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USMLE Step 1 > Biochemistry: Metabolism > Flashcards

Biochemistry: Metabolism Flashcards

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USMLE® Step 1 flashcards
1
Q

What occurs in mitochondria?

A

fatty acid oxidation (beta-oxidation), acetyl-CoA production, oxidative phosphorylation and ketogenesis, TCA cycle,

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2
Q

What occurs in the cytoplasm?

A

HMP shunt, glycolysis, synthesis of steroids on the (SER) and proteins on RER, and synthesis of fatty acids, cholesterol and nucleotides

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3
Q

What occurs in both the mitochondria and cytoplasm?

A

HUGS- heme synthesis, urea cycle, gluconeogenesis

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4
Q

What does a kinase do?

A

catalyzes the transfer of phosphate from high energy molecule like ATP to substrate

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5
Q

What does phosphorylase do?

A

adds phosphate without using ATP

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6
Q

What does phosphatase do?

A

removes phosphate

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7
Q

Dehydrogenase?

A

catalyzes redox reactions

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8
Q

Mutase?

A

relocates a functional group within a molecule

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9
Q

synthase/synthetase?

A

joins to molecules together using ATP

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10
Q

What is a monosaccharide? Examples?

A

simple sugar- can’t be hydrolyzed-glucose, fructose and galactose. Glycogen is a polysaccharide

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11
Q

TCA (tricarboxylic acid), Kreb cycle or citric acid cycle- what is it?

A

Takes acetyl-coA and makes ATP(1) and NADPH (3) and 1 FAD(2H)

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12
Q

HMP shunt? (pg 74)

A

pentose phosphate pathway- works alongside glycolysis to oxidize glucose and make NADPH, pentoses and ribose 5 phosphate (used to make nucleotides)Occurs in cytoplasm, no ATP used

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13
Q

What does the urea cycle do?

A

Ammonia is the waste product of amino acid breakdown. The cycle converts ammonia into urea for safe excretion.

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14
Q

How many ATP do you get from one glucose? What about anaerobic metabolism of glucose?

A

32 from malate-aspartate shuttle (heart and liver). only 2 from anaerobic metabolism

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15
Q

Where is NADPH created? What is it used for?

A

created in HMP shunt and used for anabolic processes- respiratory burst, cytochrome P450, glutathione

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16
Q

What is the net glycolysis equation?

A

glucose +2Pi +2ADP +2NAD+—->2 pyruvate +2 ATP +2NADH +2H+ +2H20

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17
Q

What does arsenic do? What are the side effects?

A

Inhibits lipoic acid which is a cofactor for the pyrivate dehydrogenase complex that takes pyruvate and converts to acetyl coA for the TCA cycle? Vomiting, diarrhea, long qt, garlic breath, skin pigment changes

18
Q

what is pyruvate dehydrogenase complex deficiency?

A

get a build up of pyruvate and go down lactic acid pathway so you get lots of LDH and alanine (ALT). The treatment is ketogenic so lots of lysine and leucine in high fat diet

19
Q

How many NADH, FADH2, CO2 and GTP does each TCA cycle make?

A

3 NADH, 1 FADH2, 2 CO2, 1 GTP for every 1 molecule of acetyl-coA

20
Q

What is glucose-6 P dehydrogenase deficiency?

A

Don’t have enough NADPH to keep glutathione reduced so it can’t have antioxidant effect on RBCs so you get denatured globin in RBCs (Heinz bodies) then bite cells (spleen tries to destroy them)

21
Q

What is classic galactosemia?

A

deficiency in galactose-1-phosphate uridyltransferase so you get build up of toxic galactitol- goes to lens of eye- lactose is galactose and glucose so once they start breastfeeding you get jaundice, FTT, vomiting, infantile cataracts, hepatomegaly and intellectual disability. Tx is to exclude galactose and lactose

22
Q

what is sorbitol?

A

the alcohol storage form of glucose. Some tissues can store it this way, but you need aldose

23
Q

What is lactase deficiency?

A

primary- age associated loss of allele (can’t breakdown lactose to glucose and galactose). Secondary- gastroenteritis ruins brush border (autoimmune or viral). Diagnosis- hydrogen breath test- decreased pH and increased hydrogen in breath. Tx-take lactase pills or avoid.

24
Q

What are the essential AA’s?

A

Phenylalanine, Valine, Tyrosine, Threonine, Isoleucine, Methionine, Histidine, Lysine, Leucine

25
Q

What does hyperammonemia cause? How does it happen?

A

asterixis, slurred speech, vomiting somnolence, cerebral edema, blurred vision. Caused by liver toxicity or urea cycle defects (hereditary)- NH3 depletes GABA in the CNS and alpha ketoglutarate so decreased TCA cycle

26
Q

How do lactulose and antibiotics work against hyperammonemia?

A

lactulose blocks NH4 for excretion in gut and antibiotics decrease ammonia producing gut bacteria

27
Q

What is ornithine transcarbamylase deficiency?

A

urea cycle defect- AR, get increased orotic acid in the blood and urine, hyperammonemia side effects

28
Q

What is phenylketonuria?

A

deficiency in enz that converts phenylalanine to tyrosine so you get build up of phenyl ketones: intellectual disability, eczema, fair skin, growth retardation and musty body odour. AVOID ASPARTAME

29
Q

What is maple syrup urine disease?

A

can’t break down branched AAs (isoleucine, leucine and valine), get alpha ketoacids in the blood- intellectual disability, CNS defects, death. Tx: reduce isoleucine, leucine and valine in diet and supplement with thiamine.

30
Q

What is homocystinuria?

A

AR, multiple types, but get HOMOCY-homocystinuria, osteoporosis, marfinoid habitus, ocular subluxation (down and in), cardiovasc (thrombosis and atherosclerosis), kyphosis

31
Q

What is cystinuria?

A

defect in the PCT where you get increased COLA-cystine, ornithine, lysine, arginine. Crystals forming. Treatment is to alkalinize the urine with potassium citrate/acetazolamide or chelate with penicillamine, good hydration.

32
Q

What are the types of glycogen storage diseases?

A

(pg 87) 1. Type 1: Von Gierke (severe fasting hypoglycemia, lactate, uric acid)

  1. Type 2: Pompe
  2. Type 3: Cori
  3. Type 4: McArdle (muscle build up of glycogen, myoglobinuria, muscle cramps)
33
Q

Lysosomal diseases?

A 
(pg 88) 
1. Tay Sachs
2. Fabry
3. Metachromatic leukodystrophy
4. Krabbe 
5. Gaucher
6. Niemann-Pick
Mucopokysaccharidos: Hurler and Hunter syndromes
34
Q

What are the ketone bodies?

A

acetone, acetoacetate, beta-hydroxybutrate, breath smells like acetone in ketoacidosis

35
Q

Why do you need LDL?

A

transports cholesterol from the liver to the tissues

36
Q

What do HDL and LDL have?

A

highest percentage of cholesterol, lower on TG

37
Q

Why do you need cholesterol?

A

maintains the cell membrane integrity, synthesizes bile acids, steroids and vitamin D

38
Q

What do chylomicrons do?

A

transport dietary TGs to the peripheral tissues and then liver as chylomicron remnants (mostly TG deplete at this point)

39
Q

What does VLDL do?

A

Takes TGs from the liver to peripheral tissues

40
Q

What does HDL do?

A

Takes cholesterol from the tissues to the liver

USMLE Step 1 (20 decks)

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