AQA A-level Biology paper 1 Questions
with Answers Graded A+
Large molecules often contain carbon. Why? - correct answers-they can readily form bonds with other
carbon atoms. This forms a 'backbone'. Other atoms can then attach.
Describe benedicts test for reducing sugars - correct answers-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.
What is a reducing sugar? - correct answers-a sugar that can reduce (give electrons to) another
chemical.
Describe the benedicts test for non reducing sugars - correct answers-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.
What does dilute hydrochloric acid do in the benedicts test for non reducing sugars? - correct answers-it
hydrolyses any disaccharide into monosaccharides, thus also forming reducing sugars.
Describe the structure of starch - correct answers-chains of alpha glucose
Some chains are branched= amylopetcin
Some chains are coiled= amylose
What purpose does the structure of amylose serve? - correct answers-makes the molecule compact so it
is stored more easily.
What purpose does the structure of amylopectin serve? - correct answers-more surface area for
enzymes to work on, thus glucose molecules can be released at a much quicker rate.
How is the structure of starch suited to its function? - correct answers-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
,How is the structure of glycogen suited to its function? - correct answers-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
Why do animals need highly branched glycogen? - correct answers-because animals metabolic rate is
faster than plants and so needs glucose to be released quicker.
Describe the structure of cellulose - correct answers-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
Draw alpha and beta glucose - correct answers-
How does the structure of triglycerides relate to their properties? - correct answers-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
What are the roles of lipids? - correct answers-1. Source of energy
2. Waterproofing
3. Insulation
4. Protection
How does the structure of phospholipids relate to their properties? - correct answers-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.
Draw the structure of an amino acid - correct answers-
Draw how a dipeptide forms - correct answers-
What is meant by 'primary sequence' of a protein - correct answers-the unique sequence of amino acids
that make up a protein or polypeptide chain
, What is meant by 'secondary sequence' of a protein - correct answers-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.
What is meant by 'tertiary sequence' of a protein - correct answers-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.
What is meant by 'quaternary sequence' of a protein - correct answers-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.
Describe the test for proteins - correct answers-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.
What are fiberous proteins made up of? - correct answers-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.
What are globular proteins made up of? - correct answers-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.
What kind of protein is collagen? - correct answers-fiberous
What kind of protein is haemoglobin? - correct answers-globular
What is haemoglobin made up of? - correct answers-two α polypeptide chains
Two β polypeptide chains
An inorganic prosthetic haem group (fe2+)
What is collagen made up of? Describe its structure? - correct answers-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.
What are the functions of collagen? - correct answers-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
with Answers Graded A+
Large molecules often contain carbon. Why? - correct answers-they can readily form bonds with other
carbon atoms. This forms a 'backbone'. Other atoms can then attach.
Describe benedicts test for reducing sugars - correct answers-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.
What is a reducing sugar? - correct answers-a sugar that can reduce (give electrons to) another
chemical.
Describe the benedicts test for non reducing sugars - correct answers-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.
What does dilute hydrochloric acid do in the benedicts test for non reducing sugars? - correct answers-it
hydrolyses any disaccharide into monosaccharides, thus also forming reducing sugars.
Describe the structure of starch - correct answers-chains of alpha glucose
Some chains are branched= amylopetcin
Some chains are coiled= amylose
What purpose does the structure of amylose serve? - correct answers-makes the molecule compact so it
is stored more easily.
What purpose does the structure of amylopectin serve? - correct answers-more surface area for
enzymes to work on, thus glucose molecules can be released at a much quicker rate.
How is the structure of starch suited to its function? - correct answers-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
,How is the structure of glycogen suited to its function? - correct answers-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
Why do animals need highly branched glycogen? - correct answers-because animals metabolic rate is
faster than plants and so needs glucose to be released quicker.
Describe the structure of cellulose - correct answers-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
Draw alpha and beta glucose - correct answers-
How does the structure of triglycerides relate to their properties? - correct answers-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
What are the roles of lipids? - correct answers-1. Source of energy
2. Waterproofing
3. Insulation
4. Protection
How does the structure of phospholipids relate to their properties? - correct answers-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.
Draw the structure of an amino acid - correct answers-
Draw how a dipeptide forms - correct answers-
What is meant by 'primary sequence' of a protein - correct answers-the unique sequence of amino acids
that make up a protein or polypeptide chain
, What is meant by 'secondary sequence' of a protein - correct answers-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.
What is meant by 'tertiary sequence' of a protein - correct answers-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.
What is meant by 'quaternary sequence' of a protein - correct answers-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.
Describe the test for proteins - correct answers-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.
What are fiberous proteins made up of? - correct answers-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.
What are globular proteins made up of? - correct answers-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.
What kind of protein is collagen? - correct answers-fiberous
What kind of protein is haemoglobin? - correct answers-globular
What is haemoglobin made up of? - correct answers-two α polypeptide chains
Two β polypeptide chains
An inorganic prosthetic haem group (fe2+)
What is collagen made up of? Describe its structure? - correct answers-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.
What are the functions of collagen? - correct answers-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
