AQA A LEVEL BIOLOGY EXAM PREP QUESTIONS WITH
VERIFIED ANSWERS.
1) What is directional selection? (1 mark) -- Answer ✔✔ Selection for ONE
t t t t t t t t t t t t
extreme/mean shifts over time t t t
2) Explain how antibiotic resistant strains of bacteria are produced? (3 marks) -- Answer
t t t t t t t t t t t t t
✔✔ Mutation occurs producing resistance allele, bacteria with this allele survive and
t t t t t t t t t t t t
reproduce, passing on this allele. Frequency of allele increases over time.
t t t t t t t t t t
3) What is genetic diversity? (1 mark) -- Answer ✔✔ All the different alleles of all genes
t t t t t t t t t t t t t t t t
in a population
t t
4) What type of variation is shown by human height? (1 mark) -- Answer ✔✔
t t t t t t t t t t t t t t
Continuous variation - range of values/not discrete categories/ many categories/no
t t t t t t t t t t
gaps;
5) Give two possible causes of this variation that result from meiosis during gamete
t t t t t t t t t t t t t
formation.(2 marks) -- Answer ✔✔ Crossing over / chiasmata; Random segregation /t t t t t t t t t t t t
independent assortment; In meiosis I and meiosis II; t t t t t t t
6) Describe how you would use a biochemical test to show that a solution contained a
t t t t t t t t t t t t t t t
non-reducing sugar, such as sucrose. [3] -- Answer ✔✔ ,first reducing sugars test; boil
t t t t t t t t t t t t t
with dilute HCl acid then Neutralise with NaHCǑ, add benedict and heat to 95
t t t t t t t t t t t t t t t
degrees C brick red ppt forms if reducing sugar is present
t t t t t t t t t t
7) Describe a chemical test you could carry out to show that a piece of coconut contains
t t t t t t t t t t t t t t t
lipids. [3] -- Answer ✔✔ (Crush in) ethanol / alcohol; Add (to) water (Order of
t t t t t t t t t t t t t t t t
adding is critical for this point); Emulsion / white colour
t t t t t t t t t
,8) What is the function of: a)Ribosome b)Smooth ER c)Golgi apparatus d) Chloroplast
t t t t t t t t t t t t
e)Mitochondria [5] -- Answer ✔✔ a)Protein synthesis b)Lipid synthesis and transport t t t t t t t t t t t
c)Processing and packaging proteins for secretion d)Photosynthesis e)Aerobic t t t t t t t t
respiration to produce ATP t t t
9) Explain the advantages and limitations of using a transmission electron microscope [5]
t t t t t t t t t t t
-- Answer ✔✔ Advantages: Small objects can be seen; TEM has high resolution as
t t t t t t t t t t t t t t t
wavelength of electrons shorter; Limitations: Cannot look at living cells as cells must
t t t t t t t t t t t t t
be in a vacuum; must cut section / thin specimen; Preparation may create artefact;
t t t t t t t t t t t t t t
Does not produce 3D or colored image;
t t t t t t
10) Why an electron microscope can be used to produce images [2] -- Answer ✔✔ EM
t t t t t t t t t t t t t t t
gives high resolution due to short wavelength of electrons;
t t t t t t t t
11) Explain how viruses cause damage to cells. [3] -- Answer ✔✔ uses / breaks up /
t t t t t t t t t t t t t t t t
digests host nuclear / genetic material (allow references made to DNA /RNA instead
t t t t t t t t t t t t t
of nuclear /genetic); virus DNA / genetic material inserted into hosts DNA /
t t t t t t t t t t t t t
chromosome / genetic material; host cells amino acids are used to synthesize viral t t t t t t t t t t t t t
proteins; cell lysis; by enzyme (produced by expressing a virus gene); toxin
t t t t t t t t t t t t
production;
12) Describe and explain how cell fractionation and ultracentrifugation can be used to
t t t t t t t t t t t t
isolate mitochondria from a suspension of animal cells. [5] -- Answer ✔✔ Cell
t t t t t t t t t t t t t
homogenisation to break open cells; 1. Accept suitable method of breaking open cells. t t t t t t t t t t t t
t Filter to remove (large) debris / whole cells; 2. Reject removes cell walls. Use isotonic
