the ventricles contract, the semi-lunar valves are forced open and blood is pushed into the pulmonary arteries and the aorta. 5 Deoxygenated blood is pumped through the pulmonary arteries to the lungs. 6 Oxygenated blood is pump through the aorta to the rest of the body. Biology Form Five Notes © Copyright Maryam Shah 2007 10 Blood goes to the right lung Blood comes from left lung 5 Blood comes from right lung 1 left lung 5 Blood comes from the head and arms 3 4 3 4 6 body 1 Bicuspid valve Key: Oxygenated blood; Deoxygenated t blood.
  11. 11. CHAPTER 1: TRANSPORT  Explain how blood is propelled through the human circulatory system The circulation of blood in humans is a result of the following action: (a) The pumping of the heart (b) Contracting of the skeletal muscles around veins  The pumping of heart Initiated & coordinated by the Located in the Interconnecte d tissues Myogenic Myogenic Key: SA – Sinoatrial; AV – Atrioventricular; p.m- pacemaker Pacemake r Pacemake r Biology Form Five Notes © Copyright Maryam Shah 2007 11 Hear t Made up of Cardiac muscle Characterized as means Interconnecte d tissues allows Electrical impulses to spread rapidly through the heart Need no stimulation by nerve impulses when contracts neither relaxes causing Wall of the right atrium generates Electrica l impulses Controlled by contractio n of the heaArptex of the heart Parasympathetic Nerves Sympathetic Nerves Hormones (Adrenaline) radiated from Purkinje fibres SA node (Primary p.m) causing Bundle of His fibres AV node Impulses transmitted to bundle branches The spread of impulses over the walls of atria → contraction of atria DIAGRAM 6: The position of the SA node, AV node andPurkinje Fibres
  12. 12. CHAPTER 1: TRANSPORT The contraction pushes the blood out to the lung and body. The sound of the heart contracting and the valves opening and closing produces a characteristic “lub-dub” sound. The lub sound is associated with the closure of the atrioventricular valves while dub indicates the closing of the semilunar valves.  Contraction of skeletal muscles around veins  Blood is sent through the circulatory system with the help of the contractions of the skeletal muscles around the veins.  When skeletal muscles contract, the veins constrict and blood is pushed along through the veins. The veins have one-way valves that allow blood to flow in the direction towards the heart Biology Form Five Notes © Copyright Maryam Shah 2007 12 Semilunar valves Atrioventricular valves
  13. 13. CHAPTER 1: TRANSPORT  The regulatory mechanism of blood pressure 1. Blood pressure is defined as the pressure which is exerted by the blood when it flows along a vessel. 2. It is greater in arteries than in veins 3. Flows from high pressure areas to low pressure areas. 4. SYSTOLE STAGE –contraction of the ventricles where blood pressure is the highest. 5. Normal Human blood pressure: 120/80 mmHg 6. 120 – is the systolic pressure. 7. 80 – is the diastolic pressure ( the lowest pressure during the relaxation phase (DIASTOLE STAGE) 8. Regulated by negative feedback mechanism. 9. Baroreceptors are pressure receptors located at the ARC OF THE AORTA and CAROTID ARTERIES. (Refer Diagram 7 for detail) 10.These receptors sent nerve impulses continuously to the cardiovascular centre in the medulla oblongata to help regulate the blood pressure. DIAGRAM 7: Baroreceptors in the arch of the aorta and carotid arteries Action of effectors Blood pressure increases (for example, during physical exercise) Normal blood pressure Biology Form Five Notes © Copyright Maryam Shah 2007 13 weaker cardiac muscle contraction lower the heartbeat rate Smooth muscles of the arteries relax and the arteries dilate. This reduces the resistance of blood flow in the blood vessels (Vasodilation). Blood pressure decreases Baroreceptors in arch of aorta and carotid arteries are stimulated increased rate of nerve impulses sent to cardiovascular centre in medulla oblongata in the brain Sends nerve impulses to the effectors
  14. 14. CHAPTER 1: TRANSPORT Baroreceptors in arch of aorta and carotid arteries are less stimulated decreased rate of nerve impulses sent to Action of effectors cardiovascular centre in medulla oblongata in the Stronger cardiac muscle contraction Increase the heartbeat rate Smooth muscles of the arteries contract thus increases the resistance of blood flow in the blood vessels (Vasoconstriction) Blood pressure decreases (for example, when in a state of shock) Normal blood pressure Blood pressure increases brain Sends nerve impulses to the effectors  Compare and contrast the circulatory systems in the following: humans, fish and amphibians. 2 types of circulatory systems: 1. Open circulatory system 2. Closed circulatory system 1. The open circulatory system consist of:  one or more heart  a network of vessels  and a large open space within the body (haemocoel). Biology Form Five Notes © Copyright Maryam Shah 2007 14 DIAGRAM 8: The negative feedback regulation of blood pressure
  15. 15. CHAPTER 1: TRANSPORT One or more hearts pump the haemolymph through the vessels and into the haemocoel. The haemocoel contains the soft internal organs and is filled with haemolymph. Here, a chemical exchange between the haemolymph and the body cells takes place. The haemolymph flows from the hearts into the haemocoel when the hearts contract. When the heart relax, the haemolymph is drawn through pores called ostia back into the hearts. The ostia are equipped with valves that close when the hearts contract. 2. The closed circulatory system comprises single and double circulatory system. Single circulatory system Consists of 1 atrium & 1 ventricle Blood flows from ventricle to the gill capillaries (gaseous exchange occurs) Gill capillaries converge into a vessel that carries the oxygenated blood to the body capillaries or systemic capillaries (o2 diffuses into the tissues while co2 diffuses out of the tissues and into the capillaries) The deoxygenated blood then returns to the atrium of the heart through the veins. Single circulatory means having only one circuit of blood flow that is the blood goes to the gill capillaries and then to the systemic capillaries. Biology Form Five Notes © Copyright Maryam Shah 2007 15 The open circulatory system Circulatory System In Fish
  16. 16. CHAPTER 1: TRANSPORT Double circulatory system Frogs and other amphibians have three-chambered heart (two atria & one ventricle) Deoxygenated blood from the body is delivered into the right atrium; while oxygenated blood from the lungs is delivered into the left atrium. Blood from both atria then enters a single ventricle. Although there is some mixing of oxygenated and deoxygenated blood inside the ventricle, most of the oxygenated blood remains in the left portion of the ventricle while deoxygenated blood tends to remain in the right portion of the ventricle. Biology Form Five Notes © Copyright Maryam Shah 2007 16 Circulatory System In Amphibians (b) Frog
