AQA A-level Biology paper 1 2024
1. large molecules often contain carbon. why?: they can readily form bonds
with other carbon atoms. this forms a 'backbone'. other atoms can then attach.
2. describe benedicts test for reducing sugars: add equal volumes of the sugar
sample and benedicts reagent.
heat the mixture in a water bath for 5 minutes.
brick red precipitate will form.
3. what is a reducing sugar?: a sugar that can reduce (give electrons to) another
chemical.
4. describe the benedicts test for non reducing sugars: with food sample, add
an equal volume of dilute hydrochloric acid in a test tube. place test tube in
water bath for 5 mins. add sodium hydrogencarbonate solution.
heat resulting solution with an equal volume of benedicts. solution for 5 minutes.
turns orange/brown.
5. what does dilute hydrochloric acid do in the benedicts test for non
reducing sugars?: it hydrolyses any disaccharide into monosaccharides, thus
also forming reducing sugars.
6. describe the structure of starch: chains of alpha glucose
some chains are branched= amylopetcin
some chains are coiled= amylose
7. what purpose does the structure of amylose serve?: makes the molecule
compact so it is stored more easily.
8. what purpose does the structure of amylopectin serve?: more surface area
for enzymes to work on, thus glucose molecules can be released at a much
quicker rate.
9. how is the structure of starch suited to its function?:
1. starch is insolube so it doesnt affect water potential
2. it is large enough that it doesnt diffuse out of cells
3. compact enough so that a lot of it can be stored in a small space
4. branched= each end can simultaneously be acted on by enzymes, so glucose is
quickly released
10. how is the structure of glycogen suited to its function?: 1. insoluble, so no
effect on water potential of cell
2. insoluble, so doesnt diffuse out of cells
3. compact, a lot of it can be stored in a small space
4. very highly branched= each end can simultaneously be acted on by enzymes,
so glucose is quickly released
,11. why do animals need highly branched glycogen?: because animals
metabolic rate is faster than plants and so needs glucose to be released
quicker.
12. describe the structure of cellulose: made up of straight chains of beta
glucose the chains are parallel to each other, so H bonds form cross-linkages
all the H bonds together strengthens the cellulose forms microfibrils
13. draw alpha and beta glucose:
14. how does the structure of triglycerides relate to their properties?:
1. triglycerides have a high ratio of energy-storing carbon-hydrogen bonds to
carbon atoms, so its a good source of energy.
2. low mass to energy ratio, so theyre good energy storage molecules.
3. large and non-polar, therefore insoluble, therefore don't affect osmosis.
4. high ratio of hydrogen to oxygen atoms, so can release water when oxidised,
hence provide a source of water
15. what are the roles of lipids?: 1. source of energy
2. waterproofing
3. insulation
4. protection
16. how does the structure of phospholipids relate to their properties?: 1.
polar, therefore will position itself to form a bilayer
2. the structure allows them to form glycolipids by combining with carbohydrates
within the cell-surface membrane. these are important
in cell recognition.
17. draw the structure of an amino acid:
18. draw how a dipeptide forms:
19. what is meant by 'primary sequence' of a protein: The unique sequence of
amino acids that make up a protein or polypeptide chain
20. what is meant by 'secondary sequence' of a protein: The way in which the
primary structure of a polypeptide chain folds e.g. alpha helix or beta pleated
sheets. shape is held by H bonds.
, 21. what is meant by 'tertiary sequence' of a protein: This is the overall 3-D
structure of the protein.
The shape of the protein is held together by H bonds and ionic bonds and disulfide
bridges.
22. what is meant by 'quaternary sequence' of a protein: If a protein is made
up of several polypeptide chains that are linked in various ways, the way they
are arranged is called the quaternary structure.
23 describe the test for proteins: add equal volumes of sample and sodium
hydroxide to a test tube. add a few drops of dilute copper (II) sulfate and mix.
if solution turns purple, protein is present.
24. what are fiberous proteins made up of?: made of long molecules arranged
to form fibres (e.g. in keratin). Several helices may be wound around each
other to form very strong fibres.
25. what are globular proteins made up of?: made of chains folded into a
compact structure. One of the most important classes are the enzymes.
Although these folds are less regular than in a helix, they are highly specific
and a particular protein will always be folded in the same way.
26. what kind of protein is collagen?: fiberous
27. what kind of protein is haemoglobin?: globular
28. what is haemoglobin made up of?: two ±polypeptide chains two ²
polypeptide chains
an inorganic prosthetic haem group (Fe2+)
29. what is collagen made up of? describe its structure?:
three polypeptide chains
wound around each other
each of the three chains is a coil itself
Hydrogen bonds form between these coils
Collagen molecules form further chains with other collagen molecules and form
Covalent Cross Links with each other, which are staggered along the molecules
to further increase stability. Collagen molecules wrapped around each other form
Collagen Fibrils which themselves form Collagen Fibres.
30. what are the functions of collagen?:
1. Form the structure of bones
2. Makes up cartilage and connective tissue
3. Prevents blood that is being pumped at high pressure from bursting the walls of
arteries
4. Is the main component of tendons, which connect skeletal muscles to bones
1. large molecules often contain carbon. why?: they can readily form bonds
with other carbon atoms. this forms a 'backbone'. other atoms can then attach.