t t t t t t t t t t t t t t
t solution to prevent damage to mitochondria / organelles; Keep cold to prevent /
t t t t t t t t t t t t t
reduce damage by enzymes / use buffer to prevent protein / enzyme denaturation;
t t t t t t t t t t t t t
Centrifuge (at lower speed / 1000 g) to separate nuclei / cell fragments / heavy
t t t t t t t t t t t t t t t
organelles; Re-spin (supernatant / after nuclei / pellet removed) at higher speed to get
t t t t t t t t t t t t t t
mitochondria in pellet / at bottom. t t t t t
13) Name two structures present in eukaryotic cells that are not present in the cells of
t t t t t t t t t t t t t t t
prokaryotes. [2] -- Answer ✔✔ Nucleus; mitochondria; chloroplast, Golgi, RER; SER; t t t t t t t t t t t
centrioles
, 14) Describe the fluid-mosaic structure of a cell surface membrane.(5/8 marks) -- Answer
t t t t t t t t t t t
t✔✔ Phospholipids and proteins; Phospholipid bilayer; Arrangement of phospholipid
t t t t t t t t t
molecules 'Tails to tails';'Floating'(protein) molecules / molecules can move in
t t t t t t t t t t
membrane; Intrinsic proteins extend through bilayer; Extrinsic proteins in outer layer
t t t t t t t t t t t
only;(Ref. to intrinsic and extrinsic, unqualified, gains 1 mark);Detail of channel
t t t t t t t t t t t
proteins / protein shapes / glycoproteins; Presence of cholesterol between
t t t t t t t t t t
phospholipids.
15) Describe the part played by cell surface membranes in regulating the movement of
t t t t t t t t t t t t t
substances into and out of cells.(6/10 marks) -- Answer ✔✔ 1. Non-polar/lipid soluble
t t t t t t t t t t t t
tmolecules move through phospholipid layer/bilayer;2. Small molecules/water/gases
t t t t t t t
move through phospholipid layer/bilayer;3. Ions/water soluble substances move
t t t t t t t t
through channels in proteins;4. Some proteins are gated;5. Reference to
t t t t t t t t t t
diffusion;6.Carriers identified as proteins;7. Carriers associated with facilitated t t t t t t t t
diffusion;8. Carriers associated with active transport/transport with ATP/pumps;9.
t t t t t t t t
Different cells have different proteins;10. Correct reference to cytosis;
t t t t t t t t
16) Describe the role of the enzymes of the digestive system in the complete breakdown
t t t t t t t t t t t t t t
of starch. (6 marks) -- Answer ✔✔ 1. Amylase;2. (Starch) to maltose:3. Maltase;4.
t t t t t t t t t t t t t
Maltose to glucose;5. Hydrolysis;6. (Of) glycosidic bond;
t t t t t t
17) Explain how the small intestine is adapted to its function in the absorption of the
t t t t t t t t t t t t t t t
products of digestion. (6/9 marks) 1. -- Answer ✔✔ Large surface area provided by
t t t t t t t t t t t t t t
villi / microvilli;2. long / folds increase surface area / time for absorption;3. thin
t t t t t t t t t t t t t t
epithelium;4. short diffusion pathway;5. capillary network absorbs amino acids / t t t t t t t t t t
sugars;6. lacteal for absorption of digested fats;7. Maintains a steep concentration
t t t t t t t t t t t
gradient;8. mitochondria supply ATP / energy for active transport;9. carrier proteins
t t t t t t t t t t t
(in membranes);
t
18) Describe and explain the role of diffusion in the absorption of digested food by the
t t t t t t t t t t t t t t t
ileum. (4 marks) -- Answer ✔✔ 1. movement along / down concentration gradient;2.
t t t t t t t t t t t t t
monoglycerides / micelles/fatty acids move into epithelial cells;3. monoglycerides t t t t t t t t t
move from epithelium into blood;4. chylomicrons move into lacteals / lymph;
t t t t t t t t t t
19) Describe and explain the role of facilitated diffusion in the absorption of digested food
t t t t t t t t t t t t t
tby the ileum. (3 marks) -- Answer ✔✔ 1. movement along / down concentration
t t t t t t t t t t t t t t
VERIFIED ANSWERS.
