Lecture 51- Digestion And Absorption Of Lipids; Absorption Of Vitamins And Minerals

Question 1

What are the three main lipids?

Answer 1

Triglycerides (glycerol + 3 fatty acids)
Cholesterol
Phospholipids

Question 2

How are lipids provided in diet for domestic animals?

Answer 2

Oils of vegetable or marine origin
Animal fats (tallow, lard, grease)

Question 3

Dietary lipids must be solubilized in the ________ for digestion and absorption.

Answer 3

Small intestine

Question 4

What is the function the stomach churning?

Answer 4

Churning breaks lipids into small droplets to increase surface area for enzymes

Mixes lipids, initiates enzymatic digestion

Question 5

What does gastric lipase do?

Answer 5

Hydrolysis 10% of ingested TAG into glycerol + FFAs

Question 6

What does the stomach slowly empty into the SI?

Answer 6

Chyme

Question 7

How does the small intestine digest lipids?

Answer 7

1. BILE SALTS EMULSIFY LIPIDS
2. PANCREATIC ENZYMES DIGEST DIFFERENT LIPIDS

Question 8

What does lipase + collapse allow?

Answer 8

Collapse binds to lipase and allows it to digest at lipid-water interface

Question 9

What does cholesterol ester hydrolase do?

Answer 9

Hydrolyzes cholesterol ester -> free cholesterol + FA + releases glycerol from triglycerides

Question 10

What is phospholipase A2 activated by?

Answer 10

Trypsin

Question 11

What does phospholipase A2 hydrolyze?

Answer 11

It hydrolzyes phospholipids into lysolecithin + FA

Question 12

What do bile salts solubilize products with SI lumen as _______.

Answer 12

Micelles

Question 13

What does the core of the micelle contain? What is it surrounded by?

Answer 13

Contains products

Surrounded by bile salts

Question 14

What does NOT diffuse into the enterocyte?

Answer 14

Bile salt

Question 15

Re-estrified lipids + apoproteins = ________

Answer 15

Chylomicron

Question 16

What is a chylomicron made up of?

Answer 16

Have cholesterol + TG in core, phospholipids + apoproteins around outside

Need to solubilize for absorption

Question 17

What are lymphatic capillaries?

Answer 17

Chylomicrons can move between endothelial cells of lymphatic capillaries enter the blood at the thoracic duct

Question 18

What are the five steps for the absorption of lipids?

Answer 18

1. Bile salts solubilize products within SI lumen as micelles (except glycerol)
2. Micelles diffuse to brush-border membrane of enterocyte, products released and diffuse into cell
3. Products are re-sterilized inside enterocyte to form original compounds
4. Re-sterilized lipids are packaged with apoproteins to form chylmoicrons
5. Chylmicrons packaged in secretory vesicles and exocytosed across basolateral membrane into lymphatic capillaries

Question 19

What is NOT solubilized within SI lumen as micelle?

Answer 19

Glycerol

Question 20

What are 6 abnormalities of lipid digestion and absorption?

Answer 20

1. Pancreatic insufficiency
2. Acidity of duodenal contents
3. Deficiency of bile salt
4. Bacterial overgrowth
5. Decreased intestinal cells for absorption
6. Failure to synthesize apoproteins

Question 21

What is the pH optimum for lipase?

Answer 21

6

Question 22

When does a tumor arise?

Answer 22

When there is an over production of gastrin

Question 23

What is ileal resection ?

Answer 23

No bile salt recycling

Question 24

What does a lack of Apo B causes ?

Answer 24

Abetalipoproteinemia

Chhylomicrons dont form and cant transport entothyroctes -> lymph

Question 25

For vitamin absorption what is required?

Answer 25

Co-enzymes or co-factors

FOR metabolic reactions

Question 26

Within the SI lumen,what is incorporated into micelles for absorption?

Answer 26

Fat-soluble vitamins

Question 27

What is incorporated into chylomicrons for transport?

Answer 27

Fat-soluble vitamins

Question 28

How are most water-soluble vitamins absorbed?

What is the exception?

Answer 28

Na+/dependent co-transport in SI

Vitamin B12 (cobalamin), which required inter since factor for absorption

Question 29

What are the steps for B12 absorption?

Answer 29

1. B12 released from food by pepsin
2. B12 binds to R proteins from salivary secretions
3. Proteases in SI degrade
4. B12/IF complex resists proteases, travels to ileum for absorption

Question 30

What vitamin do you need to absorb calcium in SI?

Answer 30

Vitamin D

Question 31

(TRUE/FALSE) Calcium is absorbed by both passive and active transport mechanisms

Answer 31

TRUE

Question 32

How is vitamin D activated

Answer 32

Dietary vitamin D (cholecalciferol) -> 25-hydroxycholecalciferol in liver -> 1,25-dihydrocygcholecalciferol in kidney

Question 33

What does active vitamin D promote synthesis of?

Answer 33

Calbindin D-28 K

Question 34

What does a lack of active vitamin D or calcium result in?

Answer 34

Rickets and osteomalacia

Question 35

What does heme iron mean?

Answer 35

Iron bound to hemoglobin or myoglobin

Question 36

What is the iron transporter in the luminal membrane?

Answer 36

DMT-1

Question 37

What is the heme iron digested into free iron by?

Answer 37

Lysosomal enzymes inside enterocytes

Question 38

What does iron circulate bound to? What is it stored as?

Answer 38

Iron circulates bound to transferrin

Stored as ferritin

Question 39

What does free iron bind to inside the enterocyte?

Answer 39

Apoferritin

Question 40

What does free iron bind to in the plasma?

Answer 40

Transferrin