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VETS1003 > digestion > Flashcards

digestion Flashcards

1
Q

digestion

A

breakdown of complex molecules into simple molecules

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2
Q

absorption

A

transporting simple molecules across intestinal epithelium

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3
Q

in order for nutrients to be absorbed in SI much be transported across apical (ie luminal) surface of

A

enterocytes

then across basolateral surface of cell

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4
Q

apical (luminal) surface of enterocytes covered in

A

microvilli

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5
Q

before nutrients can reach the apical surface of enterocytes of SI, what do they have to diffuse through

A

glycocalyx; jelly-like layer of glycoprotein

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6
Q

what is attached to microvilli of enterocytes

A

digestive enzymes and proteins; project into glycocalyx

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7
Q

goblet cells between enterocytes produce

A

mucous

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8
Q

fluid flows slower where

A

closer to intestinal surface; ie unstirred water layer (think like a river, faster in middle, slower at banks)

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9
Q

what is the diffusion barrier nutrients must pass through before getting absorbed

A

unstirred water layer, mucous and glycocalyx

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10
Q

why is physical digestion (breakdown of particle size) important

A
  • allows food to pass through GI tract
  • increases SA exposed to digestive enzymes
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11
Q

what does physical digestion begin and end

A

mastication

ends in distal stomach by grinding action near pylorus (aided by breakdown of connective tissue by HCl and pepsin)

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12
Q

chemical digestion of each major nutrient is achieved through the process of

A

hydrolysis; splitting of a chemical bond by the insertion of a water molecule

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13
Q

what bond is hydrolyzed in digestion of carbs

A

glycosidic bond

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14
Q

what bond is hydrolyzed in digestion of proteins

A

peptide bond

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15
Q

what bond is hydrolyzed in digestion of fats

A

ester bond

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16
Q

hydrolysis of triglyceride molecules

A

2 ester bonds are hydrolyzed to make a monoglyceride and 2 free fatty acids

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17
Q

2 general classes of enzymes that catalyze hydrolysis

A

luminal and membrane-bound

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18
Q

luminal enzymes that catalyzes hydrolysis, act in lumen and are secreted by

A

major GIT glands (salivary, gastric, pancreas)

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19
Q

luminal phase digestion results in _____ hydrolysis

A

incomplete
forms short-chain polymers

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20
Q

membrane-bound enzymes that catalyze hydrolysis act where

A

at the membrane surface of the epithelium of the small intestine

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21
Q

membranous-phase of digestion completes the

A

hydrolytic process: breaks short-chain polymers into monomers that can be absorbed

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22
Q

3 types of carbs

A

fibers
sugars
starches

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23
Q

carbs are nutrients containing

A

carbon, hydrogen and oxygen

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24
Q

fibers (carbs)

A

structural part of plants
not digested by mammalian enzymes

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25
Q

sugars (saccharides)
(carbs)
what are the 2 types

A
  • Simple (monosaccharides), e.g., glucose, galactose and fructose
  • Complex (polysaccharides) e.g., disaccharides such as lactose and sucrose, trisaccharides, oligosaccharides
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26
Q

starches (carbs)
glucose polymers with 2 major forms:

A
  • amylose (straight-chain)
    -amylopectin (branched-chain)
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27
Q

luminal phase digestion digests what type of carbs

A

starches only

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28
Q

what are starches digested by in luminal digestion

A

alpha-amylase

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29
Q

alpha amylase comes from

A

pancreas
digests starches

30
Q

how does alpha-amylase digest starches

A

The linkages within the long-chain polymers
of glucose of amylose and amylopectin are attacked by alpha-amylase. It cleaves the starch chains in the middle, resulting in the production of polysaccharides of
intermediate chain length.

These intermediates are known as dextrins in amylose, and “limit dextrins” in amylopectin .

These chains continue to be attacked and further broken down until disaccharide (maltose) and trisaccharide (maltotriose)
units are formed. The end result of luminal-phase carbohydrate digestion is the creation of lots of disaccharides, trisaccharides, and oligosaccharides from large
starch molecules.

31
Q

dextrins and limit dextrins

A

when alpha-amylase digests starch it created intermediates

These intermediates are known as dextrins in amylose, and “limit dextrins” in amylopectin

32
Q

membranous phase digestion of starch digests what kind of starches

A

complex carbs as well as polysaccharides from luminal phase starch digestion

33
Q

each complex carb has specific membrane-bound

A

enzyme in glycocalyx: sucrase, maltase, lactase

34
Q

membrane phase digestion of carbs; carbs are digested to _____ before being absorbed

A

monosaccharides

35
Q

how is protein digested in luminal phase digestion and the membranous phase digestion

A

large molecular proteins broken down into small peptide chains

These peptide chains are then digested to individual amino acids during membranous-phase digestion.

