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BMB 402 > Exam 1 > Flashcards

Exam 1 Flashcards

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1
Q

What is the net equation for glycolysis?

A

Glucose + 2NAD+ + 2ADP + 2P = 2Pyruvate + 2NADH + 2H+ + 2ATP + 2H20

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2
Q

What is the overall purpose of glycolysis?

A

Takes one molecule of glucose and breaks it into 2 molecules of glucose. Makes 2 net ATP as well as reducing power.

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3
Q

How many steps are in glycolysis?

A

10 steps

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4
Q

What are the first 5 steps of glycolysis characterized as?

A

ATP investment, invests 2 ATP

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5
Q

What are the last 5 steps of glycolysis characterized as?

A

ATP productions, produces 4 ATP

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6
Q

What are the 3 most energetically favorable steps in glycolysis and why?

A

Steps 1,3, and 10. Have large delta G from coupled reactions and spontaneous that allow glycolysis to be energetically favorable.

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7
Q

What does the first step of glycolysis accomplish?

A

Uses hexokinase/glucokinase to phosphorylate glucose via ATP hydrolysis

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8
Q

What is the importance of glucokinase?

A

Used specifically in the liver and pancreas. Levels are measured for blood glucose monitoring

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9
Q
A
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10
Q

What is step 3 of glycolysis?

A

PFK-1 phosphorylates fructose-6-p to fructose 1,6-BP via ATP hydrolysis

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11
Q

What is the rate limiting step of glycolysis?

A

STEP 3!! PFK-1 regulates flux!

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12
Q

What is an inhibitor of of PFK-1?

A

Citrate! Makes sense since citrate is produced in the citrate cycle, so if that is in excess, glycolysis does not need to occur as fast, also ATP, because then additional ATP is not needed. Also low levels of fructose 2,6-BP

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13
Q

What is an activator of PFK-1?

A

High Fructose 2,6-BP. It is a regulator of glycolysis and gluconeogenesis. Also low levels of AMP and ADP

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14
Q

What is step 6 of glycolysis?

A

Uses G3P dehydrogenase and produces 2 NADH

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15
Q

What is step 7 of glycolysis?

A

Uses Phosphoglycerate kinase and produces 2ATP

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16
Q

What is step 10 of glycolysis?

A

uses pyruvate kinase and produces 2 ATP

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17
Q

What does the direction of metabolic flux depend on?

A

Substrate availability!

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18
Q

What happens in pancreatic B cells when glucose levels are high?

A

There is an increased rate of glycolysis, increased ATP, then an increase of Ca2+ that triggers the release of insulin!

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19
Q

What are the three different fates of pyruvate?

A

In aerobic conditions, goes to the citrate cycle. In anaerobic conditions, goes to ethanol production or lactate production

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20
Q

Where is NAD+ regenerated and why is it necessary?

A

It is required at step 6 of glycolysis to continue because NADH is produced. NAD+ accepts electrons and then carries it to the ETC.

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21
Q

What is the overall purpose of the citrate cycle?

A

It is central to aerobic metabolism and ATP production, links oxidation of various metabolites to ATP synthesis through shared intermediates, provides metabolism for a number of biosynthetic pathways

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22
Q

What is the primary function of Aerobic respiration?

A

To oxidize acetyl-CoA

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23
Q

What does each turn in the citrate cycle?

A

transfer of 8 e-, generates 3 NADH, generates 1 FADH, generates 1 GTP

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24
Q

What is the role of pyruvate dehydrogenase?

