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Chapter 3- Cells
A level Biology Chapter 3 - Cells
| Question | Answer |
|---|---|
| Describe how you would use a microscope to find the mean diameter of triglyceride droplets on a slide? | Measure with eye piece graticule. Calibrate with stage micrometer repeat and calculate the mean |
| Starting with some lettuce leaves, describe how you would obtain a sample of undamaged chloroplasts. Use your knowledge of cell fractionation and ultracentrifugation to answer this question? | Chop up Cold reduces enzyme activity Buffered solution; prevents pH affecting enzymes ; Isotonic; (prevents osmosis and possible lysis) Filter and centrifuge filtrate; Centrifuge supernatant; At higher speed; Chloroplasts in second pellet |
| Mitosis is important in the life of an organism. Give two reasons why? | Growth and Repair |
| Describe the behaviour of chromosomes during mitosis? | chromosomes thicken chromosomes two identical chromatids (due to replication) chromosomes move to equator; attach to spindle fibres spindle fibres contract / centromeres divide / repel sister chromatids seperate move to opposite poles |
| Explain how this creates 2 identical cells? | each pole/end receives all genetic information/ identical copies of each chromosome; nuclear envelope forms around each group of chromosomes/ chromatids/at each pole |
| Describe two events which occur during interphase? | Increase in number of organelles, DNA replication |
| How do bacteria divide? | By binary fission. Circular DNA and plasmids replicate. |
| What is the function of the rough ER? | Protein synthesis - has ribosomes on it |
| What is the function of mitochondria? | Produce ATP for aerobic respiration. |
| What is the function of the smooth ER? | Lipid synthesis |
| What is the function of the Golgi apparatus? | Modifies proteins by adding carbohydrates to produce glycoproteins. |
| What is the function of the nucleus? | To hold the genetic information and DNA and to allow certain substances to leave enter the cell. |
| What is the function of chloroplasts? | For photosynthesis in plants produces glucose. |
| What is the structure of a mitochondrion? | Large matrix with cristae and double membrane (inner and outer membrane) |
| What is the structure of chloroplasts? | Stroma with stacks of thykaloids which are grana |
| Explain how the inner membrane is adapted to its function in a mitochondrion? | It increase the surface area for respiration. |
| The tissue was chopped in cold, isotonic buffer solution. Explain the reason for using a cold solution? | To prevent denaturation of enzymes |
| The tissue was chopped in cold, isotonic buffer solution. Explain the reason for using a buffered solution? | Prevents change of PH; prevents damage to enzymes / proteins |
| The tissue was chopped in cold, isotonic buffer solution. Explain the reason for using a isotonic solution? | To prevent osmosis happening which could cause lysis. |
| Give one feature of a prokaryotic cell that is not found in a eukaryotic cell? | no nucleus. plasmids; Capsule; |
| Explain why an electron microscope shows more detail of cell structure than a light microscope | electron beams have a shorter wavelength. Therefore has a higher resolution |
| Explain why the homogenate was filtered before spinning at low speed in the centrifuge? | To remove large debris which would interfere with the result. |
| What about organelles allows them to separated in this way? | density / size / mass / weight; |
| What is an advantage of SEM over a TEM microscope? | SEM can produce a 3D image but TEM cant. |
| Explain the importance of using a thin layer of a cell you are going to study? | A few layers of cells only so light can pass through. for SEM 3D images can be made. |
| Give two ways in which the structure of a bacterium differs from the structure of a cell lining the human small intestine? | Bacteria has flagellum Human cell has nucleus but bacteria has circular DNA and plasmids. |
| In Mitosis describe what happens in metaphase? | Spindles form and chromosomes attach to them. Chromosomes line up at the center of the cell |
| In Mitosis describe what happens during anaphase? | Chromatids are pulled apart to poles of cell. |
| Cells lining the human intestine complete the cell cycle in a short time. Explain the advantage of these cells completing the cell cycle in a short time. | Replace cells quickly. |
| Mikanolide is a drug that inhibits the enzyme DNA polymerase. Explain why this drug may be effective against some types of cancer. | Prevents/slows DNA replication so new strand not formed. |
| Give two ways in which the arrangement of prokaryotic DNA is different from the arrangement of the human DNA | Prokaryotic DNA not associated with histones. Circular vs linear |
| Contrast how an optical microscope and TEM work and contrast the limitations when studying cells? [6 marks] | TEM use electrons and optical use light TEM allows a greater resolution TEM view only dead and optical can view live specimens TEM does not show colour and optical can TEM requires thinner specimens TEM focuses using magnets and optical uses lenses |
Created by:
ksatti12