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Animal nutrition > Animal nutrition - monogastric digestion > Flashcards

Animal nutrition - monogastric digestion Flashcards

1
Q

most important salivary glands for digestion

A

parotid
mandibular
sublingual

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2
Q

pH of various species’ saliva

A

pig 7.3;
horse 7.5;
dog 7.5;
cattle 8.3

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3
Q

what enzyme does carnivore saliva contain in addition to amylase

A

lysozyme

(also found in milk, tears etc.)

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4
Q

Salivary α-amylase occurs in which 5 (main) species?

A

human, monkey, pig, rat, rabbit

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5
Q

Salivary α-amylase does not occur in which 6 (main) species?

A

very little or absent in

dog, cat, horse,
sheep, cow, goat

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6
Q

amylase digests

A

starch, glycogen, other polysaccharides

Amylase cleaves only internal alpha (1-4) glycosidic bonds, thereby reducing starch to three different oligosaccharides:

maltose (disaccharide), maltotriose (trisaccharide), and a group of alpha-limit dextrins which contain branch points from amylopectin.

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7
Q

at what pH is amylase active and inactive at?

A

is active at neutral pH,
is inactivated in stomach at pH of 2

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8
Q

The most important enzyme in the stomach is

A

pepsin

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9
Q

how is pepsin produced

A

Gastric chief cells produce pepsinogen which is cleaved to pepsin.

– pepsinogens are activated either
▪ by HCl (produced in parietal cells)
▪ autocatalytically (the existing formed pepsin activates new pepsinogen molecules)

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10
Q

pepsinogen types

A

pepsinogen A &
pepsinogen C or gastricsin (lesser known name)

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11
Q

pepsinogen A is secreted exclusively by

A

the chief cells of the gastric corpus, located in the fundic region of stomach

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12
Q

pepsinogen A includes

A

5 different, but chemically similar compounds

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13
Q

pepsinogen A optimal pH for function
vs pepsinogen C optimal pH for function

A

A: pH optimum of 1.5…2.2
C: pH optimum 3.0…3.5

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14
Q

pepsinogen C is secreted mainly by

A

pylorus cells and by the chief cells of the gastric corpus

pepsinogen C incudes 2 distinct compounds

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15
Q

pepsins are

A

acid-resistant proteinases

specificity is low
degrades about 10…18% of proteins

– prefers to break the peptide bonds near aromatic
amino acids (from the carboxyl acid side of the AA)
such as Phe, Tyr, and Trp
– do not split bonds near Glu, Asp and Leu

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16
Q

Note that Proteins do not degrade in the stomach into…?

A

into free AAs

they’re broken down into polypeptides/peptides

The pancreas secretes digestive juice that contains proteases (enzymes) that break down polypeptides into smaller peptides or single amino acids. The two major pancreatic enzymes that digest proteins are trypsin and chymotrypsin.

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17
Q

enzyme complex in young animals that coagulates milk

A

chymosin or rennin or rennet
(Chymosin, known also as rennin)

affects the milk casein in the presence of Ca2+, changes into para casein and coagulates milk

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18
Q

chymosin pH optimum is

A

5.0

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19
Q

what activates chymosin

A

exposure to acid

e.g. lactic acid (produced by microbes in forestomachs)

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20
Q

what Gastric enzyme helps to digest the
coagulated milk clot produced by chymosin

A

cathepsin

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21
Q

in the stomach, lipase is secreted by

A

the gastric chief cells in the fundic mucosa of the stomach

Has an important role only in young animals’
digestion of fats

– helps to digest curdled milk fats, as the young
animals can not create the necessary amount of
liquid bile to emulsify it in the duodenum

Note that lipase is secreted in the stomach only in young animals, this ability ceases into adulthood.

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22
Q

monogastrics’ gastric lipase pH optimum is

A

5.0…5.6

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23
Q

what occurs in the ileum

A

▪ active absorption of digested nutrients (water, vitamins and minerals)
▪ some bacterial fermentation

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24
Q

Nutrient absorption takes place at

A

the top of the microvilli

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25
Q

turnover of microvili

A

3…6 days

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26
Q

Duodenum secretion is

A

intestinal mucus produced by duodenal or Brunner’s gland.

excreted through the duct between the villi of the duodenum

does not contain any enzymes, but acts as lubricant to protect the duodenal wall

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27
Q

pH of duodenum secretion

A

is alkali (containing bicarbonate)

neutralises the acidic status of chyme coming from the stomach

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28
Q

Bile contains (3)

A

bile salts, bile pigments, and cholesterol.