  17. 17. CHAPTER 1: TRANSPORT Double circulatory system The ventricles then pumps blood through the pulmocutaneous circulation and the systemic circulation. The pulmocutaneous circulation leads to the gas exchange tissues, which are the lungs and skin. Here, gaseous exchange occurs. The oxygenated blood returns to the left atrium of the heart and most of it is then pumped into the systemic circulation. The systemic circulation carries oxygenated blood to body tissues & returns the deoxygenated blood to the right atrium through the veins Since the blood flows in two separate circuits; pulmocutaneous circulation and systemic circulation, the system is identified as double circulatory system. Biology Form Five Notes © Copyright Maryam Shah 2007 (b) Frog 17 Double circulatory system • Humans have four-chambered heart: two atria and two completely separated ventricles. • Deoxygenated blood and oxygenated blood do not mix. • The four chambers ensure an efficient and rapid delivery of highly oxygenated blood to the organs of the body. • In the pulmonary circulation, deoxygenated blood in the right ventricle is pumped into the pulmonary arteries. • These arteries carry the blood to the lungs where it passes through the blood capillaries. • This allows the removal of co2 and the intake of o2 from the air into the alveoli. Circulatory System In Humans
  18. 18. CHAPTER 1: TRANSPORT  Conceptualise the circulatory system in humans 18  The circulatory system in humans comprises two separate circulations that are the pulmonary circulation and the systemic circulation.  The pulmonary circulation carries blood from the heart to the lungs and back to the heart while the systemic circulation carries blood from the heart to all parts of the body and back to the heart.  These two separate circulations make up the double circulatory system.  It means in a complete circulation, the blood flows through the heart twice.  The Double Circulation is to ensure that oxygenated blood is constantly delivered to the cells. Biology Form Five Notes © Copyright Maryam Shah 2007 • In the systemic circulation, blood is carried from the heart to the other part of the body except the lungs. • The oxygenated blood from the lungs returns to the left atrium and flows into the left ventricle. • The oxygenated blood is then pumped into the systemic capillaries via the aorta. • Since there are two separate circuits; the systemic and the pulmonary circulations, humans are known to have a double circulatory system. • In a complete circulation, the blood flows through the heart twice. • This is to ensure that oxygenated blood is constantly delivered to the cells.
  19. 19. CHAPTER 1: TRANSPORT LEARNING OBJECTIVE: 1.3 Understanding the mechanism of blood clotting. Learning outcome : A student is able to :  Explain the necessity for blood clotting at the side of damaged blood vessels.  Explain the mechanism of blood clotting.  Predict the consequences of impaired blood clotting mechanism in an individual. Previous knowledge : The general function of blood in previous lesson. CONTENT:  Blood clotting is necessary to: (a) prevent serious blood loss when a person is injured (b) maintain blood pressure. (c) maintain the circulation of blood in a closed circulatory system. (d) prevent the entry of microorganisms and foreign substances into the body through the damaged blood vessels.  Blood clotting mechanism 2 1 Platelets stick rapidly 5 6 Biology Form Five Notes © Copyright Maryam Shah 2007 19 When a blood vessel in the body is damaged, the connective tissue in the vessel wall is exposed to blood plasma to the collagen fibres in the connective tissue and release chemicals called clotting factors that make the surrounding platelets sticky 3 The aggregation of platelets forms a plug called a platelet plug. A platelet plug can stop blood loss completely if the damage to the vessel is small. 4 When the damage in the vessel is severe, the plug is reinforced by a clot of fibrin which is formed through a series of steps. The clumped platelets, the damaged cells and clotting factors in the plasma form activators These activators (thromboplastins), together with calcium ions and vitamin K, convert the prothrombin (an inactive plasma protein) to thrombin (active plasma protein which acts as an enzyme)
  20. 20. CHAPTER 1: TRANSPORT 7 8 9  Consequences of impaired blood clotting mechanism in an individual. Blood clotting mechanism would be impaired if there are defects in the: (a) blood vessels (b) blood clotting factors or in (c) platelets. There are 2 types of blood disorders identified as the consequences of impaired blood clotting mechanism: (a) Haemophilia Biology Form Five Notes © Copyright Maryam Shah 2007 20 Thrombin catalyses the conversion of the soluble protein (fibrinogen) in blood plasma into the insoluble fibrin. Fibrin will aggregate to form a mesh of long threads over the wound, trapping red blood cells thus sealing the wound. The resulting blood clot hardens when exposed to air to form a scab. (Continue to the next page) (from previous page)
  21. 21. CHAPTER 1: TRANSPORT (b) Thrombophilia (a) Haemophilia  Haemophilia is a hereditary illness.  It is caused by a lack of clotting factors.  It impairs the body’s ability to control bleeding.  When a blood vessel is injured, a scab will not form.  The vessel will continue to bleed excessively for a very long period of time.  The bleeding can be external, due to skin by a scrape, a cut or an abrasion.  It can be internal, into muscles, joints or as hollow organs. Biology Form Five Notes © Copyright Maryam Shah 2007 21
  22. 22. CHAPTER 1: TRANSPORT  It might therefore be visible as skin bruises or invisible like bleeding in the brain.  For haemophiliacs, the bleeding even from minor cuts can cause excessive bleeding and death.  Today, haemophilia can be controlled quite successfully.  Regular injections of clotting factors like Factor VIII can prevent excessive bleeding. (b) Thrombophilia  Thrombophilia is the reverse when compared to haemophilia.  It is caused by a defect in the blood vessel walls.  The present of a blood clot attaching to the vessel walls will decelerate the blood flow. Defect in the vessel wall: the present of a blood clot  Impaired blood clotting factors and mutation of prothrombin also can cause thrombophilia.  People with thrombophilia have an increased tendency to dangerous blood clots in the arteries or veins.  A clot formation inside an unbroken blood vessel is known as thrombosis.  The blood clot is called thrombus.  Sometimes, a thrombus may dislodge and move along the blood circulatory system.  The blood clot which moves in a bloodstream is called an embolus.  The embolus moves along until it gets stuck to a narrow artery.  When this happens, the blood flow in the blood vessel is obstructed.  The consequences due to embolism depend on the size of embolus and which artery it is obstructing.  If a clot is lodged in a coronary artery, the cardiac tissue will no longer receive oxygenated blood. Biology Form Five Notes © Copyright Maryam Shah 2007 22
