Lipid Digestion and Absoprtion

Question 1

Role of phosphlipids

Answer 1

stabilize the fats which are poorly soluble

Question 2

Saturated FA

Answer 2

no double bonds (completely saturated with hydrogens)

Question 3

Monounsaturated

Answer 3

one double bond

Question 4

Polyunsaturated

Answer 4

two or more double bonds

Question 5

Hydrogenation process

Answer 5

cis double bond + H2 gives rise to a saturated FA (no double bonds)

Question 6

Partial hydrogen process increases ___

Answer 6

trans FA

go from cis double bond –> completely saturated –> collapse of double bond but H forms on opposite side of the other

Question 7

Lipids are readily able to cross the cell membrane but have poor ___ due to ____

Answer 7

solubility due to hydrophobic nature

Question 8

Emulsion

Answer 8

stabilize the fat droplet by adding amphiphatic emulsifying agents–form a surface layer separating main bulk of hydrophobic material from aqueous phase

Question 9

Once emulsified to smaller particles, the fat droplets can be acted on by ____

Answer 9

lipolytic enzymes (soluble proteins)

Question 10

Enzymes present in mouth and stomach that help with absoprtion of fat. How much of a role to they have in adult and neonate stage?

Answer 10

Lingual and gastric lipase –minimal in adult. In neonates, its activity is increased to 30-50% due to immature pancreatic enzymes. Contribute to hydolysis of TG

Question 11

Lipase concerts ____ to _____

Answer 11

triacylglycerols to FFA and diacylglycerol

Question 12

Main digestion of absoprtion of lipids occurs in _____

Answer 12

dudodenum and jejunum

Question 13

Long chain FA induce the 4 following enteroendocrine peptides:

Answer 13

1. Gastrointestinal insulinotropic peptide (GIP)
2. GLP-1 (glucagon like peptide)
3. CCK
4. Secretin

Question 14

Secretin

• stimulus
• release site
• action

Answer 14

• decreased pH
• S cell in dudodenum
• enhances bicarbonate duct secretion by pancrease optimizing pH

Question 15

CCK

• stimulus
• release site
• action (3)

Answer 15

• long chain FA and proteins
• I cells in dudodenum
• acts on following
  1. secretion of bile salt by contraction of gall bladder
  2. relaxes sphincter of Oddi
  3. pancreatic secretion

Question 16

CCK causes pancreatic secretion. List the 4 main enzymes

Answer 16

1. trypsinogen
2. pancreatic lipase and procolipase
3. cholesterol esterase
4. prophospholipase A2

Question 17

Enteropeptidase

• action
• activated by

Answer 17

• converts trypsinogen –> trypsin

- activated by CCK

Question 18

trypsin

• action
• activated by

Answer 18

• makes enzyme (procolipase to colipase, prophospholipase A2 to phospholipase A2)
• activated by enteropeptidase

Question 19

Role of phospholipase A2

Answer 19

phospholipids –> FFA + lysolecithin

Question 20

Cholesterol esterase role

Answer 20

cholesterol ester –> cholesterol

Question 21

Importance of pancreatic colipase for action of pancreatic lipase

Answer 21

pancreatic colipase penetrates the phospholipid coating and attaches to the triacylglyceride. breaks barrier for pancreatic lipase which will attach to colipase, allows lipase to do its thing

Question 22

Without colipase, what would inhibit the activity of pancreatic lipase?

Answer 22

bile salts

Question 23

Role of bile salts

Answer 23

acts as a detergent–surrounds the emulsion making smaller lipid droplets (micelles) with increased SA for lipase digestion

Question 24

Composition of mixed micelle

Answer 24

2 monoclygerols, FFA, cholesterol, and lysolecithin all stabilized by bile acids and coated with phospholipid

Question 25

Critical micelle concentration

Answer 25

the minimal concentration of bile salts required to form a mixed micelle

Question 26

(unconjugated/conjucated) bile acids require a lower concentration to form a critical micelle concentration

Answer 26

conjugated

Question 27

NPCILI and its importance clinically

Answer 27

Neimann Pick C1 Like 1 Protein

• transporter for cholesterol into the small intestine
• once inside intestine, gets converted to chole and FFA
• we have drugs like ezetimibe which will block NPCILI and thus decrease cholesterol absoprtion

Question 28

Statins

Answer 28

causes an increase in LDL receptors to pool cholesterol into the liver

Question 29

4 physiological reasons for malabsoprtion of lipids

Answer 29

1. decrease bile (intra or extra hepatic)
2. enterocytes malfunctioning
3. no pancreas – not putting out lipase, cant digest fats
4. bacterial overgrowth–Crohns