Exam 4

Question 1

What form of fat or lipid make up 95 percent of dietary consumption

Answer 1

Triglycerides

Question 2

What locations are lipids digested?

Answer 2

mouth, stomach and small intestine.
(it is the only macronutrient digested in all three locations)

Question 3

When is gastric lipase very stable?

Answer 3

In low pH and without bile

Question 4

What enzyme in the mouth starts breaking down lipids?

Answer 4

lingual lipase

Question 5

What inhibits lingual lipase as lipids move down the digestive system?

Answer 5

Lingual lipase is inhibited by the low pH in the stomach but gastric lipase is then activated.

Question 6

What produces lingual lipases?

Answer 6

the serous glands

Question 7

What produces low pH in stomach which activates gastric lipase?

Answer 7

chief cells

Question 8

Why is there minimal digestion of lipids in the stomach?

Answer 8

absence of bile salts

Question 9

What do lingual and gastric lipases work on in lipid digestion?

Answer 9

medium and short chain fatty acids

Question 10

what is released by lingual and gastric lipases after working on lipids?

Answer 10

Free fatty acids (FFA) and diglycerides (1,2-DAG)

Question 11

why are lingual and gastric lipases important for milk digestion in infants?

Answer 11

Because milk is high in medium and short fatty acids

Question 12

where do partially digested lipids exit the stomach?

Answer 12

in the Chyme

Question 13

what happens in the duodenum?

Answer 13

Bicarbonate released to neutralize acidic stomach
gallbladder releases bile
pancreas releases digestive enzymes

Question 14

where is lipid digestion complete?

Answer 14

small intestine

Question 15

In the small intestine what is the result of digestion of triglycerides?

Answer 15

Tryglycerol is broken up into 3 fatty acids and 1 glycerol

Question 16

where are majority of lipids absorbed?

Answer 16

in the jejunum

Question 17

how do you enhance lipid digestion?

Answer 17

emulsify lipids into TAG, DAG, MAG, FFAs, and cholesterol

Question 18

where does the majority of lipid digestion occur and why?

Answer 18

in the duodenum and jejunum
because of the release of bile salts and pancreatic lipase

Question 19

what are the several things that pancreatic lipase requires to function properly?

Answer 19

1. colipase
2. calcium ions, cofactor
3. bile salts

Question 20

How is protein digestion related to lipid digestion?
(How is colipase made?)

Answer 20

Trypsin activates procolipase to make colipase

Question 21

when are bile salts released?

Answer 21

in response to the presence of fat in the chyme

Question 22

what is colipase made up of and what does it do?

Answer 22

it is made up of 100 aa residues that are hydrophobic, they bind to the lipids and is thought to anchor lipase

Question 23

what is the main job for bile salts?

Answer 23

to increase the surface to volume ratio of fat globules

Question 24

inhibition of what enzymes have been produced to reduce absorption of dietary TAGs?

Answer 24

gastric and pancreatic lipase enzymes

Question 25

Inhibition of gastric and pancreatic lipase may result in weight loss due to reduced absorption of dietary TAGs but What is the downside?

Answer 25

it will go to the colon and bacteria in colon will use the dietary lipids which will lead to bloating and gas

Question 26

what is the key concept that happens in lipid digestion/ absorption?

Answer 26

a micelle is formed that is small and water soluble which can enter the enterocytes within the small intestine

Question 27

what are the 2 mechanisms of lipid absoption/digestion? (how are they moving in membranes)

Answer 27

1. lipid (micelle) diffusion across the membrane 2. Fatty acid transport protein (FATP) allows passage of fatty acids (FATP 1-4 have been characterized)

Question 28

what is the key point in mechanisms of lipid absorption/ digestion

Answer 28

neither diffusion of FATP require energy for absorpition

Question 29

How are bile salts recycled?

Answer 29

they are produced in liver and stored in gall bladder which aren't absorbed until they are in the illeal segment of the small intestine, then returned to the liver by portal vein to be resecreted as bile

Question 30

why is bile salts needed to emulsify fats?

Answer 30

fats need to be emulsified because then they would just be a big glob with minimal surface area for lipases to work on. they are broken down to create more surface area for lipases

Question 31

why are bile salts so effective in emulsifying fats?

Answer 31

they have both hydrophillic and hydrophobic ends

Question 32

what's the difference in how fatty acids get digested compared to how Diglycerides (DAG) get digested?

Answer 32

fatty acids can be turned into micelles, while DAGs must first be emulsified by bile salts which can be then turned into micelles then absorbed by the small intestine

Question 33

when you consume alot of cholesterol what enzyme will be in high volume? why?

Answer 33

cholesterol esterase, because cholesterol esterase is the storage form of cholesterol

Question 34

why are micelles an effective way of transporting lipids?

Answer 34

the micelles have hydrophobic properties inside which will help lipids transport through aqueous environments

Question 35

what gets stored into micelles?

Answer 35

fat soluble vitamins (D,E, A, and K) for maximum high fat soluble vitamin absorption you need lipids in diet.

Question 36

how is cholesterol digested?

Answer 36

they are broken down by cholesterol esterase, into fatty acids and cholesterol then emulsified by bile salts to form micelles

Question 37

Where are micelles transported?

Answer 37

they are transported to the enterocyte, ultimately to the SER which can package components into chylomicrons for the rest of the body then to the liver

Question 38

what are bile salts

Answer 38

cholesterol that has been oxidized to form to form cholic acid in combination of glycine and taurine.

Question 39

why is inhibiting cholesterol transporters more beneficial in reducing cholesteral than simply reducing animal product consumption?

Answer 39

by inhibiting transporters you would have a greater effect in lowering cholesterol than diet itself because you would be inhibiting the reabsorption of bile salts

Question 40

why is it a good

Answer 40

it will affect our metabolism

Question 41

why is approximately 70-80 percent of cholesterol esterified?

Answer 41

it is a good storage form and transport form

Question 42

appoproteins

Answer 42

stability and structure

Question 43

what is the major site of vldl and hdl?

Answer 43

liver