  23. 23. CHAPTER 1: TRANSPORT  The cardiac tissue may die and leads to a heart attack.  If a clot blocks the blood flow to the brain, it may cause stroke. LEARNING OBJECTIVE: 1.4 Synthesising the Concept of Lymphatic System. Learning outcome : A student is able to :  Describe the formation of interstitial fluid.  State the composition of interstitial fluid.  State the importance of interstitial fluid.  Describe the fate of interstitial fluid. Previous knowledge : The content of blood plasma in previous lesson. CONTENT:  How is interstitial fluid formed?  When blood flows through the capillaries a pressure is exerted on the capillaries.  The pressure is called hydrostatic pressure. Biology Form Five Notes © Copyright Maryam Shah 2007 23
  24. 24. CHAPTER 1: TRANSPORT  The pressure is generated by the pumping action of the heart.  At the same time, osmotic pressure is created between the capillaries and surrounding tissues.  This is due to the inability of large solute to penetrate the capillary walls.  However, the hydrostatic pressure is more than the osmotic pressure.  So, the fluid from the blood is pushed out by filtration.  The net pressure inside the artery is more than the outside.  Hence the water is forced out of the capillaries by filtration and fills the spaces between the cells.  The water which contains dissolved substances forms interstitial fluid.  What are the compositions of interstitial fluid?  Interstitial fluid is a clear fluid which originates from blood.  Therefore it contains most of the substances found in the blood such as water, dissolved nutrients, hormones, waste products, gasses and small proteins except erythrocytes, plasma protein and platelets.  Leucocytes are present in the interstitial fluid since they can squeeze through the pores in between the capillary cells.  What is the importance of interstitial fluid?  Fills the space found in between the cells.  Acts as the medium of diffusion of nutrients (from the blood to the cells) and waste products (from the cells into the blood)  Provides optimal environment for the cells.  Nutrients uptake and waste products elimination are examples of cellular activities.  A constant and stable environment is needed for cellular activities.  This environment of individual cell is the interstitial fluid.  For example, the pH of interstitial fluid is kept between pH 7.35 to pH 7.45 for optimal cellular activities.  The optimal temperature that is kept constant is 370C.  Neurotransmission between neuron and target cells happen across the interstitial fluid.  Intercellular communication becomes easier with the presence of interstitial fluid, hormones and neurotransmitters.  They fill up the gaps between cells.  For instance, leucocytes release hormone into the interstitial fluid.  These hormones diffuse to the nearby target cells, through interstitial fluid. Biology Form Five Notes © Copyright Maryam Shah 2007 24
  25. 25. CHAPTER 1: TRANSPORT  The more specialised synaptic signalling occurs through neurotransmitters.  Neurotransmitters are released into the interstitial fluid by neuron.  The neurotransmitters are transmitted to the target cells through interstitial fluid.  Provides moist medium for the cells.  A cell needs moist environment for effective exchange of substances.  The interstitial fluid bathes the cells.  The cells environment therefore becomes moist thus allows the exchange of materials to occur effectively.  What is the fate of interstitial fluid?  About 90% of the fluid that leaves the blood at the arterial end of the capillary re-enters at the venous end.  This is due to the net pressure inside the capillary is less than the interstitial space and also as the blood flows towards the venous end, it becomes more concentrated with solutes.  This build-up of solutes induces osmosis.  Hence, the interstitial fluid is drawn back into the blood vessel again.  The interstitial fluid must be returned to the circulatory system to maintain the normal blood volume. Biology Form Five Notes © Copyright Maryam Shah 2007 25
  26. 26. CHAPTER 1: TRANSPORT  However, not as much fluid is absorbed back into the blood capillary as is filtered out.  About 10% of the fluid that still remains in the interstitial space is equivalent to about 4 litres of fluid lost from the blood capillaries each day.  The fluid loss is returned to the blood through the lymphatic system.  If the interstitial fluid is not passed into the lymphatic system, the area will swell up. This condition is called oedema. LEARNING OBJECTIVE: 1.4 Synthesising the Concept of Lymphatic System. Learning outcome : A student is able to :  Describe the structure of lymphatic system.  Explain how the lymphatic system compliments the circulatory system.  Compare the content of blood, interstitial fluid and lymph.  Predict what will happen if interstitial fluid fails to return to the circulatory system.  Conceptualise the relationship between the lymphatic system and circulatory system Previous knowledge : The importance of interstitial fluid in previous lesson. CONTENT:  The structure of lymphatic system.  The lymphatic system is also a circulatory system.  It has vessels that branches out through the body except for the brain.  They begin with blind-ended capillaries. Biology Form Five Notes © Copyright Maryam Shah 2007 26
  27. 27. CHAPTER 1: TRANSPORT  The blind-ended capillaries originate in connective tissues of nearly all parts of body.  The capillaries converge into small lymph vessels which eventually converge into larger vessels.  Within the lymphatic vessels there are one-way valves that ensure the continuous flow of the lymph away from the tissues. These valves also prevent the backflow of lymph.  Located at intervals along the lymphatic vessels are lymph nodes. These nodes produce and store lymphocytes; hence they help to defend the body against infection.  The lymphatic vessels drain into two larger ducts: 1. Right lymphatic duct 2. Thoracic duct. Biology Form Five Notes © Copyright Maryam Shah 2007 27
  28. 28. CHAPTER 1: TRANSPORT Structure of Lymphatic vessel A – Afferent vessel; B – nodule; C –Valve D – Capsule; E – Efferent vessel  The right lymphatic duct receives lymph from the right arm, shoulder area and the right side of the head and neck.  The thoracic duct receives lymph from the left of the head, neck and chest, the left upper limb and the entire body below the ribs.  These ducts drain to the large veins in the neck: the right and left subclavian veins. Hence, lymph drains back into the blood.  Lymphatic system does not have a pump.  The lymph is propelled along its vessels by: 1. one-way valves 2. skeletal muscles contraction 3. breathing movement 4. Intestinal movement 5. smooth muscle contraction of lymphatic vessels  The lymphatic system includes other body organs such as thymus and spleen. Biology Form Five Notes © Copyright Maryam Shah 2007 28 E C D A B Lymph nodes