1) What is directional selection? (1 mark) -- Answer ✔✔ Selection for ONE
t t t t t t t t t t t t
extreme/mean shifts over time t t t
2) Explain how antibiotic resistant strains of bacteria are produced? (3 marks) -- Answer
t t t t t t t t t t t t t
✔✔ Mutation occurs producing resistance allele, bacteria with this allele survive and
t t t t t t t t t t t t
reproduce, passing on this allele. Frequency of allele increases over time.
t t t t t t t t t t
3) What is genetic diversity? (1 mark) -- Answer ✔✔ All the different alleles of all genes
t t t t t t t t t t t t t t t t
in a population
t t
4) What type of variation is shown by human height? (1 mark) -- Answer ✔✔
t t t t t t t t t t t t t t
Continuous variation - range of values/not discrete categories/ many categories/no
t t t t t t t t t t
gaps;
5) Give two possible causes of this variation that result from meiosis during gamete
t t t t t t t t t t t t t
formation.(2 marks) -- Answer ✔✔ Crossing over / chiasmata; Random segregation /t t t t t t t t t t t t
independent assortment; In meiosis I and meiosis II; t t t t t t t
6) Describe how you would use a biochemical test to show that a solution contained a
t t t t t t t t t t t t t t t
non-reducing sugar, such as sucrose. [3] -- Answer ✔✔ ,first reducing sugars test; boil
t t t t t t t t t t t t t
with dilute HCl acid then Neutralise with NaHCǑ, add benedict and heat to 95
t t t t t t t t t t t t t t t
degrees C brick red ppt forms if reducing sugar is present
t t t t t t t t t t
7) Describe a chemical test you could carry out to show that a piece of coconut contains
t t t t t t t t t t t t t t t
lipids. [3] -- Answer ✔✔ (Crush in) ethanol / alcohol; Add (to) water (Order of
t t t t t t t t t t t t t t t t
adding is critical for this point); Emulsion / white colour
t t t t t t t t t
,8) What is the function of: a)Ribosome b)Smooth ER c)Golgi apparatus d) Chloroplast
t t t t t t t t t t t t
e)Mitochondria [5] -- Answer ✔✔ a)Protein synthesis b)Lipid synthesis and transport t t t t t t t t t t t
c)Processing and packaging proteins for secretion d)Photosynthesis e)Aerobic t t t t t t t t
respiration to produce ATP t t t
9) Explain the advantages and limitations of using a transmission electron microscope [5]
t t t t t t t t t t t
-- Answer ✔✔ Advantages: Small objects can be seen; TEM has high resolution as
t t t t t t t t t t t t t t t
wavelength of electrons shorter; Limitations: Cannot look at living cells as cells must
t t t t t t t t t t t t t
be in a vacuum; must cut section / thin specimen; Preparation may create artefact;
t t t t t t t t t t t t t t
Does not produce 3D or colored image;
t t t t t t
10) Why an electron microscope can be used to produce images [2] -- Answer ✔✔ EM
t t t t t t t t t t t t t t t
gives high resolution due to short wavelength of electrons;
t t t t t t t t
11) Explain how viruses cause damage to cells. [3] -- Answer ✔✔ uses / breaks up /
t t t t t t t t t t t t t t t t
digests host nuclear / genetic material (allow references made to DNA /RNA instead
t t t t t t t t t t t t t
of nuclear /genetic); virus DNA / genetic material inserted into hosts DNA /
t t t t t t t t t t t t t
chromosome / genetic material; host cells amino acids are used to synthesize viral t t t t t t t t t t t t t
proteins; cell lysis; by enzyme (produced by expressing a virus gene); toxin
t t t t t t t t t t t t
production;
12) Describe and explain how cell fractionation and ultracentrifugation can be used to
t t t t t t t t t t t t
isolate mitochondria from a suspension of animal cells. [5] -- Answer ✔✔ Cell
t t t t t t t t t t t t t
homogenisation to break open cells; 1. Accept suitable method of breaking open cells. t t t t t t t t t t t t
t Filter to remove (large) debris / whole cells; 2. Reject removes cell walls. Use isotonic
