Citric acid cycle

Question 1

What is the citric acid cycle?

Answer 1

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

Question 2

What are the general steps 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 (Citrate) 2). The 6-carbon molecule (citrate) is broken down in stages, resulting in the formation of a new molecule of the original 4-carbon compound 3). During this process, 2 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 the molecular O2 (forming water via reduction) in a process coupled to ATP synthesis

Question 3

Where does the citric acid cycle occur?

Answer 3

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

Question 4

What is FAD (Flavin Adenine Dinucleotide) formed from?

Answer 4

Vitamin riboflavin (Vitamin B2)

Question 5

What do riboflavin (Vitamin B2) deficiencies lead to ?

Answer 5

Riboflavin (Vitamin B2) deficiencies cause lesions of the mucous membranes Examples; - Cracked sore lips and corners of mouth - Similar lesions in genital regions - Tongue swollen, tender, magenta

Question 6

What is the role of FAD?

Answer 6

Electron and proton acceptor

Question 7

How does the outer membrane of the mitochondria help with the citric acid process?

Answer 7

The outer membrane is permeable to all small electrolytes

Question 8

Where does the conversion of pyruvate to lactate occur?

Answer 8

Outside the mitochondria in the cytosol

Question 9

What is the role of Coenzyme A (CoA)?

Answer 9

Coenzyme A (CoA) forms a high energy bond with carboxylic acids such as acetate to form Acetyl CoA It can also regenerate NADH to NAD during anaerobic respiration to keep generating some ATP

Question 10

What is CoA?

Answer 10

CoA is a nucleotide that contains the vitamin pantothenic acid (Vitamin B5)

Question 11

Draw the Citric acid cycle

Answer 11

Below

Question 12

Draw the short hand equations of what occurs during the citric acid cycle and. the reaction of ketoacids being decarboxylated?

Answer 12

Below

Question 13

What kind of reaction occurs in the citric acid cycle?

Answer 13

The first step is condensation of the acetyl group of Acetyl-CoA with the keto acid oxaloacetate (Just before entering the cycle)

Then a number of degradation steps occur in the citric acid cycle, because the keto acids formed are quite reactive and they can be decarboxylated

Question 14

What occurs in the respiratory chain ?

Answer 14

Electron transfer

Question 15

Where about does oxidative phosphorylation occur?

Answer 15

Oxidative phosphorylation takes place on macromolecular assemblies in the inner mitochondrial membrane

Question 16

What occurs during oxidative phosphorylation ?

Answer 16

Hydrogen and electrons taken from fuel molecules by NAD+ are passed down a chain of electron-carrying molecules until they are passed to a molecular oxygen

Question 17

What is involved in the respiratory chain?

Answer 17

The respiratory chain consists of three large protein complexes liked together by molecules that act as electron shuttles NADH and FADH2 feed electrons into the system at different places

Question 18

Draw the respiratory and number the different complexes

Answer 18

NADH-Q reductase (Complex 1)

Cytochrome reductase (Complex 2)

Cytochrome oxidase (Complex 3)

Key;

Q = Coenzyme

Q = ubiquinone

Cyt c = Cytochrome C

Question 19

What chemical agents target the respiratory chain?

Answer 19

Rotenone - Insecticide, piscicide Antimycin A - Antibiotic Cyanide and carbon monoxide block the final step by. which hydrogen combines with oxygen

Question 20

What is the role of the respiratory chain?

Answer 20

Electrons are passed from one member of the chain to another In this the way the energy released by passing electrons from NADH or FADH2 to oxygen is used more efficiently The movement of electrons down the respiratory chain generates a H+ ion (pH) gradient across the inner mitochondrial membrane The resulting electrochemical gradient is used to drive ATP synthesis by the way of ATP synthase (= H+ - ATPase)

Question 21

Draw the diagram of how the respiratory chain works?

Answer 21

Below

Question 22

How can you relate the respiratory chain to the sodium pump?

Answer 22

The sodium pump uses ATP to generate an ion gradient, while the ATP synthase uses an ion gradient to generate ATP Think of it as working in opposite direction as sodium pump

Question 23

Oxidation of NADH and FADH2 produces how many ATP?

Answer 23

Oxidation of NADH produces 3 ATP Oxidation of FADH2 produces 2 ATP

Question 24

Why does cytoplasmic NADH produce less ATP than Mitochondrial NADH?

Answer 24

As cytoplasmic NADH has to get across the membrane and mitochondrial doesn’t

Question 25

Write the ATP yield from the breakdown of carbohydrates?

Answer 25

Below