Lecture notes cell biology

23,812 views

Published on

Published in: Education

Lecture notes cell biology

  1. 1. Lecture Notes – Cell BiologyHKDSE Biology 1 By Michael Ho~*
  2. 2. Lecture Notes – Cell BiologyMolecules of Life1. Water Water (H2O) is the most abundant compound on Earth’s surface and it is essential for all life on Earth. A water molecule consists of two hydrogen atoms covalently bonded to one oxygen atom. Attractive forces (hydrogen bonds) form between water molecules. These hydrogen bonds are sufficiently strong to create many of the properties of water.Biological Functions1. Freezing PropertiesIce is less dense than water and hence ice floats on water surface, insulating theaquatic organisms below. It allows aquatic animals to survive in cold region.2. High Latent Heat of FusionLarge amount of energy has to be removed from water to form ice. The aquaticenvironment and cell contents are slow to freeze in cold weather.3. High Latent Heat of EvaporationLarge amount of energy is required for evaporation of water. It increases heat lossand provides an effective cooling effect to mammals through sweating and plantsthrough transpiration.4. High Specific Heat CapacityLarge amount of energy is required to change the temperature. Water helps to keepthe temperature constant and hence provides a stable environment for aquatic life.5. High TransparencyLight can penetrate through water which allows photosynthesis of underwater plantsand vision for aquatic animals.6. High Surface Tension and AdhesionWater molecules are held together by hydrogen bonds which allow formation of acontinuous water column in plants for water transport.HKDSE Biology 2 By Michael Ho~*
  3. 3. Lecture Notes – Cell Biology7. High PolarityWater is a universal solvent due to its high polarity. Water can dissolve manysubstances and hence facilitates chemical reactions and serves as transportmedium.8. IncompressibilityWater is incompressible and provides turgidity for plants and support for animals withhydro-skeleton.2. Biomolecules A biomolecule is any molecule that is produced by a living organism, including Carbohydrates, Proteins, Lipids and nucleic acids. Function Carbohydrates  as main source of energy - oxidized to release energy  as an energy reserve Lipids  form an insulator under skin to reduce heat loss Proteins  build up body tissues for growth and repair (polypeptides)  as enzymes to speed up reactions Nucleic acids  carry genetic information (DNA and RNA)HKDSE Biology 3 By Michael Ho~*
  4. 4. Lecture Notes – Cell Biology3. Inorganic Ions Inorganic ions are vital for cellular activities in animals and plants.Biological Functions1. Sodium ions (Na+)  take part in the transmission of nerve impulse  maintain osmotic balance2. Potassium ions (K+)  take part in the transmission of nerve impulse  maintain osmotic balance3. Calcium ions (Ca2+)  take part in the transmission of nerve impulse  chemical component of bones and teeth4. Iron ions (Fe2+)  chemical component of haemoglobin in red blood cells5. Magnesium ions (Mg2+)  chemical component of bones and teeth as well as chlorophyll6. Nitrate ions (NO3-)  synthesis of amino acids and nucleotides7. Phosphate ions (PO4-)  synthesis of phospholipids, ATPs, bones and teethHKDSE Biology 4 By Michael Ho~*
  5. 5. Lecture Notes – Cell BiologyMicroscope Development and Cell Theory Organisms are made up of cells. Cells are very small and cannot be seen with the naked eye. People did not even know that cells existed until the microscopes were invented.Discovery of Cell In 1665, An Englishman, Robert Hooke, looked at a thin slice of cork through his two-lens microscope. He observed some tiny, hollow structures and called them ‘cells’. Hookes microscope Cork cells under Hooks microscope The ‘cells’ Hooke observed were in fact the cell walls of dead cork cells. However, no one knew about the existence of cell walls at that time.HKDSE Biology 5 By Michael Ho~*
  6. 6. Lecture Notes – Cell BiologyCell Theory In 1839, Schwann proposed the cell theory. The cell theory states that: 1. All organisms are made up of one or more cells. 2. The cell is the basic unit of life; it is the smallest unit that shows all the characteristics of life. 3. All cells come from pre-existing cells. Modern light microscope Electron microscope Large organelles in cell are discovered More organelles are discovered and studied in details maximum resolution ~0.2 m maximum resolution ~200 nmHKDSE Biology 6 By Michael Ho~*
  7. 7. Lecture Notes – Cell BiologyLight microscope The light microscope can produce an image magnified by up to 1000 times. The maximum resolution is about 0.2 m.Procedure in using the Light Microscope1. Place the microscope in a well-lit area2. Position the low power objective lens above the stage hole3. Adjust the mirror and the diaphragm to provide the best illumination4. Clip the slide on the stage5. While watching from the side, turn the coarse focus knob to lower the objective lens until it almost touches the slide6. Look through the eyepiece. Turn the coarse focus knob counter-clockwise to bring the low power objective lens until a clear image is seen7. If necessary, change to a high power objective lens8. Adjust the fine focus knob to get a sharper imagePreparing Onion Tissue SampleHKDSE Biology 7 By Michael Ho~*
