Respiration simplified:

Question 1

What does respiration produce?

Answer 1

ATP needed for other metabolic reactions.

Question 2

What is an respiration controlled by? What is it sensitive to?

Answer 2

It is an enzyme controlled reaction. It is sensitive to temperature and pH changes.

Question 3

What is broken down to release ATP in respiration?

Answer 3

Glucose, glycogen in animals and starch in plants.

Other respiratory substrate can be used if no stores of these are available.

Question 4

What are lipids hydrolysed to?

Answer 4

Glycerol and fatty acids.

Glycerol is further phosphorylated into triose phosphate and enters aerobic respiration at Krebs cycle.

Question 5

How are amino acids hydrolysed?

Answer 5

Amino group is removed - deamination.

Remaining carbon compound enters the Krebs cycle.

Question 6

What are the four stages of aerobic respiration?

Where does each take place?

Answer 6

Glycolysis - cytoplasm
Link reaction - mitochondrial matrix
Krebs cycle - mitochondrial matrix
Oxidative phosphorylation - cristae

Question 7

What are the 3 key stages of glycolysis?

Answer 7

1. Substrate level phosphorylation - two phosphate groups (from 2 ATP) added to glucose.
2. Phosphorylation - makes glucose-2-phosphate unstable and splits it into 2 x triose phosphate (3C).
3. TP molecules are oxidised to form 2 x pyruvate molecules by removing H from each - H picked up by 2 x NAD to become NADH - releases 4 ATP.

Question 8

Glycolysis

Answer 8

• does not require oxygen
• occurs in cytoplasm
• aerobic and anaerobic

Question 9

What does glycolysis produce?

Answer 9

2 NADH - actively transported to mitochondrial matrix.
2 pyruvate - actively transported to mitochondrial matrix.
Net gain of 2 ATP.

Question 10

Briefly describe the link reaction:

Answer 10

Converts pyruvate into acetyl CoA.

Question 11

How many carbons does pyruvate contain and how does this compare to acetyl CoA?

What does this mean?

Answer 11

Pyruvate - 3 carbons
Acetyl CoA - 2 carbons

So a carbon is removed in this stage in the form of carbon dioxide - decarboxylation.

Question 12

Describe the process of the link reaction:

Answer 12

• Decarboxylation.
• 2 hydrogen atoms removed to oxidise carbon - creates acetate.
• NAD + H = NADH
• CoA combines with acetate to make acetyl CoA.

Question 13

How many times does the link reaction happen per glucose molecule - why?

Answer 13

Twice as there are 2 pyruvate molecules.

Question 14

Overall products from link reaction per glucose molecule?

Answer 14

2 acetyl CoA
2 carbon dioxide
2 reduced NAD

Question 15

What reaction happens to acetyl CoA before the Krebs cycle?

Answer 15

Acetyl CoA reacts with 4C molecule. Releases coenzyme A and produces a 6C molecule that enters Krebs cycle.

Question 16

What is the Krebs cycle also known as?

Answer 16

Citric acid cycle

Question 17

What does the Krebs cycle generate? How?

Answer 17

6 NADH
2 FADH
2 ATP by substrate-level phosphorylation

In a series of oxidation-reduction reactions.

Question 18

How many carbon dioxide are lost during the Krebs cycle?

Answer 18

4

Question 19

What is the final stage of aerobic respiration?

Answer 19

Oxidative Phosphorylation

Question 20

At what stage of aerobic respiration is the most ATP synthesised and most oxygen used?

Answer 20

Oxidative phosphorylation

Question 21

Briefly, what happens during oxidative phosphorylation?

Answer 21

• Reduced coenzymes release hydrogens - split into H ions and e-
• e- pass down ETC in inner mitochondrial membrane and lose energy as they move.
• Energy released pumps protons from MM into intermembrane space.
• Creates electrochemical gradient across membrane.
• So protons move back into matrix via ATP synthase - making ATP - CHEMIOSMOSIS.
• O2 is terminal electron acceptor and combines electrons and protons - making water.

Question 22

Anaerobic respiration in plants and microbes:

What does this do?

Answer 22

Pyruvate produced in glycolysis is reduced to form 2 ethanol by gaining the H from reduced NAD.

Oxidises NAD so it can be reused in glycolysis to make more ATP.

Question 23

Anaerobic respiration in animals:

Answer 23

Pyruvate produced in glycolysis is reduced to form
2 lactate by gaining the H from reduced NAD.

Oxidises NAD so it can be reused in glycolysis to make more ATP.

Question 24

What is the yield of ATP from 1 reduced NAD and 1 reduced FAD? (aerobic)

So what is the total yield of ATP from one glucose molecule?

Answer 24

1 reduced NAD = 3 ATP molecules

1 reduced FAD = 2 ATP molecules

38 molecules of ATP in total.

Question 25

What is the efficiency of aerobic respiration?

Why?

Answer 25

Approximately 32% efficient.

Due to some protons leaking across the MM during OP, ATP being used to actively transport pyruvate and NADH into the matrix, and because some energy is lost as heat.

Question 26

What is less efficient - aerobic or anaerobic respiration?

Answer 26

Anaerobic - as only 2 ATP molecules are produced from one glucose molecule.