008 TCA Cycle and Organ Specific Shuttles

Question 1

other names for TCA

Answer 1

Tricarboxylic acid cycle (TCA)
citric acid cycle
krebs cycle

Question 2

this cycle is amphibolic

Answer 2

meaning it has both catabolism and anabolism in the pathway

Question 3

function of TCA cycle

Answer 3

oxidizing carbon fuels for harvesting high energy electrons
source of precursors for biosynthesis
takes place in the mitochondria

Question 4

precursors of acetyl CoA

Answer 4

fats/LIPIDS  (fatty acids and glycerol)
polysaccharides/CARBS (glucose, other sugars) --> pyruvate
PROTEINS (AA) essential amino acids
ethanol
acetic acid

Question 5

three energy equivalent substances

Answer 5

NADH
FADH2
GTP

Question 6

acetyl CoA

Answer 6

activated form of acetate
high energy bond embedded in thirster group
delta G= -7.5 kcal/mole

Question 7

this catalyzes the decarboxylation of pyruvate into Acetyl CoA

Answer 7

pyruvate dehydrogenase complex (PDC)

this happens in the mitochondria using the pyruvate mitochondrial carrier (PMC)

Question 8

steps 1 and 2

Answer 8

condensation and isomerization to generate isocitrate

Question 9

step 3 and 4

Answer 9

irreversible oxidation and decarboxylations (NADH, CO2, and Succinyl CoA)

Question 10

step 5

Answer 10

formation of succinate and GTP

Question 11

steps 6-8

Answer 11

produce FADH2, NADH, and regenerate oxaloacetate

Question 12

which steps are regulated and irreversible

Answer 12

steps 1,3, and 4

Question 13

in a phosphate deficiency, PDC is always in

Answer 13

phosphorylated form (inactive)
glucose—>lactate rather than acetyl coA
results in lactic acidosis (high levels in blood of lactic acid)
central nervous system affected the most

Question 14

when cellular ATP levels are low, activity of TCA is

Answer 14

increased

Question 15

high cellular levels of ATP triggers the

Answer 15

inhibition mechanism of TCA cycle (mitochondrial ETC inhibition)

Question 16

reactions that provides intermediates for pathways

Answer 16

anaplerotic reactions

Question 17

two major anaplerotic reactions

Answer 17

1. degradation of amino acids

2. carboxylation of pyruvate

Question 18

molecules used in metabolic processes takes place in the mitochondria. they can penetrate the outer membrane but

Answer 18

cannot penetrate the inner membrane, require a shuttle system to cross. this is more regulated

Question 19

reduced NADH cannot cross the mitochondrial membrane, so there are two shuttle systems

Answer 19

1. malate-aspartate shuttle

2. glycerophosphate shuttle

Question 20

malate-aspartate shuttle

Answer 20

operates in heart, liver and kidneys (energy consuming organs that work really hard)
generates reduced NADH in mito-matrix
reduced NADH enters ETC at Complex-1

Question 21

glycerophosphate shuttle

Answer 21

operates in skeletal muscle and brain (instant energy, need it now!)
Generates reduced FADH2 in the inner mito membrane
reduced FADH2 joins to ETC at CoQ