B12 Respiration

Question 1

Name the 4 main stages in Aerobic respiration and where they occur.

Answer 1

Glycolysis - cytoplasm

Link reaction - matrix of mitochondria

Krebs cycle - Matrix of mitochondria

Oxidative Phosphorylation (via electron transfer chain) -membrane of Cristae

Question 2

Outline the stages of glycolysis.

Answer 2

. Glucose is phosphorylated to phosphorylated glucose by 2 ATP

. phosphorylated glucose splits to 2x triose phosphate

. 2x Triose phosphate is oxidised to 2x pyruvate
Net gain of 2x NADH and 2x ATP per glucose

Question 3

How does pyruvate from glycolysis enter the mitochondria?

Answer 3

Via Active Transport

Question 4

What happens during the link reaction?

Answer 4

. 2x Pyruvate (3C) is oxidised to 2x Acetate (2C), with the loss of 2x CO2 and 2H+ are lost and reduce NAD to form reduced NAD (decarboxylation)

. Acetate (2C) combines with coenzyme A (CoA) to form Acetyl coenzyme A

Question 5

What happens during the link reaction?

Answer 5

. 2x Pyruvate (3C) is oxidised to 2x Acetate (2C), with the loss of 2x CO2 and 2H+ are lost and reduce NAD to form reduced NAD (decarboxylation)

. Acetate (2C) combines with coenzyme A (CoA) to form Acetyl coenzyme A

Question 6

Summary equation of link reaction.

Answer 6

Pyruvate + NAD + CoA -> Acetyl CoA + reduced NAD + CO2

Question 7

What happens in the Krebs Cycle?

Answer 7

Series of redox reactions produce:
. ATP by substrate-level phosphorylation
. Reduced coenzymes
. CO2 from decaroboxylation

Question 8

What is the ETC?

Answer 8

Series of carrier proteins embedded in in membrane of the Cristae of the mitochondria.

Produces ATP through oxidative phosphorylation via chemiosmosis during Aerobic respiration.

Question 9

What happens in the ETC?

Answer 9

Electrons released from reduced NAD & FAD undergo successive redox reactions.

The energy released is couples to maintaining proton gradient or released as heat.

Oxygen acts as final electron acceptor.

Question 10

How is a proton concentration gradient established during chemi-osmosis in aerobic respiration?

Answer 10

Some energy released from ETC is coupled to the active transport of H+ from the mitochondrial matrix into the inter-membrane space.

Question 11

How does chemiosmosis produce ATP during aerobic respiration?

Answer 11

H+ move down their concentration gradient from the inter-membrane space into the mitochondrial matrix via the 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 electron transfer chain.

(Produces water as a bi-product)

Question 13

What is the benefit of an electron transfer chain rather than a single reaction?

Answer 13

Energy is released gradually

Less energy is released as heat

Question 14

Name 2 types of molecules that can be used as an alternative respiratory substrates.

Answer 14

Amino acids from proteins

Glycerol and fatty acids from lipids

Question 15

How can lipids act as an alternative respiratory substrate?

Answer 15

Lipid -> glycerol + fatty acids

• phosphorylation of glycerol -> TP for glycolysis
• fatty acids -> acetate
  a) acetate enters link reaction
  b) H atoms produced for oxidative phosphorylation

Question 16

How can amino acids act as an alternative respiratory substrate?

Answer 16

Deaminating produces:

3C compounds -> pyruvate for link reaction

4C/5C compounds -> intermediates in Krebs cycle

Question 17

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

Answer 17

Glycolysis (anaerobic)

Krebs cycle (aerobic)

Question 18

What happens to the lactate produced in anaerobic respiration?

Answer 18

Transported to liver via bloodstream, where it is oxidised to pyruvate.

Can enter link reaction in liver cells or be converted to glycogen.

Question 19

What happens during anaerobic respiration in some microorganisms e.g. Yeast and some plant cells?

Answer 19

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 20

What is the advantage of producing ethanol/lactate during anaerobic respiration?

Answer 20

Converts reduced NAD back into NAD so glycolysis can continue.

Question 21

What is the disadvantage of producing ethanol during anaerobic respiration?

Answer 21

Cells die when ethanol concentration is above 12%

Ethanol dissolves cell membranes

Question 22

What is the disadvantage of producing lactate during anaerobic respiration?

Answer 22

Acidic, so decreases pH

Results in muscle fatigue

Question 23

Compare aerobic and anaerobic respiration.

Answer 23

Both:

Involve glycolysis

Require NAD

Produce ATP

Question 24

Contrast aerobic and anaerobic respiration.

Answer 24

Aerobic:

• produces ATP by substrate-level phosphorylation and oxidative phosphorylation
• produces much more ATP
• does not produce ethanol or lactate

Anaerobic:

• substrate level phosphorylation only
• produces fewer ATP
• produces ethanol or lactate

Question 25

Suggest how a student could investigate the effect of a names variable on the rate of respiration of a single-celled organism.

