BB451 exam 1 - Citric Acid Cycle

Question 1

pyruvate dehydrogenase complex function

Answer 1

pyruvate from glycolysis –> acetyl CoA for citric acid cycle

Question 2

pyruvate dehydrogenase complex occurs in the..

Answer 2

mitochondrion (pyruvate from cytoplasm transported into mitochondrion)

Question 3

E1

Answer 3

pyruvate decarboxylase

decarboxylation and part of oxidation

Question 4

E2

Answer 4

transfer of acetyl group to CoA –> acetyl CoA

Question 5

E3

Answer 5

handles electrons and regenerates original enzyme

Question 6

coenzymes used with pyruvate dehydrogenase complex

Answer 6

TPP, lipoamide, CoA, FAD, NAD

Question 7

ultimate electron destination

Answer 7

NAD

Question 8

mechanism of pyruvate dehydrogenase complex similar to…

Answer 8

alpha-keto-gluterate dehydrogenase complex of citric acid cycle
-both involve oxidation of alpha-keto acids

Question 9

pyruvate dehydrogenase complex step 1

Answer 9

pyruvate decarboxylated –> 2C reactive intermediate attached to TPP
*catalyzed by E1

Question 10

pyruvate dehydrogenase complex step 2

Answer 10

2C intermediate transferred to lipoamide molecules –> acetyl group

• oxidation (E1 and E2)
• single bond oxygen to double bond oxygen
• disulfide bond to sulfhydryl
• e’s passed to lipoamide

Question 11

pyruvate dehydrogenase complex step 3

Answer 11

CoA grabs acetyl group –> acetyl CoA

• left reduced sulfhydryl compound
• E2

Question 12

pyruvate dehydrogenase complex step 4

Answer 12

electrons –> FAD –> FADH2

• sulfhydryl back to disulfide bond of lipoamide
• E3

Question 13

pyruvate dehydrogenase complex step 5

Answer 13

transfer of e’s from FADH2 –> NAD –> NADH

*NADH released

Question 14

1 turn of pyruvate dehydrogenase complex cycle …

Answer 14

1 acetyl CoA and 1 NADH

glucose –> 2 pyruvate –> 2 CoA and 2 NADH

Question 15

yeast fermentation stops at

Answer 15

decarboxylation step

no oxidation

Question 16

yeast fermentation forms

Answer 16

acetaldehyde w/out gain/loss of e’s

acetaldehyde –> ethanol

Question 17

when oxygen is present with yeast/bacteria…

Answer 17

fermentation does not occur

E2 and E3 catalyze reactions as in aerobic higher organisms –> acetyl CoA

Question 18

first electron carrier in pyruvate dehydrogenase complex reactions

Answer 18

lipoamide

Question 19

mitochondrial inner membrane

Answer 19

e-transport chain
proteins and enzymes for –> ATP
permeable to: water, CO2, oxygen, CO

Question 20

cristae

Answer 20

infoldings of inner membrane

Question 21

citric acid cycle occurs in

Answer 21

mitochondrial matrix

Question 22

CAC: 2C added as ___, released as ___

Answer 22

added as acetyl CoA, released as CO2

Question 23

1 acetyl CoA—>

Answer 23

3 NADH and 1 FADH2

1 high energy phosphate (GTP in animals, ATP in plants and bacteria)

Question 24

1 glucose –> CAC –>

Answer 24

6 NADH, 2 FADH2, 2 GTP

Question 25

acetyl CoA produced from...

Answer 25

fatty acid metabolism aerobic oxidation of glucose many amino acid metabolism

Question 26

substrate level phosphorylation

Answer 26

directly make triphosphate from high energy intermediate (1 in CAC)

Question 27

most triphosphates made by ....

