Yr 11 biol semester 1 - cells topic


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Yr 11 biol semester 1 - cells topic

  1. 1. Amazing Cells…… http://www.youtube.com/watch?feature=player_detailpage&v=gFuEo2ccTPA “Introduction to cells” – Frank Gregorio http://education.kqed.org/edspace/ INTRODUCTION TO CELLS
  2. 2. What are Cells? Cells are the basic structural and functional unit of life. They are the smallest living material. Robert Hooke first discovered cells in 1665 using a simple microscope. Organisms are made up of one or more cells. One cell = unicellular More than one cell = Multicellular INTRODUCTION TO CELLS
  3. 3. Microscopes: ∗ Invented in the 1600’s. ∗ Not until the 1930’s that scientists began to study cell structure in detail. ∗ 1839 – German scientist, Theodore Schwann, developed the CELL THEORY. Cell Theory - is an important biological concept which states that: All living things are made up of cells. Organisms vary in size from unicellular to multicellular. Every cell arises from pre-existing cells. Cells are specialised to perform specialised tasks. THE CELL THEORY
  4. 4. *Read page 20 of your textbook and then answer the following questions: 1. Before the cell theory, what alternative theory existed? 2.Who disproved this earlier theory? THE CELL THEORY
  5. 5. ∗ Take in nutrients and carry out chemical reactions. ∗ Produce waste products. ∗ Make useful substances such as hair and bone. ∗ Reproduce by dividing in two. ∗ Some specialised cells can move. E.g. muscle cells contract and sperm cells can ‘swim’. ∗ Exchange gases with their surroundings. www.3dscience.com/img/Products/3D_Models/Biol WHAT DO CELLS DO?
  6. 6. THE SIZE OF CELLS •Cells are measured using a unit of length called a micrometer (µm) •1 µm = 1/1000 of a millimeter •Organelles are measured using a unit called a nanometer (nm). •1 µm = 1000 nm •Bacteria = 1 µm •Human Red Blood Cells = 10 µm •Human Liver Cells = 50 µm •Mesophyll cells (in plant leaves) = 100 µm Cell Size & Scale Interactive http://learn.genetics.utah.edu/content /begin/cells/scale/
  7. 7. MICROSCOPES There are two main types of Microscopes: Light Microscope •Can magnify up to 1500x. •Light passes through thin tissue sections. •Light is focused through a series of lenses – Eyepiece & Objective Lens. Electron Microscope •Can magnify up to 100,000x. •Beams of electrons pass through a vacuum and then through a thin layer of tissue. •Better detail resolution than light microscope (ability to see separate objects that are close together).
  8. 8. THE LIGHT MICROSCOPE Light Microscope Use - Refresher http://www.youtube.com/watch?feature=player_detailpage&v=scEhgAiazzU
  10. 10. MICROSCOPES •Magnification – The ratio of the size of the image as viewed through the microscope to the actual size of the object. •Resolution – The ability to perceive fine detail (measured as the smallest distance between two points that allows the two points to be distinguished from on another, rather than be seen as a single blurred image). •Total Magnification = Magnification of the Eyepiece Lens X Magnification of the Objective Lens
  11. 11. MICROSCOPES Activities: 1.Complete the handout “Parts of the Microscope” 2.Complete the handout “Microscope Magnification” 3.Using the light microscopes, view a minimum of 3 slides. For each slide draw a diagram that is: • Fully labeled including specimen name, total magnification and anything else of interest. • Drawn in pencil • Is appropriately sized. 4.Read page 29-34 of your textbook and then answer question 9-13 on page 34.
  12. 12. Clickview - ”The Cell – How It Works (22 minutes)” CELL STRUCTURE & FUNCTION
  13. 13. Cell Structure & Function PROKARYOTES - Bacteria EUKARYOTES – Plants, Animals, Fungi, Protists Small Size (1 - 10µm) Large Size (10 – 100µm) Circular DNA Linear DNA No Nucleus Contains nucleus Little internal organisation High level of internal organisation No membrane bound organelles Contains membrane bound organelles Single Chromosome Two or more chromosomes Cell wall made of peptidoglycan Cell Wall (if present) made of cellulose •There are two basic forms of cells: •Prokaryotic Cells – have a simple structure. •Eukaryotic Cells – have a complex structure.
