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SFM - Exam #2 > BCHM - Bioenergetics > Flashcards

BCHM - Bioenergetics Flashcards

1
Q

Where does the TCA cycle take place?

A

Inside the mitochondria

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2
Q

What is the common pathway into the TCA cycle?

A

Fats, polysaccharides, and proteins are converted into Acetyl-CoA before they can enter the TCA cycle and be used for energy.

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3
Q

What are the 3 energy equivalent substances generated via the TCA cycle?

A

NADH, FADH2, and GTP

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4
Q

Describe how Acetyl-CoA is derived from carbohydrates.

A

Glucose (6 carbons), gets oxidized during glycolysis into 2 pyruvates (3 carbons). The 2 pyruvates are then decarboxylated into 2 Acetyl Co-A molecules for TCA cycle use

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5
Q

Describe how Acetyl CoA is derived from lipids.

A

Triacylglycerols are converted into fatty acids. The fatty acids then undergo beta-oxidation to form Acetyl CoA

The oxidation of ketone bodies also forms Acetyl CoA

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6
Q

Describe how Acetyl CoA is derived from proteins.

A

Proteins are broken down into amino acids. The amino acids are then turned into Acetyl CoA

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7
Q

What does PDC stand for?

A

Pyruvate dehydrogenase complex

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8
Q

When PDC is phosphorylated, is it in its active or inactive form?

A 
Phospho = INACTIVE
Dephospho = ACTIVE
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9
Q

Where in the PDC does phosphorylation occur?

A

Phosphorylation occurs in coenzyme Thiamine pyrophosphate (TPP) of the E1 complex

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10
Q

The PDC is made up of E1, E2, and E3 subunits. What are each of the subunits comprised of?

A

E1 = TPP
E2 - Lipoic acid and CoA
E3 = NAD+ and FAD

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11
Q

What enzyme ACTIVATES the PDC?

A

Pyruvate dehydrogenase phosphatase (PDP)

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12
Q

What are the activators of pyruvate dehydrogenase phosphotase, and thus activate the PDC?

A

Ca2+ and Mg2+ activate PDP

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13
Q

What acts as inhibitory signals of the active state E1 subunit of the PDC?

A

Acetyl CoA and NADH

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14
Q

What molecules inhibit the deactivation of the PDC?

A

Pyruvate, CoA, NAD+, and ADP

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15
Q

What molecules cause the deactivation of pyruvate dehydrogenase kinase?

A

Acetyl CoA, NADH, and ATP

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16
Q

What enzyme changes PDC from being active to inactive?

A

Pyruvate dehydrogenase kinase (PDK)

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17
Q

In a phosphate deficiency, what happens to the PDC?

A

It remains phosphorylated, aka inactive. This leads to glucose being converted to lactate instead of Acetyl CoA

Buildup of lactate causes lactic acidosis, resulting in CNS effects

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18
Q

With a phosphate deficiency, what amino acid should be avoided?

A

Alanine should be avoided and a ketogenic diet is strongly recommended

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19
Q

In what steps of the TCA cycle is NADH produced?

A

Isocitrate to alpha-ketoglutarate (isocitrate dehydrogenase)

Alpha-ketoglutarate to Succinyl-CoA (alpha-ketoglutarate dehydrogenase)

Malate to oxaloacetate (malate dehydrogenase)

TOTAL OF THREE NADH PRODUCED EACH CYCLE

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20
Q

In what step of the TCA cycle is GTP produced?

A

Succinyl-CoA to Succinate (Succinyl-CoA dehydrogenase)

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21
Q

In what step of the TCA cycle is FADH2 produced?

A

Succinate to fumarate (succinate dehydrogenase)

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22
Q

How many ATP are produced by each NADH, FADH2, and GTP?

A 
NADH = 2.5 ATP
FADH2 = 1.5 ATP
GTP = 1 ATP
23
Q

What is the rate limiting step of the TCA cycle?

A

Isocitrate to alpha-ketoglutarate via the enzyme isocitrate dehydrogenase

24
Q

What is the function of the pyruvate dehydrogenase complex?

A

Convert Pyruvate into Acetyl-CoA for entrance into the TCA cycle

25
Q

Acetyl CoA combines with what molecule to form citrate?

