Lipids - Digestion

Question 1

What are the basic steps of
triglyceride digestion?

Answer 1

1) Emulsification in SI
2)Pancreatic lipases hydrolyzes

Question 2

What is cholecystokinin?

Answer 2

Signals gallbladder to release bile.

Question 3

How are lipids
emulsified (3 steps)?

Answer 3

1) Fat-rich chyme reaches SI
2) Cholecystokinin signals release of bile
3) Bile allows fat globules to disperse in aqueous environment
4) Micelles (small lipid droplets) form

Question 4

Is bile hydrophilic or hydrophobic?

Answer 4

It is amphipathic (both)

Question 5

What is the function of
pancreatic lipase?

Answer 5

Hydrolyzes the ester bond that attach fatty acids to glycerol molecule

Question 6

What are the end
productions of
triglyceride digestion?

Answer 6

• 2 free fatty acids
• 1 monoglyceride

Question 7

What do lipoproteins
consist of?

Answer 7

Central lipid core encased in a protein and phospholipids

Question 8

Why is it important that proteins and phospholipids are water soluble?

Answer 8

Allows lipids to circulate in the lymph and blood

Question 9

(1)What are apolipoproteins? (2)What are their function?

Answer 9

1 - surface proteins
2 - allow cells to identify different lipoproteins and remove them from the blood

Question 10

(1)What are chylomicrons?
(2) Where are they made
(3) What function do they serve?

Answer 10

1- lipoprotein particles that lipids packaged into a particle (
2 - enterocyte
3 - Circulation of dietary lipids (exogenous pathway)

Question 11

How are chylomicrons formed (3 steps)?

Answer 11

1 - monoglycerides + free fatty acids absorbed into enterocyte (intestinal cell)

2 - Inside enterocyte: fatty acids reattached to monoglycerides -> form triglycerides

3 - Lipids packaged into particles = chylomicrons

Question 12

What is the circulation of dietary lipids referred to as?

Answer 12

Exogenous pathway

Question 13

Once triglycerides are
digested, what are the
next steps in terms of
lipid delivery to cells?

Answer 13

Exogenous pathways:
1 - circulating chylomicrons interact with LPL.
2 - LPL hydrolyzes ester bonds - > enables fatty acids to be taken up by muscle/adipose tissue
3 - Chylomicron remnants taken up by liver

Question 14

(1)What is lipoprotein lipase (LPL)? (2)What is it’s role?

Answer 14

1 - Enzyme along the lining of capillaries associated with adipose tissues & muscle cells.

2- hydrolyzes ester bonds which enables fatty acids to be taken up by muscle/adipose tissue.

Question 15

What is the meaning of
exogenous lipids vs.
endogenous lipids
transport?

Answer 15

Exogenous:
- lipids from external sources (diet_
- transport: chylomicrons via lymphatic system + bloodstream for energy storage

Endogenous:
- synthesized within body (liver)
- VLDL and LDL

Question 16

(1)What are very low density lipoproteins (VLDLs)? (2) Where are they formed? (3) What are their function?

Answer 16

1 - more lipid relative to protein
2 - liver
3 - circulate lipids (triglycerides and cholesterol) from liver -> adipose tissue.

Question 17

(1)What are low density lipoproteins (LDLs)? (2) How/where are they formed? (3) What are their function?

Answer 17

1 - most abundant lipid associated with cholesterol

2 - In circulation -> triglycerides are removed by lipoprotein lipase and taken up by tissues and ratio of lipid:protein changes

3 - transport cholesterol in the blood and are taken up by LDL receptors

Question 18

Function of cholesterol

Answer 18

Used by cells to synthesize many substances and cell membranes.

Question 19

Describe the endogenous lipoprotein pathway (4 steps)

Answer 19

1 - Triglyceride packaging into VLDL (liver)
2 - Release of VLDL into circulation
3 - Triglycerides removed by lipoprotein lipase and taken up by tissues -> LDL
4 - LDLs transport cholesterol in the blood and are taken up by cells with LDL receptors
5 - cholesterol used by cells to synthesize substances/cell membranes

Question 20

How are each of the
lipoproteins cleared
from the blood?

Question 21

What is the relationship
between lipoprotein size
and lipoprotein
compositions?

Answer 21

1) Bigger (ie VLDL) = more lipid : protein

2) Smaller (ie LDL) = more protein : lipid

Question 22

How an elevated LDLs
increase risk of
myocardial infarctions
and/or cerebral vascular
strokes

Answer 22

Number of LDL particles increases atherogenic risk.

*independent of size/low clearance/over production

Question 23

How does elevated LDL’s do to the body to increase risks?

Answer 23

• Can infuriate arterial wall = trigger inflammatory response which promotes formation of plaque = obstructs blood vessels = stroke/myocardial infraction

Question 24

(1)What are high density lipoproteins (HDL’s)? (2)What do they do?(3) How do they protect the body?

Answer 24

1 - Protein rich lipoproteins that remove excess cholesterol

2 - transport cholesterol from the cells back to the liver.

3- protects against atherosclerotic lesions (cardiovascular disease)

Question 25

What is reverse cholesterol transport?

Answer 25

The pathway for cholesterol (plaque) reduction

Question 26

How does lifestyle impact blood lipids?

Answer 26

Unsaturated fat = lowered risk of heart disease

Question 27

What role did Ancel Keys
have in the Lipid heart
disease hypothesis?

Answer 27

Development of the lipid heart disease hypothesis - his research laid the foundation. (7 Countries study 1950’s)

Question 28

What are new dietary recommendation? (4)

Answer 28

1 - reduction in ultra-processed foods
2 - minimize foods with refined carbs + added sugar
3 - increase consumption of fresh foods and veg
4 - increasing fiber-rich foods