36
Q

are some amino acids also released during luminal phase digestion

A

yes due to number of diff enzymes involved

37
Q

proteolytic enzymes

A

aka peptidases; enzymes that break down proteins

38
Q

where are proteolytic aka peptidases released

A

from the gastric glands and the pancreas as zymogens, which are then activated in the gut lumen

39
Q

most peptidases are

A

endopeptidases, which break proteins at internal points along the amino acid chains

40
Q

exopeptidases

A

type of peptidase that release single amino acids from ends of peptide chains

41
Q

activation of zymogens that digest proteins occurs in

A

the gut lumen

42
Q

in the stomach pepsinogen and chymosinogen are activated by

pepsinogen also activated by pepsin

A

hydrochloric acid

*pepsinogen also activated by pepsin

43
Q

trypsinogen form pancreas is activated by

A

trypsin and enterokinase in duodenum

44
Q

trypsin activates (other than trypsinogen)

A

other pancreatic enzymes in lumen: Chymotrypsin, proelastase, carboxypeptidases A and B, as well as additional trypsin

45
Q

luminal phase digestion of proteins begins where

A

in the stomach

46
Q

gastric digestion of protein facilitated by

A

HCl (hydrochloric acid)

47
Q

why is gastric hydrolysis of protein important

A

most connective tissue in animals is proteins

48
Q

membranous phase digestion of protein occurs by

A

peptide-digesting enzymes (peptidases) in glycocalyx

Yields free amino acids as well as di- and tripeptides that can be absorbed

49
Q

lipids are water-

A

insoluble

50
Q

in order to digest lipids what 3 things must occur

A

1) emulsify
2) hydrolyze
3) form micelles

51
Q

emulsification of lipids

A

reducing size of lipid droplets to form stable suspension in water

52
Q

where does emulsification of lipids start

A

stomach: lipids warmed to body temp and mechanical digestion breaks lipid gobules into droplets that pass to SI

53
Q

emulsification of lipids in stomach

A

lipids warmed to body temp and mechanical digestion breaks lipid gobules into droplets that pass to SI

54
Q

emulsification of lipid in SI

A
  • Bile acids and phospholipids act as detergents
  • Reduce surface tension of the lipids
  • Droplets further decrease in size
55
Q

hydrolysis of lipids; lipid droplets are coated by

A

bile products

56
Q

how does hydrolysis of lipids occur

A
  • Lipid droplets coated by bile products
  • Enzyme ‘co-lipase’ clears a path through bile products
  • Allows pancreatic lipase to hydrolyse triglyceride molecules into 2 FFA’s and a monoglyceride molecule
  • Other lipid-digesting pancreatic enzymes include cholesterol esterase and phospholipase
57
Q

how are micelles formed

A

The products of hydrolytic lipid digestion – the free fatty acids and monoglycerides –
and other products of lipid digestion combine with bile acids and phospholipids to
form micelles.

58
Q

micelles are water-

A

soluble

59
Q

how do lipids being turned into micelles allow them to be digested

A

Micelles are small and water-soluble (unlike lipids). The soluble micelles allow the lipids to diffuse through the gut lumen into the unstirred water layer, and into close contact with the absorptive surface of the apical membrane

60
Q

Membranous-phase digestion occurs in microenvironment of

A

glycocalyx, mucous and an
unstirred water layer, with digestive enzymes in the intestinal surface membrane

61
Q

Luminal-phase carbohydrate digestion

A

gives short-chain polysaccharides. This only applies to starches !

62
Q

Sugars are digested in membranous-phase digestion. There is a separate enzyme for each

A

type of polysaccharide to break down it down to monosaccharides

63
Q

Proteins are digested by a

A

variety of luminal-phase enzymes

64
Q

Complete digestion of peptides to free amino amino acids occurs on the

A

enterocyte surface, and
within the enterocyte

65
Q

Detergent action and enzymatic action are both necessary for digestion and absorption of

A

fats

66
Q

Micelles are formed with bile acids to transport luminal fats to the

A

cell surface

67
Q

Which of the following molecules is consumed during the process of hydrolytic digestion?

A

Water

68
Q

Which of the following statements regarding the digestion of carbohydrates is INCORRECT?

A.
All carbohydrates are digested to monosaccharides before being absorbed by the enterocytes

B.
The luminal phase digestion of carbohydrates only applies to starches, because sugars are digested in the membranous phase

C.
Fibres are broken down during membranous-phase digestion

D.
Each complex carbohydrate has a specific membrane-bound enzyme, which projects into the glycocalyx

A

C.
Fibres are broken down during membranous-phase digestion

69
Q

Which of the following statements regarding the digestion of protein is CORRECT?

A.
Exopeptidases cleave proteins at internal points along amino acid chain

B.
All peptides are digested to free amino acids before being absorbed by the enterocytes

C.
Large molecular proteins are broken down into small peptide chains during luminal digestion, via the action of a single proteolytic enzyme which breaks peptide bonds

D.
The autocatalytic action of trypsin on trypsinogen forms a positive feedback loop, ensuring the rapid and complete activation of trypsinogen in the gut

A

D.
The autocatalytic action of trypsin on trypsinogen forms a positive feedback loop, ensuring the rapid and complete activation of trypsinogen in the gut

70
Q
A
70
Q

Finding triglycerides and starch in the faeces of a dog with a poor body condition score, that has a normal feed intake would suggest:

A.
Malabsorption

B.
Maldigestion

A

B.
Maldigestion

VETS1003 (23 decks)

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