Answer 25

Use respirometer (pressure changes in boiling tube cause a drop of coloured liquid to move)

Use dye as the terminal electron acceptor for the ETC.

Question 26

What is the purpose of NaOH in a respirometer set up to measure the rate of aerobic respiration?

Answer 26

Absorbs CO2 so that there’s a net decrease in pressure as O2 is consumed.

Question 27

How could a student calculate the rate of respiration using a respirometer?

Answer 27

Volume of O2 produced or CO2 consumed/ time x mass of sample

Volume = distance moved by coloured drop x (0.5 x capillary tube diameter)^2 x π

Question 28

What are the 4 stages of aerobic respiration and where do they occur

Answer 28

Glycolysis (cytoplasm)

Link reaction (mitochondrial matrix)

Krebs Cycle (mitochondrial matrix)

Oxidative phosphorylation (mitochondrial inner membrane-cristae)

Question 29

What does respiration produce

Answer 29

ATP

Question 30

What stage occurs in both anaerobic and aerobic respiration

Answer 30

Glycolysis is the first stage of anaerobic and aerobic respiration.

It occurs in the cytoplasm and is an anaerobic process.

Question 31

What are the 3 steps glycolysis involves

Answer 31

1. Phosphorylating glucose to glucose phosphate, using ATP
2. The production of triose phosphate
3. Oxidation of triose phosphate to produce pyruvate with a net gain of ATP and reduced NAD.

Question 32

What’s are the products of glycolysis

Answer 32

2 pyruvate

Net gain of 2 ATP

2 NADH

Question 33

What happens to pyruvate and NADH after they are procured in glycolysis

Answer 33

Pyruvate and NADH are actively transported from the cytoplasm into the mitochondrial matrix

Question 34

What happens in the link reaction

Answer 34

The pyruvate made in glycolysis is oxidised to acetate.
NAD picks up the hydrogen and becomes reduced NAD
Acetate the combines with coenzyme A in to produce acetylcoenzyme A

Question 35

What does the link reaction Produce if it occurs twice for every glucose molecule

Answer 35

2 x Acetyl CoA
2 CO2 released
2 reduced NAD

Question 36

What happens in the Krebs cycle

Answer 36

Acetyl-CoA reacts with a 4 carbon molecule, releasing coenzyme A and producing a 6 carbon molecule that enters the Krebs cycle

In a series of Redox reactions, the Krebs cycle generates reduced coenzymes and ATP by substrate-level phosphorylation, and carbon dioxide is lost

Question 37

What are the products per cycle of the Krebs suckle

Answer 37

3 x reduced NAD I x reduced FAD
1 x ATP
2 x CO2

Question 38

What does the Krebs cycle produce per glucose molecule

Answer 38

6 x reduced NAD
2 x reduced FAD
2 × АТР
4 x CO2

Question 39

What stage is ATP produced the most

Answer 39

Oxidative phosphorylation

Question 40

What does oxidative phosphorylation involve

Answer 40

The electron transfer chain

Movement of protons across the inner mitochondrial
membranes

Catalysed by ATP synthase

Question 41

When does anaerobic respiration occur

Answer 41

In the absence of oxygen

Question 42

Where does anaerobic respiration occur

Answer 42

In the cytoplasm only

Question 43

What happens in anaerobic respiration

Answer 43

The pyruvate produced in glycolysis is reduced to form ethanol and carbon dioxide (in plants and microbes) or lactate (in animals) by gaining the hydrogen from reduced NAD.

This oxidises NAD so that it can be reused in glycolysis and ensure more ATP is continued to be produced.

Question 44

Anaerobic respiration in animals

Answer 44

The pyruvate produced in glycolysis is reduced to form lactate in animals by gaining the hydrogen from reduced NAD.

This oxidises NAD so that it can be reused in glycolysis and ensure more ATP is continued to be produced.

Question 45

Anaerobic respiration in plants

Answer 45

The pyruvate produced in glycolysis is reduced to form ethanol and carbon dioxide in plants and microbes gaining the hydrogen from reduced NAD.

This oxidises NAD so that it can be reused in glycolysis and ensure more ATP is continued to be produced.

Question 46

Efficiency of anaerobic respiration

Answer 46

One reduced NAD can result in a yield of 3 ATP molecules, whereas I reduced FAD can result in a yield of 2 ATP molecules.

Therefore, the total yield of ATP from one glucose molecule in aerobic respiration should be 38 molecules of ATP. Aerobic respiration is approximately 32% efficient. This is due to some protons leaking across the mitochondrial membrane during oxidative phosphorylation, ATP being used to actively transport pyruvate and NADH into the matrix and because some energy is lost as heat.

Anaerobic respiration is even less efficient, because only 2 ATP molecules and produced from one glucose molecule.