5.6: Respiration

Question 1

What organelles make up the mitochondria and the functions?

Answer 1

• Cristae - increase surface area of inner membrane for oxidative phosphorylation
• Inner membrane - holss proteins that faciliate respiration
• Outer membrane - compartmentalisation
• Matrix - contains enzymes for link and krebs and contains mitochondrial DNA
• Intermembrane space - ETC pumps H+ ions into this space for ATP synthesis

Question 2

Where does glycolysis occur?

Answer 2

Cytoplasm

Question 3

What is the process of glycolysis?

4 steps

Answer 3

1. Two ATP molecules donate phosphate groups to glucose, forming hexose bisphosphate
2. The hexose bisphosphate molecule is split into two molecules of triose phosphate (TP)
3. A second phosphate group is added to each TP molecule, converting them into two molecules of triose bisphosphate
4. A hydrogen is removed from each triose bisphosphate (they are oxidised) and used to form two molecules of red NAD, two molecules of pyruvate, and four molecules of ATP through substrate-level phosphorylation

Question 4

What are the products of glycolysis?

Answer 4

• Pyruvate 2x - link and krebs
• Net gain 2 ATP
• Red NAD 2x - oxidative phosphorylation

Question 5

Where does the link reaction take place?

Answer 5

Matrix

Question 6

What is the process of link reaction?

6 steps

Answer 6

1. Pyruvate from glycolysis is actively transported into the mitochondrial matrix by specific carrier proteins
2. In the mitochondrial matrix, each pyruvate molecule is decarboxylated, losing one molecule of CO2
3. CO2 diffuses out of the mitochondria as a waste product
4. Two hydrogen atoms are removed from pyruvate to form a two-carbon molecule (acetate)
5. The hydrogen atoms are used to reduce the coenzyme NAD, forming reduced NAD (an electron carrier)
6. Acetate binds to coenzyme A, forming acetyl coenzyme A (acetyl CoA)

Question 7

What are the reactants and products of link reaction?

Answer 7

Reactants:

• Pyruvate
• NAD
• Coenzyme A

Products:

• Acetyl coenzyme A
• Red NAD
• Carbon dioxide

Question 8

What’s the difference between NAD and FAD?

Answer 8

NAD

• Takes part in all stages
• Accepts 1 proton
• Red NAD oxidised at start of ETC
• 1 Red NAD makes 3 ATP

FAD

• Only involved in Krebs
• Accepts two protons
• Red FAS oxidised further along ETC

Question 9

What are the products of krebs cycle?

Answer 9

• 3 Red NAD and red FAD
• 2 CO2
• 1 ATP through substrate level phosphorylation

Question 10

What is the process of oxidative respiration?

8 steps

Answer 10

1. Red NAD and red FAD release hydrogen, transferring protons and electrons into the mitochondrial matrix
2. High-energy electrons are passed to an electron carrier from red NAD and red FAD
3. The electrons are passed along a series of electron carrier molecules in the ETC embedded in the inner mitochondrial membrane, releasing energy as they are transferred
4. The energy is used to actively transport protons across the inner mitochondrial membrane from the mitochondrial matrix into the intermembrane space
5. The accumulation of protons in the intermembrane space sets up a steep electrochemical gradient of protons across the inner membrane
6. Protons diffuse back into the mitochondrial matrix down their electrochemical gradient through ATP synthase
7. This releases energy and catalyses the synthesis of ATP from ADP and inorganic phosphate (Pi)
8. Oxygen is the final electron acceptor, and combines with electrons and protons to form water, helping to maintain the proton gradient

Question 11

What are the reactants and products oxidatative phosphorylation?

Answer 11

Reactants:

• Red NAD & FAD
• Oxygen
• ADP and inorganic phsophate

Products:

• NAD
• FAD
• Water
• ATP

Question 12

What is the net gain for ATP?

Answer 12

34

Question 13

Where does anaaerobic respiration occur?

Answer 13

Cytoplasm

Question 14

What is the net gain of ATP in anaerobic respiration?

Answer 14

2
From glycolysis

Question 15

What is lactate fermentation?

Answer 15

• Occurs in some animals and bacteria.
• Pyruvate accepts a hydrogen from reduced NAD, catalysed by lactate dehydrogenase
• This forms lactic acid, and regenerates NAD
• Lactic acid can be oxidised back to pyruvate to generate more ATP, or it can be stored as glycogen

Question 16

What is alcoholic fermentation?

Answer 16

• Occurs in yeasts and some plants
• Pyruvate loses a molecule of CO2 and is converted into ethanal
• Ethanal accepts a hydrogen from reduced NAD
• This produces ethanol, and regenerates NAD
• Ethanol cannot be further metabolised so must be removed as a waste product

Question 17

How can lipids be used as respiratory substrate?

3 steps

Answer 17

1. Lipids are hydrolysed into glycerol and fatty acids
2. Glycerol is converted into triose phosphate and enters the glycolysis pathway
3. Fatty acids are broken down into two-carbon fragments and converted into acetyl coenzyme A, which enters the Krebs cycle

Question 18

How can proteins be used as a respiratory substrate?

3 steps

Answer 18

1. Proteins are hydrolysed into amino acids
2. The amino group is removed from the amino acids (deamination)
3. Three-carbon compounds are converted into pyruvate, while four- and five-carbon compounds are converted into intermediates in the Krebs cycle

Question 19

What is the formula for RQ?

Answer 19

Volume of carbon dioxide produced/Volume of oxygen consumed
An RQ of more than one means an anaerobic respiration is forming

Question 20

What is the RQ for:

• Carbohydrates
• Lipids
• Protein

Answer 20

• 1.0
• 0.7
• 0.9