A

converts pyruvate to acetyl-CoA. It is a complex with 5 coenzymes

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25
What are the 5 coenzymes of pyruvate dehydrogenase
NAD+, FAD, CoA, TPP, alpha lipoic acid
26
What is NAD+ derived from?
Niacin (vitamin B3)
27
What is FAD derived from?
Riboflavin (vitamin B2)
28
What is CoA derived from and what is it used for?
Derived from Vitamin B5, and used to generate acetyl CoA
29
What is TPP derived from and what is the purpose?
Derived from vitamin B1, and is required for pyruvate dehydrogenase and alpha ketoglutarate dehydrogenase
30
What is the purpose of alpha lipoic acid?
provides a reactive disulfide that participates in redox reactions
31
What is pyruvate dehydrogenase regulated by?
phosphorylation, NADH, ATP and Acetyl-CoA levels
32
What does Arsenic do?
Irreversibly blocks catalytic activity of lipoamide containing enzymes
33
What is step 1 of the citrate cycle?
Uses citrate synthase and is energetically favorable
34
What is step 3 of the citrate cycle?
Uses Isocitrate dehydrogenase, and produces NADH
35
What is step 4 of the citrate cycle?
uses alpha ketoglutarate dehydrogenase and produces NADH
36
What is step 5 of the citrate cycle?
uses succinyl-CoA synthetase and produces GTP
37
What is Step 6 of the citrate cycle?
Uses succinate dehydrogenase, and produces FADH2
38
What is step 8 of the citrate cycle?
Uses malate dehydrogenase, and generates NADH
39
What are the three main regulatory enzymes of the citrate cycle?
citrate synthase (1), isocitrate dehydrogenase (3), and alpha ketoglutarate dehydrogenase (4)
40
What is an activator of pyruvate dehydrogenase?
NAD+, CoA, ADP, Ca2+
41
What is an inhibitor of pyruvate dehydrogenase?
NADH, acetyl-CoA, ATP
42
What is an activator of citrate synthase?
ADP
43
What is an inhibitor of citrate synthase?
NADH, citrate, ATP, succinyl-CoA
44
What is an activator of Isocitrate dehydrogenase?
ADP, Ca2+
45
What is an inhibitor of isocitrate dehydrogenase?
NADH, and ATP
46
What is an activator of Alpha ketoglutarate dehydrogenase?
AMP, Ca2+
47
What is an inhibitor of alpha ketoglutarate dehydrogenase?
NADH, succinyl- CoA, ATP
48
What is an activator of pyruvate carboxylase?
acetyl-CoA
49
What is the net equation for the citrate cycle?
Acetyl-CoA + 3NAD+ + FAD + GDP + P + 2H20 = CoA + 2CO2 + 3NADH + 3H+ + FADH2 + GTP
50
What is the chemiosmotic theory?
Describes the energy conversion in essentially all organisms, a proton gradient is established across the mitochondrial inner membrane, there is movement of protons down this gradient, and ATP is produced
51
What is proton flow?
the proton gradient is initiated by outward pumping of H+ from the mitochondrial matrix by 3 large protein complexes. There is then the inward flow of H+ through the membrane bound ATP synthase protein accomplishes ATP synthesis
52
What the the ETC and what is its goal?
It describes the combined redox reactions that occur in a set of protein complexes embedded in the inner mitochondrial membrane -NAD+ is oxidized and O2 is reduced to H20 -establishes a proton gradient based on reducing power that creates ATP
53
What is uncoupling in terms of ETC and why is it important?
Uncoupling means that ATP synthesis no longer occurs, the proton gradient is established but no ATP is made. It creates heat instead, some organisms, like bears use this during hibernation when they need warmth more than energy
54
Where does NADH oxidation occur?
Complex 1
55
Where does FADH2 oxidation occur?
Complex 2
56
How many electrons are needed from both NADH and FADH2 to start the ETC?
2e- so 2NADH and 1 FADH2
57
How are the complexes arranged in the ETC?
They are arranged based on reduction potentials, complex 1 has the most negative and O2 is the most positive, each increasing , to have more of a need of accepting and moving the e-
58
What are redox loops and where does it occur?
it is the separation of protons and electrons on opposite sides of the membranes. It takes place in complex 3 (Q cycle)
59
What are proton pumps and where are they?
they are dependent on protein complex conformational changes. It occurs in complex 1 and 4
60
What is complex 1 and what happens here?
It is NADH-ubiquinone reductase. NADH hands off 2e- (oxidized) to coenzyme Q (reduced). It is the largest complex and is covalently bonded to FMN. 4H+ go across the membrane and 2H+ go with coenzyme Q.
61
What is coenzyme Q?
It is a mobile e- carrier and transports electrons from complex 1 to complex 3. It is the entry for 2e- from the citrate cycle, fatty acid oxidation, and G3P-dehydrogenase
62
What is the role of FMN in complex 1?
It is the middle man between NADH and coenzyme Q. It takes 2e- from NADH and transfers them through a series of steps to coenzyme Q.
63
What is coenzyme Q reduced to?
ubiquinol (QH2)
64
What is complex 2 and what does it do?
It is succinate dehydrogenase, it catalyzes oxidation of FADH2 which gives its electrons to coenzyme Q.
65
What is complex 3 and what does it do?
it is ubiquinone-cytochrome c oxidoreductase. QH2 hands off its electrons and cytochrome c is reduced and 4H= are translocated. it contains two different protein subunits and ubiquinone can bind
66
What is the Q cycle?
Occurs in complex 3, it converts the 2e- from one molecule of QH2 to 2 molecules of cytochrome C for them to be transported. It then can transfer e- to complex 4 by going out of the membrane.
67
What is complex 4 and what does it do?
cytochrome C oxidase. It accepts one e- at a time, then reduces O2 to water with these electrons. two H+ are then translocated across the membrane.
