Lipids and Vitamins

Question 1

Secreted lipids

Answer 1

found in bile (phospholipids)

sloughed intestinal cells and bacterial membranes

Question 2

Gastric Lipase

Answer 2

only active and stable at pH 4

located near oil-water border

Secreted by chief cells
resistant to Pepsin degradation
inactivated by pancreatic proteases in SI
cleaves FAs from TAGs ( Some of which can be absorbed in the stomach —>1FFA+1 DAG

Question 3

Pancreatic lipase

Answer 3

*Major lipolytic enzyme: secreted in large amts
released from acinar cells
dependent of colipase, alkaline pH, Ca, Bile salts FA substrates

Question 4

function of pancreatic lipase

Answer 4

associate with colipase, which allows it to get close to micelle

hydrolyze TAGs —>2 FFA+ 1MAG

Question 5

pancreatic lipase inhibitors

Answer 5

Pancreatic lipase inhibitor

results in higher concentration of TAGs in stool

Question 6

phospholipase A2

Answer 6

pancreatic, needs bile salts and alk pH

cleaves glycerophospholipid–>1 FFA (MAG)

Question 7

Carboxyl ester hydrolase

Answer 7

non substrate specific

hydrolyzes all esters (b/w all ester linkages)

—>free cholesterol and free glycerol

same action as Bile salt stimulated milk lipase (due to lack of infant pancreatic lipase activity)

Question 8

CCK

Answer 8

stimulated by FFA in the duo
stimulates bile into duo
stimulates secretion of pancreatic lipase and esterase

Question 9

Micelle

Answer 9

lipid MONOlayer with tails facing into the hydrophobic core

creates a shorter distance for enzymes to reach substrates located in the core

Question 10

Bulk water phase of the lumen

Answer 10

where hydrolysis and micelle formation take place

Question 11

Unstirred water layer

Answer 11

just next to the cell membrane, allows short and medium FA directly into enterocytes due to favorable protonated environment (High Na/H exchanger activity)
large FA chains are brought back into micelles

Question 12

re-esterification

Answer 12

occurs in the enterocyte w/in the sER

Long chain FAs are assembled into TAGs and phospholipids

Question 13

Chylomicrons

Answer 13

Apolipoproteins+TAGs + phospholipids + cholesterol esters are brought together in the sER
largest lipoproteins made of TAGs
surface coated with apos , lecithin and PLs

Question 14

Water soluble vitamins

Answer 14

abs in SI
have specific carriers and or brush border and luminal enzymes for deconjugation or phosphorylation
many Na dependent
utilize GPCR and cAMP

Question 15

Fat soluble vitamins

Answer 15

called so bc of chemical structure and storage in fat deposits
rely on lipid absorption

Question 16

Folate

Answer 16

deficiency can cause neural tube defects in developing fetus (spina bifida and anecephaly)
water soluble

Question 17

Tetrahydroafolate (THF)

Answer 17

biologically active form of folate
cofactor for synth of thymine and purines (NEED FOR DNA SYNTH)

deficiency—>inhibited DNA synth—>megaloblastic anemia (extra large cell due to inhibited RNA synthesis)

tx= pteroylmonoglutamate

Question 18

pteroylmonoglutamate

Answer 18

Helps transport Folate conjugase into enterocytes

in the liver it is changed to THF

tx for THF deficiency

Question 19

Vitamin B12 (Cobalamin)

Answer 19

only synthesized by microbes (found in animal products)
coenzyme

also causes megaloblastic anemia

• Need IF, which binds B12 in the SI

Question 20

Intrinsic factor

Answer 20

binds B12 in the SI, once it is released from haptocorrin

IF has receptor with enterocyte cell membrane, causes B12 to be brought into the cell

B12 is recycled, by being added to bile which is reabsorbed in the ilium

Question 21

Vitamin B12 deficiency

Answer 21

vegetarian diet 
pernicious anemia (loss of parietal cells)
megaloblastic anemia 
Crohns disease 
Ileal resection 

can cause decreased methionine, which can cause a lack of Folate

Question 22

Pernicious anemia

Answer 22

caused by lack of parietal cells
to to atrophy or AI attack against the cells
due to molecular mimicy against H. Pylori

Question 23

medium chain FAs

Answer 23

absorbed independently of micelles
once inside the enterocytes they can be directly transferred into the blood

fat substitute for pt with related malabsorption

Question 24

Emulsion droplet

Answer 24

contains MAGs, chol, lipases, bile salts and soaps on surface, DAGs, TAGS, and chol esters are at the core

MAGs are hydrolyzed first and FFAs are released
DAGs and TAGs replace the surface MAGS

droplet decreases in size, and SA increases which promotes more digestion of surface lipases until it becomes a micelle

Question 25

FA translocase and FA binding proteins

Answer 25

enhance translocation and preferentially bind Long Chain FAs which do not easily diffuse

Question 26

Shilling’s Test

Answer 26

***Shillng’s test
Presence of radiolabeled B12 in the urine indicates a normal test
Ø This means that it is being bound by IF and brought into plamsa
Absence in the urine is abnormal, because lack of IF will cause it to move into the feces

Then give oral IF, and test for the presence of B12 in the urine