Kreb's Cycle

Question 1

What are the other two names for the Kreb’s cycle?

Answer 1

TCA cycle
Citric acid cycle

Question 2

What can enter the Kreb’s cycle?

Answer 2

Fatty acids, glucose as pyruvate, amino acids

Question 3

What is the purpose of the Kreb’s cycle?

Answer 3

Biosynthesis and energy production

Question 4

What are the products of the energy production of Kreb’s cycle?

Answer 4

3 NADH, FADH2, 2 CO2, GTP

Question 5

What stimulates fatty acid production?

Answer 5

High carb diet with no exercise

Question 6

What two amino acids are the easiest to make?

Answer 6

Aspartate and glutamate

Question 7

What intermediate in the Kreb’s cycle is required to make hemoglobin?

Answer 7

Succinyl CoA

Question 8

What needs heme?

Answer 8

Hemoglobin, cytochromes

Question 9

What must the Kreb’s cycle be paired with to make energy?

Answer 9

Electron transport chain

Question 10

What is the starting molecule of Kreb’s cycle?

Answer 10

Acetyl-CoA

Question 11

What is the first equation of the Kreb’s cycle?

Answer 11

Oxaloacetate + acetyl-CoA (+H2O) -> citrate
(enzyme: citrate synthase)

Question 12

How do carbs enter the Kreb’s cycle?

Answer 12

Glycolysis

Question 13

What do carbs enter the Kreb’s cycle as?

Answer 13

Pyruvate

Question 14

What is the pre-Kreb’s step for pyruvate?

Answer 14

Pyruvate to acetyl CoA

Question 15

What coenzymes are needed for pyruvate to acetyl CoA?

Answer 15

B1 (TPP), B2 (FAD), B3 (NAD), B5 (CoAsh), lipoic acid

Question 16

How do fatty acids enter the Kreb’s cycle?

Answer 16

Beta oxidation into acetyl CoA

Question 17

What is the purpose of the aconitase enzyme in step two?

Answer 17

prevent acetyl-CoA -> glucose

citrate -> isocitrate
(aconitase)

Question 18

What two minerals support the function of the aconitase enzyme?

Answer 18

Iron and sulfur

Question 19

What food are rich in iron?

Answer 19

Spinach, red meat, raisins, dried apricots

Question 20

What foods are rich in sulfur?

Answer 20

Cruciferous vegetables, eggs, asparagus, onions

Question 21

What is the allosteric enzyme in the TCA cycle?

Answer 21

Isocitrate dehydrogenase

isocitrate + NAD -> a-ketoglutarate + NADH+H + CO2
(isocitrate dehydrogenase)

Question 22

What two compounds, if they build up, inhibit isocitrate dehydrogenase?

Answer 22

NADH and ATP

Question 23

What is the name of the enzyme that uses all the same co-enzymes as pyruvate dehydrogenase?

Answer 23

Alpha-ketoglutarate dehydrogenase

Question 24

Name the enzyme that converts pyruvate to OAA, and its coenzymes

Answer 24

Pyruvate carboxylase
ATP + biotin

Question 25

Name the high energy compound made in the step succinyl CoA -> succinate

Answer 25

GTP (enzyme: succinate thiokinase)

Question 26

What complex in the cytochrome chain contains the enzyme succinate dehydrogenase?

Answer 26

Complex II

Question 27

What is the location in the mitochondria of most Kreb's cycle enzymes?

Answer 27

Mitochondrial matrix

Question 28

What is the coenzyme for the enzyme fumarase?

Answer 28

H2O (in)

Question 29

What is the name of the enzyme that converts malate to OAA?

Answer 29

Malate dehydrogenase

Question 30

What coenzyme is needed for malate dehydrogenase to convert malate to OAA?

Answer 30

NAD+

Question 31

What do ketogenic compounds enter Kreb's cycle as?

Answer 31

Acetyl CoA

Question 32

Name the amino acids that are ONLY ketogenic

Answer 32

lysine, leucine

Question 33

Name the amino acids that are both ketogenic and gluconeogenic

Answer 33

Phenylalanine, isoleucine, tyrosine, tryptophan

Question 34

Where do gluconeogenic amino acids enter the Kreb's cycle?

Answer 34

Other intermediates

Question 35

What amino acids enter as pyruvate?

Answer 35

Alanine, glycine, cysteine, serine, threonine, tryptophan

Question 36

What amino acids enter as alpha ketoglutarate?

Answer 36

Histidine, arginine, proline, glutamate, glutamine

Question 37

What enzyme is used for the amino acids entering as alpha ketoglutarate?

Answer 37

SGPT

Question 38

What amino acids enter as succinyl CoA?

Answer 38

Valine, isoleucine, methionine

Question 39

What amino acids enter as fumarate?

Answer 39

Phenylalanine, aspartate, tyrosine

Question 40

What amino acids enter as oxaloacetate?

Answer 40

Aspartate, asparagine

Question 41

What enzyme is used for amino acids entering as oxaloacetate?

Answer 41

SGOT/aspartate transaminase

Question 42

What is the energy yield for 1 acetyl CoA when Kreb's and ETC are combined without accounting for heat?

Answer 42

12

Question 43

What is the energy yield for 1 acetyl CoA when Kreb's and ETC are combined with accounting for heat?

Answer 43

10

Question 44

What is the total energy yield for aerobic glycolysis (depending on shuttle) without accounting for heat?

Answer 44

36 or 38

Question 45

What is the total energy yield for aerobic glycolysis (depending on shuttle) accounting for heat?

Answer 45

30 or 32

Question 46

What three substances decrease the action of pyruvate dehydrogenase by end product inhibition?

Answer 46

NADH, acetyl CoA, ATP

Question 47

What type of diet increases the concentration of OAA?

Answer 47

High carbohydrates

Question 48

What is the impact of high carbohydrates in the diet on the rate of the TCA cycle?

Answer 48

Increases the rate

Question 49

Why does a high alcohol diet slow the rate of the Kreb's cycle?

Answer 49

Lots of NADH with alcohol dehydrogenase

Question 50

What is the impact of high levels of citric acid on glycolysis?

Answer 50

Shuts off phosphofructokinase

Question 51

What pathway is turned on by high levels of citrate in the cytoplasm

Answer 51

Fat synthesis

Question 52

What is the impact of lack of exercise on the Kreb's cycle?

Answer 52

Increases ATP which turns off the cycle

Question 53

What cycle in the liver is connected with the Kreb's cycle?

Answer 53

Urea cycle