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B2 Biochem > Lipid Digestion And Absorption > Flashcards

Lipid Digestion And Absorption Flashcards

1
Q

US adult consumption of lipids

A

81 g/day

90% TAG

10% cholesterol, cholesterol esters, phospholipids, free FAs

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2
Q

Sterified fat

A

Lipid

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3
Q

Acid stable lipases that function in the stomach between ph 4 to ph 6

A

Acid lipase

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4
Q

Secreted from glands at the back of the tongue

A

Lingual lipase

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5
Q

Secreted from gastric mucosa

A

Gastric lipase

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6
Q

Lipid enzymes in the stomach typically target:

A

TAGs containing short and medium FA chains

Less than 12 carbons

Ex: milk fat

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7
Q

Lipid enzyme are especially important when?

A

In neonates, when milk is primary food source

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8
Q

2 complementary actions of emulsification

A

Mechanical agitation and bile salt secretion

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9
Q

Increases the lipid droplet surface area via peristalsis of dietary material

A

Mechanical agitation (emulsification)

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10
Q

Where are bile salts made?

A

Liver

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11
Q

Where are bile salts stored?

A

Gall bladder

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12
Q

Where are bile salts secreted?

A

Small intestine

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13
Q

Coalescing

A

Forming one mass or whole, bile salts prevent this, detergent property

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14
Q

Enzymes secreted from the pancreas into the small intestine digest:

A

TAG, cholesteryl esters, and phospholipids

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15
Q

Has detergent properties that stabilize particles as they become smaller, preventing them from coalescing

A

Bile salts

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16
Q

The removal of specific FAs by breaking ester bonds attaching the FAs

A

Digestion in small intestine

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17
Q

Why are TAGs digested in the small intestines?

A

Because the TAg is too big for intestinal mucosal cells to endocytose efficiently

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18
Q

What is pancreatic lipase and what does it do?

A

It’s an esterase, and it cleaves 2 free FAs and 1 2-monoacylglycerol for a TAG

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19
Q

What is colipase and what does it do?

A

Pancreatic enzyme secreted into the small in the small intestine

Function: to anchor pancreatic lipase and promote its activity when inhibitory bile salts are present

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20
Q

Colipase and pancreatic lipase

A

1:1 ratio

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21
Q

What digests esterified cholesterol?

A

Cholesterol esterase

22
Q

What enzymes digest phospholipids?

A

Phospholipase A2 and Lysophospolipase

23
Q

Phospholipase A2 produces:

A

A Lysophospolipid and a free FA

24
Q

Lysophospolipase produces:

A

One FA and one glycerophosphoryl base

25
Q

What happens to glycerylphosphoryl bases?

And what are they formed from?

A

They can be absorbed, digested more , or excreted in feces. They’re produced by Lysophospolipase

26
Q

Cholesterol esterase produces what from what?

A

Cholesterol from a cholesterol ester. It cleaves the R-C=O group and replaces it with a hydrogen.

27
Q

Gut endocrine cells sense:

A

Lipids and partially digested proteins, low pH of chyme entering the intestine

28
Q

Gut Endocrine cells are found:

A

In the mucosa layer of the lower duodenum and jejunumq

29
Q

Gut endocrine cells secrete:

A

CCK and secretin

30
Q

What is CCK?

A

Small peptide hormone secreted to the blood in response to the presence of lipids and partially digested proteins

31
Q

What does CCK promote and cause release of?

A

Pancreatic enzyme secretion, and cause gall bladder to release bile

32
Q

What does CCK decrease?

A

Gastric motility, reducing release of gastric contents to the small

33
Q

What is secretin?

A

A small peptide hormone secreted to the blood in response to the low pH of chyme entering the intestine

34
Q

What does secretin promote?

A

Release of pancreatic juice, alkaline and bicarbonate rich

35
Q

Lipid digestion in the jejunum generates what 3 products?

A

Free FA, free cholesterol, and 2-monoacylglycerol

36
Q

What are micelles and what/where are they formed?

A

Disk shaped clusters of amphipathic lipids

Formed in the jejunum? From free FA, free cholesterol, 2-mono acyl glycerol, bile salts, and fat-soluble vitamins

37
Q

What are the fat soluble vitamins

A

D, E, K, A

38
Q

What are enterocytes?

A

Intestinal mucosal cells

39
Q

How are micelles arranged?

A

HydrophoBic groups are Buried. And HydropHILic groups are exposed. To the aqueous solution

40
Q

Where are micelles soluble/absorbed?

A

Soluble in the intestinal lumen, absorbed in the brush border membrane of enterocytes

41
Q

Where does complex lipid biosynthesis occur?

A

ER

42
Q

converts long chain fatty acids to their activated form by using energy from ATP -> AMP to form fatty acyl CoA

A

Thiokinase (fatty acyl-CoA synthase)

43
Q

2-monoacylglycerol is converted to TAG by adding FAs

A

TAG synthase

44
Q

Esterifies cholesterol with a FA

A

Acyl CoA-cholesterol acyltransferase

45
Q

What are chylomicron?

A

TAG and cholesterol esters surrounded by a spherical layer of phospholipids, cholesterol, and Apolipoprotein B-48

Produced at ER of enterocytes

Lymph contains chylomicrons called Chyle

46
Q

What enzyme degrades TAG in the circulating chylomicrons to free FAs and glycerol?

A

Lipoprotein lipase

47
Q

Fate of free FAs?

A

Usually taken up immediately by adjacent muscle/adipose tissue. If not, will circulate with serum albumin in blood til taken up.

48
Q

What is the fate of glycerol?

A

Taken up by the liver to produce glycerol-3-phosphate which enters glycolysis or gluconeogenesis

49
Q

Remaining components of chylomicron…

A

Endocytosed in the liver

50
Q

Poor digestion and decreased absorption can lead to:

A

Increased excretion of essential dietary lipids

51
Q

Cystic Fibrosis

A

Cystic- gallbladder
Fibrosis - digestion

Autosomal recessive

Mutations will affect Cl ion channel, affecting hydration and viscosity of mucus

Thick viscous mucus blocks the secretion of pancreatic enzymes, or pancreatic insufficiency

Results in delayed growth and energy deficiency

Treatment includes enzyme replacements and fat-soluble vitamin supplements

B2 Biochem (13 decks)

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