Anaerobic Respiration

Question 1

In the absence of oxygen why cant the Krebs cycle or the ETC continue?

Answer 1

The Krebs cycle and the ETC cannot take place because all the FAD and NAD will be reduced therefore no FAD will be able to take up the H+ produced during the Krebs cycle so the enzymes will stop working

Question 2

For glycolysis to continue anaerobically what must happen to its products?

Answer 2

• pyruvate and hydrogen must be constantly removed

- hydrogen must be released from reduced NAD in order to regenerate NAD

Question 3

(Anaerobic respiration) What happens if NAD is not regenerated from reduced NAD?

Answer 3

All NAD will be reduced to reduced NAD so there will be no NAD to take up the hydrogen from glycolysis

Question 4

How is NAD replenished in anaerobic conditions?

Answer 4

The pyruvate molecule from glycolysis accepts the hydrogen for the reduced NAD, this reoxidised NAD can then be further used in glycolysis

Question 5

(Anaerobic respiration) In plants and yeast, what is pyruvate converted into?

Answer 5

Ethanol and carbon dioxide

Question 6

(Anaerobic respiration) In animals, what is pyruvate converted into?

Answer 6

Lactate

Question 7

(Anaerobic respiration) How is ethanol produced in plants?

Answer 7

The pyruvate molecule formed at the end of glycolysis loses a carbon dioxide molecule and accepts a hydrogen from reduced NAD to produce ethanol

Question 8

(Anaerobic respiration) What is the summary equation for the production of ethanol in plants?

Answer 8

Pyruvate + reduced NAD => ethanol + carbon dioxide + oxidised NAD

Question 9

(Anaerobic respiration) How is the production of ethanol in yeast exploited by the brewing industry?

Answer 9

Yeast is grown in anaerobic conditions in which it ferments natural carbohydrates in plant products such as grapes (wine production) or barley seeds (beer products) into ethanol

Question 10

(Anaerobic respiration) Where does lactate production commonly occur?

Answer 10

In muscles as a result of strenuous activity

Question 11

What happens to oxygen levels when muscles respire anaerobically due to strenuous activity?

Answer 11

Oxygen levels go into oxygen debt

Question 12

When animals respire anaerobically how is the NAD from glycolysis removed?

Answer 12

Each pyruvate molecule produced takes up two hydrogen atoms from the reduced NAD produced in glycolysis to form lactate

Question 13

(Anaerobic respiration) What is the equation for the production of lactate in anaimals?

Answer 13

Pyruvate + reduced NAD => lactate + oxidised NAD

Question 14

(Anaerobic respiration) What happens to lactate once oxygen becomes available again?

Answer 14

The lactate is oxidised back to pyruvate which can then be further oxidised to release energy or converted into glycogen

Question 15

(Anaerobic respiration) What does lactate cause if left to accumulate in muscle tissues?

Answer 15

Cramp and muscle fatigue

Question 16

(Anaerobic respiration) Does lactate effect enzymes?

Answer 16

Yes the pH change will affect enzymes

Question 17

(Anaerobic respiration) Where is the lactate converted to glycogen?

Answer 17

The liver

Question 18

(Anaerobic respiration) In what two ways is energy from cellular respiration derived?

Answer 18

• substrate level phosphorylation

- oxidative phosphorylation

Question 19

(Anaerobic respiration) How is energy derived from substrate level phosphorylation?

Answer 19

In glycolysis and the Krebs cycle, phosphate is directly transferred from a respiratory intermediate to ADP to produce ATP

Question 20

(Anaerobic respiration) How is energy derived from oxidative phosphorylation?

Answer 20

In the ETC, energy is indirectly linked from phosphate to ADP to produce ATP, the energy involved is from the hydrogen atoms that are carried of NAD and FAD, cells produce most of their ATP in this way

Question 21

(Anaerobic respiration) In which way is most of energy derived from cellular respiration?

Answer 21

In oxidative phosphorylation

Question 22

Why is cyanide a very potent poison?

Answer 22

It is a non-competitive inhibitor of the final enzyme in the ETC

Question 23

What is the final enzyme in the ETC?

Answer 23

The cytochrome oxidase enzyme, which catalyses the addition of hydrogen ions and electrons to oxygen to produce water

Question 24

What happens when the cytochrome oxidase enzyme is inhibited?

Answer 24

Hydrogen ions and electrons accumulate on their carrier molecules bringing the ETC and the Krebs cycle to a halt

Question 25

How can cyanide be used to determine where some of the respiratory pathways occur in the cell?

Answer 25

• Mammalian liver cells are broken up (homogenized) and the resulting homogenize is centrifuge
• portions containing the nucleus, ribosomes, mitochondria and remaining cytoplasm are separated out and samples of each with the homogenate were incubated with glucose, glucose and cyanide, pyruvate and cyanide and pyruvate