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Flashcards in Biochem part deux Deck (24):
1

What are the three non-reversible, controlled steps, of glycolysis?

Hexokinase (Glucokinase)
PFK1
Pyruvate kinase

2

What tissues have glucokinase instead of hexokinase? What are the major differences between the two enzymes?

Glucokinase is in the liver and pancreatic beta-cells

Glucokinase is induced by insulin and has a higher Km and a higher Vmax

3

What activates PFK1 activity?

Low energy conditions...AMP and fructose-2,6-BP

4

What inactivates PFK1 activity?

High energy conditions...ATP and citrate (citrate is the first product of the TCA cycle)

5

Knowing that glucagon's role is to increase increase plasma glucose (kinda), would FBP2 (fructose bisphosphatase 2) or PFK2 be activated in a low insulin:glucagon ratio?

Glucagon binding its receptor will increase cAMP and activate PKA...which phosphorylates the FBP2/PFK2 complex. This activates FBP2.

This makes sense...FBP2 dephosphorylates fructose-2,6-BP to fructose-6-P...taking away an activator of PFK1

6

What is the rate limiting step of gluconeogenesis?

Fructose-1,6-bisphosphatase

7

In what cells does gluconeogenesis occur?

Hepatocytes
Kidney
Intestinal epithelium

8

Glycogen phosphorylase is the first step of glycogenolysis. What symptoms would be expected in a person deficient of this enzyme?

McArdle disease presents with increased glycogen in muscle → swelling and lysing (Rhabdomyolysis) → myoglobinuria and renal failure

Normal life expectancy

9

a-1,6-glucosidase is the deb ranching enzyme. What would be the expected symptoms in a patient deficient of this enzyme?

Cori's disease presents with mild hypoglycemia...no elevation in lactate levels or uric acid

10

A mother brings in her 1yr old because of seizures and a protuberant abdomen. A fasting glucose test is performed and found to be incredibly low. What disease does this chid have? What are other expected findings? What is treatment regimen?

This child has Von Gierke disease...a deficiency in glucose-6-phosphatase

Big kidneys and hepatomegaly are causing the big belly. And there would likely be increased serum lactate, increased uric acid, and hypertriglyceridemia

Von Gierke disease can be treated by eating frequently and by eating corn starch before bed (breaks down slow)

11

Pompe disease is a deficiency of a-1,4-glucosidase in lysosomes. How does this disease present in children? Adults?

No a-1,4-glucosidase activity causes infantile Pompe disease → severe muscle weakness, cardiomegaly, and cardiac failure → life expectance is less than 1yo

Decreased a-1,4-glucosidase activity causes adult Pompe disease → gradual onset of muscle weakness (diaphragm weakness → respiratory failure)...NO cardiac involvement

12

A mother brings in her 3yo because he doesn't like to walk and run around like he used to and his calves seem to have swollen. She says that she has an uncle who had a similar condition. What is causing this boys symptoms?

Duchenne muscular dystrophy is caused by a frameshift mutation that leads to truncated dystrophin protein and accelerated muscle breakdown

13

What are some fundamental differences between Duchenne muscular dystrophy and Becker muscular dystrophy?

AGE...Duchenne <5yo while Becker is in adolescence/early adulthood

Also, Becker is usually caused by a point mutation (compared to the frameshift mutation seen in DMD)...but both are X-linked

14

What can inhibit complex I of the ETC?

Amytal
Rotenone
MPP (same MPP that can cause Parkinsonian symptoms)

15

What can inhibit complex III of the ETC?

Antimycin A

16

What can inhibit complex IV of the ETC?

Cyanide
CO
H2S
NaN3 (azide)

17

What can inhibit complex V (ATPase) of the ETC?

Oligomycin A

18

What can uncouple the ETC?

Thermogenin (hibernation)
Aspirin
2,4-DNP

19

It is well known that fava beans can precipitate G6PD to act up, but clinically this isn't that important. Which drugs do this...because that's what could be on the test?

Sulfonamides (TMP-SMX)
Primaquine (anti-malarial)
Anti-TB drugs

20

Tall patient with intellectual disability comes to the clinic with a subluxed lens. Which direction did the eye sublux? What is likely elevated in this patient's urine?

Homocystinuria causes the lens to sublux down and in

(Marfan's subluxed eye usually goes up and out)

21

Essential fructosuria is benign. What is the deficient enzyme in essential fructosuria?

Fructokinase is deficient in essential fructosuria

22

Fructose intolerance causes hypoglycemia, jaundice, cirrhosis, and vomiting. What is the deficient enzyme in fructose intolerance?

Aldolase B is deficient in fructose intolerance

23

Galactokinase deficiency causes infantile cataracts d/t the accumulation of galactitol. What is the deficient enzyme in galactokinase deficiency? What enzyme is overactive in galactose deficiency?

As the name implies...galactokinase is deficient in galactokinase deficiency

Aldose reductase is OVERACTIVE in galactokinase deficiency (same enzyme coverts glucose to sorbitol)

24

Classic galactosemia causes FTT, jaundice, hepatomegaly, infantile cataracts, and intellectual disability. What is the deficient enzyme in classic galactosemia?

Galactose-1-P uridyltransferase is deficient in classic galactosemia