  14. 14. CELL STRUCTURE- ORGANELLES Organelles are tiny living structures inside the cell which are responsible for cell metabolism – the chemical reactions that take place within the cell. Organelles that make up cells: ∗ Cytoplasm ∗ Nucleus ∗ Mitochondria ∗ Cell Wall ∗ Cell Membrane ∗ Ribosome ∗ Endoplasmic Reticulum (ER) ∗ Chloroplast ∗ Golgi Bodies ∗ Vacuole ∗ Lysosome
  15. 15. CELL STRUCTURE- ORGANELLES *Use the following slides to fill in the table below – “Cell Structure and Function” Name of Structure Appearance Function Diagram e.g. Cytoplasm Jelly-like substance that occupies most of the cell Contains dissolved substances to support the organelles
  16. 16. CYTOPLASM The cytoplasm is a jelly like substance which occupies most of the cell in animals and a narrow band in plants. The watery fluid contains dissolved substances and tiny living structures called organelles. http://sciencecity.oupchina.com.hk/biology/ student/glossary/img/cytoplasm.jpg
  17. 17. NUCLEUS Found only in eukaryotic cells. The largest and most prominent feature of cells. Spherical and usually located centrally in animal cells and towards the edge of the cell wall in plants. Double membrane boundary is called the nuclear envelope. This contains nuclear pores. Around each pore is a protein. The nucleus controls the development and functioning of the cell. It controls growth and reproduction (mitosis) and metabolism. DNA is found in the nucleus. This is the hereditary information that is passed on through generations.
  18. 18. ROLE OF DNA IN CELLS DNA contains coded information for the synthesis of enzymes. Enzymes are important molecules that are needed to speed up chemical reactions. A sequence of DNA that codes for a protein is called a gene. One gene codes for one protein. Genes carry the information to synthesise various molecules called gene products. Even in the simplest cells there are hundreds of chemical reactions that take place which means that hundreds of enzymes are needed. Each of the enzymes needed is made up of different genetic code. So, several hundred genes are needed to carry out all necessary chemical reactions so the cell can survive and reproduce. Prokaryotic cells have several hundred genes. Eukaryotic cells have several thousand genes.
  19. 19. MITOCHONDRIA ∗ Elongated, rod shaped organelle found in the cytoplasm of all living cells. ∗ It is enclosed by a double membrane. ∗ The outer membrane forms a smooth envelope enclosing the organelle. ∗ The inner membrane is extensively folded inwards upon itself to produce a vast number of finger-like projections. ∗ This is the site of aerobic respiration – simple organic molecules (glucose) are broken down to release energy. ∗ The mitochondria is referred to as ‘the powerhouse of the cell’.
  20. 20. CELL WALL Only found in plants. The cell wall is a highly complex structure. It is made up of a tough, rigid and highly cross-linked matrix of substances. The cell wall gives shape and strength to the cell. http://library.thinkquest.org/06aug/01942/plcells/think quest/cell-wall.gif
  21. 21. CELL MEMBRANE The cell membrane is made up of two layers of fat molecules (called a lipid bilayer). Protein molecules are present between the lipid bilayer. Different types of lipids and proteins make up different types of cells. The lipid bilayer determines the basic structure of the membrane. The proteins allow substances to enter and leave the cell. http://library.thinkquest.org/C004535/media/cell_me mbrane.gif
  22. 22. ENDOPLASMIC RETICULUM This is a system of membranes that exists throughout the cytoplasm. It is important in the transport of materials from one part of the cell to another. Rough ER has ribosomes (small round organelles) attached to it. It is the site of protein and membrane synthesis. Some proteins made by rough ER may have carbohydrates attached to them and are called glycoproteins. These are used as cell membrane receptors. Smooth ER does not have ribosomes attached. It is involved in metabolic processes such as lipid synthesis and carbohydrate metabolism. There are many enzymes embedded in smooth ER to help carry out metabolic processes.
  24. 24. GOLGI BODY These are stacks of flattened sacs made of smooth membrane. They package and secrete proteins and carbohydrates made by the cell. Cells that are involved in secretion contain large amounts of golgi bodies. E.g. salivary glands. Golgi bodies also make carbohydrates for use outside the cell. They are packaged in vesicles that bud off from the golgi body, migrate to and fuse with the cell membrane to release the contents. This secretion is known as exocytosis.
  25. 25. VACUOLE ∗ The vacuole is a fluid filled space that is bounded by a membrane. It is found as a relatively large structure in plants and as very small structures in animal cells. ∗ The fluid contains solutes which include: ∗ Salts, in the form of ions ∗ Simple sugars ∗ Amino acids •The main functions of the vacuole are to maintain water and salt balance and also the shape of the cell. •The vacuole can also store wastes, contain pigment and contribute to cell growth.
