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STEP1 > Biochem II > Flashcards

Biochem II Flashcards

1
Q

You get a build up of ________ with pyruvate dehydrogenase deficiency. How can you get this deficiency?

A

lactic acid

X-linked congenital defect
acquired–arsenic exposure
B vitamin deficiency–especially thiamine (B1) in alcoholics

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2
Q

What is the treatment for pyruvate dehydrogenase deficiency?

A

vit supplementation
high fat diet
ketogenic AA (lysine, leucine)

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3
Q

What does one acetyl CoA yield? In the TCA cycle

A

1 GTP
3 NADH
1 FADH2
CO2

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4
Q

What is 1 NADH worth? 1 FADH2?

A

1 NADH=2.5 ATP

1 FADH2=1.5 ATP

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5
Q

Which complex of the TCA cycle is NADH fed into? FADH2?

A

NADH–>Complex I, NADH reductase

FADH2–>Complex II, Succinate Dehydrogenase

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6
Q

What are some things that can negatively affect Complex I?

A

Amytal (barbiturate)
Rotenone (Fish poison)
MPP (from MPTP synthetic opioid)–>can cause parkinsonism

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7
Q

WHat are some things that can negatively affect Complex III?

A

Antimycin A (fish poison)

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8
Q

What are some things that can negatively affect Complex IV?

A

Cyanide
N3 (sodium azide)
CO
H2S (hydrogen sulfide)

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9
Q

What is something that can inhibit ATPase of ETC?

A

Oligomycin A (macrolide, not used clinically)

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10
Q

What are some agents that can uncouple oxidative phosphorylation in the ETC and generate heat? MOA?

A

**increase permeability of the inner mitochondrial membrane, H+ rushes down the gradient, get heat
thermogenin (found in brown fat of hibernating bears, need heat!)
High-dose aspirin
2, 4 dinitrophenol (weight loss pill, deadly)

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11
Q

Describe the Cori cycle.

A

In muscles or RBCs when there is anaerobic metabolism, only glycolysis, get all of these pyruvates that are converted into lactic acid.
They are shuttled over to the liver where they are converted back to pyruvate by lactate dehydrogenase
then Pyruvate is converted back to glucose to be shipped back to muscle or RBCs
**get 2 ATP from anaerobic glycolysis, takes 6 ATP to make the glucose from lactic acid.

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12
Q

What is the basic purpose of the alanine cycle?

A

basically, muscle uses protein for energy and gives the excess nitrogen to the liver to be excreted as urea by the kidney. Given in the form of glutamine and alanine.

The liver in return gives glucose to the muscle.

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13
Q

Describe the alanine cycle.

A

Protein–>AA
AA–>ketoacids, alpha ketoglutarate–>glutamate
glutamate –>glutamine. Transfer to liver. Goes into urea cycle.

Glucose –>Pyruvate–>Alanine. Transfered to liver to make glucose again, which is shipped back.

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14
Q

What do transaminases (aka aminotransferases) do in the alanine cycle?

A

Takes place in the liver.

cause the formation of AA to alpha ketoacids by transferring nitrogen onto alpha ketoglutarate to make glutamate

and alpha ketoacids are used for energy metabolism. Get glucose from them that is transferred back to muscle.

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15
Q

What are the 2 most important transaminases?

A

ALT (alanine aminotransferase)

AST (aspartate transaminase)

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16
Q

Describe the reaction accomplished by AST.

A

aspartate + alpha ketoglutarate–> oxaloacetate + glutamate

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17
Q

Describe the reaction accomplished by ALT.

A

alanine + alpha ketoglutarate–>pyruvate + glutamate

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18
Q

What is the cofactor needed for AST/ALT and other transaminases to work?

A

Vit B6

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19
Q

What are the 2 nitrogen transporters in the blood?

A

glutamine

alanine

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20
Q

What are the enzymes required for pyruvate dehydrogenase complex to work?

A 
TLC For Nobody
thiamine/Vit B1/TPP/Pyrophosphate
Lipoic acid
CoA/Vit B5/pantothenic acid
FAD/Vit B2/Riboflavin
NAD/VIt B3/Niacin
21
Q

What does arsenic do to the pyruvate dehydrogenase complex?

A

inhibits lipoic acid

garlic breath
rice water stools
vomiting

22
Q

Which other enzyme requires the TLC For Nobody cofactors as well?

A

alpha ketoglutarate dehydrogenase

23
Q

What are the things that pyruvate can be converted into?

A

Acetyl CoA (via pyruvate dehydrogenase)–TCA
Lactic acid (via lactate dehydrogenase)–Cori Cycle
Oxaloacetate (via pyruvate carboxylase)–gluconeogenesis
Alanine (via ALT)–Alanine Cycle/Cahill cycle

24
Q

What are the important things to remember about the TCA cycle?

A

1st enzyme: citrate synthase:
Acetyl CoA–>citrate

Rate limiting enzyme: isocitrate dehydrogenase:
Isocitrate–>alpha ketoglutarate

alpha KG dehydrogenase
alpha KG–>succinyl CoA

energy output: 1 GTP, 3 NADH, 1 FADH2, 2 CO2

25
Q

where does the pentose phosphate pathway take place?

