UBC- Class Review > Exam 3 prep > Flashcards

Exam 3 prep Flashcards

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1
Q

What is the overall reaction catalyzed by pyruvate kinase?

A

PEP + ADP → Pyruvate + ATP

Pyruvate kinase is the enzyme responsible for this reaction in glycolysis.

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2
Q

Name two allosteric inhibitors of pyruvate kinase.

A
  • IATP
  • Alanine

Alanine is synthesized from pyruvate, linking metabolism to amino acid synthesis.

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3
Q

What is a feed-forward activation in the context of glycolysis?

A

Fructose-1,6-bisphosphate activates pyruvate kinase

This activation helps coordinate the upper and lower portions of glycolysis.

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4
Q

What is the main function of the pyruvate dehydrogenase complex?

A

Conversion of pyruvate to Acetyl-CoA

This conversion links glycolysis to the citric acid cycle.

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5
Q

Where does the conversion of pyruvate to Acetyl-CoA take place in eukaryotic cells?

A

Mitochondrial matrix

The pyruvate dehydrogenase complex (PDC) is located here.

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6
Q

What type of reaction is involved in the conversion of pyruvate to Acetyl-CoA?

A

Decarboxylation / oxidation

This process results in the formation of Acetyl-CoA from pyruvate.

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7
Q

List the components of the pyruvate dehydrogenase complex.

A
  • Pyruvate dehydrogenase (E1)
  • Dihydrolipoamide transacetylase (E2)
  • Dihydrolipoamide dehydrogenase (E3)

Each component plays a role in the enzymatic activity of the complex.

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8
Q

What is the role of Thiamine Pyrophosphate (TPP) in the pyruvate dehydrogenase complex?

A

Cofactor bound to E1

TPP is essential for the decarboxylation of pyruvate.

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9
Q

What does Coenzyme A (CoA) carry?

A

Acyl groups

CoA is involved in the transfer of acyl groups in metabolic reactions.

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10
Q

What is the significance of the Krebs cycle?

A

It completely oxidizes Acetyl-CoA to CO2 and generates high energy electrons

These electrons are used in oxidative phosphorylation to produce ATP.

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11
Q

What is the first reaction in the Krebs cycle?

A

Condensation of oxaloacetate and Acetyl-CoA to form citrate

This step is catalyzed by citrate synthase.

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12
Q

What is the function of aconitase in the Krebs cycle?

A

Converts citrate to isocitrate

This involves dehydration and rehydration steps.

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13
Q

What is produced during the conversion of isocitrate to α-ketoglutarate?

A

NADH and CO2

This reaction is catalyzed by isocitrate dehydrogenase.

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14
Q

Which enzyme converts α-ketoglutarate to succinyl-CoA?

A

α-ketoglutarate dehydrogenase complex

This reaction also produces NADH and CO2.

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15
Q

What is generated when succinyl-CoA is converted to succinate?

A

GTP

This is the only step in the Krebs cycle that directly produces a usable energy molecule. (Nucleoside diphosphate kinase coverts GTP to ATP)

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16
Q

What does succinate dehydrogenase produce from succinate?

A

FADH2 and fumarate

This reaction is part of the Krebs cycle and involves oxidation.

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17
Q

True or False: The Krebs cycle is also known as the citric acid cycle.

A

True

It is also referred to as the tricarboxylic acid (TCA) cycle.

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18
Q

What regulates the pyruvate dehydrogenase complex?

A
  • Acetyl CoA
  • NADH
  • ATP

These molecules inhibit the complex, while pyruvate, NAD+, and ADP stimulate it.

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19
Q

What is the role of PDC associated kinase?

A

Phosphorylates E1 to inhibit the pyruvate dehydrogenase complex

This regulation is crucial for controlling the activity of the complex.

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20
Q

Fill in the blank: The conversion of pyruvate to Acetyl-CoA is called _______.

A

pyruvate decarboxylation

This process is a key step in cellular respiration.

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21
Q

What happens to FAD during the regeneration of lipoamide?

A

It gets reduced to FADH2

This occurs in the last step of the pyruvate dehydrogenase complex activity.

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22
Q

What is the reaction for converting GTP to ATP?

A

GTP + ADP = GDP + ATP

Catalyzed by Nucleoside Diphosphate Kinase

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23
Q

What does succinate dehydrogenase oxidize and what does it generate?

A

Succinate to fumarate, generating FADH2

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24
Q

Where is succinate dehydrogenase located?

