Chapter 12

Question 1

Where does the citric acid cycle occur within the cell?

Answer 1

Mitochondria

Question 2

Where are mitochondria most abundant in the body?

Answer 2

Muscle and liver cells

Question 3

Why cant RBCs generate energy from the CAC?

Answer 3

They lack of mitochondria

Question 4

Where do RBCs get energy from?

Answer 4

Glycolosis

Question 5

Where are the enzymes for CAC located?

Answer 5

In the mitochondrial matrix

Question 6

Why is the CAC considered part of the aerobic metabolic process?

Answer 6

Because of its link to the electron transport chain and oxidative phosphorylation

Question 7

What coenzymes are generated by the CAC?

Answer 7

NADH and FADH2

they pass their electrons to oxygen to generate energy for the cell

Question 8

Where do the reduced coenzymes from CAC go?

Answer 8

Electron transport chain

Question 9

Where does glycolysis occur in the cell?

Answer 9

Cytoplasm

Question 10

Where is succinate dehydrogenase located?

Answer 10

In the inner membrane of the mitochondria

Question 11

Where must pyruvate travel to for the CAC?

Answer 11

From the cytosol into the mitochondrial matrix through a transporter in the inner membrane

Question 12

Where does oxidative phosphorylation occur?

Answer 12

Inner membrane of the mitochondria

Question 13

What must be activated for it to enter the CAC?

Answer 13

Pyruvate must be activated to acetyl-CoA

reactive thiol group that has higher energy bonds

Question 14

What happens during conversion of pyruvate to Acetyl-CoA?

Answer 14

Oxidative decarboxylation of pyruvate (irreversible oxidation)
First carbons of glucose to be fully oxidized

Question 15

What catalyzes the conversion of pyruvate to acetyl-coa?

Answer 15

Pyruvate dehydrogenase complex (3 enzyme complex)

Question 16

What are the prosthetic groups of the pyruvate dehydrogenase complex?

Answer 16

TPP
Lipoyllysine
FAD

Question 17

What are the co-substrates for pyruvate dehydrogenase complex?

Answer 17

NAD+ and CoA-SH

Question 18

What is removed from pyruvate as CO2 by pyruvate dehydrogenase?

Answer 18

Carboxyl group

Question 19

How many coenzymes are required by pyruvate dehydrogenase complex?

Answer 19

5 coenzymes

Question 20

Is conversion of pyruvate to Acetyl-CoA reversible?

Answer 20

No it is irreversible

Question 21

What are the products of converting pyruvate to acetyl-CoA?

Answer 21

Acetyl-CoA

NADH

Question 22

What do the 5 coenzymes of pyruvate dehydrogenase complex do?

Answer 22

Assist in transfer of functional groups

Question 23

What do the 5 coenzymes for pyruvate dehydrogenase complex act as?

Answer 23

Oxidants or carriers for intermediates of this enzyme complex

Question 24

What kind of complex is PDC?

Answer 24

A large multienzyme complex

Question 25

What are the three enzymes in PDC?

Answer 25

``` Pyruvate dehydrogenase (E1) Dihydrolipoyl transacetylase (E2) Dihydrolipoyl dehydrogenase (E3) ```

Question 26

What are the advantages of a multienzyme complex?

Answer 26

Short distance between catalytic sites allows channeling of substrates from one catalytic site to another Channeling minimizes side reactions The regulation of activity of one subunit affects the entire complex

Question 27

What is the first step of CAC?

Answer 27

The C-C bond formation between acetate(2C) and oxaloacetate(4C) to make citrate (6C) Releases CoA-SH Claisen condensation

Question 28

What is the second step in the CAC?

Answer 28

Isomerization via dehydration/rehydration to make isocitrate Release water

Question 29

What does steps 3-4 of CAC do?

Answer 29

Oxidative decarboxylations to give 2 NADH Release of 2 CO2 Makes alpha-ketoglutarate (3) and Succinyl CoA

Question 30

What happens in step 5 of CAC?

Answer 30

Substrate-level phosphorylation to make succinate Gives GTP from GDP Makes CoA-SH

Question 31

What does step 6 of CAC do?

Answer 31

Dehydrogenation to give FADH2 to make fumerate

Question 32

What does step 7 of CAC do?

Answer 32

Hydration to make malate

Question 33

What happens in step 8 of CAC?

Answer 33

Dehydrogenation to give NADH Makes oxaloacetate

Question 34

What is the mnemonic for CAC?

Answer 34

``` Citrate Is Krebs Starting Substrate For Making Oxaloacetate ```

Question 35

In step one how is acetyl-CoA and Oxaloacetate combined?

Answer 35

By condensation

Question 36

Is step one favorable or unfavorable?

Answer 36

Favorable and irreversible

Question 37

What is step 1 of CAC regulated by?

Answer 37

Substrate availability

Question 38

What is step one of CAC inhibited by?

Answer 38

Increased concentrations of ATP, NADH, Citrate, Succinyl CoA

Question 39

What is step 1 of CAC stimulated by?

Answer 39

ADP

Question 40

What is unique about step 1 of CAC?

Answer 40

It is the only reaction with a C-C bond formation

Question 41

What does the activity of Step 1 of CAC depend on?

Answer 41

Oxaloacetate

Question 42

What is the first part of step 2 of CAC?

Answer 42

Loss of water (dehydration) from citrate to give a cis C-C double bond

Question 43

What kind of alcohol is citrate?

Answer 43

A tertiary alcohol | poor substrate for oxidation so needs to be changed

Question 44

What is the second part of step 2 of CAC?

Answer 44

Inserting water to cis-aconitate to make isocitrate

Question 45

What kind of alcohol is isocitrate?

Answer 45

A secondary alcohol | good substrate for oxidation

Question 46

What kind of reaction is the second step in CAC?

Answer 46

Dehydration - hydration reaction

Question 47

Is step 2 favorable?

Answer 47

No it is unfavorable and reversible

Question 48

What pulls step 2 forward?

Answer 48

Product concentration kept low

Question 49

What is produced in step 3?

Answer 49

NADH is produced

Question 50

What inhibits step 3 of CAC?

Answer 50

high levels of ATP or NADH

Question 51

What kind of reaction is step 3 ?

Answer 51

Oxidation and decarboxylation

Question 52

What stimulates step 3 of CAC?

Answer 52

ADP and Ca+2

Question 53

What is released in step 3 of CAC?

Answer 53

Carbon dioxide