Respiration

Question 1

Name the 4 stages of Aerobic respiration

Answer 1

Glycolysis: Cytoplasm

Link reaction: Mitochondrial Matrix

Krebs cycle: Mitochondrial Matrix

Oxidative phosphorylation via electron transfer chain: Membrane of Cristae

Question 2

Outline the stages of glycolysis

3

Answer 2

1. Glucose is phosphorylated to glucose phosphate by 2x ATP
2. Glucose phosphate splits into 2x triose phosphate (TP)
3. 2x TP is oxidised to 2x Pyruvate

Net gain of 2x reduced NAD & 2x ATP per glucose.

Question 3

Draw a flowchart to represent what happens during glycolysis

Answer 3

Compare to diagram

Question 4

How does pyruvate from glycolysis enter the mitochondria?

Answer 4

Via active transport

Question 5

What happens during the link reaction?

Answer 5

1. Oxidation of pyuravate to acetate.

Per pyruvate molecule: net gain of 1xCO₂ (decarboxylation) & 2H atoms (used to reduce
1x NAD)

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

Question 6

What are the two types of cellular respiration

Answer 6

Aerobic respiration - Requires oxygen and produces carbon dioxide, water and much ATP

Anaerobic respiration - takes place in the absence of oxygen and produces lactate (in animals) or ethanol and carbon dioxide (in plants and fungi) only little ATP

Question 7

Glycolysis

Answer 7

The splitting of the 6-carbon glucose molecule into two 3-carbon pyruvate molecules

Question 8

Link reaction

Answer 8

The 3-carbon pyruvate molecules enter into series of reactions which lead to the formation of acetylecoenzyme A, a 2-carbon molecule.

Question 9

Give a summary equation for the link reaction.

Answer 9

pyruvate + NAD + CoA

→

acetyl CoA + reduced NAD + Co₂

Question 10

Krebs cycle

Answer 10

The introduction of acetyl coenzyme A into a cycle of oxidation-reduction that yield some ATP and a large quantity of reduced NAD and FAD.

Question 11

What happens in the Krebs cycle?

Answer 11

Series of redox reactions produces:

• ATP by substrate-level phosphorylation
• Reduced coenzymes.
• Co₂ from decarboxylation

Question 12

Oxidative phosphorylation

Answer 12

The use of the electrons associated with reduced NAD and FAD, released from the Krebs cycle to synthesise ATP with water produced as by-product.

Question 13

What is the electron transfer chain (ETC)?

Answer 13

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

Produces ATP through oxidate phophorylation via chemiosmosis during aerobic respiration.

Question 14

What happens in the electron transfer chain (ETC)?

Answer 14

Electron released from reduced NAD & FAD undergo successive redox reactions>

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

Oxygen acts as final electron acceptor.

Question 15

How is a proton concentration gradient establushed during chemiosmosis in aerobic respiration>

Answer 15

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

Question 16

How does chemiosmosis produce ATP during aerobic respiration>

Answer 16

H⁺ ions (protons) move down their concentration gradient from intermembrane space into mitochondrial matrix via the channel protein ATP synthase.

ATP synthase catalyses ADP + Pi → ATP

Question 17

State the role of oxygen in aerobic respiration.

Answer 17

Final electron acceptor in electron transfer chain.

Prodcues water as a byproduct

Question 18

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

Answer 18

• Energy is released gradually

- Less energy is released as heat.

Question 19

Name 2 types of molecule that can be used as alternative respiratiory substrates.

Answer 19

• (Amino acids from) proteins

- (Glycerol and fatty acids from) lipids

Question 20

How can lipids act as an alternative respiratory substrate>

Answer 20

Lipid → glycerol + 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 21

How can amino acids act as an alternative respiratory substrate?

Answer 21

Deamination produces:

1. 3C Compounds → pyruvate for link reaction,
2. 4C/5C compounds → intermediates in Kerbs cycle.

Question 22

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

Answer 22

Glycolysis (anaerobic)
Krebs cycle (aerobic)

Question 23

What happens during anaeobic respiration in animals?

Answer 23

Only glycolysis continues
Reduced NAD + pyrvuate

Oxidised NAD (for further glycolysis) + lactate

Pyruvate acts as hydrogen acceptor

↓ reduced Nad
↪ Oxidised NAD

lactate

Refer to PM

Question 24

What happens to the lactate produced in anaerobic respiration?

Answer 24

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

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

Question 25

What happens during anaerobic respirtation in some microorganis e.g yeast and some plants cells?

Answer 25

Only glycolysis continues,

Pyruvate is decarboxylated to form ethanal.

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

Question 26

Draw a flowchart to show how ethanol is prduced during anaerobic respiration.

Answer 26

Pyruvate

decarboxylation 
                           ↓ ↪  Co₂
                     ethanal 
Reduction         ↓    reduced NAD
                              ↪ oxidised NAD
                 ethanol

Refer to PM

Question 27

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

Answer 27

Converts reduced NAD back into NAD so glycolysis can continue

Question 28

What is the disadvantage of producing ethanol during anerobic respiration?

Answer 28

• Cells die when ethanol concentration is above 12%

- Ethanol dissolves cell membranes

Question 29

What is the disadvantage of producing lactate during anaerobic respiration?

Answer 29

Acidic, so decreases pH

Results in muscle fatigue.

Question 30

Compare aerobic and anaerobic respiration.

Answer 30

• Both involve glycolysis
• Both require NAD
• Both produce ATP

Question 31

Constrast aerobic and anaerobic respiration

Answer 31

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 32

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

Answer 32

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 33

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

Answer 33

Absorb CO₂ so that there is a net decrease in pressure as O₂ is not consumed.

Question 34

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

Answer 34

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