Answer 27

oxidative phosphorylation in mitochondria

Question 28

step 1 CAC

Answer 28

oxaloacetate + acetyl CoA --> citrate 4C + 2C --> 6C enzyme = citrate synthase very energetically favorable - pulls cycle

Question 29

step 2 CAC

Answer 29

citrate isocitrate isomerization enzyme = aconitase

Question 30

aconitase inhibited by

Answer 30

fluorocitrate | fluoroacitate is poison used by citrate synthase to make fluorocitrate

Question 31

step 3 CAC

Answer 31

``` isocitrate --> alpha-KG 6C --> 5C NAD+ --> NADH enzyme = isocitrate dehydrogenase first decarboxylation (release CO2) isocitrate is oxidized ```

Question 32

dehydrogenase means..

Answer 32

oxidation is occurring (losing e-)

Question 33

alpha-KG

Answer 33

useful intermediate, convert to glutamic acid or back

Question 34

step 4 CAC

Answer 34

alpha-KG + NAD + CoA --> succinyl CoA + NADH enzyme: alpha-KG dehydrogenase puts CoA onto succinate, driving force from oxidation almost same as pyruvate dehydrogenase complex reactions big band: very energetically favorable

Question 35

step 5 CAC

Answer 35

``` succinyl CoA --> succinate 5C --> 4C GDP --> GTP enzyme: succinyl CoA synthetase substrate level phosphorylation (requires high energy from CoA) ```

Question 36

step 6 CAC

Answer 36

succinate --> fumerate enzyme= succinate dehydrogenase add 2e- and 2H onto FAD --> FADH2

Question 37

step 7 CAC

Answer 37

fumerate + H2O --> malate | enzyme = fumarase

Question 38

step 8 CAC

Answer 38

``` malate --> oxaloacetate NAD --> NADH enzyme = malate dehydrogenase hydroxyl oxidized to ketone malate loses e- to NAD ```

Question 39

step 8 is rare oxidation because...

Answer 39

not energetically favorable, delta G 0prime is positive | oxaloacetate pulled away by citrate synthase reaction --> pulls reaction forward

Question 40

overall... CAC is energetically ___

Answer 40

favorable

Question 41

most important regulation of CAC

Answer 41

availability of NAD+ and FAD NADH and FADH2 turn cycle off e- transport/oxidative phosphorylation regenerate NAD and FAD

Question 42

exercising heavily..

Answer 42

low ATP, low O2 in muscle cells | high NADH and CAC stops

Question 43

relaxed state..

Answer 43

high ATP, high NADH NADH increase when cell can catch up --> CAC stops --> citrate accumulates --> acetyl CoA increases --> get fat (acetyl CoA to make fatty acids)

Question 44

when all NADH and FADH2 of cycle --> ATP

Answer 44

30-38 ATPs / glucose | compare to 2 from glycolysis

Question 45

limiting reagent needed to keep cycle turning

Answer 45

oxygen (ultimately convert NADH --> NAD) NAD needed to 3 reactions is CAC cant get around need for oxygen (like glycolysis does with fermentation)

Question 46

anaplerotic reactions

Answer 46

"filling up" the intermediates of metabolism | intermediates involved in metabolism of amino acids, fatty acids, nucleotides, and sugars

Question 47

arsenic poisoning

Answer 47

arsenic knocks out pyruvate dehydrogenase and alpha-KG dehydrogenase treatment: BAL, takes arsenic away from lipoic acid

Question 48

glyoxylate cycle in

Answer 48

plants, bacteria, and yeast

Question 49

2 additional enzyme for glyoxylate cycle

Answer 49

isocitrate lyase | malate synthase

Question 50

isocitrate lyase

Answer 50

cleavage of isocitrate --> glyoxylate and succinate

Question 51

malate synthase

Answer 51

linkage of acetyl CoA to glyoxylate --> malate

Question 52

glyoxylate cycle can

Answer 52

form glucose from acetyl CoA because bypass decarboxylation reactions of CAC acetyl CoA converted to useful material (instead of just fatty acids)

Question 53

glyoxylate cycle produces less ___ than CAC

Answer 53

less NADH, because skips decarboxylation | less ATP produced

Question 54

____ influences CAC or glyoxylate cycle

Answer 54

energy state of cell need energy: CAC abundant energy: glyoxylate cycle

Question 55

every turn of glyoxylate cycle -->

Answer 55

2 oxaloacetates instead of 1