Nutrient Digestion II - Fats, Vitamins and Minerals

Question 1

In what form is almost all fat ingested as?

Answer 1

Triacylglycerides

Question 2

What molecule is responsible for fat digestion in the small intestine?

Answer 2

Pancreatic lipases

Question 3

How do TAGs present in water?

Answer 3

Large lipid droplets

Question 4

Digestion can only take place at what point on a lipid droplet? What implication does this have on speed of digestion?

Answer 4

The surface (interface) therefore digests very slowly

Question 5

What process helps to speed up digestion and uptake of lipids from small intestine?

Answer 5

Emulsification

Question 6

What two steps occur in the emulsification process?

Answer 6

Mechanical disruption and emulsification

Question 7

How is mechanical disruption of lipid droplets achieved?

Answer 7

Smooth muscle contraction grinds and mixes lumenal contents

Question 8

What emulsifier is used to break up lipid droplets?

Answer 8

Bile (mixture of bile salts and phospholipids)

Question 9

What is an amphipathic molecule?

Answer 9

A molecule with both polar and non-polar regions

Question 10

The formation of smaller conglomerate molecules also help speed up monoglyceride digestion. What are these molecules called?

Answer 10

Micelles

Question 11

What are micelles comprised of?

Answer 11

Monoglycerides
Bile salts
Phospholipids
Fatty acid

Question 12

After crossing into the intestinal epithelial cells, what is the fate of free fatty acids?

Answer 12

They are reformed into TAGs in the smooth endoplasmic reticulum and covered in amphipathic proteins

Question 13

What organelle facilitates the transport of TAGs in the epithelial cells?

Answer 13

Golgi Apparatus

Question 14

What are extracellular fat droplets called after they have been absorbed?

Answer 14

Chylomicrons

Question 15

What are chylomicrons comprised of?

Answer 15

Phospholipids, cholesterol, fat soluble vitamins

Question 16

Approximately how large a diameter are chylomicrons?

Answer 16

Approx. 1 micron in diameter

Question 17

How do chylomicrons move between epithelial cells and the blood?

Answer 17

Through lacteals (lymphatic vessels in the small intestine)

Question 18

How many classes of vitamins are there? What are they?

Answer 18

Two:

Fat-soluble
Water-soluble

Question 19

What are examples of fat-soluble vitamins?

Answer 19

A D E K

Question 20

What are examples of water-soluble vitamins?

Answer 20

B C and folic acid

Question 21

Describe the structure of vitamin B12?

Answer 21

Large, charged molecule

Question 22

What happens when someone has a deficiency of vitamin B12?

Answer 22

Pernicious anaemia

Question 23

What is pernicious anaemia?

Answer 23

Failure of RBCs to maturate

Question 24

How are fat soluble vitamins digested?

Answer 24

Follow same pathway as fat

Question 25

How are water-soluble vitamins digested?

Answer 25

Binds to intrinsic factor in the stomach and absorbed by specific mechanism in the distal ileum

Question 26

What percentage of daily ingested iron is absorbed into the blood?

Answer 26

10%

Question 27

How is iron transported across the brush boarder? Where is it absorbed to?

Answer 27

DMT1 into duodenal enterocytes

Question 28

Once inside duodenal enterocytes, how are iron ions stored?

Answer 28

In ferritin complex

Question 29

Where is unbound iron found?

Answer 29

Across the serosal membrane and into the blood

Question 30

What form does iron in the blood take?

Answer 30

Transferrin

Question 31

How is ferritin expression regulated?

Answer 31

Based on the body's iron status Hyperaemia leads to increased expression (more iron bound in enterocytes) Anaemia leads to decreased expression (more iron released to blood)