A

Embedded in the inner mitochondrial membrane

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25
What is the role of FADH2 in the electron transport chain?
It contributes electrons to the ETC
26
What reaction occurs when fumarate is converted to malate?
A hydration reaction where water is added across the double bond in fumarate by fumarase
27
What enzyme oxidizes malate to oxaloacetate?
Malate dehydrogenase
28
What is generated during the oxidation of malate to oxaloacetate?
NADH
29
What is the net equation of the Krebs cycle?
Acetyl CoA + 3 NAD+ + FAD + GDP + P1 + H2O -> CoA + 3 NADH + FADH2 + GTP + 2 CO2
30
What stimulates citrate dehydrogenase?
ADP
31
What inhibits citrate dehydrogenase?
NADH and ATP
32
What are the products of oxidative phosphorylation?
ATP, water, and regenerated electron carriers
33
What is the electron transport chain (ETC)?
A series of complexes that transfer electrons to produce ATP
34
What is the function of ATP synthase?
To generate ATP using the proton motive force (PMF)
35
What is the role of ubiquinone (coenzyme Q) in the ETC?
It acts as an electron carrier shuttle between complexes I/II and III
36
What is the net equation for the reaction catalyzed by complex IV (cytochrome c oxidase)?
4 cytochrome c (reduced) + O2 + 4 H+ -> 4 cytochrome c (oxidized) + 2 H2O
37
What type of transport is involved in pumping H+ from the matrix to the intermembrane space?
Secondary active transport
38
True or False: Complex II is a proton pump.
False
39
What are reactive oxygen species (ROS)?
Byproducts of electron transport that can damage DNA and proteins
40
What is the standard reduction potential (E')?
A measure of a molecule's affinity for electrons
41
What inhibitors can block electron transfer in the ETC?
Azide, carbon monoxide, and cyanide
42
What is the role of cytochrome c?
It transports electrons from complex III to complex IV
43
What does the Nerst equation relate to in terms of thermodynamics?
Gibbs free energy to standard reduction potentials
44
What is the approximate ATP yield from NADH?
2.5 ATP per NADH
45
What is the Gibbs free energy change (ΔG°') for ATP synthesis?
-30.5 kJ/mol
46
What is the significance of the proton motive force (PMF)?
It drives ATP synthesis via ATP synthase
47
Fill in the blank: The formation of ATP as a result of electron transfer from NADH and FADH2 to _______ is called oxidative phosphorylation.
oxygen
48
What happens when ETC is inhibited?
Carriers will become oxidized instead of being reduced.
49
What is ATP synthase?
The complex used for the generation of ATP.
50
What are the two components of ATP synthase?
* Fo: embedded in the IMM, containing half channels for proton flow * F1: extends into the matrix, synthesizes ATP.
51
What is the function of the Fo component in ATP synthase?
Generates a spinning motion through proton flow.
52
How many β-subunits are arranged in the ATP synthase complex?
Three β-subunits.
53
What is the loading conformation of the β-subunit?
Where ADP and Pi can bind and become trapped.
54
What occurs at the tight site of the β-subunit?
ATP synthesis occurs and is tightly bound to the β-subunit.
55
What is the open site of the β-subunit characterized by?
A release conformation with low affinity for ATP or ADP.
56
What does the spin from the Fo component cause?
It causes each of the three β-subunits to cycle through loose, tight, and open conformations.
57
What is the ATP yield per NADH?
2.5 ATP/NADH.
58
What is the ATP yield per FADH2?
1.5 ATP/FADH2.
59
What is the structure of Subunit C in ATP synthase?
Consists of 2 α-helices that spin in the membrane.
60
How many C subunits are typically found in human ATP synthase?
10 C subunits.
61
What is the role of subunit a in ATP synthase?
It acts as a clamp and does not rotate.
62
What is the significance of the aspartic acid in Subunit C?
When aspartate gets protonated to aspartic aacid, it will cause the F_0 to rotate (an almost full rotation, and clockwise) ## Footnote It can be protonated or deprotonated depending on pH.
63
What is oxidative phosphorylation?
The process of ATP synthesis coupled with the electron transport chain.
64
What is the impact of a high ATP/ADP ratio on cellular respiration?
O2 consumption drops.
65
What is 'acceptor control'?
The regulation of cellular respiration by the availability of ADP as a phosphate acceptor.
66
What does 2,4-dinitrophenol do in oxidative phosphorylation?
It uncouples the ETC and ATP synthase by carrying H+ across the IMM.
67
What is the role of the glycerol-3-phosphate shuttle?
Transports electrons from NADH to the ETC.
68
What happens during the malate-aspartate shuttle?
NADH is generated in the matrix and aspartate moves to the cytosol.
69
What are the steps of glycogen synthesis?
* Glucose to Glucose-6-phosphate * G6P to Glucose-1-phosphate * GIP + UTP to UDP-glucose.
70
What are the two ways to restore low blood glucose levels?
* Gluconeogenesis * Glycogen breakdown.
71
What is the structure of glycogen?
A polymer of glucose residues with α(1-4) and α(1-6) linkages.
72
What is the role of the reducing end in glycogen?
It has a free anomeric carbon that can reduce other molecules.
73
What happens to glucose during glycogen breakdown?
It undergoes phosphorolysis and debranching.
74
What is the significance of glycogen for the brain?
It allows for the release of glucose during low blood glucose levels.
75
