Lipid Metabolism

Question 1

What are the dietary lipids?

Answer 1

-triacylglycerols (TAGS)
-fat soluble vitamins (FSVs)
-cholesterol and cholesteryl esters (CEs)
-phospholipids (PLs)

Question 2

TAG digestion in the stomach

Answer 2

using gastric lipase:
breaks down some TAGS into DAGS (diacylglycerol) + fatty acids (FAs)

Question 3

TAG digestion in the small intestine (short story)

Answer 3

-bile creates emulsification droplets
-pancreatic colipase and lipase

Question 4

TAG digestion in the small intestine (long story)

Answer 4

-cholecystokinin is secreted by the duodenum
-acts on pancreas to secrete digestive enzymes pancreatic pancreatic lipase & colipase
-acts on gallbladder to secrete bile
-bile breaks up fat gobules into small emulsification droplets
-colipase allows lipase to enter emulsification droplets
-lipase breaksdown TAGS & DAGs into MAGS (monoacylglycerol) and free fatty acids

Question 5

What are the products of digestion?

Answer 5

MAGS and FAs

Question 6

Lipid absorption

Answer 6

mixed bile salt micelles transport lipids to brush border for absorption

Question 7

Emulsification droplets become what once digestion is complete?

Answer 7

mixed bile salt micelles

Question 8

Absorption of MAGs + FAs occurs via

Answer 8

transporters at the brush border

Question 9

What do products of digestion go?

Answer 9

the endoplasmic reticulum

Question 10

What carries MAGs + FAs to the endoplasmic reticulum

Answer 10

transport proteins

Question 11

What transport protein specifically carries the products of digestion to the ER?

Answer 11

via fatty acid binding protein (FABP)

Question 12

What happens in the ER?

Answer 12

MAGs + FAs turn into TAGs

Question 13

What happens in the ER after the reesterification of TAGs

Answer 13

the TAGs are then packaged into chylomicrons and enter the lymph for transport to the heart

Question 14

What happens during ruminant lipid digestion

Answer 14

-TAGs turn into glycerol + FAs
-biohydrogenation of PUFAs

Question 15

What is the process of lipid digestive in a ruminant?

Answer 15

-microbes breakdown TAGs into glycerol + FAs and the glycerol is converted to UFAs which are absorbed through the rumen wall
-FAs from plant material are polyunsaturated fattyacids (PUFAs)
-microbes bihydrogenate PUFAs into saturated fatty acids (SFAs)
-SFAs continue on through the digestive tract for absorption in the S.I.

Question 16

What are the various lipoproteins?

Answer 16

-chylomicrons
-very low density lipoproteins (VLDL)
-low density lipoproteins (LDL)
-high density lipoproteins (HDL)

Question 17

Whats apolipoprotein?

Answer 17

protein associated with lipoproteins
that is used for:
-structural
-enzyme cofactors
-ligands for receptors

Question 18

What do chylomicrons have?

Answer 18

Apo B48

Question 19

Where do Chylomicrons enter? from?

Answer 19

enter the lymph from the s.i. for transport to the heart

Question 20

What happens with chylomicrons after they enter the lymph?

Answer 20

-when enters the bloodstream, chylomicron will associate w/ Apo C-2
-chylomicron travel through the bloodstream and when the Apo C-2 binds to lipoprotein lipase on capillary wall, TAGS in chylomicron is broken down into glycerol + FAs
-once 80% of TAG have been released, the chylomicron dissociates from Apo C-2 & become chylomicron remnant

Question 21

Where do FAs go?

Answer 21

they enter the cell and are used for energy

Question 22

Where does glycerol go?

Answer 22

goes to the liver

Question 23

How is chylomicron remnant removed from bloodstream?

Answer 23

via apo B48 receptor on liver

Question 24

What do VLDLs have?

Answer 24

Apo 100 and Apo E

Question 25

Where do VLDLs go? from?

Answer 25

released into bloodstream from liver

Question 26

What happens with VLDL when released into the bloodstream?

Answer 26

- when enters bloodstream, VLDL will associate w/ Apo C-2 -VLDL travel through the bloodstream and when the Apo C-2 binds to lipoprotein lipase on capillary wall, TAGS in VLDL is broken down into glycerol + FAs -when over 1/2 of TAG is released by VLDL, Apo C-2 dissociates & VLDL becomes IDL -when over 80% of TAG has been removed apo E dissociates & IDL becomes LDL

Question 27

How is TAG removed from IDL?

Answer 27

apo E binding to receptors on capillary walls

Question 28

What do LDLs have?

Answer 28

Apo B100

Question 29

What happens with LDL?

Answer 29

when apo B100 binds to receptors on capillary walls, cholesterol diffuses out of the LDL into tissue

Question 30

How are LDLs removed?

Answer 30

LDLs are removed from circulation by Apo B100 receptors on liver

Question 31

What do HDLs have?

Answer 31

Apo A-1

Question 32

What are HDLs secreted by?

Answer 32

HDLS

Question 33

What do HDLs do?

Answer 33

perform reverse cholesterol transport -when Apo A-1 binds to receptors on capillary walls, cholesterol is removed from tissues and diffuses into HDL

Question 34

What removes HDL from circulation?

Answer 34

liver removes via apo A-1 receptor

Question 35

What are the biological roles for lipids?

Answer 35

-energy source -structural components of membranes -lubricants -signaling molecules

Question 36

Fatty acid synthesis

Answer 36

-liver and adipose tissue -lactating mammary gland