  29. 29. CHAPTER 1: TRANSPORT  Thymus is a soft, bilobed organ which is located behind the sternum. It is surrounded by a connective tissue capsule. The connective tissue extends inside the thymus thus dividing it into lobules. The lobules contain lymphocytes which eventually will mature into T-lymphocytes (or T-cells) in thymus.  The spleen lies in the upper abdominal cavity. It is the largest lymphatic organ. The spleen contains blood instead of lymph. The white pulp of spleen contains lymphocytes while the red pulp contains red blood cells, macrophages and lymphocytes.  Explain how the lymphatic system compliments the circulatory system 1. By maintaining the blood volume and pressure  Plasma is forced out into the interstitial spaces when the blood flows through the capillaries.  85% of the fluid that leaves the blood at the arterial end of the capillary re-enters at the venous end.  The other 15% diffused into the lymphatic vessels to form lymph.  The lymphatic system restores excess interstitial fluid into the circulatory system.  This process maintains the normal blood volume and hence the pressure. 2. As means of transportation of fatty acids and plasma proteins  Blood capillaries are not permeable to plasma protein.  On the other hand, lymphatic vessels are permeable to big molecules such as plasma proteins and fatty acids.  They are porous.  So the lymphatic capillaries collect any plasma protein in the interstitial space.  These proteins might have leaked into the interstitial space.  In the small intestine, the fatty acids are not absorbed into the capillaries.  Instead they are absorbed into the lymphatic vessels called lacteals.  Lacteals transport fatty acids and drain them into the circulatory system. 3. Centre of production of blood cells  Monocytes, macrophages and lymphocytes are cells found in the blood.  They defend the body against pathogens.  These blood cells are produced by spleen and lymph nodes.  These cells mature and are released into the circulatory system. Biology Form Five Notes © Copyright Maryam Shah 2007 29
  30. 30. CHAPTER 1: TRANSPORT 4. Centre of destruction of blood cells  The spleen filters worn out red blood cells and deformed platelets.  Macrophages found in the spleen destroy these blood cells by phagocytosis.  Compare the content of blood, interstitial fluid and lymph. BLOOD INTERSTITIAL FLUID LYMPH SIMILARITIES Contents: 1. Water is the main component. 2. All of them contain glucose,amino acids,minerals, vitamins,hormones,enzymes and respiratory gases. Functions: 1. All of them make up the internal environment of the body. 2. All of them function in transport of substances. 3. All of them function in the body’s defense system. DIFFERENCES Biology Form Five Notes © Copyright Maryam Shah 2007 30
  31. 31. CHAPTER 1: TRANSPORT BLOOD Contents: 1. Erythrocytes present. 2. Plasma proteins present. 3. Contains white blood cells. Functions: 1. Transports mainly water-soluble substances. INTERSTITIAL FLUID Contents: 1. Erythrocytes absent. 2. Plasma proteins absent. 3. Has the least white blood cells. Functions: 1. Functions in providing nutrients to body cells and removing their waste products. LYMPH Contents: 1. Erythrocytes absent. 2. Plasma proteins absent. 3. Has the most white blood cells. Functions: 1. Transports mainly lipid-soluble substances. Comparison on the content of blood, interstitial fluid and lymph  Predict what will happen if interstitial fluid fails to return to the circulatory system.  If the excess fluid is not returned to the bloodstream, body tissues will become swollen because too much fluid is retained.  An excessive accumulation of interstitial fluid in the spaces between the cells will result in a condition known as oedema. It is not a disease but a clinical condition.  It occurs when the body’s normal balance of fluid intake and output is disturbed.  Oedema may be caused by a blocked lymphatic vessel.  A prolonged oedema will cause the skin to swell and stretch. The skin will become taut and shinny. Biology Form Five Notes © Copyright Maryam Shah 2007 31
  32. 32. CHAPTER 1: TRANSPORT  The prolonged and excessive swelling will cause the connective tissues under the skin to be damaged.  This will lead to skin hardening.  Conceptualise the relationship between the lymphatic system and circulatory system Interstitial space Venule arteriole  As the blood flows through the circulatory system, fluid from the plasma diffuses into the interstitial spaces in the arterial end.  The interstitial fluid is reabsorbed into the bloodstream at the venous end.  The interstitial fluid that has not been reabsorbed into the bloodstream diffuses into the lymph capillaries.  The lymph collected throughout the body drains into the blood circulation via the thoracic ducts and the right lymphatic duct that join the veins in the neck. Comparison between the blood circulatory system and the lymphatic system. Biology Form Five Notes © Copyright Maryam Shah 2007 32 lymph capillary network of capillaries body cells lymphatic vessel Interstitial fluid lymph
  33. 33. CHAPTER 1: TRANSPORT Circulatory System Similarities Lymphatic System  Both are circulatory systems  The medium is contained in vessels Circulatory System Differences Lymphatic System  Closed continuous circuit throughout the body.  Comprises heart, arteries, veins and capillaries. Structure  Open circuit from the tissues into lymphatic vessels.  Comprises right lymphatic duct and thoracic duct, lymph nodes, lymphatic vessels and capillaries thymus and spleen Blood Medium Lymph Erythrocytes, Composition of leucocytes, platelets, medium dissolved substances, waste products and protein plasma. Leucocytes, dissolved substances, waste products and protein plasma. Collects and distributes oxygen, nutrients, waste products, and hormones to the tissues of entire body. Role of medium Collects and removes waste products left behind in the tissues. By the kidneys. Filtration By lymph nodes. Blood is visible and damaged blood vessels caused obvious signs Vessel damage Lymph is invisible and damaged lymphatic system is difficult to detect Blood is propelled throughout the body by the pumping of the heart and the muscular movement. Propulsion Lymph is not pumped. It passively flows from the tissues into the lymph capillaries aided by muscular movement, breathing mechanism and blood circulation. Biology Form Five Notes © Copyright Maryam Shah 2007 33
  34. 34. CHAPTER 1: TRANSPORT LEARNING OBJECTIVE: 1.5 Understanding the role of the circulatory system in body’s defense mechanism Learning outcome : A student is able to :  State another function of the circulatory system.  Identify the three lines of defence mechanism.  Describe phagocytosis.  State the meaning of antigen and antibody.  State the meaning of immunity and immunisation.  Relate antigen and antibody to immunity.  Name and give examples of various types of immunity.  State the effects of human immunodeficiency virus (HIV) on the body’s defence mechanism.  Describe the transmission of HIV.  Suggest ways to prevent the spread of acquired immune deficiency syndrome (AIDS). Previous knowledge : The general functions of blood circulatory system in previous lesson. CONTENT:  State another function of the circulatory system. Besides transport, the circulatory system of our body is also important to protect our body from infectous diseases caused by harmful microorganisms called pathogens.  Identify the three lines of defence mechanism. Defence Mechanism Comprises of Classified into Classified into Tears n Saliva; Immune System HCl (gastric juice) Biology Form Five Notes © Copyright Maryam Shah 2007 34 Non Specific Specific First line of defence Second line of defence Third line of defence Consist of Consist of Skin Mucous membrane Phagocytic white blood cells by way of Production of antibody by the lymphocytes
