Lipoproteins

Question 1

Front

Answer 1

“Back”

Question 2

Primary role of VLDL

Answer 2

“Transport triglycerides (TGs) from liver to muscles/adipose tissue.”

Question 3

What triggers VLDL production?

Answer 3

“Excess dietary carbs/fats → liver converts them to TGs → packs into VLDL.”

Question 4

Key structural component of VLDL

Answer 4

“ApoB-100 (essential for VLDL assembly/secretion).”

Question 5

Enzyme that breaks down VLDL TGs in blood

Answer 5

“Lipoprotein lipase (LPL) → releases FFAs for tissues.”

Question 6

What does VLDL become after losing TGs?

Answer 6

“First → IDL (Intermediate-Density Lipoprotein), then → LDL.”

Question 7

Why is LDL ‘bad cholesterol’?

Answer 7

“Delivers cholesterol to arteries → atherosclerosis.”

Question 8

Clinical: High VLDL = ?

Answer 8

“Hypertriglyceridemia (seen in metabolic syndrome, diabetes).”

Question 9

Gene defect causing high VLDL

Answer 9

“LPL deficiency (Type I hyperlipidemia) → sky-high TGs.”

Question 10

Drug target to lower VLDL

Answer 10

“Fibrates (activate LPL) or omega-3s (reduce liver TG synthesis).”

Question 11

USMLE/PLAB Q: Alcohol raises VLDL how?

Answer 11

↑ Liver de novo lipogenesis → ↑ TG packaging into VLDL.

Question 12

What are lipoproteins?

Answer 12

Protein-lipid complexes that transport hydrophobic lipids (TAG, cholesterol) in blood.

Question 13

What is the structural composition of lipoproteins?

Answer 13

Core: TAG + Cholesterol esters. Surface: Phospholipids + Free cholesterol + Apoproteins.

Question 14

List the 5 major types of lipoproteins.

Answer 14

1. Chylomicrons, 2. VLDL, 3. LDL, 4. HDL, 5. Free Fatty Acids (FFA)-Albumin complex.

Question 15

What is the primary function of chylomicrons?

Answer 15

Transport dietary TAG from intestine to tissues via lymphatics.

Question 16

What is the normal range for fasting chylomicrons?

Answer 16

Undetectable in fasting blood (cleared within 2-8 hrs post-meal).

Question 17

What is the function of VLDL?

Answer 17

Transports endogenous TAG from liver to peripheral tissues.

Question 18

What is the normal VLDL range?

Answer 18

5-40 mg/dL (calculated as TAG/5).

Question 19

What is the function of LDL?

Answer 19

Delivers cholesterol to peripheral tissues (bad cholesterol).

Question 20

What is the optimal LDL level?

Answer 20

<100 mg/dL (high levels cause atherosclerosis).

Question 21

What is the function of HDL?

Answer 21

Reverse cholesterol transport (good cholesterol).

Question 22

What is the normal HDL range?

Answer 22

> 40 mg/dL (men), >50 mg/dL (women) (higher is cardioprotective).

Question 23

How are Free Fatty Acids (FFA) transported?

Answer 23

Bound to albumin in blood (not a lipoprotein).

Question 24

Which apoprotein activates LPL (Lipoprotein Lipase)?

Answer 24

Apo C-II (critical for TAG breakdown in chylomicrons/VLDL).

Question 25

Which apoprotein is recognized by LDL receptors?

Answer 25

Apo B-100 (present on LDL and VLDL).

Question 26

Which apoprotein is the major component of HDL?

Answer 26

Apo A-I (activates LCAT for cholesterol esterification).

Question 27

What happens in Apo C-II deficiency?

Answer 27

Hyperchylomicronemia (LPL can't break down TAG → milky plasma).

Question 28

What is the density order of lipoproteins?

Answer 28

Chylomicrons (least dense) → VLDL → LDL → HDL (most dense).

Question 29

Which lipoprotein has the highest TAG content?

Answer 29

Chylomicrons (~90% TAG by weight).

Question 30

Which lipoprotein has the highest cholesterol content?

Answer 30

LDL (~50% cholesterol).

Question 31

What is the role of LCAT?

Answer 31

Enzyme activated by Apo A-I (HDL) to esterify cholesterol → forms HDL-C.