Krebs

Question 1

Main step in Krebs prep stage

Answer 1

c-c-c pyruvate has carbon removed by pyruvate dehydrogenase (PDH) becomes Acetyl coA

Question 2

PDH

Answer 2

Pyruvate dehydrogenase-makes ccc pyruvate into cc Acetyl coA. Huge complex made up of three enzymes and five coenzymes. Has lipoic acid covalently bound.

Question 3

First four steps in Krebs

Answer 3

Claisen condensation
Dehydration /rehydration
Oxidative decarboxylation
Oxidative decarboxylation

Question 4

Claisen condensation, enzyme, and intermediate

Answer 4

*citrate synthase coverts methyl in Acetyl CoA to methylene in *citrate

Question 5

Dehydration/rehydration

Answer 5

Aconitase repositions OH group in citrate to *cis Aconitate and *Isocitrate

Question 6

Oxidative decarboxylation

Answer 6

Isocitrate dehydrogenase oxidizes OH to carbonyl, stabilizes carbanion *alpha ketoglutarate *succinyl coA

Question 7

Last four steps in Krebs

Answer 7

Substrate level phosphorylation
Dehydrogenation
Hydration
Dehydrogenation

Question 8

Substrate level phosphorylation

Answer 8

Succinyl CoA synthetase hydrolyzes succinyl CoA to succinate. Thioester leads to high energy phosphate bond, negative G. GTP/ATP

Question 9

Dehydrogenation 1

Answer 9

Succinate dehydrogenase introduces double bond in center create fumarate

Question 10

Hydration

Answer 10

Fumarase adds water, removes double bond in fumarate creates malate

Question 11

Dehydrogenation 2

Answer 11

Malate dehydrogenase generates carbonyl creates OAA (oxaloacetate)

Question 12

Products of Krebs (prep included)

Answer 12

2 NADH prep
6 NADH
2 ATP
2 FADH

Question 13

Products from glycolysis and Krebs

Answer 13

4 ATP
10 NADH
2 FADH
Ready for ETC

Question 14

Three irreversible steps in Krebs

Answer 14

Claisen comdensation, and both oxidative decarboxylations

Question 15

Aconitase

Answer 15

Enzyme used in dehydration/rehydration
FeS center
Cysteine residues bind to Fe

If Fe low uptake increased and storage deceased

Question 16

Vertebrates cannot…

Answer 16

Convert Acetyl coA to carbs(or fatty acids to carbs)

Question 17

Glyoxylaye cycle

Answer 17

Bypass that allows microbes and invertebrates to convert to carbs (done by plants)

Question 18

Enzymes unique to glyoxylaye

Answer 18

Isocitrate lyase and malate synthase

Question 19

What are the three stages in Krebs

Answer 19

Acetyl coA production
Acetyl coA oxidation
ETC/oxidative phosphorylation

Question 20

OAA uniformly labeled is condensed with Acetyl coA, how much radioactivity in OAA after one cycle

Answer 20

1/2

Question 21

Acetyl coA labeled reacts with unlabeled OAA how many on OAA after one cycle

Answer 21

All

Question 22

Two CO2 produced in first cycle Krebs have their origin from

Answer 22

Two carboxyl groups from OAA

Question 23

Which enzymes are irreversible

Answer 23

Citrate synthase
Isocitrate dehydrogenase
a ketoglutarate dehydrogenase

Question 24

How many electrons from Krebs will enter ETC

Answer 24

20

Question 25

How many NADH can convert 4FE 4S to a fully reduced state

Answer 25

2

Question 26

How many intermediates in Krebs can be trannaminated to amino acids

Answer 26

Three

Question 27

Which intermediates and what amino acids

Answer 27

Pyruvate to alanine OAA to aspartate A ketoglutarate to glutamate

Question 28

Krebs only operates when O2 is present because

Answer 28

O2 accepts electrons from ETC

Question 29

Subsequent step after removing CO2 and attaching Acetyl group

Answer 29

Reduction of lipoic acid

Question 30

When does Krebs directly yield reducing owner NADH or FADH

Answer 30

Succinate to fumarate by succinate dehydrogenase

Question 31

If succinyl coA is labeled at C1 where in fumarate

Answer 31

Equally in C1 and C4

Question 32

What would slow or stop Krebs

Answer 32

High ATP and high NADH

Question 33

What intermediate does the glyoxylate cycle pass

Answer 33

Succinate

Question 34

Why is Claisen condensation irreversible

Answer 34

The standard free energy is so negative

Question 35

The iron in FeS clusters participate in rxns by

Answer 35

Gaining or losing electrons

Question 36

Intermediates in Krebs at used in a one step biosynthesis of

Answer 36

Amino acids

Question 37

Which intermediate is not removed by another metabolic pathway

Answer 37

Isocitrate