Respiration

Question 1

Describe the order of events in glycolysis.

Answer 1

• Glucose is phosphorylated, 2 ATP molecules release a phosphate group each, these bind to glucose to form hexose bisphosphate.
• Lysis occurs and hexose bisphosphate splits into 2 triose phosphate molecules.
• A free inorganic phosphate group is added to both TP molecules, forming triose bisphosphate.
• Each TBP has 2 phosphate groups removed, which forms 2 ATP molecules per pyruvate. Each also has a H removed, which reduces NAD+.

Question 2

What are the products of glycolysis?

Answer 2

• 4 ATP (net gain of 2), 2 reduced NAD, 2 pyruvate.

Question 3

What is substrate level phosphorylation?

Answer 3

• The production of ATP without the use of the electron transport chain.

Question 4

What is the other name for the link reaction? Why?

Answer 4

• Oxidative decarboxylation.
• Pyruvate is decarboxylated (CO2) removed and oxidised (H removed).

Question 5

Is glycolysis aerobic or anaerobic?

Answer 5

• anaerobic.

Question 6

Describe the steps of the link reaction.

Answer 6

• Pyruvate is decarboxylated (CO2 removed) and oxidised (H removed to form reduced NAD).
• Acetyl group formed, which combines with coenzyme A to form acetylcoenzyme A (acetyl CoA).

Question 7

Where does glycolysis occur?

Answer 7

• Cytoplasm/cytosol.

Question 8

How does Pyruvate get into the mitochondrial matrix?

Answer 8

• Active transport via specific carrier proteins.

Question 9

How does Pyruvate get into the mitochondrial matrix?

Answer 9

• Active transport.

Question 10

Where does the link reaction occur?

Answer 10

• Mitochondrial matrix.

Question 11

How is the NADH produced by the link reaction used?

Answer 11

• It is used in oxidative phosphorylation later on.

Question 12

What happens to the CO2 produced by the link reaction?

Answer 12

• It will diffuse away and be removed as metabolic waste or, in autotrophic organisms, it may be used as a raw material in photosynthesis.

Question 13

Where does the Krebs cycle take place?

Answer 13

• the mitochondrial matrix.

Question 14

What are the products of the Krebs cycle?

Answer 14

• 3 reduced NAD
• 1 reduced FAD (FADH2)
• Oxaloactetae (which is recombined with a new acetyl group)
• 2 CO2
• 1 ATP

Question 15

What is the purpose of the reduced NAD and FAD produced by Krebs?

Answer 15

• They are used in the electron transport chain and for oxidative phosphorylation.

Question 16

Describe the steps of the Krebs cycle.

Answer 16

1. Acetyl CoA delivers an acetyl group to the Krebs cycle. The 2C acetyl group combines with 4C oxaloacetate to form 6C citrate.
2. Citrate undergoes dehydrogenation and decarboxylation, producing 1 reduced NAD and CO2. a-Ketoglutarate (5C) is formed.
3. a-Ketoglutarate (5C) undergoes further decarb and dehydro. This forms a Succinyl CoA (4C), and releases 1 CO2 and 1 reduced NAD.
4. This Succinyl CoA (4C) reacts further to produce Succinate (4C). In the process ADP is phosphorylated to produce ATP.
5. Succinate (4C) reacts to form fumarate (this produces FADH2 from FAD).
6. Fumarate (4C) is then converted into Malate (4C).
7. Malate is then converted into Oxaloacetate (this produces NADH from NAD+). Oxaloacetate is combined with a new acetyl group.
   Steps 4-7 can be summarised as ‘the 4 carbon molecule undergoes further decarb and dehydro before OAA is eventually regenerated.

Question 17

State the differences between FAD and NAD.

Answer 17

• NAD+ is reduced in all steps of respiration, FAD is only reduced in Krebs.
• NAD is responsible for the synthesis of 3 ATP, FAD for 2.

Question 18

Where does oxidative phosphorylation occur?

Answer 18

• Inner mitochondrial membrane.

Question 19

How many ATP molecules are produced total? How many in ETC?

Answer 19

• 38, 34.

Question 20

What is the final electron acceptor in ETC?

Answer 20

• Oxygen.

Question 21

What is the role of electrons in the ETC?

Answer 21

• They reduce protein complexes, releasing energy which allows for the active transport of H+ ions into the inter-membrane space.

Question 22

How is ATP generated by the ETC/OP?

Answer 22

• H+ ions diffuse back across the mitochondrial inner membrane by chemiosmosis along the proton gradient. They go through ATP synthase which transfers the energy from the electronchemical proton gradient to ADP and Pi to make ATP.