Bile is not an enzyme, it emulsifies fats by action of bile acids and their salts.

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29
Q

Bile activates

A

pancreatic lipase

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30
Q

3 duodenal secretions (secreted into duodenal lumen)

A

duodenal mucus
bile acid
pancreatic juice

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31
Q

Pancreatic juice contains 3 different types of digestive enzymes

A

➢ proteolytic -> 50% of protein digestion
➢ amylolytic -> 50% of carbohydrate digestion
➢ lipolytic -> 90% of lipid digestion

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32
Q

division for proteolytic pancreatic enzymes

A

endopeptidases
exopeptidases

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33
Q

What do endopeptidases do?

A

proteolytic enzymes that break peptide bonds inside the
molecule of non-terminal AAs (from the carboxyl side)

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34
Q

what type of enzyme is trypsin?

A

a proteolytic endopeptidase that cuts polypeptides (?) after Arginine or Lysine

35
Q

what type of enzyme is chymotrypsin?

A

a proteolytic endopeptidase that cuts polypeptides (?) after Phe, Trp, Tyr & His, Met, Leu

36
Q

name 3 proteolytic endopeptidases that arent trypsin or chymotrypsin

A

elastase
collagenase
serine protease

37
Q

What do exopeptidases do?

A

splits terminal peptide bonds (i.e. process releases a single AA or dipeptide from the carboxyl acid side of a peptide chain)

38
Q

name 2 proteolytic exopeptidases

A

carboxypeptidase A & B

39
Q

precursor to carboxypeptidase

A

procarboxypeptidase

40
Q

precursor to trypsin and chymotrypsin

A

trypsinogen
chymotrypsinogen

41
Q

Trypsin has autocatalytic properties meaning

A

it can activate:
– new molecules of trypsin
– other proteolytic enzymes

This makes it the most important proteolytic enzyme.

42
Q

name the main amylolytic pancreatic enzyme

A

alfa-amylase

is similar in its effect to salivary α-amylase
continues the hydrolysis of starch and glycogen
started by salivary α-amylase

is active in the lumen of the duodenum, because
here is the main amount α-amylase

43
Q

how does pancreatic amylase differ between species?

A

It’s active in monogastric animals, but lacks in herbivores (small amount + low activity).

44
Q

Main lipolytic pancreatic enzyme

A

alfa-lipase

45
Q

describe lipases’ cleaving action

A

hydrolyses triglycerides, and removes the FA
residues preferably from 1st and 3rd positions

forms 2-monoglycerides and free FAs

(smaller part of the 2-monoglycerides hydrolyse
further into glycerol and FA, but only to a smaller extent)

46
Q

Name 4 lesser lipolytic pancreatic enzymes

A

Phospholipases (A1, A2, C etc.)
cholesterol esterase
tocopherol esterases
retinyl esterases

47
Q

what degrades cholesterides

A

cholesterol esterase (specificity is low)

▪ produces cholesterol and FA

48
Q

what releases α-tocopherol from tocopherol esters

A

tocopherol esterases

49
Q

what hydrolyses retinol esters

A

retinyl esterases

▪ produces retinol and free FAs

50
Q

Key moment in lipid digestion is their

A

emulsification

The main fat emulsifying agents are the bile acids and their salts.

51
Q

Lipids are also emulsified by some proteins such as

A

casein.

52
Q

Lipids are also emulsified by some salts of

A

free FAs

(and monoglycerides which were liberated during digestion)

53
Q

another name for enteropeptidase

and what is its function

A

enterokinase

activates pancreatic juice proteolytic enzymes

54
Q

aminopeptidase does what

A

breaks peptide bonds from the amino terminus (NH2) side of oligopeptides (as does exopeptidase)

55
Q

dipeptidase does what

A

breaks dipeptides

56
Q

Nucleoprotein degrading enzymes: (3)

