PPQ's

Question 1

Which metabolic process occurs to go from a glucose molecule to a pyruvate molecule? (1)

Answer 1

Glycolysis.

Question 2

All organisms require energy in order to remain alive. Plants use solar energy to combine water and carbon dioxide into complex organic molecules. Both plants and animals then break down organic molecules in respiration. Energy released in this process is used in the formation of ATP.
Describe the structure of ATP. (4)

Answer 2

• Nitrogenous base.
• Adenine.
• Pentose.
• Ribose.
• Three phosphate groups.
• Phosphorylated nucleotide.

Question 3

Which metabolic process occurs to go from a pyruvate molecule to an ethanol molecule? (1)

Answer 3

Ethanol fermentation / Anaerobic respiration.

Question 4

What is the site of the krebs cycle? (1)

Answer 4

Matrix.

Question 5

In which metabolic process is Acetyl Co-A utilised? (1)

Answer 5

Aerobic respiration.

Question 6

The diagram shows that fatty acids can be converted into acetyl CoA units by a process known as β-oxidation. Both this process and the Krebs cycle require NAD. The Krebs cycle also requires FAD. The hydrogen atoms released in β-oxidation and the breakdown of acetyl CoA in the Krebs cycle reduce the NAD and FAD molecules.
State the number of reduced NAD and reduced FAD molecules that are formed in the Krebs cycle from one molecule of acetyl CoA. (2)

Answer 6

reduced NAD = 3.

reduced FAD = 1.

Question 7

State where the reduced NAD and reduced FAD molecules are reoxidised and describe what happens to the hydrogen atoms. (4)

Answer 7

• cristae.
• NADH dehydrogenase.
• hydrogen split into protons and electrons.
• electron carriers / ETC.
• energy released from electrons.
• protons pumped across membrane.
• protons accumulate in intermembrane space.
• proton gradient / electrochemical gradient.
• protons pass through the ATPase / ATPsynthase.
• oxygen as final hydrogen acceptor.
• formation of water.

Question 8

What is the site of decarboxylation? (1)

Answer 8

Matrix.

Question 9

Which metabolic process occurs to go from a pyruvate molecule to Carbon Dioxide and Water? (1)

Answer 9

Aerobic respiration.

Question 10

The liver is responsible for producing enzymes which detoxify alcohol by breaking it down into smaller units. This breakdown by enzymes uses NAD. This means that other reactions that use NAD are less likely to take place. The build up of fats in the liver is one of the first signs of liver damage due to excessive alcohol intake.
Using the information in the diagram above, explain why the build up of fats occurs in the liver of an individual who consumes large amounts of alcohol. (3)

Answer 10

• fats/fatty acid
• not respired
• NAD used in breakdown of alcohol
• NAD is, limiting/in short supply/AW
• fats formed from fatty acids plus glycerol;
• AVP; e.g. further detail of alcohol/fat metabolism

Question 11

Explain the following terms:

Decarboxylation and Dehydrogenation. (1)

Answer 11

Decarboxylation = removal of carbon dioxide/carboxyl.
Dehydrogenation = removal of hydrogen.

Question 12

ATP is made directly by substrate level phosphorylation in the Krebs cycle.
State the number of ATP molecules that are made directly per ‘turn’ of the cycle. (1)

Answer 12

1.

Question 13

Many seeds contain food stores, including starch, proteins and lipids. A fully developed seed of H. annuus contains between 40% and 50% of unsaturated fatty acids, including oleic acid and linoleic acid. These fatty acids can be used as respiratory substrates for the production of ATP.
Explain why seeds need ATP. (2)

Answer 13

• Releases energy.
• For germination.
• For growth / protein synthesis / spindle formation / organelle replication / other named process.

Question 14

What is the site of oxidative phosphorylation? (1)

Answer 14

Cristae.

Question 15

In which metabolic process is ATP utilised? (1)

Answer 15

Glycolysis.

Question 16

Explain the advantages of storing lipid for use as a respiratory substrate in seeds. (2)

Answer 16

• higher energy density/release twice as much energy per, g/unit mass.
• compared to, glucose/protein.
• 39 kJ g–1.
• higher proportion of, hydrogen atoms/carbon-hydrogen bonds.
• advantage for dispersal/named advantage.
• AVP; e.g. ref to coenzyme A formation

Question 17

Herbicides (weedkillers) interfere with electron transport by accepting electrons.
Suggest how this causes plants to die. (3)

Answer 17

• no photophosphorylation.
• no ATP produced.
• no reduced NADP produced.
• no Calvin cycle / no light-independent stage.
• no GT to TP / no TP to RuBP.
• no fixation of carbon dioxide.

