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2024 AQA BIOLOGY EXAM STYLE QUESTIONS WITH ANSWERS
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2024 AQA BIOLOGY EXAM STYLE QUESTIONS WITH ANSWERS
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2024 AQA BIOLOGY EXAM STYLEQUESTIONS WITH ANSWERS
explain the structure of phospholip makes them able to form bilayer of cell
membraney - CORRECT-ANSWERSphospholipid head are hydrophilic and the
tail is hydrophobic. they form a double layer with the hydrophylic head
facing the water and the hydrophibic tail faces inwars. the center of the
membrane bilayer hydrohoic so water soluable substances cant easily pass
through
Name two structures in a eukaryotic cell that cannot be identified using an
optical microscope - CORRECT-ANSWERSMitochondrion / ribosome /
endoplasmic reticulum / lysosome / cell-surface membrane.
Explain how cellulose molecules are adapted for their function in plant cells. -
CORRECT-ANSWERSLong and straight chains;
2. Become linked together by many hydrogen bonds to form fibrils;
3. Provide strength (to cell wall).
Describe the induced-fit model of enzyme action - CORRECT-
ANSWERS(before reaction) active site not complementary to/does
not fit substrate;
2. Shape of active site changes as substrate binds/as
enzyme-substrate complex forms
E. coli has no cholesterol in its cell-surface membrane. Despite this, the cell
maintains a constant shape. Explain why. - CORRECT-ANSWERSCell unable to
change shape;
2. (Because) cell has a cell wall;
3. (Wall is) rigid / made of peptidoglycan / murein.
Cholesterol increases the stability of plasma membranes. Cholesterol does
this by making membranes less flexible.
(f) Suggest one advantage of the different percentage of cholesterol in red
blood cells compared with cells lining the ileum.
.......................... - CORRECT-ANSWERSRed blood cells free in blood / not
supported by other cells so cholesterol helps to maintain shape
The scientists expressed their results as Percentage of lipid in plasma
membrane by mass. Explain how they would find these values. - CORRECT-
,ANSWERSDivide mass of each lipid by total mass of all lipids (in that type of
cell);
2. Multiply answer by 100.
Describe how you could use cell fractionation to isolate chloroplasts from leaf
tissue.
........................................................................................................................ -
CORRECT-ANSWERSHow to break open cells and remove debris;
2. Solution is cold / isotonic / buffered;
3. Second pellet is chloroplast.
Describe a technique that could be used to
(i) break open the cells; - CORRECT-ANSWERShomogeniser / blender / pestle
and mortar / description
e.g. grind with sand;
what ais the role of a granum and stroma - CORRECT-ANSWERSA - granum /
thylakoid;
chlorophyll molecules to trap light / light absorbing pigments /
light dependent reaction / part of light dependent reaction;
2
B - stroma;
(contains enzymes for) carbon dioxide fixation / light-independent reaction /
part of light-independent reaction;
(allow ribosome role of protein in photosynthesis)
The structure of the organelles visible in the photograph could not have been
seen using an optical(light) microscope. Explain why. - CORRECT-
ANSWERSHas low resolution / not high enough resolution;
Accept converse relating to EM
2. (Because) wavelength of light not short enough / too long;
(2)
(ii) Describe how the Golgi apparatus is involved in the secretion of enzymes.
- CORRECT-ANSWERS(Golgi apparatus) modifies (protein)
OR
packages / put into (Golgi) vesicles
OR
transport to cell surface / vacuole;
Describe and explain how centrifuging the culture allowed the scientists to
obtain a cell-free liquid. - CORRECT-ANSWERSDescribe and explain how
centrifuging the culture allowed the scientists to obtain a cell-free liquid.
Hydrogen bonds are important in cellulose molecules. Explain why.
,............................................................................................................. -
CORRECT-ANSWERSHolds chains / cellulose molecules together / forms cross
links between chains / cellulose molecules / forms microfibrils, providing
strength / rigidity (to cellulose / cell wall);
2. Hydrogen bonds strong in large numbers;x
Describe how you could use the emulsion test to show the presence of oil in
a sample of fish.
........ - CORRECT-ANSWERS(Shake with) ethanol / alcohol;
1. Accept named alcohol
2. Then add (to) water;
2. Order must be correct
3. White / milky / cloudy (layer
two reasons why tyiglycerides are good for energy storage - CORRECT-
ANSWERSthey are insolubale
they cantain a large amounct of chemical energy with can be released
Describe the structure of proteins - CORRECT-ANSWERSPolymer of amino
acids;
2. Joined by peptide bonds;
3. Formed by condensation;
4. Primary structure is order of amino acids;
5. Secondary structure is folding of polypeptide chain due to hydrogen
bonding;
Accept alpha helix / pleated sheet
6. Tertiary structure is 3-D folding due to hydrogen bonding and ionic /
disulfide bonds;
7. Quaternary structure is two or more polypeptide chains
Explain how heating an enzyme leads to it being denatured. - CORRECT-
ANSWERSChange amino acids;
Allowing formation of more hydrogen bonds / disulphide bridges;
Glycogen and protein are both polymers. Explain why there can only be one
type of glycogen molecule, but there can be many types of protein. -
CORRECT-ANSWERSGlycogen consists of glucose/one type of monomer.
Many different amino acids combine to form proteins.
Describe a chemical test you could carry out on sample A to show that
lactose is a reducing sugar. - CORRECT-ANSWERSheat with Benedict's;
yellow/brown/orange/red;
Explain how the shape of an enzyme molecule is related to its function. -
CORRECT-ANSWERSspecific 3D tertiary structure/shape;
, substrate complementary shape;
(reject same shape)
substrate (can bind) to active site/ can fit into each active site;
) Describe the structure of proteins.
.......................................................... - CORRECT-ANSWERS1. Polymer of
amino acids;
2. Joined by peptide bonds;
3. Formed by condensation;
4. Primary structure is order of amino acids;
5. Secondary structure is folding of polypeptide chain due to hydrogen
bonding;
Accept alpha helix / pleated sheet
6. Tertiary structure is 3-D folding due to hydrogen bonding and ionic /
disulfide bonds;
7. Quaternary structure is two or more polypeptide chains.
. Explain how cellulose gives cotton its strength. - CORRECT-
ANSWERSstraight/unbranched chains;
(idea of more than 1) chains lie side by side / form (micro)fibrils;
idea of H bonds holding chains together;
Explain how a change in the primary structure of a globular protein may
result in a different three-dimensional structure. - CORRECT-
ANSWERSsequence of amino acids changes;
tertiary structure changes/folds in a different way;
bonds form in different places;
(Reject peptide bonds)
c) Describe how a saturated fatty acid differs in molecular structure from an
unsaturated fatty acid.
...................................................................................................................... -
CORRECT-ANSWERS) absence of a double bond;
in the (hydrocarbon) chain;
unable to accept more hydrogen / saturated with hydrogen;
) Explain why triglycerides are not considered to be polymers. - CORRECT-
ANSWERSnot made of monomers/many repeating units;
what are tyrgylcerides used for - CORRECT-ANSWERSto store fats
what makes the sampe for protein an alkali - CORRECT-ANSWERSsodim
hydroxide e
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