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Biochemistry > Chapter 12 > Flashcards

Chapter 12 Flashcards

1
Q

Where does the citric acid cycle occur within the cell?

A

Mitochondria

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2
Q

Where are mitochondria most abundant in the body?

A

Muscle and liver cells

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3
Q

Why cant RBCs generate energy from the CAC?

A

They lack of mitochondria

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4
Q

Where do RBCs get energy from?

A

Glycolosis

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5
Q

Where are the enzymes for CAC located?

A

In the mitochondrial matrix

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6
Q

Why is the CAC considered part of the aerobic metabolic process?

A

Because of its link to the electron transport chain and oxidative phosphorylation

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7
Q

What coenzymes are generated by the CAC?

A

NADH and FADH2

they pass their electrons to oxygen to generate energy for the cell

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8
Q

Where do the reduced coenzymes from CAC go?

A

Electron transport chain

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9
Q

Where does glycolysis occur in the cell?

A

Cytoplasm

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10
Q

Where is succinate dehydrogenase located?

A

In the inner membrane of the mitochondria

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11
Q

Where must pyruvate travel to for the CAC?

A

From the cytosol into the mitochondrial matrix through a transporter in the inner membrane

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12
Q

Where does oxidative phosphorylation occur?

A

Inner membrane of the mitochondria

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13
Q

What must be activated for it to enter the CAC?

A

Pyruvate must be activated to acetyl-CoA

reactive thiol group that has higher energy bonds

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14
Q

What happens during conversion of pyruvate to Acetyl-CoA?

A

Oxidative decarboxylation of pyruvate (irreversible oxidation)
First carbons of glucose to be fully oxidized

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15
Q

What catalyzes the conversion of pyruvate to acetyl-coa?

A

Pyruvate dehydrogenase complex (3 enzyme complex)

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16
Q

What are the prosthetic groups of the pyruvate dehydrogenase complex?

A

TPP
Lipoyllysine
FAD

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17
Q

What are the co-substrates for pyruvate dehydrogenase complex?

A

NAD+ and CoA-SH

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18
Q

What is removed from pyruvate as CO2 by pyruvate dehydrogenase?

A

Carboxyl group

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19
Q

How many coenzymes are required by pyruvate dehydrogenase complex?

A

5 coenzymes

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20
Q

Is conversion of pyruvate to Acetyl-CoA reversible?

A

No it is irreversible

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21
Q

What are the products of converting pyruvate to acetyl-CoA?

A

Acetyl-CoA

NADH

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22
Q

What do the 5 coenzymes of pyruvate dehydrogenase complex do?

A

Assist in transfer of functional groups

23
Q

What do the 5 coenzymes for pyruvate dehydrogenase complex act as?

A

Oxidants or carriers for intermediates of this enzyme complex

24
Q

What kind of complex is PDC?

A

A large multienzyme complex

25
Q

What are the three enzymes in PDC?

A 
Pyruvate dehydrogenase (E1)
Dihydrolipoyl transacetylase (E2)
Dihydrolipoyl dehydrogenase (E3)
26
Q

What are the advantages of a multienzyme complex?

A

Short distance between catalytic sites allows channeling of substrates from one catalytic site to another
Channeling minimizes side reactions
The regulation of activity of one subunit affects the entire complex

27
Q

What is the first step of CAC?

A

The C-C bond formation between acetate(2C) and oxaloacetate(4C) to make citrate (6C)

Releases CoA-SH
Claisen condensation

28
Q

What is the second step in the CAC?

A

Isomerization via dehydration/rehydration to make isocitrate

Release water

29
Q

What does steps 3-4 of CAC do?

A

Oxidative decarboxylations to give 2 NADH

Release of 2 CO2
Makes alpha-ketoglutarate (3)
and Succinyl CoA

30
Q

What happens in step 5 of CAC?

A

Substrate-level phosphorylation to make succinate

Gives GTP from GDP
Makes CoA-SH

31
Q

What does step 6 of CAC do?

A

Dehydrogenation to give FADH2 to make fumerate

32
Q

What does step 7 of CAC do?

A

Hydration to make malate

33
Q

What happens in step 8 of CAC?

A

Dehydrogenation to give NADH

Makes oxaloacetate

34
Q

What is the mnemonic for CAC?

A 
Citrate
Is
Krebs
Starting
Substrate 
For
Making
Oxaloacetate
35
Q

In step one how is acetyl-CoA and Oxaloacetate combined?

A

By condensation

36
Q

Is step one favorable or unfavorable?

A

Favorable and irreversible

37
Q

What is step 1 of CAC regulated by?

A

Substrate availability

38
Q

What is step one of CAC inhibited by?

A

Increased concentrations of ATP, NADH, Citrate, Succinyl CoA

39
Q

What is step 1 of CAC stimulated by?

A

ADP

40
Q

What is unique about step 1 of CAC?

A

It is the only reaction with a C-C bond formation

41
Q

What does the activity of Step 1 of CAC depend on?

A

Oxaloacetate

42
Q

What is the first part of step 2 of CAC?

A

Loss of water (dehydration) from citrate to give a cis C-C double bond

43
Q

What kind of alcohol is citrate?

A

A tertiary alcohol

poor substrate for oxidation so needs to be changed

44
Q

What is the second part of step 2 of CAC?

A

Inserting water to cis-aconitate to make isocitrate

45
Q

What kind of alcohol is isocitrate?

A

A secondary alcohol

good substrate for oxidation

46
Q

What kind of reaction is the second step in CAC?

A

Dehydration - hydration reaction

47
Q

Is step 2 favorable?

A

No it is unfavorable and reversible

48
Q

What pulls step 2 forward?

A

Product concentration kept low

49
Q

What is produced in step 3?

A

NADH is produced

50
Q

What inhibits step 3 of CAC?

A

high levels of ATP or NADH

51
Q

What kind of reaction is step 3 ?

A

Oxidation and decarboxylation

52
Q

What stimulates step 3 of CAC?

A

ADP and Ca+2

53
Q

What is released in step 3 of CAC?

A

Carbon dioxide

Biochemistry (10 decks)

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