Question 18

After chasing prey, a cheetah breathes rapidly (pants) for half an hour before it can run again.
Explain why panting is necessary. (4)

Answer 18

heat loss:

• body / blood temperature rises.
• may affect / denature, enzymes / proteins.
• panting cools body.
• evaporative cooling.

fate of lactate:

• (high) lactate concentration needs to be reduced.
• due to anaerobic respiration.
• panting provides extra oxygen / oxygen debt.
• lactate oxidised to pyruvate.

respiratory gases:

• myoglobin would be reoxygenated.
• haemoglobin would be reoxygenated.
• ATP/PC resynthesised in muscle tissues.
• removal of extra carbon dioxide.

Question 19

Explain why there is no build up in the concentration of phosphate ions inside mitochondria as a result of the inward passage of phosphate ions. (2)

Answer 19

• phosphate ions are used to produce ATP
• in oxidative phosphorylation / Krebs cycle / chemiosmosis / ETC / ATP synthase.
• ATP leaves mitochondria.

Question 20

Triose phosphate moves out of chloroplasts by passing through carrier proteins that are part of the chloroplast envelope. These proteins allow an inorganic phosphate ion to pass inwards at the same time as triose phosphate moves outwards.
Suggest why the movement of triose phosphate out of chloroplasts is an example of facilitated diffusion rather than active transport. (2)

Answer 20

• Carrier / transport / transmembrane protein involved.
• Concentration of TP higher in chloroplasts (than cytoplasm).
• Product of photosynthesis / light-independent reaction / Calvin cycle.
• TP moves down concentration gradient from high to low.
• ATP not involved / no energy used.

Question 21

Many biologists believe that both mitochondria and chloroplasts evolved at an early stage in the history of the earth from prokaryotic organisms that inhabited the cytoplasm of eukaryotic host cells.
State two structural features of mitochondria and chloroplasts that are also present in prokaryotic cells. (2)

Answer 21

• Free / naked DNA: not surrounded by a membrane / envelope.
• Ribosomes, smaller than those in cytosol / similar size to prokaryotic ones.
• Circular DNA / loop.
• Absence of introns.

Question 22

When plants are grown in glasshouses during autumn and winter, when the natural light intensities are low, it is important that temperatures are kept relatively low.
With reference to respiration and photosynthesis, explain why it is essential to do this. (3)

Answer 22

• Light intensity limiting factor.
• Low photosynthesis rate.
• Respiration rate increases with temperature.
• Respiration rate close to the rate of photosynthesis.
• Net primary productivity is lower / sugars broken down more quickly than they are formed.

Question 23

Describe how a simple respirometer is assembled and then used to measure respiration rates. (8)

Answer 23

• Suitable material eg maggots, seeds;
• Use of inert material for control eg glass beads;
• Suitable quantity eg same mass organism and inert substance;
• Absorbent for CO2;
• Manometer or equivalent for measuring;
• Workable respirometer;
• Equilibration for temp/maggots to acclimate;
• Allow for expansion of air;
• Screw clips kept open at this point;
• Insertion of liquid dye;
• Movement of liquid indicates uptake of O2;
• Distance measured;
• Repeat readings;
• Mean taken;
• Manometer zeroed between readings/explained/use of syringe;
• Volume of O2 consumed calculated NB need diameter/radius of capillary tube;
• Remove soda lime and repeat;
• Now measure difference between O2 uptake and CO2 produced;
• RQ formula;

Question 24

What is the RQ (Respiratory Quotient) of glucose?

Answer 24

1, (6CO2 released and 6O2 used).

Question 25

Of the following 3 substrates, which has the highest and which has the lowest respiratory quotient?

• Lipid
• Protein
• Glucose

Answer 25

Glucose = 1.0 (highest)
Protein = 0.9
Lipids = 0.7 (lowest)

Question 26

Explain how the stoma open and close. (2)

Answer 26

• Sodium moves into guard cells and water follows (via osmosis) resulting in increased turgor, and stoma opening.
• Active process.

Question 27

Where does most of a plant’s biomass come from? (1)

Answer 27

CO2 in the air and water in the soil.

Question 28

At midday, what is happening in the leaf of a plant? (1)

Answer 28

Mainly photosynthesis and some respiration.

Question 29

At midnight, what is happening in the leaf of a plant? (1)

Answer 29

Only respiration.

Question 30

In which organisms does photosynthesis happen? (1)

Answer 30

Plants.