Fat Storage, Absorption, Digestion

Question 1

True or False: Fats are more reduced than sugars or amino acids.

Answer 1

True

Question 2

Fats can be stored without water because fats are ______.

Answer 2

Hydrophobic

Question 3

What do lipid droplets contain?

Answer 3

• Triacylglycerol (TAGs)

- Cholesteryl Esters (CEs)

Question 4

Does the lipid droplet contain a phospholipid monolayer or bilayer?

Answer 4

Monolayer

Question 5

Name two organelles that are near lipid droplets.

Answer 5

• Mitochondria (can use fat to generate energy AKA fatty acid oxidation)
• Endoplasmic reticulum (can make lipids/fats which can be transported inside the lipid droplet)

Question 6

What are 2 issues with digesting/absorbing fat?

Answer 6

1. TAGs are insoluble in an aqueous environment (small intestine, cytoplasm, circulation)
2. Humans can’t directly transfer TAGs across the plasma membrane (b/c TAGs are hydrophobic and can get stuck in the membrane)

Question 7

Lis the 3 solutions that digest and transport fats.

Answer 7

1. Emulsify fats (help from bile salts)
2. Digest TAGs with Human Pancreatic Lipase
3. Enclose the TAGs into soluble containers

Question 8

Bile salts are _____, and they assemble around hydrophobic molecules to form _____ _______.

Answer 8

Amphipathic, mixed micelles

Question 9

The emulsified fat globules increase ____ ____ and accessibility for digestion by _____ ______ ______.

Answer 9

Surface area, Human pancreatic lipase

Question 10

What other dietary lipids are found in mixed micelles?

Answer 10

Fat soluble vitamins and dietary cholesterol

Question 11

Human pancreatic lipase hydrolyze _____ bonds present in fat.

Answer 11

Ester

Question 12

What does fat break down into? (list the specific molecules)

Answer 12

Two molecules of fatty acids and one molecule of 2-mono-acyl-glycerol

Question 13

From the mixed micelles, the products of HPL can be transported into _______ _____ cells.

Answer 13

Intestinal epithelial

Question 14

HPL uses ____ and ___ as substrates.

Answer 14

Water, fat

Question 15

Describe the structure of human pancreatic lipase (3 key points).

Answer 15

• It contains a Ser, His, Asp catalytic triad
• Contains a “lid”
• Consists of plenty of disulfide bonds

Question 16

Human pancreatic lipase requires the activity of what enzyme?

Answer 16

Colipase

Question 17

What are the 2 requirements of activation of HPL?

Answer 17

1. Requires colipase

2. Requires contact with mixed micelle

Question 18

The ___ ____ flips and interacts with colipase.

Answer 18

Lid domain

Question 19

What does flipping of the lid domain results in? (2 key points)

Answer 19

1. Exposes the catalytic triad

2. Exposes a hydrophobic patch

Question 20

Interaction with the mixed micelle and colipase allows HPL to adapt an ____ ____ which leads to an exposed hydrophobic patch, allows HPL to insert in the _____ of the mixed micelle, where it has access to both ____ and ____.

Answer 20

Active conformation, monolayer, fats and water

Question 21

Fatty acid _____ _____ solubilize fatty acids within a protein shell.

Answer 21

Binding proteins

Question 22

Name a drug that inhibits the activity of HPL.

Answer 22

Orlistat

Question 23

How does orlistat work molecularly?

Answer 23

It forms a covalent bond w/ catalytic Serine