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Biochemistry 3630 > Ch 14 Citric Acid Cycle > Flashcards

Ch 14 Citric Acid Cycle Flashcards

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1
Q

Where does the citric acid cycle occur?

A

In mitochondria

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2
Q

What are the alternative names for the citric acid cycle?

A

Tricarboxylic acid (TCA) cycle, Kreb’s cycle

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3
Q

Who discovered the citric acid cycle and in what year?

A

Sir Hans Adolf Krebs, 1937

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4
Q

What is the net result of each round of the citric acid cycle?

A

Loss of two carbons as CO2 for each acetyl-CoA that enters the cycle

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5
Q

What are the three types of high-energy products produced in the citric acid cycle?

A
  • 1 GTP
  • 3 NADH
  • 1 FADH2
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6
Q

What does NADH stand for?

A

Nicotinamide adenine dinucleotide

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7
Q

What are the oxidized and reduced forms of NAD?

A

NAD+ (oxidized), NADH (reduced)

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8
Q

What are the oxidized and reduced forms of FAD?

A

FAD (oxidized), FADH2 (reduced)

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9
Q

What are the goals of the citric acid cycle?

A
  • Produce electron carriers (NADH, FADH2)
  • Produce GTP
  • Generate metabolic intermediates
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10
Q

What is the role of coenzyme A in the citric acid cycle?

A

Serves as a cofactor for acyl transfer reactions

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11
Q

What is the mnemonic for the citric acid cycle?

A

Citrate Is Kreb’s Starting Substrate For Making Oxaloacetate

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12
Q

True or False: The citric acid cycle produces ATP directly.

A

False

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13
Q

What is the only step in the citric acid cycle where energy in the form of ATP/GTP is generated?

A

Formation of succinate and GTP

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14
Q

What happens during the reaction catalyzed by citrate synthase?

A

Condensation reaction of acetyl-CoA and oxaloacetate to form citrate

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15
Q

What type of reaction is catalyzed by isocitrate dehydrogenase?

A

Oxidative-decarboxylation reaction

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16
Q

What is produced during the oxidative-decarboxylation reaction catalyzed by α-ketoglutarate dehydrogenase?

A

NADH and CO2

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17
Q

What vitamin deficiency is associated with a lack of NAD+?

A

Pellagra (niacin deficiency)

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18
Q

What is the role of manganese in the citric acid cycle?

A

Helps stabilize negative charges of reaction intermediates

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19
Q

Fill in the blank: The citric acid cycle is also known as the _______.

A

Kreb’s cycle

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20
Q

What is the fate of the six carbon atoms from glucose in the citric acid cycle?

A

They are released as CO2

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21
Q

How many turns of the citric acid cycle occur for each glucose molecule?

A

Two turns

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22
Q

What are the main products generated from one cycle of the citric acid cycle?

A

3 NADH, 1 FADH2, 1 GTP, 2 CO2

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23
Q

What is the energy yield from 1 NADH and 1 FADH2 during oxidative phosphorylation?

A
  • 1 NADH = 2.5 ATP
  • 1 FADH2 = 1.5 ATP
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24
Q

What regulates the citric acid cycle?