  35. 35. CHAPTER 1: TRANSPORT  Describe phagocytosis. Pseudopodium Bacteria-containing vacuole Enzyme-containing lysosome  State the meaning of antigen and antibody. Antigen is a protein molecule or soluble polysaccharides that can be found in the walls or membranes of a pathogen while antibody is a globulin protein molecule produced by lymphocytes in response to the entry of pathogens or antigens.  State the meaning of immunity and immunisation. Immunity is body’s ability to fight diseases caused by infection of pathogens. Immunisation is the process of obtaining immunity through either vaccination or injection of antiserum.  Relate antigen and antibody to immunity. I mmunity is the body’s ability to fight diseases caused by infection of pathogens or any foreign substance when introduced into the body. The foreign substance which is also known as antigen will induce the production of antibodies by the lymphocytes. Antigen is destroyed and Biology Form Five Notes © Copyright Maryam Shah 2007 35 A B C D E A - Neutrophyl moves towards the bacteria once it senses the chemical secretions released by the microbe. (Chemotaxis) B - Neutrophyl attaches itself against the bacteria. (Adherence) C - Neutrophyl projects its pseudopodium to trap the bacteria into a vacuole. (Ingestion) D - The enzyme-containing lysosome fuses with the bacteria-containing vacuole. E - The bacteria cell is digested by the enzyme and the product of the digestion is absorbed into the entire cell of neutrophyl. (Digestion)
  36. 36. CHAPTER 1: TRANSPORT antibodies remain in the body. The infected person gets well. Further entry of the same type of antigen is quickly destroyed by antibodies caused by the presence of memory cells. The person does not get ill again. He is said to be immuned to the disease. This is known as the immune response.  Name and give examples of various types of immunity.  State the effects of human immunodeficiency virus (HIV) on the body’s defence mechanism. During HIV infection, the virus attacks the lymphocytes known as T-Cells which are responsible in protecting the body from infection of pathogens. The reduction of the number of T-cells cause the improper function of the immune system to fight against HIV as well as other secondary infections (caused by bacteria and other viruses).  Describe the transmission of HIV. HIV can be transmitted through seminal fluid, blood, breast milk and vaginal discharge. Transmission may occur during blood transfusion from donor to recipient; or during sexual contact with an HIV carrier or AIDS patient; or through sharing of needles especially among drug addicts; or from an HIV positive mother to the baby either during the foetal stage or during breast feeding. Biology Form Five Notes © Copyright Maryam Shah 2007 36 IMMUNITY Comprises of ACTIVE IMMUNITY PASSIVE IMMUNITY Comprises of Comprises of Natural Active Immunity Artificial Acquired Active Immunity Natural Passive Immunity Artificial Acquired Passive Immunity Examples Examples Examples Examples Tuberculosis, Smallpox and Measles Rubella, Hepatitis B, Poliomyelitis Antibody found in colostrum during breast feeding Antiserum for tetanus and diphtheria
  37. 37. CHAPTER 1: TRANSPORT  Suggest ways to prevent the spread of acquired immune deficiency syndrome (AIDS). Avoiding drug use and never share needles for drugs, steroids, medications, tattooing or body piercing. Counselling to the HIV positive patients, so that they do not spread the virus to others Practising safe sex using condoms as a barrier to prevent contact with infectious semen Educating the school children and public about the risk factors of AIDS through awareness campaigns Strict screening of blood before transfusion Biology Form Five Notes © Copyright Maryam Shah 2007 37
  38. 38. CHAPTER 1: TRANSPORT LEARNING OBJECTIVE: 1.6 Appreciating a Healthy Cardiovascular System Learning outcome : A student is able to :  Select and practise suitable ways to maintain a healthy cardiovascular system Previous knowledge : The functions of cardiovascular system in previous lesson. CONTENT:  Cardiovascular diseases and its descriptions: Type of cardiovascular diseases Definition of diseases Heart Failure The inability of the heart to pump blood at an adequate rate Heart Attack Sudden interruption or insufficient blood to the heart Stroke A sudden loss of brain function caused by a blockage or a rupture of a blood vessel to the brain Cardiomyopathy Disease or disorder of the heart muscle High Blood Pressure High pressure in the arteries  Risk factors contributing to cardiovascular diseases: Biology Form Five Notes © Copyright Maryam Shah 2007 38 High Blood Pressure The heart works harder than normal The heart expands and contracts at a faster rate Heart & arteries become more prone to injuries Diet high in LDL stress (bad cholesterol) Heart attacks, strokes, and arteriosclerosis makes As a result thus increases the risk of As a consequence caused by
  39. 39. CHAPTER 1: TRANSPORT High Blood cholesterol Physically inactive  Ways to maintain a healthy cardiovascular system: 1. Avoid smoking - The nicotine content in a cigarette smoke will cause the contraction of artery and increase the blood pressure. As a result the heart has to pump harder in order to ensure the blood flows. 2. Avoid misused of drugs - Drugs like cocaine can cause irregular beat of the heart and therefore might lead to heart attack and stroke. 3. Maintain suitable body weight - Maintaining body weight according to Body Mass Index (BMI) is advisable to reduce the risk of having high blood pressure and cardiovascular diseases. 4. Take healthy food (balanced diet) - Low in salt and sugar content, low in saturated fat and cholesterol. 5. Eat more fruits and vegetables - Antioxidant – containing food, vitamins A, C and E may destroy the free radicals that damage the artery wall 6. Stay fit - Optimum exercise for 30 minutes every 3 times a week may help you to hinder stress and reduce body weight. Biology Form Five Notes © Copyright Maryam Shah 2007 39 Obesity and Overweight coronary heart diseases, stroke & peripheral vascular diseases over intake of carbohydrates n fats Improper diet Lacks of vitamin Bs and folic acid in diet amount of amino acid Homocysteine found in the blood The oxidation of good cholesterol to LDL caused by caused by increases promotes closely related to Diabetes mellitus Low in High-density related to Lipoprotein (HDL) and high triglycerides levels Tobacco smoke