2. describe benedicts test for reducing sugars: add equal volumes of the sugar
sample and benedicts reagent.
heat the mixture in a water bath for 5 minutes.
brick red precipitate will form.
3. what is a reducing sugar?: a sugar that can reduce (give electrons to) another
chemical.
4. describe the benedicts test for non reducing sugars: with food sample, add
an equal volume of dilute hydrochloric acid in a test tube. place test tube in
water bath for 5 mins. add sodium hydrogencarbonate solution.
heat resulting solution with an equal volume of benedicts. solution for 5 minutes.
turns orange/brown.
5. what does dilute hydrochloric acid do in the benedicts test for non
reducing sugars?: it hydrolyses any disaccharide into monosaccharides, thus
also forming reducing sugars.
6. describe the structure of starch: chains of alpha glucose
some chains are branched= amylopetcin
some chains are coiled= amylose
7. what purpose does the structure of amylose serve?: makes the molecule
compact so it is stored more easily.
8. what purpose does the structure of amylopectin serve?: more surface area
for enzymes to work on, thus glucose molecules can be released at a much
quicker rate.
9. how is the structure of starch suited to its function?:
1. starch is insolube so it doesnt affect water potential
2. it is large enough that it doesnt diffuse out of cells
3. compact enough so that a lot of it can be stored in a small space
4. branched= each end can simultaneously be acted on by enzymes, so glucose is
quickly released
10. how is the structure of glycogen suited to its function?: 1. insoluble, so no
effect on water potential of cell
2. insoluble, so doesnt diffuse out of cells
3. compact, a lot of it can be stored in a small space
4. very highly branched= each end can simultaneously be acted on by enzymes,
so glucose is quickly released
,11. why do animals need highly branched glycogen?: because animals
metabolic rate is faster than plants and so needs glucose to be released
quicker.
12. describe the structure of cellulose: made up of straight chains of beta
glucose the chains are parallel to each other, so H bonds form cross-linkages
all the H bonds together strengthens the cellulose forms microfibrils
13. draw alpha and beta glucose:
14. how does the structure of triglycerides relate to their properties?:
1. triglycerides have a high ratio of energy-storing carbon-hydrogen bonds to
carbon atoms, so its a good source of energy.
2. low mass to energy ratio, so theyre good energy storage molecules.
3. large and non-polar, therefore insoluble, therefore don't affect osmosis.
4. high ratio of hydrogen to oxygen atoms, so can release water when oxidised,
hence provide a source of water
15. what are the roles of lipids?: 1. source of energy
2. waterproofing
3. insulation
4. protection
16. how does the structure of phospholipids relate to their properties?: 1.
polar, therefore will position itself to form a bilayer
2. the structure allows them to form glycolipids by combining with carbohydrates
within the cell-surface membrane. these are important
in cell recognition.
17. draw the structure of an amino acid:
18. draw how a dipeptide forms:
19. what is meant by 'primary sequence' of a protein: The unique sequence of
amino acids that make up a protein or polypeptide chain
20. what is meant by 'secondary sequence' of a protein: The way in which the
primary structure of a polypeptide chain folds e.g. alpha helix or beta pleated
sheets. shape is held by H bonds.
, 21. what is meant by 'tertiary sequence' of a protein: This is the overall 3-D
structure of the protein.
The shape of the protein is held together by H bonds and ionic bonds and disulfide
bridges.
22. what is meant by 'quaternary sequence' of a protein: If a protein is made
up of several polypeptide chains that are linked in various ways, the way they
are arranged is called the quaternary structure.
23 describe the test for proteins: add equal volumes of sample and sodium
hydroxide to a test tube. add a few drops of dilute copper (II) sulfate and mix.
if solution turns purple, protein is present.
24. what are fiberous proteins made up of?: made of long molecules arranged
to form fibres (e.g. in keratin). Several helices may be wound around each
other to form very strong fibres.
25. what are globular proteins made up of?: made of chains folded into a
compact structure. One of the most important classes are the enzymes.
Although these folds are less regular than in a helix, they are highly specific
and a particular protein will always be folded in the same way.
26. what kind of protein is collagen?: fiberous
27. what kind of protein is haemoglobin?: globular
28. what is haemoglobin made up of?: two ±polypeptide chains two ²
polypeptide chains
an inorganic prosthetic haem group (Fe2+)
29. what is collagen made up of? describe its structure?:
three polypeptide chains
wound around each other
each of the three chains is a coil itself
Hydrogen bonds form between these coils
Collagen molecules form further chains with other collagen molecules and form
Covalent Cross Links with each other, which are staggered along the molecules
to further increase stability. Collagen molecules wrapped around each other form
Collagen Fibrils which themselves form Collagen Fibres.
30. what are the functions of collagen?:
1. Form the structure of bones
2. Makes up cartilage and connective tissue
3. Prevents blood that is being pumped at high pressure from bursting the walls of
arteries
4. Is the main component of tendons, which connect skeletal muscles to bones