  8. 8. Lecture Notes – Cell BiologyTransmission electron microscope The transmission electron microscope makes use of electron beams that pass through the specimen to form an image. It produces two-dimensional, black and white images magnified by up to 800,000 times.Scanning electron microscope The scanning electron microscope makes use of an electron beam to scan over the surface of a specimen. It produces three-dimensional, black and white images magnified by up to 30,000 times.Advantages of electron microscopy electrons have a shorter wavelength than light, providing a higher resolution the maximum useful magnification is higher than that of light microscopeDisadvantages of electron microscopy Specimens are always dead and so the structure of a living specimen using electron microscope can NEVER be studied The processes involved in preparing specimens might damage / distort their true structureHKDSE Biology 8 By Michael Ho~*
  9. 9. Lecture Notes – Cell BiologyResolution and MagnificationResolution: The ability to distinguish between structures that are very close togetherMagnification: The ratio of the size of an object and its image Magnification = Unit of length Symbol Factor Gigametre Gm Megametre Mm Kilometre km Metre m Centimetre cm Millimetre mm Micrometre m Nanometre nm Picometre pmConcept Check1. The following is the compound light microscope.Eyepiece of 50x and objective of 100x was used,the magnification of the image would be ________________ = ________HKDSE Biology 9 By Michael Ho~*
  10. 10. Lecture Notes – Cell Biology2. The following shows the images produced by 2 types of microscope. _________________ _________________ ______________________________HKDSE Biology 10 By Michael Ho~*
  11. 11. Lecture Notes – Cell Biology3. (a) What is the type of microscope used for studying this cell? (1 mark) .............................................................................................................................. (b) The cell was stained with uranium salts in preparation for a transmission electron microscope. Explain how this stain caused the nucleus to show a dark shade compared to the light shade of the cytoplasm. (4 marks) .............................................................................................................................. .............................................................................................................................. .............................................................................................................................. (c) Calculate the actual length of the nucleus. (2 marks) .............................................................................................................................. (d) Distinguish the terms resolution and magnification. (2 marks) .............................................................................................................................. .............................................................................................................................. (e) Determine the magnification of this micrograph. (2 marks) ..............................................................................................................................HKDSE Biology 11 By Michael Ho~*
  12. 12. Lecture Notes – Cell BiologyProkaryotae and Eukaryotae Prokaryotae Eukaryotaelack a distinct nucleus bounded by a have a true nucleus that is separatedmembrane from cytoplasm by a nuclear envelopelack membrane-bound organelles such cytoplasm contains membrane-boundas mitochondria and chloroplasts organellesinfolding of cell membrane forms mitochondria for respirationmesosomes for respirationSingle circular DNA and some small Genetic material (DNA) is carried on acircular DNA called plasmids in number of chromosomescytoplasmProkaryotic cellProkaryotae are a kingdom of organisms including the bacteria and cyanobacteria.HKDSE Biology 12 By Michael Ho~*
  13. 13. Lecture Notes – Cell BiologyEukaryotic CellHKDSE Biology 13 By Michael Ho~*
  14. 14. Lecture Notes – Cell Biology1. Nucleus a) Structure  It is enclosed by a nuclear membrane of double membranes that is perforated by nuclear pore.  It contains chromatin.  It is enclosed by a nuclear membrane of double membranes that is perforated by nuclear pore.  It contains chromatin.HKDSE Biology 14 By Michael Ho~*
  15. 15. Lecture Notes – Cell Biology b) General functions of nucleus  It contains genetic materials (DNA) and can be able to synthesize DNA.  It synthesizes genetic messages (mRNA) to be transported to cytoplasm through nuclear pore for protein synthesis.2. Cytoplasm  It contains water and dissolved substances.  Function: It is the site of cellular activities.3. Endoplasmic Reticulum (ER) a) Structure  It is the complex network of folded membranes running throughout the cytoplasm. It consists of two types: rough ER and smooth ER.  Rough ER has many ribosomes attached on the outer surface while smooth ER has none.HKDSE Biology 15 By Michael Ho~*
  16. 16. Lecture Notes – Cell Biology b) Function (i) Rough ER  Rough ER is concerned with the transport of protein synthesized by ribosomes on its surface. (ii) Smooth ER  Smooth ER is concerned with the synthesis and transport of lipids and steroids.HKDSE Biology 16 By Michael Ho~*
