Lecture 4: Bioenergetics

Question 1

What three molecules are associated with substrate lvl phosphorylation?

Answer 1

1. Phosphoenolpyruvate
2. 1,3-biphosphoglycerate
3. Phosphocreatine

Question 2

Pyruvate Dehydrogenase Complex (kinase and phosphatase)

Answer 2

1. Pyruvate Dehydrogenase Kinase
   (+) - ACoA, NADH, ATP
   (-) - Pyruvate, CoA, NAD, ADP
2. Pyruvate Dehydrogenase Phosphatase
   (+) - high Ca/Mg

Question 3

PDC Phosphatase Deficiency

Answer 3

• ALWAYS phosphorylated (inactive)
• Glucose to Lactate (Lactic Acidosis)
• restrict Alanine intake

Question 4

What are the 3 regulated enzymes of the TCA cycle?

Answer 4

1. Citrate Synthase
2. Isocitrate Dehydrogenase (NADH)
3. a-ketoglutarate Dehydrogenase (NADH)

Question 5

What is the Rate Limiting Step of the TCA Cycle?

Answer 5

Isocitrate Dehydrogenase

Question 6

Eo’ and delta G

Answer 6

• lower Eo’ –> lower electron deficiency, gives them up easily to pair w/higher Eo’
• inversely related to delta G

Question 7

What two factors constitute the proton-motive force?

Answer 7

1. pH gradient

2. membrane potential

Question 8

Inhibitors of Complex I

Answer 8

amytal, rotenone, myxothiazol, piericidin A

• barbituates

Question 9

Inhibitors of Complex II

Answer 9

malonate

Question 10

Inhibitors of Complex III

Answer 10

antimycin

Question 11

Inhibitors of Complex IV

Answer 11

CO, cyanide, H2S

Question 12

Inhibitors of Complex V

Answer 12

oligomycin

Question 13

ETC Uncoupling molecules for: Membrane Damage, Proton Carriers, Proton Channel

Answer 13

1. Membrane Damage: AraC, AZT
2. Proton Carriers: DNP, Aspirin
3. Proton Channel: Thermogenin (UCP-1)

Question 14

Malate-Aspartate Shuttle

Answer 14

• move NADH into mito matrix via malate
• reversible
• provides NADH to Complex I
• heart, liver, kidney

Question 15

Glycerophosphate Shuttle

Answer 15

• move NADH into mito matrix via glycerol-3-phosphate
• irreversible
• provides FADH2 to coenzyme Q
• skeletal muscle, brain

Question 16

Acetyl CoA in other metabolic pathways

Answer 16

 Sole building block for the synthesis of lipids such as fatty acids and isoprenoids (sterols and steroid hormones)

Question 17

What is coenzyme A?

Answer 17

 Activator of acyl groups

Activation of acyl groups w/CoA facilitates transacylation, condensation, oxidation-reduction reactions

Question 18

How much energy do we get from glucose vs fatty acids? (ATP)

Answer 18

FA provides 129 ATP compared to glucose providing 36-38

Question 19

What is Pyruvate Dehydrogenase Deficiency (neonatal lactic acidosis) and how can it be treated?

Answer 19

• Defects in PDC (E1)
• Neonatal Lactic Acidosis (high serum lvls of pyruvate and lactate)
• Administer vitamin B1, lipoic acid, biotin

Question 20

Arsenite and how it affects lipoic acid

Answer 20

• links SH bonds in lipoic acid
• suicide inhibitor, binds thiol group irreversibly
• takes time to poison person; detected in hair

Question 21

What is Beriberi and Wernicke-Korsakoff Syndrome a deficiency of?

Answer 21

insufficient thiamine

Question 22

How does citrate affect rate-limiting enzymes?

Answer 22

• indicates ATP-rich state (inhibit PFK1 in glycolysis)
• promotes storage of excess energy as fat (promotes ACoA carboxylase)
• helps maintain energy charge of cells in desired range

Question 23

ATP:ADP and NADH:NAD ratio range

Answer 23

0.8-0.95

Question 24

How does rat poison inhibit the TCA cycle?

Answer 24

• fluoroacetate inhibits TCA cycle, forms fluorocitrate (citrate analog)
• competitive inhibitor of anconitase; leads to citrate buildup
• inhibits citrate synthase, citrate buildup inhibits glycolysis

Question 25

Succinyl CoA in heme synthesis

Answer 25

• condensation of succinyl-CoA and glycine, w/decarboxylation, generates ALA as first step of heme biosynthesis
• rxn catalized by ALA synthase, rate limiting enzyme of heme biosynthesis (B6 cofactor)

Question 26

What is ferredoxin?

Answer 26

• small proteins (electron carriers) in mit cytochrome P-450

- varieties are used from heme and steroid hormones

Question 27

Ubiquinone Radical

Answer 27

• can pass electron to O2 to generate free radical superoxide
• superoxide dismutase converts superoxide to H2O2

Question 28

Cytochrome-c and apoptosis

Answer 28

• cytochrome-c released via mitochondrial permeability transition pore complex
• biochemical marker for cells undergoing apoptosis

Question 29

What is rotenone?

Answer 29

• naturally occurring pesticide (fish poison)

- potent inhibitor of Complex 1 (treat w/vitamin K)

Question 30

What is the difference between cyanide vs CO as an inhibitor?

Answer 30

cyanide - noncompetitive inhibitor

CO - competitive inhibitor

Question 31

Aspirin Overdose

Answer 31

• acute poisoning causes hypothermia

- DNP can also cause hypothermia

Question 32

Hypoxia and ATP preservation

Answer 32

• decrease activity of respiratory chain/proton motive force

- low pH in mito matrix cause IF1 (small inhib protein) to bind to ATP Synthase and prevent hydrolysis of ATP