  40. 40. CHAPTER 1: TRANSPORT LEARNING OBJECTIVE: 1.7 The Transport of Substances In Plants Learning outcome: A student is able to:  State the necessity for transport of substances in plants.  Identify the vascular tissue in stem, root and leaf.  State the role of vascular tissue in the transport of substances.  Describe the structure of vascular tissue.  Relate the structure of xylem to transport.  Relate the structure of phloem to transport.  Predict the effect of removing a ring of phloem tissue from a plant. Previous knowledge : The concept of transport of substances in the human circulatory system had been studied in previous lesson. CONTENT:  State the necessity for transport of substances in plants. Water and mineral salts absorbed by the roots have to be transported to all parts of the plant. Water is an important component of cells. It acts as solvent and is often a reactant in cell metabolism. Mineral ions are required for chlorophyll synthesis, healthy plant growth and development. Organic food materials synthesised by the leaves during photosynthesis need to be sent to growing regions, storage organs and other parts of plants.  Identify the vascular tissue in stem, root and leaf.  The vascular tissues transport substances in plants.  There are two types of vascular tissues: xylem and phloem.  Xylem transports water and dissolved mineral salts absorbed by the roots up the stems and to the leaves. In woody plants, the xylem tissue also provides mechanical support to the plant.  Phloem transports organic substances from the leaves down to the storage organs and from the storage organs such as the roots up to the growing regions such as the buds.  Vascular tissues are found in the roots, stems and leaves of a plant. Biology Form Five Notes © Copyright Maryam Shah 2007 40
  41. 41. CHAPTER 1: TRANSPORT The various arrangement of vascular tissue in root, stem and leaf  Describe the structure of vascular tissue.  The stem has an epidermal layer that helps maintain the shape of the stem. a. In young plants, the epidermal cells secrete a waterproof cuticle. b. In older plants, the epidermis may be absent, and is replaced by bark.  Inside the epidermis is the cortex layer. The cortex layer is made up of collenchyma cells which provide support and flexibility to the stem.  The inner parts of the stems consist of vascular bundles and the pith which is the central region of a stem. a. The pith is used for food storage in young plants. b. The pith may be absent in older plants, making them hollow.  In dicotyledonous plants, the vascular tissues of the stem are grouped together to form vascular bundles. a. The vascular bundles are arranged in a ring around the pith. Biology Form Five Notes © Copyright Maryam Shah 2007 41 The Stem
  42. 42. CHAPTER 1: TRANSPORT b. In each vascular bundle, xylem is found towards the inside of the stem with the phloem on the outside. A tissue called the cambium lies between the xylem and the phloem.  In monocotyledonous plants, the vascular bundles are scattered throughout the stem. Dicotyledonous Stem Vascular bundle Note that: The vascular bundle encircles the pith. The phloem is found on the outer side while xylem on the inner side of the bundle. Vascular tissue Note that: The vascular bundles are scattered throughout the stem Note that: The vascular bundle is in a star shape whereby the phloems fill the area between the xylems Note that: The vascular bundles form a ring around the pith, with the xylem tissue alternating with the phloem tissue. Biology Form Five Notes © Copyright Maryam Shah 2007 42 The root Phloem Xylem Phloem Xylem Monocotyledonous Stem Dicotyledonous Root Phloem Xylem Pith Phloem Xylem Monocotyledonous Root Cambium Pith
  43. 43. CHAPTER 1: TRANSPORT  The outmost layer is the epidermis. The epidermis of the roots does not have waxy cuticles.  The epidermis absorbs water and dissolved mineral ions from the soil.  Specialised epidermal cells grow outwards to form root hairs.  Root hairs increase the surface area for water absorption.  The region between the epidermis and the vascular cylinder is the cortex. The cortex is made up of parenchyma cells which store starch grains.  Located immediately after the cortex is a single layer of cells called the endodermis.  Next to the endodermis is the pericycle. The pericycle consists of sclerenchyma tissue which provides mechanical support for the roots.  In the roots, the vascular tissue is located in the vascular cylinder consists of vascular tissue and the pericycle.  The vascular tissues of roots are continuous with the vascular tissues of stems.  In a dicotyledonous plant, the xylem radiates from the centre of the vascular cylinder, usually forming the shape of a star while the phloem fills the area between the xylem.  In a monocotyledonous plant, a. the vascular cylinder has a central core called the pith. b. the pith contains parenchyma cells. c. the vascular tissues form a ring around the pith, with the xylem tissue alternating with the phloem tissue. Biology Form Five Notes © Copyright Maryam Shah 2007 43 The leaf Xylem Phloem Vascular bundle
  44. 44. CHAPTER 1: TRANSPORT  The leaf consists of a broad portion called the lamina (leaf blade).  The leaf blade is connected to the stem by a stalk called the petiole.  Inside the petiole are the vascular tissues of xylem and phloem that are continuous with those in the stem, root and lamina.  The leaf blade contains leaf veins. Vascular tissues are found in the leaf veins.  Xylem forms the upper part of a vascular bundle in the leaf while phloem forms the lower part of the vascular bundle. a. The xylem transports water and mineral salts to the leaves. b. The phloem transports sucrose and other products of photosynthesis from the leaves.  Relate the structure of xylem to transport.  Xylem contains four types of cells: 1. xylem vessels 2. tracheids 3. fibres (a type of sclerenchyma) 4. parenchyma  The parenchyma stores food substances while the fibres provide support to the xylem.  Xylem vessels and tracheids are water-conducting cells.  They are elongated cells arranged end to end.  During growth, the walls of the xylem vessels and tracheids are thickened with lignin deposits making them strong and impermeable so that they do not collapse under the tension created by the upward pull of water during transpiration (transpirational pull).  The lignin also prevents the entry of food substances. Hence, the cytoplasm of these cells disintegrates leaving a cavity in the centre of the cells. As a result, mature xylem vessels and tracheids are hollow and dead.  The walls of the xylem vessels and tracheids are perforated by a series of holes called pits. The pits allow water and mineral salts to pass sideways between the cells. Biology Form Five Notes © Copyright Maryam Shah 2007 44 Sclerenchyma cells Parenchyma cells Tracheids Xylem vessel