A

Regulation occurs at the three irreversible steps

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25
What is a potential consequence of mutations in citric acid cycle enzymes?
Linked to cancer
26
What is the energy yield of 1 NADH?
2.5 ATP ## Footnote NADH is a key electron carrier in cellular respiration, contributing to the production of ATP during oxidative phosphorylation.
27
What is the energy yield of 1 QH2?
1.5 ATP ## Footnote QH2 represents ubiquinol, which is part of the electron transport chain.
28
How many ATP are generated from the citric acid cycle?
32 ATP ## Footnote This total includes ATP produced from all cycles and associated processes.
29
What regulates the citric acid cycle?
Three irreversible steps ## Footnote These steps are critical control points in the cycle.
30
What is the effect of a high ATP/ADP ratio on the citric acid cycle?
Inhibits the cycle ## Footnote A high ATP/ADP ratio indicates sufficient energy, leading to reduced cycle activity.
31
What is the effect of a low NADH/NAD+ ratio on the citric acid cycle?
Activates the cycle ## Footnote A low NADH/NAD+ ratio suggests a need for energy production.
32
What is the mnemonic for the citric acid cycle?
Citrate is Krebs' starting substrate for making oxaloacetate ## Footnote This mnemonic helps remember the order of substrates in the cycle.
33
What are the main substrates in the citric acid cycle in order?
* Citrate * Isocitrate * α-Ketoglutarate * Succinyl-CoA * Succinate * Fumarate * Malate * Oxaloacetate ## Footnote Understanding the flow of substrates is essential for grasping the cycle's function.
34
What is the impact of a high NADH/NAD+ ratio on the citric acid cycle?
Inhibits the cycle ## Footnote A high NADH/NAD+ ratio indicates that the cell has sufficient reducing power, leading to decreased cycle activity.
35
What characterizes cells in a resting metabolic state regarding the citric acid cycle?
* Use little energy * High ATP/ADP ratio * High NADH/NAD+ ratio ## Footnote These conditions lead to decreased activity of the cycle.
36
What characterizes cells in an active metabolic state regarding the citric acid cycle?
* Use more energy than resting cells * Low ATP/ADP ratio * Low NADH/NAD+ ratio ## Footnote Active cells need to produce more ATP, thus activating the cycle.
37
Where are NADH, GTP, FADH2, CO2, and coenzyme A produced in the TCA cycle?
Various points in the cycle ## Footnote Each of these molecules is generated at specific steps within the cycle.
38
Where are ATP and O2 found in the TCA cycle?
ATP is produced in the cycle, O2 is not directly produced ## Footnote Oxygen is used in the electron transport chain, not in the cycle itself.
39
What is the Citric Acid Cycle also known as?
TCA Cycle ## Footnote TCA stands for Tricarboxylic Acid.
40
What are the three types of high-energy products generated in the Citric Acid Cycle?
* 1 GTP * 3 NADH * 1 FADH2
41
Which steps in the Citric Acid Cycle are highly regulated?
Steps 0, 1, 3, and 4
42
What is the significance of hydroxylation of collagen?
Cofactor: Ascorbic acid (Vitamin C) ## Footnote Deficiency leads to Scurvy.
43
Define activation in metabolic pathways.
Formation of a more reactive, higher energy substance
44
What is Coenzyme A's role in metabolic pathways?
Key co-enzyme for attaching molecules to the sulfhydryl end (-SH) for subsequent release
45
What happens during thioester hydrolysis?
Releases a large amount of free energy
46
What does the term 'amphibolic' mean in relation to the Citric Acid Cycle?
Functions in both anabolic and catabolic reactions
47
What is the consequence of reaction 8 being endergonic in the Citric Acid Cycle?
Oxaloacetate is harder to form
48
What happens to pyruvate during exercise?
Some pyruvate is converted to α-ketoglutarate
49
What are anaplerotic reactions?
Reactions that replenish citric acid cycle intermediates
50
What is the role of acetyl-CoA in lipid anabolism?
Starts lipid synthesis in the cytosol
51
Fill in the blank: The Citric Acid Cycle is a source of starting materials for the biosynthesis of _______.
[lipids, proteins, carbohydrates]
52
True or False: Glycogen is converted to glucose during caloric restriction.
True
53
What is the primary function of transaminases?
Interconversion of amino acids
54
What is the result of low oxaloacetate levels?
Elevated acetyl-CoA levels
55
What is the biochemical function of Biotin (Vitamin B7)?
Cofactor for carboxylation reactions
56
What are the main components that feed into the Citric Acid Cycle during catabolism?
* Proteins * Carbohydrates * Fatty acids
57
What are the consequences of insufficient oxaloacetate in the Citric Acid Cycle?
Elevated levels of Acetyl-CoA and activation of pyruvate carboxylase
58
What is the function of NADPH produced during lipid anabolism?
Used in fatty acid synthesis
59
What happens to citric acid cycle intermediates diverted to other pathways?
They can be replenished
60
What is the role of glutamate in amino acid formation?
Precursor of glutamine, arginine, and proline
61
How does exercise affect the Citric Acid Cycle?
Boosts activity up to 100-fold
62
What is the main difference between catabolic and anabolic pathways in the context of the Citric Acid Cycle?
Catabolic pathways degrade while anabolic pathways synthesize
63
Fill in the blank: The hydrolysis of a thioester is more exergonic than the hydrolysis of an ordinary _______.
[oxygen ester]
64
What are the two types of regions found in lipids?
Positive or negative regions and nonpolar regions
65
List the forms of lipids with extended chains.
* Fatty acids * Triacylglycerols * Sphingolipids * Phosphoacylglycerols
66
What are the cyclic forms of lipids?
* Cholesterol * Steroid hormones
67
Define a lipid.
A lipid is a group of organic compounds that are insoluble in water but soluble in organic solvents.
68
What is a fatty acid?
An unbranched-chain carboxylic acid (with COO-), most commonly with 12 - 20 carbons.
69
What is a saturated fatty acid?
A fully hydrogenated fatty acid with no C=C double bonds or alkenes.
70
What does the 'acyl' nomenclature refer to?
It refers to the naming convention used for fatty acids and their derivatives.
71
What are the common saturated fatty acids with 12 carbons?
* Lauric acid (Dodecanoic acid) * Structure: CH3(CH2)10COOH
72
Identify the common saturated fatty acid with 14 carbons.
* Myristic acid (Tetradecanoic acid) * Structure: CH3(CH2)12COOH
73
What is the common name for a saturated fatty acid with 16 carbons?
Palmitic acid (Hexadecanoic acid)
74
What is the structure of stearic acid?
CH3(CH2)16COOH
75
What is the common name for a saturated fatty acid with 20 carbons?
Arachidic acid (Eicosanoic acid)
76
What is the structure of behenic acid?
CH3(CH2)20COOH
77
Fill in the blank: Fatty acids usually contain ______ numbers of carbons.
even
78
What is the relationship between chain length and melting temperature in fatty acids?
The longer the chain, the higher the melting temperature.

Biochemistry 3630 (32 decks)

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