Respiration

Question 1

Why do organisms need to respire

Answer 1

Energy needed for:
- Active transport
- Metabolic reactions
- Muscle contraction

Question 2

Describe the structure of a mitochondrion

Answer 2

Surrounded by a double membrane

Folded inner membrane forms cristae

Fluid matrix

Question 3

Name the stages in aerobic respiration and where they occur

Answer 3

Glycolysis - Cytoplasm
Link reaction - matrix
Krebs cycle - Matrix
Oxidative phosphorylation - cristae

Question 4

Outline the stages of glycolysis

Answer 4

Glucose phosphorylated to hexose bisphosphate by 2xATP

Hexose bisphosphate splits into 2x triose phosphate

2x TP is oxidised to 2x pyruvate

Net gain of 2x reduced NAD and 2x ATP per glucose

Question 5

How does pyruvate from glycolysis enter the mitochondria

Answer 5

Via active transport

Question 6

What happens during the link reaction

Answer 6

Decarboxylation of pyruvate to acetate: Net gain of 1x CO2 + 1NADH

Acetate combines with CoA to form acetylcoenzyme A

Question 7

Give a summary equation for the link reaction

Answer 7

pyruvate + NAD + CoA
———>
Acetyl CoA + reduced NAD + CO2

Question 8

What happens in the krebs cycle

Answer 8

Acetyl coenzyme A acts as a carrier
It reacts with oxaloacetate to produce citrate

Citrate is converted to a Five carbon molecule by decarboxylation and dehydrogenation
CO2 and NADH is produced

Five carbon molecule is dehydrogenated and decarboxylated to a four carbon structure
CO2 and NADH produced
ATP produced by substrate level phosphorylation

4c molecule is dehydrogenated to produce NADH and FADH

Question 9

What is the electron transfer chain

Answer 9

Series of carrier proteins embedded in membrane of the cristae of mitochondria

Produces ATP through oxidative phosphorylation via chemiosmosis during aerobic respiration

Question 10

What happens in the electron transfer chain

Answer 10

Electrons released from reduced NAD & FAD, undergo redox reactions

Energy released is coupled to maintaining proton gradient or released as heat

Oxygen acts as final electron acceptor

Question 11

How does chemiosmosis produce ATP during aerobic respiration

Answer 11

Some energy released from the ETC is coupled to active transport of H+ ions from matrix to intermembrane space

H+ ions move down the concentration gradient into mitochondrial matrix via channel protein ATP synthase

ATP synthase catalyses ADP + Pi —> ATP

Question 12

State the role of oxygen in aerobic respiration

Answer 12

Final electron acceptor in ETC

Question 13

Name the stages in respiration that produce ATP by substrate level phosphorylation

Answer 13

Glycolysis

Krebs cycle

Question 14

What happens during anaerobic respiration in animals

Answer 14

Only glycolysis continues

reduced NAD + pyruvate
——–>
oxidised NAD + lactate

Question 15

What happens during anaerobic respiration in some microorganisms

Answer 15

Only glycolysis continues

Pyruvate is decarboxylated to form ethanal

Ethanal is reduced to ethanol using reduced NAD to produce oxidised NAD for further glycolysis

Question 16

What are the benefits of being able to respire anaerobically

Answer 16

ATP production for vital metabolic processes

Ethanol/Lactate converts reduced NAD back into NAD so glycolysis can continue

Question 17

What is the respiratory quotient

Answer 17

RQ = carbon dioxide produced / oxygen consumed

Question 18

Why do different respiratory substrates have different relative energy values

Answer 18

Depends on the number of hydrogens which are oxidised to water

Question 19

What is chemiosmosis

Answer 19

The movement of ions across a membrane down an electrochemical gradient

Question 20

What is the net gain of the Krebs cycle

Answer 20

2 CO2

3 NADH

1 ATP

1 FADH2