Topic 5 A: Respiration

Question 1

When is ATP broken down?

Answer 1

The breakdown of ATP, from glucose, occurs during respiration.

Question 2

Glycolysis simple summary?

Answer 2

• splits one molecule of glucose into smaller molecules of pyruvate
• doesn’t require oxygen - its an anaerobic process
• takes place in cytoplasm of cells because glucose cannot cross the outer mitochondrial membrane

Question 3

Stage one of glycolysis?

Answer 3

Phosphorylation of glucose:
- 2 phosphate molecules added to glucose to form fructose biphosphate (or glucose phosphate), which is unstable.
- 2 ATP molecules hydrolysed to allow this to occur.

Question 4

Stage two of glycolysis?

Answer 4

Production of triosephsophate:
- splitting occurs because glucose phosphate is unstable ( due to 6C) into 2 triosephosphate molecules with 3C and 1 phosphate.

Question 5

Stage three of glycolysis?

Answer 5

Oxidation of triosephosphate:
- one NAD (coenzyme) gains hydrogen from each TP molecule (2 in total)
- TP is oxidised (lost hydrogen) and NAD is reduced (NADH+)
- (2) pyruvate molecules created

Question 6

Final products of glycolysis?

Answer 6

• 2 pyruvate
• 2 NADH
• 2 ATP (net gain - used 2 at the beginning)

Question 7

Exam question : Describe the process of glycolysis? (4)

Answer 7

1. phosphorylation of glucose occurs using ATP
2. splits into 2 TP and is oxidised to form pyruvate
3. NADH created
4. net gain of 2 ATP

Question 8

How does pyruvate reach the link reaction?

Answer 8

Actively transported into mitochondrial matrix for this stage (using transport protein)

Question 9

Overall function of the link reaction?

Answer 9

Converts 2 pyruvate molecules into acetyl co-enzyme A (acetyl Co-A)

Question 10

Overall equation of the link reaction?

Answer 10

pyruvate + NAD + CoA = acetyl Co-A + reduced NAD + CO2

Question 11

Link reaction process?

Answer 11

1. pyruvate oxidised (lost H) into acetate, H lost is picked up by NAD x2 (reduced)
   (the loss of hydrogen is known as dehydrogenation)
2. pyruvate is a 3C molecule, acetate is 2C. Pyruvate loses one C in form of CO2 (decarboxylation)
3. acetate converts into acetyl Co-A by reacting with co enzyme A

Question 12

Krebs cycle process - Part one - The creation of citrate

Answer 12

1. acetyl CoA comes from link reaction
2. acetyl CoA reacts with oxaloacetate to create six-carbon citrate
3. citrate then converted back into oxaloacetate through series of small reactions, cycle repeats
4. CoA back into link reaction after citrate is formed
   - the purpose of acetyl CoA is to bring acetate into the krebs cycle

Question 13

Krebs cycle process - Part two - Formation of 5 carbon compound

Answer 13

1. citrate converted into 5C compound
2. this happens because decarboxylation (loss of CO2) and dehydrogenation occurs (NAD to NADH)
3. intermediate compound (5C) formed.

Question 14

Krebs cycle process - Part three - Regeneration of 4 carbon compound

Answer 14

1. decarboxylation and dehydrogenation of intermediate compound occurs
2. one molecule of reduced FAD is produced from FAD
3. two molecules of reduced NAD is produced from NAD

Question 15

Krebs cycle process - Part four - Production of ATP

Answer 15

1. produced by the direct transfer of a phosphate group
2. direct transfer known as substrate-level phosphorylation

Question 16

Products of the krebs cycle?

Answer 16

• 1 CoA
• 1 oxaloacetate
• 2 CO2
• 1 ATP
• 3 reduced NAD
• 1 reduced FAD

Question 17

Where does oxidative phosphorylation take place?

Answer 17

• in the cristae

Question 18

Oxidative phsophorylation simple definition?

Answer 18

• when energy carried by electrons and reduced co-enzymes (NAD and FAD) are used to make ATP

Question 19

Part one of oxidative phosphorylation?

Answer 19

• reduced NAD and FAD lose hydrogen atoms (oxidised)
• hydrogen atoms split into protons (H+) and electrons (e-)

Question 20

Part two of oxidative phosphorylation?