68
What are the two structural components of ATP synthase?
F1- encodes catalytic activity F0- acts as a proton channel crossing the inner mitochondrial membrane
69
How do protons flow through the ATP synthase to synthesize ATP?
They flow through the F0 part, spinning the rotor which goes from loose to tight to open. Every turn of the rotor 120 degrees results in ADP being combined with P. ATP is then release in the open position.
70
What is the purpose of the malate-aspartate shuttle and G3P shuttle?
Because NADH and FADH2 cannot get through the membrane, they pass their electrons to these shuttles to move them across the membrane where they then pass them back off to NAD+ and FAD to be then again reduced.
71
How is ATP and ADP transported out of and into the cell?
Through the ATP translocase! It is an antiporter protein which changes conformation based on which molecule is moving across the membrane.
72
What is phosphate transolcase?
Translocates one P and one H+ into the matrix. Can be a symporter or an antiporter. It is electrically neutral.
73
What is the Malate-aspartate shuttle and where does it occur?
It is the primary shuttle in liver cells. All reactions are reversible, and the supply is NAD+ is maintained because it passes its electrons off and then returns back to the respective processes.
74
What is the G3P- shuttle?
It delivers e- from NADH to the mitochondrial matrix using FAD. They then go into the ETC through coenzyme Q.
75
How is oxidative phosphorylation regulated?
ADP and ATP levels control aerobic respiration. The ratio of NADH/NAD+ in the mitochondrial matrix controls multiple steps in the citrate cycle.
76
What diseases impact the ETC?
Rotenone, Cyanide, CO, oligomycin
77
What is the pentose phosphate pathway?
It reduces 2 NADP+ to NADPH. It also produces ribose-5-phosphate from glucose-6-phosphate. It occurs in the cytoplasm
78
What is ribose-5-phosphate used for?
used to make nucleotides and coenzymes
79
What is gluconeogenesis?
It is the production of glucose from non-carbohydrate compounds. It occurs when dietary sources are low. It occurs mostly in the cytoplasm except the first step where acetyl CoA is turned into pyruvate via pyruvate carboxylase.
80
Which steps in gluconeogenisis are different compared to glycolysis?
Steps 1,2,9, and 11. Have different enzymes because those processes are spontaneous.
81
What is biotin and why is it needed?
It is a water soluble vitamin that acts as a coenzyme for pyruvate carboxylase.
82
What are the 4 major sources of carbon for gluconeogenesis?
Glycerol from triglycerides, amino acids, lactate and CO2 fixation from chloroplasts
83
How is step 1 regulated in gluconeogenesis?
Pyruvate carboxylase is activated by acetyl CoA and inhibited by ADP
84
How is step 2 regulated in gluconeogenesis?
Phosphoenolpyruvate carboxylkinase is inhibited by ADP.
85
What is the Cori Cycle?
Alternative Pathway when lactate builds up from anaerobic metabolism. It does not require malate transfer. It provides a mechanism for lactate to be made into glucose which then can be used for energy and replenish glycogen stores in the liver.
86
What is glucose-6-phosphotase?
Enzyme that allows for glucose-6-p to transported into the cell. It occurs in the liver and kidney which have high rates of gluconeogenesis
87
How does the dual enzyme work to control hormonal regulation and glucose degredation and synthesis?
The PFK-2 side is activated to promote glycolysis from insulin, because the patient has high blood sugar and it needs to be degradeded. When there is low blood sugar and glucagon is present, FBPase is active and promotes gluconeogensis, as new glucose needs to be introduced.
88
How is the dual enzyme able to change its function?
Phosphorylation and kinases!
89
What are the three key enzymes involved in glycogen synthesis and degredation?
Glycogen phosphorylase Glycogen synthase Glycogen branching and debranching
90
What activates glycogen phosphorylase?
epinephrine and Glucagon
91
What activates glycogen synthase?
Insulin
92
What is glycogen?
A complex that consists of glycogenin protein, 50,000 glucose subunits , with alpha 1,6 branches every 8-12 residues. 20-40 of these complexes form a glycogen particle
93
What does glycogen generate in muscles?
glucose-6-p
94
Why is glycogen degredation important?
It is the primary source of glucose for ATP production during muscle contraction, it is initiated by glycogen phosphorylase 1
95
What does the glycogen phosphorylase dimer do?
It catalyses cleavage of alpha 1,4 bonds at nonreducing ends. It keeps cleaving until within 4 units of the 1,6 bond. Has two conformations R (active) and T (inactive)
96
What is glycogen debranching enzyme?
It recognizes the partially degraded branch and transfers three glucose units to the nonreducing end then cleaves the 1,6 bond to release the glucose
97
What is required for glycogen synthesis?
synthesis of uridine diphosphate glucose, helps to attach a new glucose unit to the growing chain
98
What is glycogen synthase?
It attaches a glucose to the nonreducing end of the glycogen chain
99
What is glycogen branching enzyme?
It transfers 7 glucose residues from one end of a glycogen to a nearby chain
100
What is the role of glycogenin?
It is an anchor protein for the glycogen core complexes. It also catalyzes glycosyltransferase and synthesis reactions needed to generate glycogen. it also extends the chain to 7 glucose residues
101

BMB 402 (3 decks)

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