AQA A LEVEL BIOLOGY : CELLS| COMPLETE
QUESTIONS AND CORRECT ANSWERS |UPDATED FOR
A AN A+ SCORE
Can you describe how prokaryotic cells differ from eukaryotic cells? - Correct Answer
✅💯Prokaryotic cells:
- have no nucleus
- smaller 70S ribosomes
- cytoplasm lacks membrane-bound organelles
- much smaller cell
- cell wall contains murein (a glycoprotein)
- plasmids may be found in prokaryotic cells
Eukaryotic Cells:
- have nucleus
- 80S ribosomes
- membrane-bound organelles
- larger cell
- cell wall made of cellulose or chitin
- no plasmids
Can you describe the principles of cell fractionation and ultracentrifugation in separating cell
components? - Correct Answer ✅💯1. Homogenisation
- tissue is broken up in a cold, isotonic buffer solution to release the organelles into a solution
2. Filtration
- the homogenised cell solution is filtered through a gauze
- this separates any large cell debris
3. Ultracentrifugation
- the cell fragments are poured into a test tube and placed in a centrifuge and spun at a low
speed
,- a thick sediment - the pellet - is at the bottom of the tube and the fluid above is the
supernatant
- the supernatant is drained into a new tube and spun again at a higher speed
- a new pellet forms and again, the supernatant is drained off and spun again at an even higher
speed
- this process is repeated at higher speeds each time until all the organelles are separated out
Can you describe the pros and cons of optical microscopes? - Correct Answer ✅💯Pros:
- cheap
- images in colour
- no training required
- live specimens
Cons:
- low magnification x1500
- low resolution
- 2D images
Can you describe the pros and cons of scanning electron microscopes? - Correct Answer
✅💯Pros:
- 3D images
- high magnification
- high resolution
- thick specimens
Cons:
- expensive
- training is required
- no colour images
Can you describe the pros and cons of transmission electron microscopes? - Correct Answer
✅💯Pros:
- high resolution images
- high magnification
- visible internal structures
, Cons:
- expensive
- training is required
- no colour images
- 2D images
- only thin specimens
Can you describe the structure of virus particules? - Correct Answer ✅💯- no plasma
membrane, cytoplasm, ribosomes
- a core of genetic material : DNA or RNA
- capsid surrounding core
- attachment proteins around edge of capsid
Can you explain that viruses are acellular and non-living? - Correct Answer ✅💯Viruses are
nucleic acids surrounded by protein so they are not living.
Can you list other features of prokaryotic cells? - Correct Answer ✅💯Prokaryotic cells can
have:
- one or more plasmids
- a slime capsule surrounding the cell
- one or more flagella
Can you name and explain an example of a eukaryotic cell with specific adaptations? -
Correct Answer ✅💯A sperm cell:
- Many mitochondria for ATP production which to allow movement
- Undulipodium (tail) for movement towards egg
- Acrosome (specialised lysosome) to help the sperm penetrate the egg
- Diploid nucleus, as it is a gamete
Comment on osmosis in plant cells when water moves in/out. - Correct Answer
✅💯Protoplast (cell parts within cell wall) pushes on cell wall when swells - turgid.
If water leaves by osmosis, a point is reached where protoplast no longer presses on cellulose
cell wall - incipient plasmolysis.
Further loss of water by osmosis -> cell contents shrink further and protoplast pulls away
from cell wall - cell is said to be plasmolysed.
QUESTIONS AND CORRECT ANSWERS |UPDATED FOR
A AN A+ SCORE
Can you describe how prokaryotic cells differ from eukaryotic cells? - Correct Answer
✅💯Prokaryotic cells:
- have no nucleus
- smaller 70S ribosomes
- cytoplasm lacks membrane-bound organelles
- much smaller cell
- cell wall contains murein (a glycoprotein)
- plasmids may be found in prokaryotic cells
Eukaryotic Cells:
- have nucleus
- 80S ribosomes
- membrane-bound organelles
- larger cell
- cell wall made of cellulose or chitin
- no plasmids
Can you describe the principles of cell fractionation and ultracentrifugation in separating cell
components? - Correct Answer ✅💯1. Homogenisation
- tissue is broken up in a cold, isotonic buffer solution to release the organelles into a solution
2. Filtration
- the homogenised cell solution is filtered through a gauze
- this separates any large cell debris
3. Ultracentrifugation
- the cell fragments are poured into a test tube and placed in a centrifuge and spun at a low
speed
,- a thick sediment - the pellet - is at the bottom of the tube and the fluid above is the
supernatant
- the supernatant is drained into a new tube and spun again at a higher speed
- a new pellet forms and again, the supernatant is drained off and spun again at an even higher
speed
- this process is repeated at higher speeds each time until all the organelles are separated out
Can you describe the pros and cons of optical microscopes? - Correct Answer ✅💯Pros:
- cheap
- images in colour
- no training required
- live specimens
Cons:
- low magnification x1500
- low resolution
- 2D images
Can you describe the pros and cons of scanning electron microscopes? - Correct Answer
✅💯Pros:
- 3D images
- high magnification
- high resolution
- thick specimens
Cons:
- expensive
- training is required
- no colour images
Can you describe the pros and cons of transmission electron microscopes? - Correct Answer
✅💯Pros:
- high resolution images
- high magnification
- visible internal structures
, Cons:
- expensive
- training is required
- no colour images
- 2D images
- only thin specimens
Can you describe the structure of virus particules? - Correct Answer ✅💯- no plasma
membrane, cytoplasm, ribosomes
- a core of genetic material : DNA or RNA
- capsid surrounding core
- attachment proteins around edge of capsid
Can you explain that viruses are acellular and non-living? - Correct Answer ✅💯Viruses are
nucleic acids surrounded by protein so they are not living.
Can you list other features of prokaryotic cells? - Correct Answer ✅💯Prokaryotic cells can
have:
- one or more plasmids
- a slime capsule surrounding the cell
- one or more flagella
Can you name and explain an example of a eukaryotic cell with specific adaptations? -
Correct Answer ✅💯A sperm cell:
- Many mitochondria for ATP production which to allow movement
- Undulipodium (tail) for movement towards egg
- Acrosome (specialised lysosome) to help the sperm penetrate the egg
- Diploid nucleus, as it is a gamete
Comment on osmosis in plant cells when water moves in/out. - Correct Answer
✅💯Protoplast (cell parts within cell wall) pushes on cell wall when swells - turgid.
If water leaves by osmosis, a point is reached where protoplast no longer presses on cellulose
cell wall - incipient plasmolysis.
Further loss of water by osmosis -> cell contents shrink further and protoplast pulls away
from cell wall - cell is said to be plasmolysed.