  45. 45. CHAPTER 1: TRANSPORT  Tracheids are longer and have a smaller diameter compared to xylem vessels. They are pointed at the ends. The end walls breakdown in the pits and this allows water to pass from cell to cell.  The end walls of the xylem vessels are open so that the cells join end to end to form a long continuous hollow tube.  This arrangement allows water to flow upwards continuously from one cell to the next.  Relate the structure of phloem to transport.  Phloem tissue is composed of four types of cells: 1. sieve tubes 2. companion cells 3. fibres (a type of sclerenchyma) 4. parenchyma  Organic substances such as sucrose and amino acids are transported along the sieve tubes of the phloem. (a) The sieve tube is a cylindrical column comprising long cells arranged end to end. (b) The sieve tube is a living cell. (c) When mature, it has no nucleus and its cytoplasm is pushed to the sides of the cell. (d) The end walls of each cell are perforated by pores to form sieve plates which allow substances to pass from one cell to another. (e) Each sieve tube cell is kept alive and its function is supported by one or more companion cells.  A companion cell is a normal cell with a nucleus and a large number of mitochondria, indicating that it has active metabolism. It provides the sieve tube cell with proteins, ATP and other nutrients.  The parenchyma stores food substances while the fibres provide support to the phloem.  Below are the differences in structure and function between phloem and xylem. Biology Form Five Notes © Copyright Maryam Shah 2007 45 Sclerenchyma cells Parenchyma cells Sieve tubes Companion cells
  46. 46. CHAPTER 1: TRANSPORT Xylem Aspect Phloem Composed of tracheids and vessel elements Composed of sieve tubes and companion cells Cell walls are thick Cell walls are thin Impermeable cell walls Permeable cell walls Dead at functional maturity Living at functional maturity No cytoplasm Cytoplasm is in a form of strand that lines the cell Cell walls are lignified Cell walls are made of cellulose Transports water and mineral ions to all parts of plants FUNCTION Transports sucrose and other organic compounds Flows upwards (Root → Stem → Leaves) Flows both up and down (source → sink)  Predict the effect of removing a ring of phloem tissue from a plant.  The tissue just above the ring swells whereas that below the ring withers.  The removal of phloem tissue interrupts the downward movement of the organic substances synthesised in the leaves.  The accumulation of organic substances causes the swelling above the ring.  The leaves above the ring do not wilt because the xylem has not been removed. Hence the flow of water in the xylem vessels is not disrupted. Biology Form Five Notes © Copyright Maryam Shah 2007 46
  47. 47. CHAPTER 1: TRANSPORT LEARNING OBJECTIVE: 1.8 The Transport of Organic Substances and Water In Plants Learning outcome: A student is able to:  state what translocation is.  explain the importance of translocation in plants.  describe the process of transpiration.  explain the importance of transpiration.  describe the pathway of water from the soil to the leaves.  state external conditions affecting transpiration.  design experiments to study factors affecting the rate of transpiration.  explain the role of root pressure in the movement of water in plants.  explain the role of cohesion and adhesion of water in the movement of water in plants.  conceptualise the transport mechanism in plants Previous knowledge : The concept of transport of water and organic substances had been studied in previous lesson. CONTENT:  State what translocation is. Translocation is the movement of sugar, other organic and inorganic solutes from one place to another within the plant through phloem. Concentration gradient drives this process. The locations where the solutes are produced are the sources. The locations where these solutes are needed are the sinks. The sources have high concentration of solutes while the sinks have low concentration of solutes.  Explain the importance of translocation in plants. Biology Form Five Notes © Copyright Maryam Shah 2007 47
  48. 48. CHAPTER 1: TRANSPORT (a) The survival of a plant depends on the transport of organic substances from the leaves to the storage organs such as the roots, fruits or to the growth regions such as buds. (b) Translocation enables sucrose the product of photosynthesis, to be stored or converted into other sugars when it reaches its destination.  Explain the importance of transpiration.  Transpiration is the loss of water vapour through evaporation in plants.  This loss of water is replaced by the absorption of water from soil by the plant roots. (a) only 1% of this water is used by plant cells for photosynthesis and to remain turgid. (b) The remaining 99% evaporates from the leaves and is lost to the atmosphere through transpiration.  About 90% of transpiration takes place through the stomata of the leaves. Transpiration also occurs through the lenticels of woody stems. Stomatal pore Lenticels  Transpiration is important in: (a) helping in the absorption and transport of water and mineral ions from the roots to the different parts of the plants. (b) producing a cooling effect in plants. (c) helping to supply water to all plant cells for metabolic processes. (d) helping to prevent plants from wilting by maintaining cell turgidity.  The continuous stream of flowing water from the roots to leaves is called the transpiration stream.  describe the process of transpiration. 1. The surfaces of the mesophyll cells are covered by a thin layer of water. 2. Heat from the sun causes the water on the external surfaces of the mesophyll cells to evaporate, thus saturating the air spaces in the mesophyll with water vapour. Biology Form Five Notes © Copyright Maryam Shah 2007 48
  49. 49. CHAPTER 1: TRANSPORT 3. Outside the stomata, the air in the atmosphere is less saturated. 4. This means that the concentration of water vapour in the atmosphere is lower than the concentration of water vapour in the air spaces of the leaf. 5. Hence, the water vapour in the air spaces of the leaf evaporates and diffuses into the atmosphere through the stomata. 6. The movement of air carries water vapour away from the stomata. 7. The loss of water from a mesophyll cell makes the cell hypertonic to an adjacent cell. 8. Water from the adjacent cell diffuses into the mesophyll cell by osmosis. 9. In the same way, water continues to diffuse from the neighbouring cells into the adjacent cells by osmosis. 10.Eventually water is drawn from the xylem vessels in the veins. 11.A pulling force is then created to pull water up the xylem vessels as a result of the evaporation of water vapour from the mesophyll cells. 12.This pull is called the transpirational pull.  describe the pathway of water from the soil to the leaves.  explain the role of root pressure in the movement of water in plants.  explain the role of cohesion and adhesion of water in the movement of water in plants. The pathway of water from the soil to the leaves is assisted by: (a) root pressure. (b) capillary action. (c) transpirational pull Biology Form Five Notes © Copyright Maryam Shah 2007 49
