UNIT 6: LIPIDS: Digestion and Function

Question 1

Where does lipid digestion begin?

Answer 1

Saliva
- lingual lipase

Triglycerides –> FFA and DG
no detergents present

Question 2

What happens to lipids in the stomach?

Answer 2

• acid environment denatures proteins and muscle contraction promotes emulsification
• gastric lipase
• hydrolysis of TF sn-3 –> FFA and DA

Question 3

What is the role of bile?

Answer 3

• bile secretes into duodenum, act as a detergent and facilitate micelle formation

Question 4

How does fat enter the small intestine?

Answer 4

• as large lipid droplets

emulsified by mechanical shearing and detergent effects of bile

Question 5

What is the role of pancreatic lipase

Answer 5

Pancreatic lipase

- hydrolyze TG at sn-2 and sn-3

Question 6

What is the role of cholesterol esterase?

Answer 6

works with pancreatic lipase

- hydrolyze cholesterol-esters to release free cholesterol and FFA

Question 7

What is the role of phospholipase?

Answer 7

release FFA and 2-lysophospholipid

Question 8

Pancreatic lipase attacks what bonds?

Answer 8

ester bonds

- hydrolyze to release from TG

Question 9

What happens right when 2lysoPL, MG, FFA, free cholesterol enter the inside of the enterocyte?

Answer 9

need to convert and reesterfy to form phospholipid, triglycerol, and cholesterol esters to prevent detergent actions

Question 10

Once inside the enterocyte, where do the neutral/amphipathic lipids go?

Answer 10

to the golgi

Question 11

What happens to the lipids in the golgi?

Answer 11

packaged as a chylomicron

Question 12

What is bigger? Mixed micelles (prior to enterocyte) or chylomicrons (after packagingi n golgi)

Answer 12

Chylomicrons are much much bigger

Question 13

Where do chylomicrons go after the enterocyte?

Answer 13

Leaves the intestinal cell and into the lacteal, enters the lymphatic system
–> destination: hepatocyte

Question 14

What happens to chylomicrons prior to entering the hepatocyte?

Answer 14

• Apoproteins bind the chylomicron surface (Apo-C,-E,-B)

- lipoprotein lipase deplete TG core

Question 15

What is the role of apoproteins?

Answer 15

• improve binding function to regulate metabolism further

- increase water solubility

Question 16

How does lipoprotein lipase act on a chylomicron?

Answer 16

• LPL is bound to endothelial cell surface
• binds to ApoC
• deplete TG core - release FFA
• FFA taken up by cells that require more FFA (heart, skeletal)

Question 17

What is a chylomicron remnant?

Answer 17

• a chylomicron depleted of TF
• shrink in size
• leftover is cholesterol esterase

Question 18

How does the liver cell recognize the chylomicron remnant?

Answer 18

• liver receptor binds ApoE on chylomicron remnant

Question 19

How are LPL anchored?

Answer 19

LPL are anchored to endothelial cells via a proteoglycan anchor
- LPL enzyme binds ApoC on chylomicron

Question 20

ApoB, ApoC, ApoE bind to…?

Answer 20

all are bound to

• chylomicron
• VLDL
• LDL