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Gastrointestinal > Digestion and Absorption > Flashcards

Digestion and Absorption Flashcards

1
Q

Two types of digestive enzymes are?

A

Luminal and Membranous

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2
Q

Luminal enzymes are pretty self-explanatory

A

Membranous enzymes are those which are inserted into the membranes of cells linng the gut

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3
Q

What are some of the barriers to absorption in the gut?

A

1) Unrestricted water layer
2) Glycocalyx
3) Microvilli membrane
4) Cytoplasm
5) Basolateral membrane
6) Basement membrane
7) Capillary Fenestrae

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4
Q

Basal cells of the gut lie where?

A

In crypts…..stem cells move up the villi and differentiate as they do. How do the stem cells divide?——Assymetrically, one stays in the crypt to be another stem cell and one matures.

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5
Q

Gut lining is sloughed off every 3 days

A

ok

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6
Q

50% of calories in the American Diet are what

A

Carbs

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7
Q

What starts carb digestion?

A

Salivary Amylase

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8
Q

Salivary amylase does what

A

Hydrolyzes alpha 1,4 linkages to yield disaccharides (maltose, Maltotriose, and alpha limit dextrins (1,4 and 1,6))

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9
Q

Alpha 1,6 dextrins are digested by what membrane proteins?

A

Glucoamylase (5%)

Isomaltase (95%)

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10
Q

Alpha 1,4 dextrins are digested by what membrane proteins

A

Glucoamylase (60%)
Sucrase (20)
Isomaltase (20)

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11
Q

Maltotrose digested by what membrane proteins

A

Basically the same as alpha 1,4 dextrin because it is also a 1,4 linkage
G- 25
Sucrase- 25
I_ 50

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12
Q

Lactose carb digested by

A

Lactase

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13
Q

Sucrose carb digested by

A

Sucrase

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14
Q

Trehalose found in

A

Mushrooms….digested by trehalase

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15
Q

KNOW…all of these carbs turn into glucose at least partially. Which ones also turn into galactose and Fructose

A

Lactose— glucose and galactose

Sucrose— glucose and fructose

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16
Q

Glucose is absorbed primarily by what method?

A

Active transport

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17
Q

The fact that glucose is absorbed by active transport means what about its abosorption in the absence of oxygen

A

Not much of it happens.

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18
Q

SGLT-1

A

Luminal glucose absorption

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19
Q

How does SGLT-1 work?

A

It binds 2 sodiums and either a glucose or a galactose and brings them into the cell. The sodium is then exported out of the enterocyte by a Na K ATPase, if this doesn’t work, SGLT-1 doesn;t work.

20
Q

Glut-5 brings in?

A

Fructose

21
Q

Most common carb enzyme deficiency?

A

Lactase

22
Q

Glut-2

A

transports glucose through the blood

23
Q

What starts protein digestion?

A

Pepsin

24
Q

Pepsin does what

A

Its an endopeptidase so it cleaves peptide linkages

25
Q

Trypsinogen is converted to trypsin by what enzyme>

A

Enterokinase

26
Q

What does it mean to say that trypsin is auto-catalytic

A

Once it is activated it activates more of itself

27
Q

Pepsin and pancreatic proteases break down protein into what three things:

A

Di and Tri- peptides, Large Peptides and Free Amino Acids

28
Q

Large peptides are then shunted to either the Di and tri peptides or free amino acid

A

ok

29
Q

Lipid soluble amino acids may leave via?

A

SImple diffusion

30
Q

Triglycerides are broken down by pancreatic lipase into

A

2 monoglyceride + 2 FFA

31
Q

What the hell does colipase do?

A

It is secreted with pancreatic lipase, it is not an enzyme. It allows pancreatic lipase to get in close enough to an emulsion droplet in order to act on it. Binds to the emulsion droplet and displaces the bile acid, then binds to the pancreatic lipase and anchors it to the droplet.

32
Q

What activates pro-colipase

A

Trypsin

33
Q

Micelles contain what

A

cholesterol, fatty acids, monoglycerides.

34
Q

The order of fat absorption

A

CCK—> Micelle—> Triglyceride re-esterification —> Chylomicron —> Lacteal

35
Q

What is a lacteal

A

Lacteals are the lymph vessels that take up fat

36
Q

Two routes by which water and electrolytes are absorbed

A

Transcellular and paracellular (tight junctions)

37
Q

All of the mechanisms for sdium absorption depend on what?

A

Na K ATPase

38
Q

Some chloride absorption is linked to HCO3- secretion. THis process occurs where

A

Colon

39
Q

Water absorbed mostly in small or large bowel

A

Small- leaky tight junctions here

40
Q

POMC signals for what and via what

A

POMC stimulation leads to low food intake and high metabolism.
Stimulated via alpha MSH

41
Q

Hunger stimulates — and —– to increase food intake

A

NPY and AGRP

42
Q

Leptin does what

A

released from fat cells to downregulate food intake….fat people make a ton of leptin but they are insensitive to it. Leptin usually stimulates POMC (no more eating) and blocks NPY (hunger).

43
Q

Ghrelin secreted by

A

Stomach . It increases apetite.

44
Q

Peptide YY (PYY)

A

stimulates POMC

45
Q

Intestinal smooth muscle contraction stimulated by

A

Ach

Gastrointestinal (58 decks)

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