Cellular Energetics 8/10

Question 1

amphibolic

Answer 1

biochemical process that involves both anabolism and catabolism

Question 2

TCA cycle is amphibolic because

Answer 2

involved in aerobic catabolism of carbs, lipids, amino acids; intermediates of TCA are starting points for many anabolic reactions

Question 3

anabolic reactions

Answer 3

transfer energy from ATP to complex molecules (endergonic, reduction)

Question 4

catabolic reactions

Answer 4

transfer energy from complex molecules to ATP (exergonic, oxidation)

Question 5

rate limiting step of glycolysis

Answer 5

conversion of fructose-6-phosphate to fructose-1,6-bisphosphate by phosphofructokinase 1. (Also converts ADP to ATP)

Question 6

steps in glycolysis with substrate level phosphorylation

Answer 6

1. phosphoglycerate kinase converts 1,3-BPG to phosphoenolpyruvate, ADP->ATP
2. pyruvate kinase converts phosphoenolpyruvate to pyruvate, ADP->ATP

Question 7

glycolysis ATP yield

Answer 7

produces 2 ATP in anaerobic conditions, 7 ATP in aerobic conditions (because each NADH = 2.5 ATP)

Question 8

glycolysis substrates

Answer 8

2 ATP, 2 NADH, and 2 pyruvate molecules

Question 9

NADH ATP yield

Answer 9

10 H+ ions = 2.5 ATP per NADH

Question 10

FADH2 ATP yield

Answer 10

6H+ ions = 1.5 ATP per FADH2

Question 11

Complex I

Answer 11

complex of ETC in which NADH transfers 2e- to Q. Q is reduced to Qh2, NADH oxidized to NAD+. 4 H+ ions pumped across membrane, establishing the H+ gradient.

Question 12

Complex II

Answer 12

complex of ETC in which FADH2 transfers e- directly to Q, bypassing complex 1. FADH2 is oxidized to FAD, Q reduced to Qh2. Qh2 directly delivers the e- from complex 1 and 2 to complex 3. No H+ ions are pumped from this complex.

Question 13

Complex III

Answer 13

complex of ETC in which Qh2 transfers e- to cytochrome C. H+ ions are pumped into intermembrane space, contributing to the gradient. Cytochrome C can only accept one electron at a time.

Question 14

Complex IV

Answer 14

complex of ETC in which the final H+ ions are pumped across the membrane. Electrons are passed from cytochrome C to the final electron acceptor, oxygen. O2 splits and each O takes 2H+ ions from the matrix, forming 2 molecules of H2O.

Question 15

Complex V (ATP synthase)

Answer 15

final stage of ETC. H+ ions are pumped through ATP synthase against their gradient, generating energy in the form of ATP.

Question 16

adenylate kinase

Answer 16

enzyme that catalyzes the interconversion of adenine dinucleotides: 2ADP AMP + ATP.
Signals to AMP sensors to increase ATP consumption or production.
Uses anabolic and catabolic reactions to maintain adenylate charge at metabolic steady state ~0.9.

Question 17

adenylate charge

Answer 17

= [ATP] + 0.5 [ADP] / [ATP] + [ADP] + [AMP]

Question 18

transphosphorylation

Answer 18

high energy compounds can recycle ATP by coupling to ADP. They must have more negative free energy of hydrolysis than ATP to catalyze the phosphorylation of ADP to ATP.
Ex: creatine phosphate + ADP -> creatine + ATP, deltaG= -3 kcal/mol.
Ex: phosphocreatine and ADP couple to replenish ATP in skeletal muscles (catalyzed by creatine kinase)

Question 19

Why are fats more caloric than carbs?

Answer 19

fats are more reduced than carbs, thus they require greater oxygen for hydrolysis and thus release more energy (9kcal/g vs 4 kcal/g)

Question 20

Respiratory quotient (RQ)

Answer 20

measure of the ratio of CO2 produced to O2 consumed by an organism.
= amt CO2 produced/amt O2 consumed.
*valuable because gives info regarding the nature of the substrate being used for energy. Fat = 0.7, Carb = 1.0, Protein = 0.82, mixed feeding = 0.85, overfeeding = 1.1-1.2.

Question 21

TCA cycle substrates

Answer 21

pyruvate, citrate, isocitrate, alpha ketoglutarate, succinyl coA, succinate, fumarate, malate, oxaloacetate

Question 22

enzymes of TCA that convert NAD+ to NADH

Answer 22

isocitrate dehydrogenase, alpha ketoglutarate dehydrogenase, malate dehydrogenase

Question 23

enzyme of TCA that converts FAD to FADH2

Answer 23

succinate dehydrogenase

Question 24

tricarboxylate transporter

Answer 24

exchanges a citrate made in the mitochondrial matrix during the TCA cycle for a malate (citrate ends up in cytoplasm); citrate is converted back to Acetyl coA (by ATP citrate lyase) for fatty acid synthesis in the cytoplasm of the cell.
*citrate in cytoplasm also blunts glycolysis by inhibiting PFK-1.

**inhibitors of tricarboxylate transporter reduce fatty acid synthesis.