A

– nucleases
– nucleotidase
– nucleosidase

57
Q

name 2 nucleases

A

RNA → ribonuclease
DNA → deoxyribonuclease

▪ occurs in oligo- and mononucleotides

58
Q

nucleosidase cleaves

A

nucleosides

for example: adenosine into ribose + adenine

59
Q

name 4 saccharolytic enzymes produced by small intestinal mucosa

A
  • sucrase
  • lactase
  • maltase
  • isomaltase
60
Q

sucrase splits

A

sucrose into fructose and glucose

61
Q

lactase splits

A

lactose into galactose and glucose

62
Q

maltase splits

A

maltose into two glucose

63
Q

isomaltase splits

A

the bonds which cannot be broken by amylase or maltase due to α-1,6 linkages

64
Q

isomaltose and dextrins are hydrolysed into

A

respectively into glucose and maltose

65
Q

All saccharolytic enzymes are located, and act, in

A

the brush border of the small intestine

66
Q

Final hydrolysis of proteins and carbohydrates in the small intestine takes place at

A

the top of the microvilli (brush border) membrane (glycocalyx), where the active site of the enzymes is positioned into the gut lumen

67
Q

Protein digestion in the small intestine results in

A

amino acids

– also a certain amount of di- and tripeptides are
produced, which are transported into the intestinal cells,
where they are then finally digested into amino acids

68
Q

Carbohydrate digestion in the small intestine results
in

A

monosaccharides

– undigestable remaining carbohydrates contain β-type links (hemicellulose, cellulose), and lignin

69
Q

there are no enzymes synthesized in what part of GI tract

A

mammalian large intestine

– but there are plentiful symbiotic microbes which produce enzymes

So, indigestible nutrients are subjected to further degradation in the large intestine by microbial enzymes.

70
Q

name the final products of microbial digestion
of polysaccharides (3)

A

the volatile fatty acids (VFA)
▪ acetic acid
▪ propionic acid
▪ butyric acid

Note that simple sugars are not produced!

71
Q

Microorganisms synthesize what type of vitamins

A

B-group vitamins, which are used by the host animal (but extent of absorption is questionable via the large intestine)

+ vit K

72
Q

salivary amylase begins the break down of?

A

starch and glycogen

mono-, di-, oligo- and polysaccharides are produced via cleavage

73
Q

Where does carbohydrate digestion not take place?

A

in the stomach

but it does take place in the mouth and duodenum

74
Q

disaccharides are digested in?

A

disaccharides into maltose, sucrose, lactose in the duodenum

75
Q

disaccharides are digested where by what?

A

disaccharides are digested in the later parts of the small intestine, into glucose, fructose, galactose, by disaccharidase (maltase, sucrase) isomaltase

76
Q

cruded protein digestion in a monogastric animal begins where by what to produce what?

A

in the stomach by pepsins and hydrochloric acid (HCl) which produce polypeptides and oligopeptides (NOT amino acids yet)

(in nursing animals this is slightly different. they use chymosin + lactic acid & then cathepsin which can digest the coagulated milk) confirm this.

77
Q

crude protein digestion after the stomach in monogastrics:

A

activator enteropeptidase in the duodenum is required to activate proteolytic pancreatic enzymes:
trypsin
chymotrypsin
carboxypeptidase

to produce di- & tripeptides, and amino acids

78
Q

crude protein digestion in monogastrics after the duodenum use what to produce what

A

aminopeptidase
dipeptidase

to produce

dipeptides, amino acids (which can be absorbed into the intestinal wall and partially excreted with feces)

79
Q

Salivary α-amylase is produced more in …
A. cattle
B. dogs
C. pigs
D. goats

A

C. pigs

actually not very active in dogs

80
Q

Protein is digested in the stomach into …

A

A. polypeptides

81
Q

The enzymes trypsin and chymotrypsin are …

A. exopeptidases –> split terminal peptide bonds
B. endopeptidases –> break peptide bonds inside
the molecule

A

B. endopeptidases –> break peptide bonds inside
the molecule

82
Q

Enzyme α-lipase digests …

A

C. fats

83
Q

Proteolytic pro-enzymes produced in the pancreas are activated in the duodenum by …

A. enteropeptidase
B. enterokinase
C. trypsin
D. all the above mentioned enzymes

A

D. all the above mentioned enzymes

84
Q

The end product of carbohydrate digestion in the large intestine is…

A

A. volatile fatty acids

Animal nutrition (19 decks)

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