  26. 26. CHLOROPLAST ∗ Thylakoids store the pigment chlorophyll. Chlorophyll captures energy for photosynthesis. ∗ Equation for photosynthesis: Light 6CO2 + 6H2O C6H12O6 + 6O2 Chlorophyll ∗ The first stage of p/s occurs in the grana. The final stage, which needs enzymes, occurs in the stroma. Glucose is produced. •The chloroplast is a type of plastid (a small particle involved in storage) and carries out the process of photosynthesis. •Chloroplast are bounded by two membranes. Internally there are flattened sacs called thylakoids. These are arranged in stacks called grana. The fluid surrounding these sacs is called stroma
  27. 27. LYSOSOME Small, spherical, membrane-bound organelles that are found in the cytoplasm of the cell. They are formed by the golgi bodies. Can contain enzymes which breakdown macromolecules. http://www.biology4kids.com/file s/art/cell_lysosome1.gif
  28. 28. RIBOSOME Small, spherical shaped organelles. Often attached to Endoplasmic Reticulum. Site of Protein Synthesis.
  29. 29. PLANT VS ANIMAL CELLS Read page 25 & 26 of your textbook. Class discussion – what are the key differences between plant and animal cells? Draw a fully labeled diagram of a plant cell and an animal cell (pg. 25). Answer questions 4-6 on page 29 of your textbook.
  30. 30. PLANT VS ANIMAL CELLS Practical – Investigating Plant & Animal Cells (See Handout)
  31. 31. CELLS REVIEW Clickview – “Inside Cells – Cells And Their Organelles” (28 minutes)
  32. 32. QUIZ- CELLS & THEIR ORGANELLS Complete the quiz “Cells and their Organelles” and hand up to be checked.
  33. 33. SURFACE AREA TO VOLUME RATIO The surface area of a cell refers to its exposed cell membrane. The volume of a cell refers to the quantity of protoplasm that must be supplied with its requirements for metabolism. For all cells, the membrane area must of sufficient size for the entire cell contents or volume to be supplied with its requirement for metabolism by diffusion at the highest rate. This process will then occur in the shortest possible time.
  34. 34. SURFACE AREA TO VOLUME RATIO 1 cm Cube SA : Vol 6 : 1 Surface Area is six times the Volume 3 cm Cube SA : Vol 2 : 1 Surface Area is twice times the Volume The membrane area is sufficient size for diffusion to supply the entire cell volume at a high rate. The membrane area is insufficient in size for diffusion to supply the entire cell volume at a high rate. Diffusion will take considerably longer.
  35. 35. SURFACE AREA TO VOLUME RATIO •As cells increase in size, their surface area to volume ratio decreases. As a cell gets bigger there is less surface area available to supply the increasing volume. •Increase in cell size could be detrimental to the cell as there may not be enough surface area available to allow enough nutrients to reach the interior of the cell. Therefore, surface area to volume ratio has an effect on cell size. •DNA can also have an effect on cell size. If the volume is too large, it may not be able to produce enough proteins and enzymes to maintain a cell. 10 L 10 L
  36. 36. SURFACE AREA TO VOLUME RATIO • Read page 60-61 of your textbook and then answer question 8 & 9 on page 62. • Practical – ‘Surface Area to Volume Ratio’
  37. 37. MOVEMENT OF SUBSTANCES IN AND OUT OF CELLS The transport of molecules into and out of a cell can be divided into two main categories: 1.Passive Transport – no energy required (Movement of molecules is with the concentration gradient) 2.Active Transport – energy required (Movement of molecules is against the concentration gradient)
  38. 38. MOVEMENT OF SUBSTANCES IN AND OUT OF CELLS Active & Passive Transport can be further divided into: Active Passive Exocytosis Endocytosis Diffusion Osmosis Pinocytosis Phagocytosis Transport Facilitated Diffusion
  39. 39. DIFFUSION Diffusion – the kinetic movement of molecules or ions from an area of high concentration to an area of low concentration. * Does not require energy
  40. 40. OSMOSIS Osmosis – the diffusion of water across a membrane. Water will move from an area of low solute concentration to high solute concentration. .
  41. 41. SELECTIVE EXCHANGE A membrane is not equally permeable to all substances. Factors that can affect permeability include: Size of particle – particles need to be smaller than the pore. Charge of particle – charged particles are more difficult to go through. Some proteins can act as channels, and others are carrier proteins. This selects for particles that can move across. We say the membrane is selectively permeable.
  42. 42. SELECTIVE EXCHANGE Facilitated Diffusion – Passive movement across a membrane through a protein carrier. “Cell Membrane Passive Transport – Cell Biology” http://youtube.com./watch? v=JShwXBWGMyY
  43. 43. ACTIVE TRANSPORT This is the opposite of Diffusion Active Transport – substances move across the membrane against a concentration gradient. A living cell and ATP is needed. Carrier proteins are always needed, therefore this process is selective.