t t t t t t t t t t t t t t
t solution to prevent damage to mitochondria / organelles; Keep cold to prevent /
t t t t t t t t t t t t t
reduce damage by enzymes / use buffer to prevent protein / enzyme denaturation;
t t t t t t t t t t t t t
Centrifuge (at lower speed / 1000 g) to separate nuclei / cell fragments / heavy
t t t t t t t t t t t t t t t
organelles; Re-spin (supernatant / after nuclei / pellet removed) at higher speed to get
t t t t t t t t t t t t t t
mitochondria in pellet / at bottom. t t t t t
13) Name two structures present in eukaryotic cells that are not present in the cells of
t t t t t t t t t t t t t t t
prokaryotes. [2] -- Answer ✔✔ Nucleus; mitochondria; chloroplast, Golgi, RER; SER; t t t t t t t t t t t
centrioles
, 14) Describe the fluid-mosaic structure of a cell surface membrane.(5/8 marks) -- Answer
t t t t t t t t t t t
t✔✔ Phospholipids and proteins; Phospholipid bilayer; Arrangement of phospholipid
t t t t t t t t t
molecules 'Tails to tails';'Floating'(protein) molecules / molecules can move in
t t t t t t t t t t
membrane; Intrinsic proteins extend through bilayer; Extrinsic proteins in outer layer
t t t t t t t t t t t
only;(Ref. to intrinsic and extrinsic, unqualified, gains 1 mark);Detail of channel
t t t t t t t t t t t
proteins / protein shapes / glycoproteins; Presence of cholesterol between
t t t t t t t t t t
phospholipids.
15) Describe the part played by cell surface membranes in regulating the movement of
t t t t t t t t t t t t t
substances into and out of cells.(6/10 marks) -- Answer ✔✔ 1. Non-polar/lipid soluble
t t t t t t t t t t t t
tmolecules move through phospholipid layer/bilayer;2. Small molecules/water/gases
t t t t t t t
move through phospholipid layer/bilayer;3. Ions/water soluble substances move
t t t t t t t t
through channels in proteins;4. Some proteins are gated;5. Reference to
t t t t t t t t t t
diffusion;6.Carriers identified as proteins;7. Carriers associated with facilitated t t t t t t t t
diffusion;8. Carriers associated with active transport/transport with ATP/pumps;9.
t t t t t t t t
Different cells have different proteins;10. Correct reference to cytosis;
t t t t t t t t
16) Describe the role of the enzymes of the digestive system in the complete breakdown
t t t t t t t t t t t t t t
of starch. (6 marks) -- Answer ✔✔ 1. Amylase;2. (Starch) to maltose:3. Maltase;4.
t t t t t t t t t t t t t
Maltose to glucose;5. Hydrolysis;6. (Of) glycosidic bond;
t t t t t t
17) Explain how the small intestine is adapted to its function in the absorption of the
t t t t t t t t t t t t t t t
products of digestion. (6/9 marks) 1. -- Answer ✔✔ Large surface area provided by
t t t t t t t t t t t t t t
villi / microvilli;2. long / folds increase surface area / time for absorption;3. thin
t t t t t t t t t t t t t t
epithelium;4. short diffusion pathway;5. capillary network absorbs amino acids / t t t t t t t t t t
sugars;6. lacteal for absorption of digested fats;7. Maintains a steep concentration
t t t t t t t t t t t
gradient;8. mitochondria supply ATP / energy for active transport;9. carrier proteins
t t t t t t t t t t t
(in membranes);
t
18) Describe and explain the role of diffusion in the absorption of digested food by the
t t t t t t t t t t t t t t t
ileum. (4 marks) -- Answer ✔✔ 1. movement along / down concentration gradient;2.
t t t t t t t t t t t t t
monoglycerides / micelles/fatty acids move into epithelial cells;3. monoglycerides t t t t t t t t t
move from epithelium into blood;4. chylomicrons move into lacteals / lymph;
t t t t t t t t t t
19) Describe and explain the role of facilitated diffusion in the absorption of digested food
t t t t t t t t t t t t t
tby the ileum. (3 marks) -- Answer ✔✔ 1. movement along / down concentration
t t t t t t t t t t t t t t