A

Oxaloacetate generated via the TCA cycle

26
Q

When cellular levels of ATP are low, what happens to the TCA cycle?

A

Increased activity of TCA cycle to produce more ATP

26
Q

When cellular levels of ATP are low, what happens to the TCA cycle?

A

Increased activity of TCA cycle to produce more ATP

27
Q

What are the two major anaplerotic reactions in the TCA cycle?

A

Degradation of amino acids and carboxylation of pyruvate

28
Q

What amino acids are degraded to replenish alpha-ketoglutarate?

(5 of them)

A

Glutamine, proline, histidine, arginine, and glutamate

29
Q

What amino acids degrade to form Succinyl CoA in the TCA cycle?

(4 of them)

A

Threonine, methionine, isoleucine, and valine

The metabolic byproducts for propionyl CoA, which then replenishes Succinyl CoA

30
Q

What amino acids are degraded to form fumarate in the TCA cycle?

(3 of them)

A

Phenylalanine, tyrosine, and aspartate

31
Q

What amino acids are degraded to form oxaloacetate in the TCA cycle?

(2 of them)

A

Asparagine and aspartate

32
Q

Describe 2-Oxoglutaric aciduria (Alpha-ketoglutaric acid)

A

Rare disorder displaying developmental delay and severe neurologic problems in infants including metabolic acidosis, microcephaly, and intellectual disability

33
Q

Describe Fumarase deficiency

A

Severe neurological impairment. Fatal outcome within first 2 years of life
Encephalomyopathy, dystonia, urinary excretion of TCA intermediates are common

34
Q

What three key goals must be accomplished for a successful OxPhos?

A
  1. transfer of electrons from NADH and FADH2 to O2
  2. establish proton gradient across INNER membrane and intermembrane space
  3. Synthesize ATP
35
Q

In the TCA cycle, the first goal is the transfer of electrons. Describe how this happens

A

Electrons flow from molecules with low Standard Redox Potential to those with the highest.

36
Q

What causes the pumping of H+ through the mitochondrial inner membrane?

A

Electron transfer through the respiratory chain.

37
Q

What two factors constitute a proton-motive force (pmf) to drive ATP synthesis by Complex V?

A
  1. pH gradient

2. membrane potential

38
Q

How many H+ molecules are required to form 1 ATP via the ATP Synthase (Complex V)?

A

4 H+ required to form 1 ATP via Complex V

39
Q

What molecule inhibits proton transport through Complex V?

A

Oligomycin

40
Q

What inhibits Complex I?

A

Amytal, Rotenone, Myxothiazol, and Piericidin A

ARM Pit

41
Q

What inhibits Complex II?

A

Malonate

42
Q

What inhibits Complex III?

A

Antimycin

43
Q

What inhibits Complex IV?

A

CO, Cyanide, and H2S

44
Q

What inhibits Complex V?

A

Oligomycin

45
Q

What inhibits Complex V?

A

Oligomycin

46
Q

A high ATP/ADP ratio will do what?

A

Decrease ATP concentrations

47
Q

A low ATP/ADP ratio will do what?

A

Increase ATP concentration

48
Q

What occurs during uncoupling in OxPhos?

A

Protons uncouple from their carrier electrons and reenter the mitochondrial matrix. The TCA cycle is accelerated and ATP synthase is inhibited (no ATP synthesis). There is heat generation

49
Q

What are the two mechanisms of action for Superoxide Dismutase?

A
  1. Cu/Zn SOD (SOD1) - cytosolic

2. Mn/Zn SOD (SOD2) - mitochondrial

50
Q

In what organs is the Malate-Aspartate Shuttle active?

A

Heart, liver, and kidneys

51
Q

What is the function of the malate-aspartate shuttle?

A

Generates NADH into the mitochondrial matrix and pumps NADH through the electron transport chain at Complex 1

52
Q

What organs is the glycerophosphate-shuttle active?

A

Skeletal muscle and the brain

53
Q

What is the function of the glycerophosphate-shuttle?

A

Generate FADH2 in the inner mitochondrial membrane and join into the ETC at CoQ

SFM - Exam #2 (4 decks)

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