  17. 17. Lecture Notes – Cell Biology4. Mitochondrion a) Structure  rod-shaped, bounded by a double membrane.  outer membrane is smooth while inner membrane is highly folded. b) Function  it carries out aerobic respiration, producing ATP molecules which are the form of energy to drive cellular activity.HKDSE Biology 17 By Michael Ho~*
  18. 18. Lecture Notes – Cell Biology5. Chloroplast (found in some plant cells only) a) Structure  It contains chlorophyll to absorb light for photosynthesis.  It is surrounded by double membranes and contains a system of flattened membrane-bond sacs to hold chlorophyll. b) Function  It is the site of photosynthesis producing sugars from carbon dioxide and water using light energy trapped by chlorophyll.  it converts light energy to chemical energy.HKDSE Biology 18 By Michael Ho~*
  19. 19. Lecture Notes – Cell Biology6. Vacuole a) Structure  It is a fluid-filled sac bounded by a membrane.  Plant cells usually have a large central vacuole which is surrounded by a membrane called tonoplast and contains a fluid called cell sap. b) Functions  It helps keep plant cells in a turgid state.  Osmotic uptake of water results in cell expansion during cell growth.  It is used for the storage of water and food, etc.  It provides a place to hold harmful substances or metabolic wastes so as not to interfere the normal metabolism of the cytoplasm.7. Cell Wall It is made up of cellulose and is therefore rigid. It is fully permeable. Function: gives shape, support and protection to the cell.Structural Differences between a Plant Cell and an Animal Cell Plant cell Animal cell has cell wall has NO cell wall has large vacuole has NO large vacuole has chloroplasts has NO chloroplastsHKDSE Biology 19 By Michael Ho~*
  20. 20. Lecture Notes – Cell BiologyConcept CheckHKDSE Biology 20 By Michael Ho~*
  21. 21. Lecture Notes – Cell BiologyCell Membrane1. Chemical composition membranes isolated from red blood cells were chemically analyzed and found to be composed of phospholipids and proteins.HKDSE Biology 21 By Michael Ho~*
  22. 22. Lecture Notes – Cell Biology2. Model of membrane structure Cell membranes are actually phospholipid bilayers. Such a bilayer could exist as a stable boundary between 2 aqueous media, because the molecular arrangement shelters the hydrophobic tails from water, while exposing the hydrophilic heads to water. Fluid Mosaic Model  The membrane is a fluid phospholipid bilayer with a mosaic of protein molecules floats in it.  Both phospholipid and protein molecules are mobile to varying degree within the membrane which is therefore, regarded as a fluid structure.  Proteins penetrate into the hydrophobic interior of the membrane - some penetrate only part of the way into the membrane while others penetrate all the way through.  The arrangement of proteins varies according to the type and function of the membrane.HKDSE Biology 22 By Michael Ho~*
  23. 23. Lecture Notes – Cell Biology3. Properties of membranes Selective permeability  Hydrophobic / non-polar / water-insoluble substances and simple, small molecules can move across the phospholipid bilayer freely.  Ions / water / water-soluble substances can move across the membrane through the channel proteins or carrier proteins. Fluidity of membranes  The phospholipid and some protein molecules can move laterally.  It allows the membrane to change its shape and fuse itself during cell division. Specific in function Different membranes have their unique collections of proteins which determine most of the membrane’s specific functions.Functions of membrane proteins: Membrane protein Function channel protein to transport certain ions and water-soluble substances carrier protein needed in active transport receptor protein to receive chemical signals enzyme to speed up reactions in the cell with antigen molecules attached to form glycoprotein for recognition protein recognition purposesHKDSE Biology 23 By Michael Ho~*
  24. 24. Lecture Notes – Cell BiologyMechanisms of Membrane Transport1. By diffusion Diffusion is the net movement of particles down a concentration gradient / from a region of higher concentration to a region of lower concentration. When the particles have become evenly distributed (i.e. concentration gradient = 0), there will be no net movement of particles. No metabolic energy is required, hence no ATP is required. The diffusion of a substance will be unaffected by concentration differences of other substances. The diffusion rate is determined by: 1. diffusion distance 2. temperature 3. size 4. shape of the substance 5. electrical chargesHKDSE Biology 24 By Michael Ho~*
  25. 25. Lecture Notes – Cell Biology2. By active transport It is the movement of substances across the cell membrane in the expense of energy from respiration (ATP is required). Substances can be moved against a concentration gradient, i.e. from a region of lower concentration to a region of higher concentration. The substance is moved in one direction only. Specific carriers (proteins) are required.Examples:- food absorption at the small intestine: By _______________ + ________________- absorption of some minerals by roots: By _______________ + ________________HKDSE Biology 25 By Michael Ho~*
  26. 26. Lecture Notes – Cell Biology3. By phagocytosis It is the intake of large solid particles (e.g. cells) by invagination of cell membrane, forming a food vacuole. It is carried out by some single-celled organisms (e.g. Amoeba) and certain types of white blood cells. It requires energy and must involve the cell membrane.4. By osmosis It refers to the net movement of water molecules from a region of higher water potential to a region of lower water potential (down a potential gradient) across a selectively permeable membrane.HKDSE Biology 26 By Michael Ho~*