  44. 44. ACTIVE TRANSPORT & ATP • ATP is used to transport the ion/molecule against the concentration gradient. • The phosphate attaches to the channel protein – it becomes a phosphorylated protein. • Another type of molecule is then picked up on the other side of the membrane, and once this has been transported across the protein becomes dephosphorylated.
  45. 45. ENDOCYTOSIS • This is the process where particles and large molecules are taken into the cell. The membrane encloses them in a vacuole. There are two types of endocytosis: • Phagocytosis • Pinocytosis
  46. 46. PHAGOCYTOSIS •This involves the intake of particles. •The membrane folds near the particle, it encloses it in a vacuole, it then breaks away from the membrane and enters the cytoplasm. •These vacuoles are called lysosomes and contain digestive enzymes which breakdown the particle. •Phagocytes are selective for particles. •Certain cells in our immune system are phagocytic.
  47. 47. PINOCYTOSIS •This is the intake of liquids and large molecules into tiny vesicles that form at the surface of the cell. •This process may be selective or non-selective.
  48. 48. EXOCYTOSIS • This is the opposite of endocytosis. • Secreted materials which are produced by the cell are packaged into a vesicle which migrates to the plasma membrane and releases the contents. • Manufactured material comes from the ER and packaging occurs by the golgi body. “Cell Membrane, Exocytosis & Endocytosis” http://youtube.com./watch?v=K7yku3sa4Y8
  49. 49. MOVEMENT OF SUBSTANCES IN AND OUT OF CELLS Activities: •Read page 62- 66 of the textbook and then answer questions 10-13 on page 67. •Clickview – “Keeping It All Together – Cell Membrane” (31 minutes) •Homework – Use your textbook/internet to draw a diagram for each of the following: • Diffusion • Osmosis • Facilitated Diffusion • Endocytosis • Exocytosis •Review Material so far and add to your glossary.
  50. 50. CELLS ISSUES INVESTIGATION •Task Outline – see handout •Part A • 1 Lesson in Computer Room – Friday Week 4 • Due Mon Week 6 •Part B • Three lessons in Computer Room • Due Monday Week 8 •Part C • Due Friday Week 8 (Supervised Assessment in Class)
  51. 51. ENZYMES •Enzymes are proteins that can increase the rate at which chemical reactions happen. •Enzymes are usually proteins, and they act on one or more compounds (called the substrate) •Enzymes may: ∗ Break a single substrate down into two or more simpler molecules (Catabolic Reactions) ∗ Cause two substrate molecules to form bonds and become a single molecule
  52. 52. ENZYMES How Do They Work? Animation – How Enzymes Work http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_enzymes_work.html
  53. 53. ENZYMES Lock & Key Hypothesis Vs Induced Fit Model…. • The substrate binds to the active site on the enzymes using weak bonds (often hydrogen). • This causes a change in the shape of the enzyme and the substrate – The Induced Fit Model. • It is NOT a lock and Key relationship. • However, each enzyme catalyses only one type of reaction because the active site on the enzyme and its substrate are structurally complimentary (‘fit’ together).
  54. 54. ENZYMES Enzymes & Activation Energy…. • Enzymes increase reaction rates by lowering activation energy. • The initial energy required to start a reaction is known as the activation energy in a chemical reaction. • These reactions initially require energy, but then release free energy once the reaction is commenced – Striking of a match Activation Energy http://www.youtube.com/watch?v=Dd1yi2aVoOc
  55. 55. ENZYMES • Enzymes do not change the direction of a reaction or the amount of product. • Most chemical reactions are reversible and the same enzyme can catalyse a reaction in either direction: ∗ If there is more substrate present, the net reaction will be to the right. ∗ If there is a net accumulation of product, the net reaction will be to the left. • Enzymes are not used up in the reaction, and they remain unchanged at the end of the reaction.
  56. 56. ENZYMES Factors affecting enzyme activity….