What is the total ATP yield for the complete oxidation of one glucose molecule?
Approximately 30-32 ATP.
76
What is the function of ATP/ADP translocase?
Exchanges ATP from the matrix for ADP from the cytosol.
77
What drives the exchange of ATP and ADP across the IMM?
The charge gradient created by the proton motive force.
78
What enzyme is responsible for converting G6P to glucose-1-phosphate (GIP)?
Phosphoglucose Mutase
79
What enzyme converts glucose-1-phosphate (GIP) into UDP-glucose?
UDP-glucose pyrophosphorylase
80
What is the activated form of glucose produced during glycogen synthesis?
UDP-glucose
81
What energy cost is associated with glycogen synthesis?
2 ATP equivalents ## Footnote Glucose —> Glucose-3-Phosphate (By glucokinase)
82
What is the primer required for glycogen synthesis initially supplied by?
Glycogenin
83
What enzyme creates branches in glycogen?
Branching enzyme
84
What process is called when a glucose residue is removed from a glycogen chain?
Phosphorolysis
85
What enzyme is responsible for phosphorylating glucose during phosphorolysis?
Glycogen phosphorylase
86
What happens to *alpha*(1->6) linked glucose during the debranching step of glycogen breakdown?
It is cleaved by glucosidase
87
After glucose is phosphorylated to GIP, which enzyme converts it to G6P?
Phosphoglucose mutase
88
What are the pathways G6P can take in muscle and liver tissues?
* Glycolysis to produce ATP in muscles * Dephosphorylation to free glucose in the liver * Pentose phosphate pathway to generate ribose and NADPH
89
What is gluconeogenesis?
The process of generating glucose from non-carbohydrate precursors
90
What molecules can be used to make glucose during gluconeogenesis?
* Lactate/Pyruvate * Proteins * Glycerol
91
What is the first bypass reaction in gluconeogenesis?
Generation of oxaloacetate by pyruvate carboxylase
92
What enzyme generates phosphoenolpyruvate (PEP) in gluconeogenesis?
Phosphoenolpyruvate carboxy kinase
93
What is the final product generated from fructose-1,6-bisphosphate in gluconeogenesis?
Fructose-6-phosphate
94
What is the net reaction for gluconeogenesis?
2 pyruvate + 2 GTP + 4 ATP + 6 H2O + 2 NADH + 2 H+ -> Glucose + 2 GDP + 6 Pi + 2 NAD+
95
What regulates gluconeogenesis?
Bypass reactions that are allosterically regulated
96
How does insulin affect blood glucose levels?
Promotes the uptake of glucose and decreases gluconeogenesis
97
What hormone is secreted when glucose levels are low?
Glucagon
98
What is the role of epinephrine during stress?
Promotes gluconeogenesis and glycogen breakdown
99
What happens to glucose levels during starvation? And how does the brain compensates?
Glucose levels becomes low. The brain can use ketone bodies as an energy source, but still requires some glucose
100
What is the consequence of long-term hyperglycemia?
Neurological, cardiovascular, renal, and vision damage
101
What occurs during hypoglycemia?
Potential loss of consciousness and brain damage
102
What is the role of glucogenic amino acids?
Can be used to form glucose
103
What is the function of acetyl CoA in gluconeogenesis?
Cannot be converted back to pyruvate
104
What is the significance of glucose transporters (GLUTs)?
Facilitate glucose uptake into cells
105
What happens to gluconeogenesis and protein breakdown during fasting? | At around 2 days of fasting
They slow down but do not stop. Some tissues like RBC still require glucose. ## Footnote This is particularly important for maintaining energy levels in critical tissues.
106
What are the consequences of prolonged fasting?
Fatty acid stores become exhausted, ketone body levels fall, proteins are consumed, muscles waste away, and the immune system fails. ## Footnote Eventually, this leads to a high risk of death from infection.
107
What are glucose transporters (GLUTs)?
Proteins that help transport glucose via facilitated diffusion. ## Footnote Their expression levels vary by cell type.
108
Which GLUT is found in all cell types and has a km of 1 mM?
GLUT 1&3 ## Footnote * These transporters continuously brings glucose into cells. * Found in all cell types * found in large amounts in the Brain and RBCs
109
What is the km of GLUT 2 and where is it found?
Km is 13-17 mM; found in the liver and pancreas. ## Footnote It ensures glucose is metabolized in the liver at high rates and triggers insulin release in the pancreas.
110
Where is GLUT 4 predominantly found and what is its km?
Found in muscle cells, adipocytes, and the heart; its km is 5 mM. ## Footnote GLUT 4 is only used when there are large amounts of glucose.
111
What triggers the movement of GLUT 4 to the plasma membrane?
Stimulation by insulin. ## Footnote This process allows for increased glucose uptake in response to high blood glucose levels.
112
What happens to blood glucose levels during the fed/fast cycle?
They vary based on dietary intake, glycogen stores, and gluconeogenesis. ## Footnote This cycle is crucial for maintaining energy balance.
113
How do plasma levels of ketone bodies change during fasting?
They initially rise but may fall if fasting is prolonged beyond a certain period. ## Footnote Ketone bodies serve as an alternative energy source during fasting.
114
What factors influence blood levels of different fuel substrates during fasting?
Duration of fasting and individual metabolic responses. ## Footnote This varies from person to person.
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