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Flashcards in Lecture 31 Deck (39):
1

What are the two main checkpoints in TCA (citric acid cycle)?

-pyruvate Dehydrogenase complex
-citrate synthase

2

What are two other regulated reactions other than the two main checkpoints in the TCA cycle?

-isocitratre dehydrogenase
-a-ketogluterate dehydrogenase complex

3

What do all the four regulated reactions in the TCA cycle have in common?

-Highly exergonic
-these reactions keep the cycle going (usually) in a clockwise direction
-if the flow of metabolites at these reactions is slowed the whole cycle will slow down

4

What is associated with the energy rich state of the cell?

High Concentrations of ATP, acetyl-CoA, NADH, succinyl-CoA, and citrate

5

What is associated with energy poor state of the cell?

-these are your activators because they are substrates or because they work through allosteric effects
-AMP, NAD+, CoA, ADP

6

What is an allosteric activator at three of the four regulator steps?

Ca2+

7

What inhibits PHD?

ATP, Acetyl-CoA, NADH, and Fatty Acids

8

What activates PHD?

AMP, CoA, NAD+, Ca2+

9

what inhibits citrate synthase?

NADH, succinyl-CoA, citrate, ATP

10

What activates citrates synthase?

ADP

11

What inhibits isocitrate dehydrogenase?

ATP

12

What activates isocitrate dehydrogenase?

Ca2+, ADP

13

What inhibits a-ketogluterate dehydrogenase complex?

Succinyl-CoA, NADH

14

What activates a-ketogluterate dehydrogenase complex?

Ca2+

15

PDH complex covalent modification?

-In mammals but not in smaller eukaryotes or prokaryotes
-phosphorylation of the E1 subunit regulates the activity
-there is kinase and a phosphatase activity that puts on or takes off a phosphate on the E1 subunit

16

What would put the PDH complex in the active state?

NAD+, CoA, ADP, and pyruvate inhibit the kinase activities the PDH complex tends to the unphosphorylated state-active state

17

What would put the PDH complex in the inactive State?

NADH, Acetyl-CoA induce the kinase, so the PDH complex becomes more phosphorylated and is inactive

18

What regulates the activity of the pyruvate dehydrogenase complex subunits E2 and E3

-by the concentrations of NAD+/NADH and HS-CoA/Acetyl-CoA
-NAD+ activates E3
-NADH inhibits E3
-HS-CoA activates E2
-Acetyl-CoA inhibits E2

19

In the TCA cycle what input channels are there?

Pyruvate
a-ketogluterate
Fumurate
Succinate
Aspartate

BUT NOT Oxaloacetate nor acetyl-CoA

20

In the TCA cycle was output channels are there?

phosphoenolpyruvate
citrate
malate
Aspartate

21

What is the most likely reason that high amounts of metabolites would enter the TCA cycle?

from catabolism of carbohydrates or fatty acids (ex: from the diet)

22

anaplerotic reactions

the reactions that replenish the metabolites in the citric acid cycle

23

What is the main anaplerotic reaction?

replenishment of oxaloacetate

24

What side of the TCA cycle does the metabolites needed for anabolic reactions come from? What is the consequence of any withdrawel from this?

Right side of the TCA cycle
-decrease in the oxaloacetate concentration

25

Glyoxylate cycle

in microorganisms and plants
-uses two molecules of acetyl-CoA in each cycle and does not release CO2
-results in efficient biosynthesis of oxaloacetate
-succinate is produced and is transferred to the citric acid cycle

26

Where does the TCA cycle occur?

eukaryotes-mitochondrial matrix
bacteria-cytosol

27

What is gained per each cycle of the TCA cycle?

for each acetyl-CoA oxidized by the cycle, the energy gain is three NADH, one FADH2, and one ATP(GTP)

28

Mitochondrion

has two bilayer membranes
-outer and inner membrane

29

Phase 1 of catabolism is located where?

Glycolysis-to the point of pyruvate takes place in the cytoplasm
-outside of the outer membrane of the mitochondrion

30

Outer membrane of mitochondrion

-porous thus is easy equilibration of material from the cytoplasm across the outer membrane into the inter membrane space

31

Inner membrane of mitochondrion

75% protein by weight
-completely closed and transporters are needed for movement of molecules

32

Phase 2 of catabolism

citric acid cycle plus fatty acid oxidation and acid degradation
-takes place in the inner membrane of the mitochondria
-reduced electron carriers (NADH and FADH) will accumulate inside the inner membrane

33

Entry of Pyruvate into the TCA cycle

-called oxidative decarboxylation because CO2 is lost from pyruvate and there is oxidation
-enzyme: pyruvate dehydrogenase complex

34

Pyruvate dehydrogenase

-enzyme used to covert pyruvate to acetyl-CoA
-contains three types of subunits (E1, E2, and E3)

35

E1 subunit of pyruvate dehydrogenase complex

pyruvate dehydrogenase
-coenzyme: TDP (aka TPP)

36

E2 subunit of pyruvate dehydrogenase complex

dihydrolipoamide acetyltransferase
-coenzyme:lipollysine

37

E3 subunit of pyruvate dehydrogenase complex

dihydrolipoamide dehydrogenase
-coenzyme: FAD

38

Reaction 1 of TCA cycle

enzyme: Citrate synthase
-Acetyl-CoA is a high energy compound and it is used as a substrate contributor to the large standard free energy decrease making the reaction and irreversible one

39

Succinate Dehydrogenase


-located in the inner side of the inner mitochondrial membrane