Krebs cycle

Question 1

Glycolysis: Recall
• Glucose (6C) is converted to __ pyruvate molecules (3C)
• Other products of glycolysis include:
• 2 moles of ATP
• 2 moles of NADH
• 2 moles of H2O
• Happens in the __

Answer 1

2

cytosol

Question 2

__ produced from glycolysis in the cytosol
enters the mitochondria.

Answer 2

Pyruvate

Question 3

Pyruvate is converted to Acetyl CoA through the action of

Answer 3

pyruvate dehydrogenase complex

Question 4

Oxidative decarboxylation of pyruvate

Answer 4

Pyruvate dehydrogenase (E1)

Question 5

Transfer of acetyl group to CoA

Answer 5

Dihydrolipoyl transacetylase (E2)

Question 6

Regeneration of the oxidized form of lipoamide

Answer 6

Dihydrolipoyl dehydrogenase (E3)

Question 7

Final common pathway for the oxidation of fuel
molecules

Answer 7

Krebs Cycle

Question 8

Krebs Cycle Operates under

Answer 8

aerobic conditions only

Question 9

Krebs Cycle Location:

Answer 9

Mitochondrial matrix

Question 10

• serves both catabolic and anabolic processes:

• CENTRAL to the catabolism of carbohydrates, fatty acids and amino acids
• Provides precursors for many BIOSYNTHETIC
pathways

Answer 10

amphibolic pathway

Question 11

Oxaloacetate (4C) combines with the acetyl
group (2C) of acetyl-CoA to form citrate (6C)

• Condensation reaction

Answer 11

Citrate Synthase

Question 12

• Dehydration then hydration
• isomerizatio

Answer 12

2 & 3. Aconitase

Question 13

• Removal of CO2
• Oxidation of ―OH by NAD+ to give NADH,H+
• First oxidative decarboxylation

Answer 13

4. Isocitrate Dehydrogenase Complex

Question 14

• Removal of CO2 from α-KG and formation of NADH,H+
• Second oxidative decarboxylation

Answer 14

5. α-Ketoglutarate Dehydrogenase Complex

Question 15

Hydrolysis of the THIOESTER BOND releases CoA-SH and energy.

Released energy is used to form GTP from GDP and Pi

Answer 15

6. Succinyl-CoA Synthetase

Question 16

• Removal of H2 from succinate to form a double bond (oxidation)

• H2 is accepted by FAD to form FADH2 (reduction)

Answer 16

7. Succinate Dehydrogenase

Question 17

Hydration of the double bond

Answer 17

8. Fumarase

Question 18

Regeneration of oxaloacetate via oxidation of malate

Answer 18

9. Malate Dehydrogenase

Question 19

__ C atoms (as acetyl-CoA) enter the cycle in
condensation with oxaloacetate (6C)

Answer 19

Two

Question 20

Two decarboxylation reactions REMOVE 2C as 2CO2 (6C − 2C = __).

Answer 20

4C

Question 21

__ oxidation reactions provide hydrogens for 3NADH and FADH2

Answer 21

Four

Question 22

A direct phosphorylation of GDP forms GTP.
• __ are consumed

Answer 22

2H2O

Question 23

When Precursors are Depleted..
• TCA cycle intermediates (__ and __) have to be replaced when they are used as biosynthetic precursors.

Answer 23

oxaloacetate, malate

Question 24

Reactions that generate these intermediates are
called

Answer 24

ANAPLEROTIC REACTIONS

Question 25

Anaplerotic means

Answer 25

“filling-up”

Question 26

Vitamin B1 deficiency -

Answer 26

Beriberi

Question 27

Vitamin B1 (Thiamine) is the precursor for the co-enzyme

Answer 27

thiamine pyrophosphate (TPP)

Question 28

an important co-enzyme of pyruvate dh and α-KG dh complexes

Answer 28

thiamine pyrophosphate (TPP)

Question 29

Vit B1 deficiency leads to __, a neurologic and cardiovascular disorder

Answer 29

beriberi

Question 30

Pyruvate dh Complex Inhibitors: (3)

Answer 30

NADH, Acetyl CoA, ATP

Question 31

Pyruvate dh Complex Activators: (4)

Answer 31

NAD+, CoA-SH, ADP, AMP

Question 32

High levels of the inhibitors signal __ of biosynthetic precursors and _ energy state

Answer 32

abundance, high

Question 33

Citrate Synthase Inhibitors: (4)

Answer 33

NADH, Succinyl CoA, citrate, ATP

Question 34

Citrate Synthase Activators: (1)

Answer 34

ADP

Question 35

Isocitrate dh Complex Inhibitors: (2)

Answer 35

NADH, ATP

Question 36

Isocitrate dh Complex Activators: (1)

Answer 36

ADP

Question 37

α-Ketoglutarate dh Complex Inhibitors: (3)

Answer 37

NADH, succinyl CoA, ATP

Question 38

α-Ketoglutarate dh Complex Activators: (2)

Answer 38

ADP, Ca2+

Question 39

NADH from TCA cycle is __ • Readily oxidized for ATP production

Answer 39

mitochondrial

Question 40

NADH from glycoysis is __ • Inner mitochondrial membrane is NOT PERMEABLE for cytosolic NADH

Answer 40

cytosolic

Question 41

Solution: e−s from NADHcytosolic rather than NADH are carried across the mit. membrane • How: Use of __

Answer 41

Shuttle Systems

Question 42

Active in the heart and liver

Answer 42

MALATE-ASPARTATE SHUTTLE

Question 43

carries the e−s from cytosolic NADH across the mit. membrane and passes it onto mitochondrial NAD+ to form NADH

Answer 43

MALATE-ASPARTATE SHUTTLE

Question 44

Prominent in the brain and muscle cells

Answer 44

GLYCEROL-3-PHOSPHATE SHUTTLE

Question 45

Electrons from cytosolic NADH is ultimately accepted by FAD in the mitochondria to form FADH2

Answer 45

GLYCEROL-3-PHOSPHATE SHUTTLE

Question 46

Electrons from cytosolic NADH are accepted by DHAP to from __

Answer 46

glycerol-3-phsophate (G3P)

Question 47

passes these electrons to mitochondrial FAD to form FADH2

Answer 47

G3P glycerol-3-phsophate

Question 48

Glycerol-3-Phosphate Shuttle Recall: __ enters complex II of ETC • Results to a LOWER ATP yield (1.5 ATPs / cytosolic NADH)

Answer 48

FADH2

Question 49

Shuttle regenerates NADH inside the mitochondrial matrix

Answer 49

Malate-Aspartate Shuttle

Question 50

Malate-Aspartate Shuttle • Recall: __ enters complex I of the electron transport chain • Capable of MAXIMIZING ATP YIELD from NADH produced in glycolysis (2.5 ATPs / cytosolic NADH)

Answer 50

NADH