3.5.2 Respiration

Question 1

Name the 4 main stages in aerobic respiration and where they occur

Answer 1

Glycolysis - cytoplasm
Link reaction - mitochondrial matrix
Krebs cycle - mitochondrial matrix
Oxidative phosphorylation - via ETC membrane of cristae

Question 2

Outline the stages of glycolysis

Answer 2

1. Glucose is phosphorylated to glucose phosphate by 2x ATP
2. Glucose phosphate splits into 2x TP
3. 2x TP is oxidised to 2x pyruvate
   Net gain of 2x NADH and 2x ATP per glucose

Question 3

Draw flowchart for glycolysis

Answer 3

Google/notes

Question 4

How does pyruvate from glycolysis enter the mitochondria

Answer 4

Active transport

Question 5

What happens during the link reaction

Answer 5

1. Oxidation of pyruvate to acetate
   per pyruvate molecule: net gain of 1xCO2 (decarboxylation) and 2H used to reduce NAD
2. Acetate combines with CoA to form acetylcoenzyme A

Question 6

Summery equation for link reaction

Answer 6

pyruvate + NAD + CoA –>
acetyl CoA + NADH + Co2

Question 7

What happens in the krebs cycle

Answer 7

series of redox reactions produces
ATP by substrate level phosphorylation
Reduced coenzymes
CO2 from decarboxylation

Question 8

Outline the stages of the krebs cycle

Answer 8

google/notes

Question 9

What is the ETC

Answer 9

Series of carrier proteins embedded in the membrane of the cristae of mitochondria
Produces ATP through oxidative phosphorylation via chemiosmosis during aerobic respiration

Question 10

What happens in the ETC

Answer 10

Electrons released from NADH and FADH undergo successive redox reactions
The energy releases is coupled to maintaining the proton gradient or released as heat
Oxygen acts as final electron acceptor

Question 11

How is a proton conc gradient established during chemiosmosis in aerobic respiration

Answer 11

Some energy released from the ETC is coupled to the active transport of H+ ions (protons) from the mitochondrial matrix into the intermembrane space

Question 12

How does chemiosmosis produce ATP during aerobic respiration

Answer 12

Protons move down their conc gradient from the intermembrane space into the mitochondrial matrix via the channel protein ATP synthase
ATP synthase catalyses ADP + Pi –> ATP

Question 13

State the role of oxygen in aerobic respiration

Answer 13

Final electron acceptor in the ETC

Question 14

What is the benefit of an ETC rather than a single reaction

Answer 14

Energy is released gradually
Less energy is released as heat

Question 15

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

Answer 15

Amino acids from proteins
Glycerol and fatty acids from lipids

Question 16

How can lipids act as an alternative respiratory substrate

Answer 16

Lipid –> glycerol and fatty acids
1. Phosphorylation of glycerol –> TP for glycolysis
2. Fatty acid —> acetate
a) acetate enters link reaction
b) H atoms produced for oxidative phosphorylation

Question 17

How can amino acids act as an alternative respiratory substrate

Answer 17

Deamination produces
1. 3C compounds –> pyruvate for link reaction
2. 4/5C compounds –> intermediates in krebs cycle

Question 18

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

Answer 18

Glycolysis (anaerobic)
Krebs cycle (aerobic)

Question 19

What happens during anaerobic respiration in animals

Answer 19

Only glycolysis continues
NADH + Pyruvate –> NAD + lactate

Question 20

What happens to the lactate produced in anaerobic respiration

Answer 20

Transported to liver via bloodstream, where it is oxidised to pyruvate
Can enter link reaction in liver cells or be converted to glycogen

Question 21

What happens during anaerobic respiration in some microorganisms eg yeast and some plant cells

Answer 21

Only glycolysis continues
Pyruvate is decarboxylated to form ethanal
Ethanal is reduced to ethanol using NADH to produced NAD for further glycolysis

Question 22

Draw a flowchart to show how ethanol is produced during anaerobic respiration

Answer 22

google/notes

Question 23

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

Answer 23

Converts NADH back into NAD do glycolysis can continue

Question 24

What is the disadvantage of producing ethanol during anaerobic respiration

Answer 24

Cells die when ethanol conc is above 12%
Ethanol dissolves cell membranes

Question 25

What is the disadvantage of producing lactate during anaerobic respiration

Answer 25

Acidic, so decreases pH
Results in muscle fatigue

Question 26

Compare aerobic and anaerobic respiration

Answer 26

Both involve glycolysis
Both require NAD
Both produce ATP

Question 27

Contrast aerobic and anaerobic respiration

Answer 27

Aerobic - produces ATP by substrate-level phosphorylation and oxidative phosphorylation
Produces much more ATP
Doesnt produce ethanol or lactate

Anaerobic - substrate level phosphorylation only
Produces fewer ATP
Produces ethanol or lactate

Question 28

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

Answer 28

1. Use respirometer (pressure changes in boiling tube cause a drop of coloured liquid to move)
2. Use a dye as the terminal electron acceptor for the ETC

Question 29

What is the purpose of sodium hydroxide solution in a respirometer set up to measure the rate of aerobic respiration

Answer 29

Absorbs the CO2 so that there is a net decrease in pressure as O2 is consumed

Question 30

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

Answer 30

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 pie