  57. 57. ENZYMES ∗Practical – Enzyme Activity ∗Read page 37-39 of the textbook and then answer Question 1 to 6
  58. 58. ∗ All cells divide at some stage in their life cycle. ∗ When a cell divides one cell splits into two daughter cells Cell Division
  59. 59. ∗ When the cell divides to produce two daughter cells each of the cells being produced need their own DNA. ∗ Thus before cell division the amount of DNA in the cell needs to double. ∗ This process is referred to DNA replication Cell Division
  60. 60. ∗ Bacteria divide by a process known as binary fission. ∗ This means that each bacterial cell essentially divides in 2. ∗ Most bacteria have a single chromosome of DNA. ∗ Prior to cell division this chromosome replicates itself and the two chromatids remain coiled together in the cytoplasm ∗ Each daughter cell produced is genetically identical to the to the parent cell. Cell Division – Binary Fission
  61. 61. ∗ This method of reproduction can occur within 20 minutes or so. ∗ This can result in exponential growth of bacterial population Cell Division – Binary Fission
  62. 62. ∗ Mitosis is the term that describes the division process that eukaryotic cells undergo ∗ An easy way to remember mitosis is that it produces two cells at the end. (MI- TWO- SIS) ∗ Cells undergo a cell cycle in which there are times of growth, then preparation for division including the duplication of chromosomes. ∗ There are 4 phases of Mitosis * Prophase * Metaphase * Anaphase *Telophase Mitosis
  63. 63. ∗ This resting phase where the cell is growing is called interphase. ∗ During interphase the DNA is present in the nucleus in the form of chromatin, which is basically stretched out chromosomes. ∗ At the end of interphase the DNA in the nucleus replicates itself. ∗ At the conclusion of interphase the cell starts mitosis. Interphase
  64. 64. ∗ Changes in the nucleus and cytoplasm occur during prophase. ∗ In the nucleus the chromatid fibres coil tightly and become visible under the microscope. ∗ Each chromosome has duplicated and consists of two Identical sister chromatids joined at the centromere. ∗ In the cytoplasm microtubules appear as spindle fibres and centrioles move toward the poles of the cell. These are both a part of the cytoskeleton. Mitosis - Prophase
  65. 65. ∗ In the cytoplasm, microtubules or spindle fibres radiate from the poles toward the cells equator and the chromosomes become aligned at the metaphase plate which is an imaginary line halfway along the cell. ∗ The microtubules become attached to the centromeres and the centrioles (in animals). ∗ This whole structure is called a spindle. Mitosis - Metaphase
  66. 66. ∗ Anaphase begins with the pairs of centromeres of the chromosomes divide and the sister chromatids are pulled apart. ∗ Each chromatid is now considered to be a daughter chromosome. ∗ These chromosomes are drawn toward the opposite poles of the cell by microtubules attached to the centromeres. Mitosis - Anaphase
  67. 67. ∗ As the daughter chromosomes are drawn to the opposite poles, daughter nuclei begin to form and the nucleoli reappear. ∗ The chromosomes uncoil to form chromatin and the cytoplasm forms a cleavage furrow. ∗ The cell pinches in along this furrow and the microtubules involved act like a ligature pinching it off. Mitosis - Telophase
  68. 68. ∗ http://www.youtube.com/watch?v=HYKesI9jL8c ∗ It is very important that cells which divide by mitosis or binary fission have the same chromosomes as the parent if they are to function normally. ∗ This is ensured by DNA replication producing two copies of all the DNA in the cell. Secondly mitosis acts to make sure that sister chromatids separate evenly and become identical chromosomes. Mitosis
  69. 69. ∗ Cells won't divide all the time. ∗ Cells need to control when they are going to divide. ∗ Factors which control cell division can be external, ie outside the cell or inside the cell. ∗ If certain nutrients aren't present outside the cell then it will not divide. This is called nutrient dependence. ∗ Research has shown that some cells will only divide when they are attached to something. This is called anchorage dependence. Regulation of Cell Division
  70. 70. ∗ Some factors regulate the cell cycle that aren't chemical in nature. Contact inhibition is an example of this. ∗ If a cell is surrounded by other cells it will not generally divide. ∗ This is called contact inhibition or density dependence. ∗ If cells are removed from around it then cells at the edge will divide until the gap is closed Regulation of Cell Division
  71. 71. ∗Carcinogens are chemicals that cause cancer. ∗Cancer is uncontrolled cell division. ∗Cancer is caused by mutations in the DNA of cells. These mutations cause changes in the structure and function of some of the chemicals that regulate cell division Cancer
  72. 72. ∗ Cancer begins with one abnormal cell. This cell divides through mitosis and forms a small growth. ∗ This growth can then metastasise or break apart and the abnormal cells will keep growing in other parts of the body, forming secondary tumours. ∗ http://www.youtube.com/watch?v=rrMq8uA_6iA Cancer
  73. 73. Cancer
  74. 74. ∗ Cancer can be treated by radiotherapy, in which a concentrated dose of radiation is targeted at the cell which will damage the DNA in the cell further, stopping the cells from growing, and chemotherapy, which does a similar thing but with chemicals to kill off the infected cells. Clickview – Catching Cancer (50 mins) Treatment