05c: Lipid Digestion

Question 1

Emulsification begins when presence of (X) is detected in (Y). This causes (Z) orifice to (open/close) a bit.

Answer 1

X = fat
Y = duodenum
Z = pyloric sphincter
Close (propelling chyme retrograde into stomach)

Question 2

List the two enzymes that stabilize the emulsification of fat. Where they come from tho?

Answer 2

1. Lingual lipase (serous glands of tongue)

2. Gastric lipase (chief cells)

Question 3

Emulsification: lipid droplet is coated by (X). Where did (X) come from?

Answer 3

X = amphipathic molecules (DAG and free FA)

From action of lingual/gastric lipases

Question 4

Compared to bile salt micelles, emulsification droplets are (macro/micro)-scopic in size. How does emulsification aid in breakdown of the lipids?

Answer 4

Macroscopic;

Increases surface area for lipolytic enzymes

Question 5

T/F: Pancreatic lipase is secreted in the pro-enzyme (inactive) form.

Answer 5

False

Question 6

Pancreatic lipase works in (X) environment, (fully/partially) breaking down TAGs. What’s the function of (Y), its cofactor?

Answer 6

X = oil-water interface ONLY
Partially;
Y = colipase (anchors and protects it from denaturation from bile salt)

Question 7

Micelles are formed from (X) number of (Y) monomers.

Answer 7

X = 2 (dimer)
Y = bile salt

Question 8

T/F: High bile salt concentration will greatly increase solubility of DAG, MAG, and FA, but not TAG.

Answer 8

False - only of MAG and FAs

Question 9

List the three components that form mixed micelle.

Answer 9

1. Bile salt
2. Cholesterol
3. Lecithin (phospholipid)

Question 10

Gallstone formation: more likely if there’s excess (cholesterol/lecithin/bile salts) relative to (cholesterol/lecithin/bile salts).

Answer 10

Cholesterol;

Lecithin and bile salts

Question 11

Gallstone formation: more likely if there’s excess (X) reabsorption.

Answer 11

X = water and electrolytes

Question 12

CCK-PZ is released from (X) in response to (Y).

Answer 12

X = proximal small intestine
Y = detection of FAs (and certain AAs)

Question 13

CCK-PZ plays key role in (X) breakdown. Its targets/actions include:

Answer 13

X = fat

1. Pancreas (acinar cells to secrete enzymes)
2. Gallbladder (to release bile)

Question 14

Optimal pH for pancreatic lipase is (X). It’s destroyed by pH less than (Y).

Answer 14

X = 6-7
Y = 3

Question 15

Bile acid reabsorption is (passive/active) in duodenum/jejunum and (passive/active) in ileum. Where is the absorption greatest?

Answer 15

Passive;
Active;

Greatest in ileum

Question 16

Micellar dispersion increases rate of fat absorption by increasing concentration of (X) in (Y) by (Z)-fold.

Answer 16

X = lipolytic products
Y = aqueous phase
Z = 1000

Question 17

T/F: Lipase hydrolyzes TAGs faster than products are removed by micellar solubilization.

Answer 17

True

Question 18

T/F: All lipid processing requires micelles.

Answer 18

False - only significantly insoluble lipids (i.e. long-chain TAGs)

Question 19

T/F: Some lipid processing involves micellar dispersion without hydrolysis.

Answer 19

True - cholesterol and ADEK vitamins

Question 20

T/F: Medium-chain TAGs are processed via hydrolysis (without micellar dispersion).

Answer 20

True (fairly water-soluble)

Question 21

Micelle uptake of cholesterol: what does the structure look like? Where does the cholesterol reside?

Answer 21

Bile salts on outside (bread of sandwich) and alternating FAs/cholesterol on inside

Question 22

Lipolytic products that have been solubilized in micelles are thought to be rapidly exchanging with (X) space. The absorption/uptake of these products is (passive/active).

Answer 22

X = surrounding aqueous solution

Passive

Question 23

A(n) (X) transport mechanism for cholesterol absorption exists.

Answer 23

X = carrier-mediated

Question 24

TAGs are reformed near (X) within enterocyte. They are then transported through (Y) and exocytosed in which form?

Answer 24

X = Y = ER

Assembled into large chylomicrons

Question 25

Proper chylomicron assembly and exocytosis is dependent on presence of (X) on surface. Where is (X) synthesized?

Answer 25

X = apoprotein In enterocyte

Question 26

Chylomicron will travel in (X) of lymphatic system until it reaches venous system, specifically (Y).

Answer 26

``` X = thoracic duct Y = superior vena cava ```

Question 27

(X) lipids are too good for chylomicrons and adipose tissue. They pass into (Y) and undergo oxidation by (Z) organ.

Answer 27

``` X = medium chain FAs Y = portal blood Z = liver ```

Question 28

Before absorption into blood, TAGs in chylomicron undergo (X) by (Y) enzyme.

Answer 28

``` X = hydrolysis; Y = lipoprotein lipase ```

Question 29

Which tissues have highest concentration of lipoprotein lipase?

Answer 29

Adipose and muscle

Question 30

Which tissue/cells make lipoprotein lipase?

Answer 30

Adipocytes

Question 31

Cholesterol esterified with FA is (more/less/equally) soluble in mixed micelle than unconjugated cholesterol. This is because esterification removes (X), making the (hydrophobic/hydrophillic/amphipilic) molecule (hydrophobic/hydrophillic/amphipilic).

Answer 31

Less; X = -OH moiety Amphilphilic; Hydrophobic