Mock: Bio Mols Pt 2

Question 1

Give two ways in which the properties of ATP make it a suitable source of energy in biological processes.

Answer 1

1. Energy released in small / suitable amounts;
2. Soluble;
   [3. Involves a single / simple reaction;]
   Reject “broken down easily / readily”. Reject “quickly / easily resynthesised”

Question 2

Humans synthesise more than their body mass of ATP each day. Explain why it is necessary for them to synthesise such a large amount of ATP

Answer 2

1. ATP cannot be stored / is an immediate source of energy; 2. ATP only releases a small amount of energy at a time

Question 3

Suggest three reasons why it is more efficient to attach lactase to the beads

Answer 3

1. (Lactase / beads) can be reused / not washed away;
2. No need to remove from milk
3. Allows continuous process;

Question 4

The lactose-free milk made after hydrolysis with lactase tastes sweeter than the cow’s milk containing lactose.
Suggest why.

Answer 4

(Lactose hydrolysed to) galactose and glucose

So more sugar molecules;

Question 5

Give two ways in which the structure of starch is similar to cellulose.

Answer 5

1. Are polymers / polysaccharides / are made of monomers / of monosaccharides;
2. Contain glucose / carbon, hydrogen and oxygen;

Question 6

Give two ways in which the structure of starch is different from cellulose.

Answer 6

1. Starch monomers: alpha glucose, cellulose: beta glucose

2. Starch has helical shape, cellulose forms fibrils

Question 7

Explain one difference in the structure of the starch molecule and the cellulose molecule shown in the diagram above

Answer 7

Position of hydrogen and hydroxyl groups on carbon atom 1 inverted

Question 8

In the control experiments, cooked wheat was chopped up to copy the effect of chewing.
Suggest a more appropriate control experiment. Explain your suggestion.

Answer 8

Add boiled saliva;

Everything same as experiment but salivary amylase denatured.

Question 9

In humans, the enzyme maltase breaks down maltose to glucose. This takes place at normal body temperature.
Explain why maltase:
• only breaks down maltose
• allows this reaction to take place at normal body temperature. (5 marks)

Answer 9

1. Tertiary structure / 3D shape of enzyme (means);
2. Active site complementary to maltose / substrate
3. Description of induced fit;
4. Enzyme is a catalyst / lowers activation energy / energy required for reaction

5 . By forming enzyme-substrate complex;

Question 10

Describe competitive and non-competitive inhibition of an enzyme (5 marks)

Answer 10

1. Inhibitors reduce binding of enzyme to substrate / prevent formation of ES complex;
   (Competitive inhibition),
2. Inhibitor similar shape (idea) to substrate;
3. (Binds) in to active site (of enzyme);
4. (Inhibition) can be overcome by more substrate;
5. Inhibitor binds to site on enzyme other than active site;
6. Prevents formation of active site / changes (shape of) active site

Question 11

Describe and explain the link between oxygen concentration, rate of respiration and rate of uptake of potassium ions

Answer 11

greater rate of oxygen consumption / leads to greater rate of respiration and greater rate of uptake

oxygen required for respiration;
respiration produces ATP / releases energy;

potassium ions taken up by active transport

Question 12

Other than ethical reasons, suggest two reasons why they chose to use cats as model organisms

Answer 12

(Are mammals so) likely to have same physiology / reactions as humans
Large number (available)

Question 13

A triglyceride does not contain sucrose or glycosidic bonds. Give one other way in which the structure of a triglyceride is different to olestra

Answer 13

Contains glycerol

Question 14

Hydrogen bonds are important in cellulose molecules. Explain why

Answer 14

1. Hold chains together

2. Hydrogen bonds strong in large numbers

Question 15

Explain two ways in which fatty acids are important in the formation of new cells

Answer 15

Fatty acids used to make phospholipids;

Fatty acids respired to release energy used for cell production

Question 16

Describe the primary structure of proteins

Answer 16

(Sequence of AAs) Joined by peptide bonds;

Formed by condensation reactions;

Question 17

Describe how proteins are digested in the human gut.

Answer 17

Hydrolysis of peptide bonds;
Endopeptidases break polypeptides into smaller peptide chains; Exopeptidases remove terminal amino acids;
Dipeptidases hydrolyse / break down dipeptides into amino acids

Question 18

Other than being smaller, give two ways in which prokaryotic DNA is different from eukaryotic DNA.

Answer 18

(Prokaryotic DNA)
1. Circular / non-linear (DNA);
2. Not (associated) with proteins / histones
(no references to plasmids!!)

Question 19

The events that take place during interphase and mitosis lead to the production of two genetically identical cells. Explain how

Answer 19

DNA replicated;
(Involving) specific / accurate / complementary base-pairing;
Accept: semi conservative replication
(Ref to) two identical / sister chromatids;
Each chromatid / moves / is separated to (opposite) poles / ends of cell.

Question 20

During replication, the two strands of a DNA molecule separate and each acts as a template for the production of a new strand.
Use your knowledge of enzyme action to explain why the arrows point in opposite directions.

Answer 20

!!!shape of the nucleotides is different / nucleotides aligned differently!!!!
And DNA has antiparallel strands
Enzymes have active sites with specific shape;
Only substrates with complementary shape / only the 3’ end can bind with active site of enzyme / active site of DNA polymerase

Question 21

HSV can remain inactive inside the body for years. Explain why this virus can be described as inactive

Answer 21

No more (nerve) cells infected (Because) virus is not replicating.

Question 22

Use your knowledge of enzyme action and DNA replication to explain why new nucleotides can only be added in a 5’ to 3’ direction

Answer 22

1. Reference to DNA polymerase;
2. (Which is) specific;
3. Only complementary with / binds to 5’ end (of strand);
4. Shapes of 5’ end and 3’ end are different / description of how different.

Question 23

Which organ produces maltase

Answer 23

Pancreas

Question 24

Give one function of lysosomes

Answer 24

Break down cells

Question 25

Scientists treated liquid from strain A with a protein-digesting enzyme before adding it to a culture of human cells. No cell damage was recorded.
Suggest why there was no damage to the cells.

Answer 25

1. Enzyme (a protein) is broken down (so no enzyme activity);
2. No toxin (as a result of protein-digesting enzyme activity);
3. (So) toxin is protein.

Question 26

How could an antidote can reduce poisoning by cyanide

Answer 26

(Antidote reacts with / binds to cyanide) so cyanide cannot bind to enzyme / cytochrome oxidase

Question 27

The movement of the woodlice in low relative humidity is an advantage to their survival. Explain how

Answer 27

Low humidity results in more woodlice moving

So increased movement increased chance of leaving dry / unfavourable environment so reduce water loss / reduce evaporation;

Question 28

Describe the structure of a cellulose molecule and explain how cellulose is adapted for its function in cells (6 marks)

Answer 28

1. made from β-glucose;
2. joined by condensation / removing molecule of water / glycosidic bond
3. 1 : 4 link specified or described;
4. “flipping over” of alternate molecules;
5. hydrogen bonds linking chains / long straight chains;
6. cellulose makes cell walls strong / cellulose fibres are strong;