respiration

Question 1

Water is a waste product of aerobic respiration. Describe how water is formed at the end of aerobic respiration.

Answer 1

• oxygen is terminal/final electron acceptor;
• combines with electrons and protons (to form water);

Question 2

Explain how the amount of ATP is increased by reactions occurring inside a mitochondrion.

Answer 2

• oxidation of/removal of electrons and H+
• from pyruvate
• acetyl CoA / 6 carbon compound; (credit oxidative decarboxylation)
• substrate level production of ATP / ATP produced in Krebs cycle;
• production of reduced NAD / FAD (allow they take up hydrogen);
• in matrix of mitochondria;
• electrons fed into electron transport chain / used in oxidative
• (Electrons) pass along carriers/through electron transport chain/through series of redox reactions;
• Energy released;
• Protons move into intermembrane space;
• ADP/ADP + Pi;
• ATP synthase;

Question 3

Describe the roles of the coenzymes and carrier proteins in the synthesis of ATP.

OR

Describe the events of oxidative phosphorylation

Answer 3

• NAD/FAD reduced / hydrogen attached to NAD/FAD;
• H+ ions/electrons transferred from coenzyme to coenzyme/carrier to carrier (ETC on cristae of inner membrane)
• Energy released (from electrons) through series of redox reactions;
• Energy released used to pump H+/ protons into intermembrane space;
• H+/ protons flow back through ATP synthase to produce ATP from ADP and phosphate.

Question 4

The mitochondria in muscles contain many cristae. Explain the advantage of this.

Answer 4

• larger surface area for electron carrier system / oxidative phosphorylation;
• provide ATP / energy for contraction;

Question 5

Give two reasons why the respirometer was left for 10 minutes when it was first placed in the water bath.

Answer 5

• Equilibrium reached;
• Allow for expansion/pressure change in apparatus;
• Allow respiration rate of seeds to stabilise;

Question 6

Explain why a log scale is used to record the number of cells/bacteria.

Answer 6

• Large range/difference/increase in numbers;
• Accept reference to exponential (increase)

Question 7

Explain why converting pyruvate to lactate allows the continued production of ATP by anaerobic respiration.

Answer 7

• Regenerates NAD / Oxidises reduced NAD;
• (So) glycolysis continues;

Question 8

describe how ATP is made in the mitochondria

Answer 8

ATP is produced in the Krebs cycle
link reaction produces reduced NAD
e- released from reduced NAD
e- pass along electron transport chain
through a series of reactions
energy released
ATP from ADP + Pi
ATP synthase

Question 9

anaerobic respiration

Answer 9

the link/krebs and e- transport chain stop as there is no O2 to act as the final electron acceptor
glycolysis doesn’t require o2 and can continue in the absence of o2
but for glycolysis to continue NAD must be regenerated
H from reduced NAD in glycolysis is accepted by pyruvate
pyruvate is now reduced to lactate in animals and ethanol & CO2 in plants