Citric Acid Cycle and Respiratory Chian

Question 1

What is the citric acid cycle?

Answer 1

Common path by which all fuel molecules are broken down to carbon dioxide and water

Question 2

Provide a broad overview of the citric acid cycle

Answer 2

1. A 2-carbon molecule is condensed with a 4-carbon molecule to form a 6-carbon molecule
2. The 6-carbon molecule is broken down in stages, finally resulting in formation of a new molecule of the original 4-carbon compound
3. During this process, two molecules of CO2 and one molecule of GTP are formed.
4. At the same time 3 molecules of NADH and one molecule of
   FADH2* are formed. –The hydrogen is eventually combined with molecular O2 (forming water) in a process coupled to ATP synthesis

Question 3

What is FAD and what is it formed from?

Answer 3

Flavin adenine dinucleotide

Formed from vitamin riboflavin (vitamin B2)

Question 4

What does deficiency in riboflavin (vitamin. B2) cause?

Answer 4

lesions of the mucous membranes

cracked, sore lips and corners of mouth; similar lesions in genital regions; tongue swollen, tender, magenta

Question 5

What parts of the citric acid cycle occur within the mitochondria?

Answer 5

All of them

Question 6

Where in the mitochondria does the citric acid cycle occur?

Answer 6

All reactions from the breakdown of pyruvate, including all steps of the citric acid cycle take place in the MATRIX of the mitochondria

Question 7

When pyruvate enters the mitochondrion, what happens?

Answer 7

After pyruvate has been translocated into the mitochondrion it undergoes decarboxylation to become acetate.

Question 8

What does coenzyme A (CoA) do in translocation of pyruvate and decarboxylation to acetate?

Answer 8

Coenzyme A (CoA) forms a high energy bond with carboxylic acids such as acetate

Question 9

What is CoA?

Answer 9

Coenzyme A is a nucleotide that contains

the vitamin pantothenic acid (= vitamin B5)

Question 10

What is the first step of the citric acid cycle?

Answer 10

condensation of the acetyl group of Acetyl-CoA with the keto acid oxaloacetate to form citrate synthase

Question 11

What is the bodies response to handling reactive ketogenic acids?

Answer 11

They can be decarbonated into a more stable form, eg:

Isocitrate -> Oxalosiccinate -> α-Ketoglutarate + CO2

Question 12

What is the respiratory chain also known as in the citric acid cycle?

Answer 12

electron transfer chain/oxidative phosphorylation

Question 13

Where does the respiratory chain take place?

Answer 13

on macromolecular assemblies in the inner mitochondrial membrane

Question 14

What is the respiratory chain?

Answer 14

Hydrogen and electrons taken from fuel molecules by NAD+ are

passed down a chain of electron-carrying molecules until they are passed to molecular oxygen

Question 15

The respiratory chain consists of 4 complexes, what are they?

Answer 15

Complex I - NADH-q reductase
Complex II - FADH2 in flavoproteins
Complex III - Cytochrome reductase
Complex IV - Cytochrome oxidase

Question 16

What are the three large protein complexes that are linked together by molecules that act as electron shuttles in the respiratory chain?

Answer 16

Complex I - NADH-q reductase
Complex III - Cytochrome reductase
Complex IV - Cytochrome oxidase

Question 17

What molecules feed electrons into the system at different places?

Answer 17

NADH and FADH2

Question 18

What do NADH and FADH2 do in the respiratory chain?

Answer 18

feed electrons into the system at different places

Question 19

What chemical agents target the respiratory chain?

Answer 19

Rotenone –Insecticide, piscicide (Complex I inhibitor)

Antimycin A –Antibiotic (Complex III inhibitor)

Question 20

What effects do cyanide and carbon monoxide have on the respiratory chain?

Answer 20

block the final step by which hydrogen combines with

oxygen (Complex IV inhibitors)

Question 21

How is energy released in the respiratory chain?

Answer 21

Electrons are passed from one member of the chain to another

In this way the energy released by passing electrons from NADH or FADH2 so oxygen is used more efficiently

Question 22

What does the movement of electrons down the chain generate?

Answer 22

a H+ ion (pH) gradient across the inner mitochondrial membrane

Question 23

Where are the H+ ions (protons) pumped to to create the ion gradient in the respiratory chain?

Answer 23

proteins are pumped into the intermembrane space

Question 24

What is the ion gradient used for in the respiratory chain?

Answer 24

The electrochemical gradient is used to drive ATP synthesis by way of ATP synthase (= H+-ATPase)

Question 25

Describe the action of ATP synthase

Answer 25

Think of it as a system that works in the opposite direction from the sodium pump (Na-K ATPase) in the surface membrane
The sodium pump uses ATP to generate an ion gradient, while the ATP synthase uses an ion gradient to generate ATP
Oxidation of each molecule of NADH produces about 2.5 molecules of ATP, while each molecule of FADH2 generates 1.5 ATP molecules

Question 26

What is the ATP yield from the breakdown of a carbohydrate going through glycolysis and the citric acid cycle?

Answer 26

30-32???*

Question 27

What does the oxidation of NADH and FADH2 in ATP synthase yield in terms of ATP synthesis?

Answer 27

Oxidation of each molecule of NADH produces about 2.5 molecules of ATP, while each molecule of FADH2 generates 1.5 ATP molecules