Fat and Lipoprotein digestion

Question 1

What are fatty acids?

Answer 1

various lengths of carbon chains saturated or unsaturated with hydrogen

Question 2

What are the type of fatty acids?

Answer 2

short chain volatile fatty acids, medium chain, or long chain

Question 3

What is pharyngeal lipase?

Answer 3

a lipase secreted by the salivary glands that has a high affinity for the micellar structure of milk fat; only important in newborns

Question 4

What is the role of the stomach in lipid digestion?

Answer 4

emulsification of fats with chyme by churning action of the stomach

Question 5

What is emulsification?

Answer 5

to suspend one liquid in another (fat droplets in water or chyme)

Question 6

What pancreatic enzymes are important in fat digestion?

Answer 6

pancreatic lipase and colipase

Question 7

What fats does pancreatic lipase help digest?

Answer 7

triglycerides to monoglycerides, diglycerides, and free fatty acids

Question 8

What does pancreatic lipase need to be activated?

Answer 8

it can only bind to fat in the presence of colipase and bile salt

Question 9

When does pancreatic lipase work on fats?

Answer 9

it acts on fats that are in emulsion - works at water/fat interface

Question 10

What is the precursor for colipase?

Answer 10

procolipase- cleaved by trypsin

Question 11

Why can short chain fatty acids reach the intestinal brush border?

Answer 11

because they are water soluble enough that they can cross the unstirred water layer and glycocalyx to reach it

Question 12

How do short chain fatty acids cross the apical and basal lateral membranes?

Answer 12

via non-ionic diffusion

Question 13

What is non-ionic diffusion?

Answer 13

when weak acids and bases cross the membrane in their non-dissociated form and reassociate on the other side

Question 14

How do short chain fatty acids move into extracellular fluid and portal circulation?

Answer 14

via passive diffusion down their concentration gradient

Question 15

What is a detergent?

Answer 15

one end of the molecule is hydrophobic which allows it to from ionic bonds with hydrophobic fatty acids, the other end is very hydrophilic making the fatty acid fairly water soluble

Question 16

What pancreatic enzymes work with bile salts on the emulsified fat?

Answer 16

pancreatic lipase, colipase, and cholesterol ester hydrolase

Question 17

What does colipase allow for?

Answer 17

the formation of cross bridge between lipase and bile salts

Question 18

What does cholesterol ester hydrolase do?

Answer 18

removes ester groups from cholesterol esters and lipid esters

Question 19

What is a micelle?

Answer 19

water soluble packages of fatty acids, monoglycerides, cholesterol, and vitamins A, D, and E

Question 20

What do micelles do?

Answer 20

carry the lipid load to the cell surface across the unstirred water layer to bilipid cell membrane where the lipid soluble fatty acids, monoglycerides, and cholesterol can diffuse freely

Question 21

What happens to the bile salts that carry lipids away from fat droplets?

Answer 21

they are too water soluble so they re-enter the lumen and grab another load of lipids

Question 22

What do intestinal epithelial cells do?

Answer 22

secrete intestinal lipase

Question 23

What does intestinal lipase do?

Answer 23

converts any remaining di-triglyceride to mono-glycerides and fatty acids to finish fat digestion

Question 24

What happens to fatty acids once they are taken into the endoplasmic reticulum of the epithelial cells?

Answer 24

they are converted back into triglycerides

Question 25

How do newly formed triglycerides maintain the fatty acid gradient from intestinal lumen to cell cytosol?

Answer 25

they lower the free fatty acid within the cytosol once they are created

Question 26

How do the newly formed triglycerides get out of the intestinal cells into the blood?

Answer 26

they are packaged into chylomicrons to cross the basal lateral membrane of the epithelial cell

Question 27

What are chylomicrons made up of?

Answer 27

80% triglyceride, vitamin A, D, E, 9% phosphoglycerides, 3% cholesterol, and 2% lipoprotein

Question 28

What is the purpose for the lipoprotein in the chylomicron?

Answer 28

they are on the outside of it so it makes the whole globule water solumble enough to move into the extracellular fluid

Question 29

Chylomicrons are too big to enter the portal venous system, so where do they go?

Answer 29

they are picked up by the lacteals and enter general circulation through the thoracic duct

Question 30

What is enterohepatic circulation?

Answer 30

when bile salts reach the ileum, go across it and enter the portal blood where they are extracted by liver cells and put back into bile ducts

Question 31

What can cause a loss of bile acids?

Answer 31

diarrhea - flushed out

Question 32

What will a loss of bile acids do?

Answer 32

lead to poor fat digestion

Question 33

In circulation, what do chylomicrons gain and from what?

Answer 33

they get apolipoprotein C and E from high density lipoprotein carriers

Question 34

What does apolipoprotein C do?

Answer 34

it allows for the chylomicron to bind to Apo C receptors on adipose, mammary, skeleral and heart muscle, and liver where it releases its triglycerides

Question 35

What is a VLDL?

Answer 35

a package used to transport triglyceride and cholesterol out of the liver - can deliver triglycerides to peripheral tissue

Question 36

What is a LDL?

Answer 36

a remnant of VLDL - still has lots of cholesterol which it can deliver ot tissue - bad cholesterol

Question 37

What is a HDL?

Answer 37

a high density lipoprotein carrier that can exchange apo C and E with chylomicrons and VLDL, can also pick up triglycerides from chylomicrons