  27. 27. Lecture Notes – Cell Biology a) Water potential ()  It is the tendency of water molecules to move.  The more solute dissolved in water, the lower is its water potential.  Since the water potential of pure water is defined as zero, the water potential of solutions always a negative value. b) Water relations in animal cells  In hypotonic solution: 1. water potential of the external solution is higher than that if the cell 2. water enters the cell by osmosis 3. cell becomes swell and then burst  In hypertonic solution: 1. water potential of the external solution is lower than that of the cell 2. water leaves the cell by osmosis 3. cell becomes shrinks  In isotonic solution: cell has no change in size and shapeHKDSE Biology 27 By Michael Ho~*
  28. 28. Lecture Notes – Cell Biology c) Water relations in plant cells  In hypotonic solution: The cell becomes turgid ∵ The rigid cell wall prevents the cell form bursting  In hypertonic solution: The cell becomes plasmolysed (its cytoplasm shrinks and detaches from the cell wall)  In isotonic solution: The cell becomes flaccidConcept Check1. One end of the middle portion of a spring onion leaf has been cut lengthwise into 4 sections and then immersed in different concentration of sucrose solution. Arrange the solutions in ascending concentration.2. Why is it incorrect to say that sea water is a hypertonic solution. (1 mark)HKDSE Biology 28 By Michael Ho~*
  29. 29. Lecture Notes – Cell BiologyIn hypotonic solution In isotonic solution In hypertonic solution In the cells of the epidermis of the leaf of certain plants that contain colored pigment, the liquid inside the vacuoles are colored. They can be seen under the microscope without staining. Normal condition Plasmolysed condition Concept Check Why can plasmolysis not take place in an animal cell? (2 marks) HKDSE Biology 29 By Michael Ho~*
  30. 30. Lecture Notes – Cell BiologyType 1 – Dialysis TubingDialysis tubing: differentially permeable has many small pores which allow small molecules (e.g. water, glucose, ions) to pass through but not large ones (e.g. sucrose, proteins) Before carrying out the experiment, make sure that 1. the knot of the dialysis tubing should be tied tightly 2. the outside of the dialysis tubing should be rinsed with distilled water 3. the dialysis tubing should be examined for any damage(a) Describe and explain the change in the water level of the capillary tube in set- up A. (3 marks)........................................................................................................................................................................................................................................................................................................................................................................................................................(b) Describe and explain the change in the water level of the capillary tube in set- up B. (3 marks)........................................................................................................................................................................................................................................................................................................................................................................................................................HKDSE Biology 30 By Michael Ho~*
  31. 31. Lecture Notes – Cell BiologyType 2 – Potato Container(a) Explain the level of solution inside the potato bowl in set-up A after 12 hours. (4 marks)................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(b) Explain the level of solution inside the potato bowl in set-up B after 12 hours. (4 marks)................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................HKDSE Biology 31 By Michael Ho~*
  32. 32. Lecture Notes – Cell BiologyType 3 – Potato StripA 10cm long potato strip was placed in a sugar solution. Its length was measured atregular intervals over a period of 3 hours. The results are shown in the table below: Time (hour) Length of the potato strip (cm) 0 10.0 0.5 9.7 1.0 9.4 1.5 9.1 2.0 8.9 2.5 8.8 3.0 8.8(a) Explain the change in length of the potato strip in the first hour. (4 marks)................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(b) (i) Which period of time does the length of potato strip remain unchanged? (1 mark)........................................................................................................................................ (ii) Explain why there was no change in length during this period? (2 marks)................................................................................................................................................................................................................................................................................(c) What perimeter can be measured instead of the length of potato strip? (1 mark)........................................................................................................................................HKDSE Biology 32 By Michael Ho~*

×