Biochemistry (FA)

Question 1

Pyruvate Carboxylase – substrate, product, cofactors, location

Answer 1

• Mitochondria
• Pyruvate to Oxaloacetate
• requires Biotin, ATP, activated by acetyl CoA
  (Gluconeogenesis)

Question 2

PEP Carboxykinase – location, substrate, product, cofactors

Answer 2

• Cytosol
• Oxaloacetate to PEP
• requires GTP
  (Gluconeogenesis)

Question 3

Fructose 1,6-bisphosphatase - location, substrate, product, cofactors

Answer 3

• Cytosol

- Fructose 1,6-bisphosphate to Fructose-6-P

Question 4

Glucose-6-phosphatase – location, substrate, product, cofactors

Answer 4

• ER
• G-6-P to Glucose
  (Gluconeogenesis – liver)

Question 5

Apolipoprotein E - function?

Answer 5

Mediates remnant uptake

seen on all

Question 6

Apolipoprotein A-I - function?

Answer 6

Activates LCAT

seen on VLDL & HDL

Question 7

Apolipoprotein C-II - function?

Answer 7

Lipoprotein lipase cofactor

seen on Chylomicrons, VLDL, & HDLs

Question 8

Apolipoprotein B-48 - function?

Answer 8

Mediates chylomicron secretion

seen on Chylomicrons & Chylomicron remnants

Question 9

Apolipoprotein B-100 - function?

Answer 9

Binds LDL receptor

seen on VLDL, IDL, & LDL

Question 10

Lipoprotein Lipase (LPL) function?

Answer 10

Degradation of TG circulating in chylomicrons & VLDLs

Question 11

Hepatic TG lipase (HL) function?

Answer 11

Degradation of TG remaining in IGL

Question 12

Hormone-sensitive lipase function?

Answer 12

Degradation of TG stored in adipocytes

Question 13

Lecithin-cholesterol Acyltransferase (LCAT) function?

Answer 13

Catalyzes esterification of cholesterol.

LCAT is bound to plasma HDL and LDL. As it esterifies cholesterol in HDL, it allows HDL to participate in reverse cholesterol transport.

Esterification makes the cholesterol more hydrophobic → sequestered in the core of the lipoprotein.

Question 14

CETP (cholesteryl ester transfer protein) function?

Answer 14

Facilitates the transfer of cholesteryl ester (added by LCAT) from HDL to VLDL, IDL, and LDL in exchange for triacylglycerol.

Question 15

ACAT (acylcoenzyme A: cholesterol acyltransferase) function?

Answer 15

ACAT (acylcoenzyme A: cholesterol acyltransferase) esterifies cholesterol inside the liver (for storage) and intestine (for transport in chylomicrons).

Free cholesterol in the bloodstream is esterified by LCAT (lecithin-cholesterol acyltransferase)

Question 16

Familial Type I Hyperchylomicronemia

Answer 16

• inc’d Chylomicrons, TG, Cholesterol
• Autosomal Recessive
• Lipoprotein Lipase deficiency or altered apolipoprotein C-II
• Causes: Pancreatitis, Hepatosplenomegaly, & eruptive/pruritic xanthomas (no inc’d risk for atherosclerosis

Question 17

Familial Type IIa Hypercholesterolemia

Answer 17

• inc’d LDL & Cholesterol
• Autosomal Dominant
• Absent or dec’d LDL receptors
• Causes: accelerated atherosclerosis, tendon (Achilles) xanthomas, & corneal arcus

Question 18

Familial Type IV Hypertriglyceridemia

Answer 18

• inc’d VLDL & TG
• Autosomal Dominant
• Hepatic overproduction of VLDL
• Causes pancreatitis

Question 19

Abetalipoproteinemia

Answer 19

Autosomal recessive mutation in microsomal triglyceride transfer protein (MTP) gene

• dec’d B-48 & B-100
• dec’d Chylomicron & VLDL synthesis & secretion
• Symptoms appear in first few months of life
• Intestinal biopsy shows lipid accumulation w/in enterocytes due to inability to export absorbed lipid as chylomicrons

Findings: Failure to thrive, steatorrhea, acanthocytosis, ataxia, night blindness

Question 20

______ has 5’ –> 3’ synthesis & proofreads w/ 3’ –> 5’ exonuclease.

Answer 20

DNA Polymerase III

Question 21

______ is unique in its ability to excise RNA primer w/ 5’ –> 3’ exonuclease.

Answer 21

DNA Polymerase I

also has same other functions as DNA Polymerase III

Question 22

______ adds DNA to 3’ ends of chromosomes to avoid loss of genetic material w/ every duplication

Answer 22

Telomerase

Question 23

Nonhomologous end joining brings together 2 ends of DNA fragments to repair double-stranded breaks. This is mutated in what disease?

Answer 23

Ataxia Telangiectasia

Question 24

Patients w/ _____ make antibodies to spliceosomal snRNPs.

Answer 24

Lupus

Question 25

α-amanitin, found in Amanita phalloides (death cap mushrooms), inhibits ________. What does this cause if ingested?

Answer 25

Inhibits RNA Polymerase II (makes mRNA)

Causes severe hepatotoxicity if ingested

Question 26

Young child with fatty diarrhea, failure to thrive (malabsorption), & neurologic manifestations. Labs show decreased cholesterol in blood.

Answer 26

Abetalipoproteinemia

• dec’d synthesis of apolipoprotein B leads to inability to generate chylomicrons, & therefore dec’d secretion of cholesterol & VLDL into bloodstream. Fat accumulates in the enterocytes.