TCA cycle and Oxidative Phosphorylation

Question 1

What does TCA cycle stand for and what is it?

Answer 1

Tricarboxylic acid cycle aka Krebs cycle and is the final pathway where oxidative metabolism of AA, carbs, and fatty acids converge

AEROBIC PATHWAY

Question 2

Where does the Citric acid cycle occur?

Answer 2

The cycle occurs in mitochondria close to the electron transport chain (ETC)

Question 3

What happens to reduced co-enzymes produced by glycolysis, lipid metabolism, and TCA cycle?

Answer 3

The reduced co enzymes such as NADH are oxidised

Question 4

The cycle is not viewed as a closed circle but instead as a?

Answer 4

A traffic circle with compounds entering and leaving as required (many intermediates too)

Question 5

What can catabolism of some AAs lead to?

Answer 5

Can generate intermediates of the cycle important to glucose formation from AAs

Question 6

Where are TCA cycle enzymes located?

Answer 6

TCA cycle enzymes are located in a free or attached state to the inner mitochondrial membrane close to respiratory enzymes

Question 7

Following glycolysis, pyruvate moves into the mitochondria however it is catalysed into Acetyl CoA? How and what helps it become this?

Answer 7

Pyruvate dehydrogenase aids the oxidative decarboxylation reaction that turns pyruvate +CoA into acetyl CoA + CO2

This reaction produces 2 ATP and 2NADH

Question 8

What co enzymes help pyruvate dehydrogenase form acetyl CoA?

Answer 8

NAD,FAD,CoA, thiamine

Question 9

Explain step one of the citric acid cycle

Answer 9

Acetyl CoA (C2) joins with oxaloacetate (C4) via citrate synthase (no energy required) to form CITRATE (C6)

Question 10

Explain step two of the citric acid cycle involving citrate

Answer 10

Citrate is isomerised and hydroxyl group moved via h20 moving in and out to form isocitrate (C6)
Enzyme involved is aconitase

Question 11

What is the step in the citric acid cycle involving isocitrate?

Answer 11

Isocitrate dehydrogenase produces NADH and CO2 by removing a carboxyl and hydrogen from the isocitrate, forming Alpha-ketoglutarate (C5)

Question 12

Explain the step in the citric acid cycle involving alpha ketoglutarate

Answer 12

a-ketoglutarate dehydrogenase produces NADH and CO2 and succinyl CoA (C4)

(Same as isocitrate step basically)

Question 13

Explain the step of the citric acid cycle involving succinyl CoA?

Answer 13

Succinate thiokinase forms succinate (C4) and byproduct of GTP

Question 14

Explain the step involving succinate

Answer 14

Succinate (C4) oxidised into numerate (C4) and byproduct of FADH2 is formed

Question 15

Explain the step involving fumarate

Answer 15

Fumarate catalysed by fumarase to form malate no byproducts

Question 16

Explain last step of citric acid cycle involving malate

Answer 16

Malate dehydrogenase forms oxaloacetate and byproduct of NADH

Circle of life the two extra carbons that enter the cycle leave as CO2

Question 17

How many NADH, FADH2, and direct ATP are formed?

Answer 17

3 NADH= 3 ATP each = 9 ATP
1 FADH2 = 2 ATP each = 2 ATP
1 direct ATP

Total ATP of citric acid cycle = 12 ATP

Question 18

How many runs does the citric acid cycle do from one glucose molecule and where do the byproducts go such as NADH,CO2?

Answer 18

Two runs for each glucose (pyruvate is C3 and two are formed)

Byproducts go to ETP electron transport chain

Question 19

Transamination of amino acids what does it lead to in citric acid cycle?

Answer 19

Leads to formation of TCA cycle intermediates

Question 20

What happens to the FADH2 and NADH generated in glycolysis and citric acid cycle?

Answer 20

These reduced coenzymes can enter the electron transport chain where each coenzyme donates a pair of electrons to specialised electron carriers

Question 21

Where are the electron carriers and coenzymes and what are they called?

Answer 21

They are embedded within the inner membrane

Complex I
CoQ
Complex III
Cytochrome C
Complex IV
Complex V (ATP Synthase)

Question 22

What is the process of oxidative phosphorylation (ETP)

Answer 22

As electrons are passed down energy is lost from them and placed into the production of ATP

Question 23

What do the electrons do specifically to lead to ATP production

Answer 23

Electrons from NADH FADH2 pass through complexes generating a proton motive force which is used to produce ATP via ATP synthase

Question 24

How many ATP are produced from the oxidation of a single glucose molecule? (remember glucose gives two pyruvate)

Answer 24

40-2= 38 ATP in total