A

liver
adrenal cortex
mammary glands (during lactation)
**think about FA and cholesterol synthesis

RBCs
**think about dealing with ROS damage

26
Q

What do you get from the HMP shunt/Pentose Phosphate Pathway?

A

NADPH

Ribose-5-P

27
Q

What is ribose-5-P from PPP used for?

A

ribulose-5-P–>PRPP used in ribonucleotide synthesis, think pyrimidines and purines

28
Q

What are the purposes for NADPH produced by the PPP?

A
  1. glutathione reduction in RBCs
  2. fatty acid and cholesterol biosynthesis
  3. Generation of ROS in phagolysosomes
  4. Function of CytP450 enzymes
29
Q

Where does pentose phosphate pathway/HMP shunt take place? What are the 2 phases?

A

all in the cytosol

  1. Oxidative (irreversible)
  2. nonoxidative (reversible)
30
Q

What is the most important enzyme in the PPP?

A

glucose-6-P dehydrogenase

glucose-6-P–>2 NADPH + Ribulose-5-P

31
Q

Describe NADPH function in the phagolysosome.

A

O2–>O2- (superoxide) via NADPH oxidase
O2- –>H2O2 via superoxide dismutase
H2O2–>HOCl via myeloperoxidase

32
Q

Once again, which organisms are patients with chronic granulomatous disease susceptible to?

A

catalase + organisms that can break down H2O2

b/c when you have NADPH oxidase deficiency, you depend on hydrogen peroxide to kill bugs.

33
Q

G6PD deficiency is inherited how? More common in which ethnicity? One good thing about it?

A

X-linked recessive
Blacks
possible increased malarial resistance

34
Q

What are the histo things you see with G6PD deficiency?

A 
Heinz bodies (inclusion from denatured hemoglobin)
Bite cells (from splenic macrophages)
35
Q

Why is glutathione important in RBCs? How do you keep it reduced and functional?

A

H2O2–>H2O via glutathione peroxidase (oxidizes glutathione)

Replenish glutathione via glutathione reductase, which requires NADPH

get that NADPH via G6PD dehydrogenase of PPP

Hemolytic ANEMIA

36
Q

Which drugs are patients with G6PD deficiency more susceptible to injury from? B/c they can’t replenish their glutathione in RBCs? With these drugs get hemolytic anemia

A 
Spleen purges nasty inclusions from damaged cells
Sulfonamides
Primaquine
Nitrofurantoin (antibiotic for UTI, safe in pregnancy)
Isoniazid
Fava beans
dapsone (antibiotic used in leprosy)
Chloroquine
37
Q

What is different about the hemolytic anemia produced by glycolysis enzyme deficiency and that produced by G6PD deficiency?

A

Glycolysis enzyme deficiency, ex: pyruvate dehydrogenase
buildup of lactic acid or something, can’t get energy, eventually swell up and lyse

G6PD deficiency get hemolytic anemia via ROS damage and splenic macrophages taking a bite out of you

38
Q

Describe the basics of fructose metabolism.

A

Fructose–>(via fructokinase)–>F-1-P–>(via aldolase B)–>Dihydroxyacetone + glyceraldehyde

39
Q

Which enzyme deficiency produces essential fructosuria? Symptoms?

A

Fructokinase deficiency
relatively asymptomatic b/c don’t get accumulation of fructose in cells b/c it hasn’t been phosphorylated yet

fructose appears in blood and urine

40
Q

How are the fructose and galactose errors of metabolism inherited?

A

autosomal recessive

41
Q

What is the enzyme deficiency that leads to fructose intolerance? Symptoms?

A

aldolase B deficiency
get buildup of F-1-P in cells and decrease available phosphate, inhibiting glycogenolysis and gluconeogenesis

get hypoglycemia, hepatomegaly, jaundice, cirrhosis, vomiting

42
Q

After consumption of which foods would you see bad symptoms w/ fructose intolerance? Treatment?

A

after consumption of fruit, juice, honey

Treatment: decrease intake of fructose and sucrose (fructose + glucose)

43
Q

Which enzyme deficiency leads to galactokinase deficiency? symptoms?

A

haha
galactokinase deficiency!!
galactitol accumulates, esp in lens and can cause infantile cataracts
other than that asymptomatic

44
Q

Which enzyme deficiency causes classic galactosemia? Symptoms?

A

G-1-P uridyltransferase
more severe
get accumulation of galactitol–>infantile cataracts
failure to thrive
hepatomegaly, jaundice
intellectual disability
increases susceptibility to E coli as neonate

45
Q

What is the treatment for classic galactosemia?

A

exclude galactose and lactose from diet

lactose=galactose + glucose

46
Q

Describe galactose metabolism.

A

Galactose–>(via galactokinase)–>galactose-1-phosphate–>(via uridyltransferase)–>Glucose-1-Phosphate

excess galactose–>galactitol via aldose reductase

47
Q

Which ethnicities is lactose intolerance common in? Aside from hereditary deficiency, what else can cause this intolerance?

A

Common in african americans, native americans, Asians

loss of brush border due to gastroenteritis
autoimmune diseases

48
Q

What is the pH of stool and what is different about breath w/ lactose tolerance test in those that are lactose intolerant?

A

stool pH is lower

hydrogen content is increased in breath

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