Metabolism

Question 1

Ethanol metabolism

Answer 1

Ethanol converted to acetaldehyde by alcohol dehydrogenase and NAD+
Acetaldehyde converted to acetate by acetaldehyde dehydrogenase and NAD+
NAD+ is limiting reagent

Question 2

Metabolic changes seen as result of ethanol metabolism

Answer 2

Increased NADH/NAD+ ratio leads to:

• lactic acidosis
• fasting hypoglycemia
• hepatosteatosis

Question 3

Fomepizole

Answer 3

Inhibits alcohol dehydrogenase. Used as antidote for methanol or ethylene glycol poisoning

Question 4

Site of fatty acid sythesis

Answer 4

Acetyl coA produced in mitochondria; fatty acid synthesis occurs in cytosol

Question 5

Site of ketogenesis

Answer 5

mitochondria

Question 6

Metabolic processes that can happen in cytosol or mitochondria

Answer 6

Heme synthesis, urea cycle, gluconeogenesis

Question 7

Mutase function

Answer 7

Relocates a functional group within a molecule

Question 8

Difference between a kinase and a phosphorylase

Answer 8

Kinase uses ATP to add high energy phosphate. Phosphorylase adds inorganic phosphate without using ATP

Question 9

Carbamoyl phosphate synthetases

Answer 9

I: rate limiting enzyme in urea cycle
II: rate limiting enzyme in de novo pyrimidine synthesis

Question 10

Phosphofructokinase-1

Answer 10

Rate limiting enzyme in glycolysis

Question 11

Fructose-1,6-bisphosphatase

Answer 11

Rate limiting enzyme in gluconeogenesis

Question 12

Isocitrate dehydrogenase

Answer 12

Rate limiting enzyme in TCA cycle

Question 13

Glycogen synthase

Answer 13

Rate limiting enzyme in glycogenesis

Question 14

Glycogen phosphorylase

Answer 14

Rate limiting enzyme in glycogenolysis

Question 15

G6PD

Answer 15

Rate limiting enzyme in HMP shunt

Question 16

Glutamine phosphoribosylpyrophosphate amidotransferase

Answer 16

Rate limiting enzyme in de novo purine synthesis

Question 17

Acetyl co-A carboxylase

Answer 17

rate limiting enzyme in fatty acid synthesis

Question 18

canitine acetyltransferase I

Answer 18

rate limiting enzyme in fatty acid oxidation

Question 19

HMG-CoA synthase

Answer 19

rate limiting enzyme in ketogenesis

Question 20

NADPH function

Answer 20

Produced in HMP shunt. Used in anabolic processes, respiratory burst, cytochrome P450 system, and glutathione reductase

Question 21

Hexokinase vs glucokinsae

Answer 21

Hexokinase: Used by most tissues to convert glucose to glucose-6-phosphate. Has high affinity but low capacity and is not affected by insulin

Glucokinase: Used by liver and beta cells of pancreas to convert glucose to glucose-6-phosphate. Has low affinity but high capacity and is induced by insulin so that excess glucose is stored in the liver in times of excess.

Either way, step requires ATP (carried out by kinase)

Question 22

Pyruvate dehydrogenase complex

Answer 22

Converts pyruvate to acetyl coA using NAD+ as cofactor

Question 23

Possible pathways for pyruvate

Answer 23

1) alanine
2) oxaloacetate: regenerate for TCA cycle, gluconeogenesis
3) acetyl coA: TCA cycle
4) lactate

Question 24

Krebs cycle intermediates

Answer 24

Pneumonic: citrate is kreb’s starting substrate for making oxaloacetate

• citrate
• isocitrate
• alpha-ketoglutarate
• succinyl coA
• succinate
• fumarate
• malate
• oxaloacetate

Question 25

Classic Galactosemia

Answer 25

Impaired galactose-1-phosphate metabolism by galactose-1-phosphate uridyltransferase. Presents with vomiting, lethargy, and failure to thrive soon after breastfeeding begun

Question 26

Anastrozole

Answer 26

Aromatase inhibitor

Question 27

Galactokinase deficiency

Answer 27

Galacticol accumulates. Relatively mild. Galactose in blood and urine. Infantile cataracts, failure to track objects, failure to develop social smile.

Question 28

Essential amino acids

Answer 28

Glucogenic: Met, Val, His
Glucogenic/ketogenic: Ile, Phe, Thr, Trp
Ketogenic: Leu, Lys

Question 29

Acidic amino acids

Answer 29

Asp and Glu, neg charge at body pH

Question 30

Basic amino acids

Answer 30

Arg, lys, his. No charge at body pH

Question 31

Hyperammonemia

Answer 31

Excess NH4+ which depletes alpha-ketoglutarate, leading to inhibition of TCA cycle.

Treat by limiting protein and giving lactulose to acidify GI tract and trap NH4+ for excretion.