  50. 50. CHAPTER 1: TRANSPORT The movement of water through transpirational pull  During transpiration, water evaporated from the spongy mesophyll cells.  Transpiration in the leaves forces the movement of water from the soil up the stem.  The water vapour fills the air spaces between the spongy mesophyll cells.  Water vapour diffuses to the atmosphere through the stomata.  The lost of water from a mesophyll cell makes the cell hypertonic as compared to an adjacent cell/ increase the cell osmotic pressure.  As a result, the water molecule diffuses from the adjacent cells by osmosis.  In the same way, water continues to diffuse into adjacent cells from neighbouring cells.  Eventually, water is drawn from the xylem vessels in the veins.  A pulling force is thus created to draw water up the xylem vessels due to the evaporation of water from the mesophyll cells.  This pull is called the transpirational pull. The movement of water through capillary action  The cohesive and adhesive properties of water which is due to hydrogen bonding holds the water molecules together and enables a continuous column of water along the stem and upwards to the leaves.  The long narrow xylem vessels of stem provide capillary action that drives water from the roots to the tree top.  The water molecules adhere to one another by cohesive forces. The cohesion of water prevents the water column from breaking apart as it is pulled upwards.  The water molecules adhere to the walls of the xylem vessels by adhesive forces. The adhesion of water molecules to the walls of xylem vessels and tracheids prevents gravity from pulling the water down the column.  The cytoplasm of root hair cells is hypertonic to the surrounding soil water.  The water from the soil thus moves into the cell sap of the adjacent cells in the cortex by osmosis. Biology Form Five Notes © Copyright Maryam Shah 2007 50 The movement of water through root pressure
  51. 51. CHAPTER 1: TRANSPORT  In this way, water continues to move inwards from cell to cell until eventually it reaches the cortex.  Water flows through the cytoplasm, vacuoles and cell walls of the parenchyma cells in the cortex until it reaches the endodermis.  Once it reaches the endodermal cells, the water moves through the cytoplasm and vacuoles instead of the cell walls due to the presence of special features called Casparian strips which line the sides of the endodermal cells.  The Casparian strip is impermeable to water thus blocking the water flow. The water somehow continues to move inwards through the cytoplasm and vacuoles until it gradually reaches the xylem vessels.  The gradient of water concentration which exists across the cortex creates a pushing force that results in the inflow of water into the xylem.  At the same time, ions from the soil are actively pumped into the xylem and this causes osmotic pressure to increase.  These phenomena produces root pressure that helps to push water and mineral ions into the xylem from the roots upwards to the stem.  State external conditions affecting transpiration. The external conditions that affect the rate of transpiration are: (a) Light intensity (b) Temperature (c) Air movement (d) Relative humidity  An increase in light intensity increases the rate of transpiration.  Light stimulates the opening of the stomata.  As a result, the stomata open wider. Hence, more water vapour evaporates through the stomata. Biology Form Five Notes © Copyright Maryam Shah 2007 51 Light intensity
  52. 52. CHAPTER 1: TRANSPORT  An increase in temperature increases the rate of transpiration.  As the temperature increases the rate of evaporation of water from the surfaces of the mesophyll cells also increases.  As the water vapour that diffuses through the stomata accumulates near the leaf surface, a faster air movement helps to remove the water vapour.  Air movement increases the concentration gradient between the water vapour in the leaf and that outside the leaf. This increases the transpiration rate.  When the air is still, the transpiration rate decreases or stops altogether. Biology Form Five Notes © Copyright Maryam Shah 2007 52 Temperature Air movement
  53. 53. CHAPTER 1: TRANSPORT  High humidity surrounding the leaves reduces the evaporation of water from the stomata.  This causes transpiration to slow down.  A rise in temperature lowers the relative humidity of the surrounding air, and this increases the rate of transpiration. Effect of the relative humidity on the rate of transpiration  Explain the regulation of transpiration by the stomata  Stomata are found abundantly on the lower epidermis of a dicotyledonous leaf.  Each stoma is surrounded by two guard cells which regulate gaseous exchange by opening and closing the stoma.  To allow the plant to photosynthesise and at the same time, prevent the excessive loss of water, the stomata open in response to high light intensity and a decrease in the levels of carbon dioxide in the air spaces of the leaf.  Stomata open during the day and close at night. Biology Form Five Notes © Copyright Maryam Shah 2007 53 Relative humidity
  54. 54. CHAPTER 1: TRANSPORT stomatal pore opens stomatal pore closes thick inner wall chloroplast The opening of a stoma The closing of a stoma  The mechanism of the opening of a stoma. 1. During the day, light stimulates photosynthesis in the guard cells. 2. They start synthesising glucose and generate the energy required for active transport. 3. The guard cells accumulate potassium ions (K+) from adjacent cells through active transport. 4. They become hypertonic and water enters the cells by osmosis. 5. As a result, they swell up and become turgid. 6. Since the inner cell walls of the guard cells are thicker than the outer walls, the guard cells bend outward and the stoma opens. This is because the thinner outer wall stretches more than the thicker inner wall.  The mechanism of the closing of a stoma. 1. At night, when photosynthesis does not take place, potassium ions exit the guard cells and water also leaves the cells by osmosis. 2. The guard cells become flaccid and the stoma closes.  conceptualise the transport mechanism in plants Biology Form Five Notes © Copyright Maryam Shah 2007 54 guard cell pair attached at both ends
  55. 55. CHAPTER 1: TRANSPORT Cooling effects maintaining constant osmotic pressure in plants Capillary action affected by Light intensity water movement Biology Form Five Notes © Copyright Maryam Shah 2007 Transport mechanism in plants of substances Water & mineral Food xylem phloem consists of Vascular tissues involves Vessels and tracheids Translocation Transpirational pull Root pressure transported by Transpiration Sieve tubes Involves in Air movement Temperature Relative humidity make up important for effects absorption of water and mineral ions and mineral salt driven by results in in driven by driven by The opening and regulated by closing of stomata 55

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