Answer 20

• electrons are embedded within the inner membrane
• they then pass along electron transfer chain, and every time an electron moves to the next protein, it releases enough energy to transport a proton to the inner membrane space
• this occurs via active transport
• the movement of H+ ions from low to high creates electrochemical gradient

Question 21

Part three of oxidative phosphorylation?

Answer 21

• protons move back down the electrochemical gradient from inner membrane to the matrix via ATP synthase.
• this occurs through facilitated diffusion
• this drives ATP synthesis (ADP+Pi)

Question 22

Why is this process described as being oxidative?

Answer 22

• protons + electrons + oxygen = water
• oxygen = final electron acceptor

Question 23

What would happen if oxygen wasn’t present?

Answer 23

• reduced co-enzymes cannot be oxidised to regenerate NAD and FAD
• protons wouldnt be transported across the membrane and no electrochemical gradient will form
• no more electrons would be able to move down the chain
• ATP not synthesised

Question 24

ATP reference point for aerobic respiration processes?

Answer 24

• 2.5 ATP made from each reduced NAD
• 1.5 ATP made from each reduced FAD

Question 25

How much ATP made during glycolysis?

Answer 25

product = 2 ATP & 2 NADH - 7 ATP

Question 26

How much ATP made during link reaction?

Answer 26

product = 2 NADH - 5 ATP

Question 27

How much ATP made during krebs cycle?

Answer 27

product = 2 ATP & 6 NADH & 2 FADH - 20 ATP

Question 28

How much ATP made during oxidative phosphorylation?

Answer 28

- 28 ATP

Question 29

Total molecules of ATP within aerobic respiration?

Answer 29

- around 32

Question 30

What else can be used as respiratory substances?

Answer 30

Lipids and proteins.

Question 31

Hydrolysis if lipids and proteins?

Answer 31

lipids = glycerol and fatty acids proteins = amino acids

Question 32

Energy of lipids compared to glucose?

Answer 32

lipids release more than double the amount of energy than glucose.

Question 33

Respiration and lipids?

Answer 33

- fatty acids are broken down into acetyl coA which enters krebs cycle - glycerol is phosphorylated and then converted into triose phosphate, then enters through glycolysis into krebs cycle.

Question 34

Respiration and proteins?

Answer 34

- amino acid group is removed, this is called deamination, 3C compounds converted into pyruvate. - four and five carbon compounds converted to immediate compounds.

Question 35

Where does anaerobic respiration occur?

Answer 35

- in the cytoplasm

Question 36

Steps of anaerobic respiration?

Answer 36

1. glycolysis 2. fermentation (yeast or lactate)

Question 37

Main purpose of anaerobic respiration?

Answer 37

- to release small amounts of ATP and to oxidise NAD - this is crucial because we have to ensure the NAD can be reused in glycolysis again

Question 38

Total energy formed in anaerobic respiration?

Answer 38

2 ATP

Question 39

1. Ethanol fermentation process?

Answer 39

1. glycolysis (glucose into pyruvate) 2. pyruvate loses CO2 (decarboxylation) 3. reduced NAD (from glycolysis) transfers hydrogen to ethanal to form ethanol. 4. ethanal is reduced to ethanol by enzyme, alcohol dehydrogenase - ethanal is the final hydrogen acceptor

Question 40

Ethanol fermentation equation?

Answer 40

pyruvate + reduced NAD = ethanol + CO2 + oxidised NAD

Question 41

2. Lactate fermentation process?

Answer 41

1. glycolysis (glucose to pyruvate) 2. reduced NAD (from glycolysis) transfers hydrogen to pyruvate to from lactate 3. pyruvate is reduced to lactate by the enzyme lactate dehydrogenase - pyruvate is the final hydrogen acceptor

Question 42

Lactate fermentation equation?

Answer 42

pyruvate + reduced NAD = lactate + oxidised NAD

Question 43

What happens to the lactate after?

Answer 43

- further metabolised back into pyruvate or converted into glycogen

Question 44

Exam question: Malonate inhibits a reaction in the Krebs cycle. Explain why malonate would decrease the uptake of oxygen in a respiring cell.

Answer 44

1. less coenzymes / fewer electrons removed 2. oxygen is final electron acceptor

Question 45

Exam question: In muscles, pyruvate is converted to lactate during prolonged exercise. Explain why converting pyruvate to lactate allows the continued production of ATP by anaerobic respiration.

Answer 45

1. oxidises reduced NAD 2. so glycolysis continues