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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
turnover of microvili
3...6 days
26
Duodenum secretion is
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
27
pH of duodenum secretion
is alkali (containing bicarbonate) neutralises the acidic status of chyme coming from the stomach
28
Bile contains (3)
bile salts, bile pigments, and cholesterol. Bile is not an enzyme, it emulsifies fats by action of bile acids and their salts.
29
Bile activates
pancreatic lipase
30
3 duodenal secretions (secreted into duodenal lumen)
duodenal mucus bile acid pancreatic juice
31
Pancreatic juice contains 3 different types of digestive enzymes
➢ proteolytic -> 50% of protein digestion ➢ amylolytic -> 50% of carbohydrate digestion ➢ lipolytic -> 90% of lipid digestion
32
division for proteolytic pancreatic enzymes
endopeptidases exopeptidases
33
What do endopeptidases do?
proteolytic enzymes that break peptide bonds inside the molecule of non-terminal AAs (from the carboxyl side)
34
what type of enzyme is trypsin?
a proteolytic endopeptidase that cuts polypeptides (?) after Arginine or Lysine
35
what type of enzyme is chymotrypsin?
a proteolytic endopeptidase that cuts polypeptides (?) after Phe, Trp, Tyr & His, Met, Leu
36
name 3 proteolytic endopeptidases that arent trypsin or chymotrypsin
elastase collagenase serine protease
37
What do exopeptidases do?
splits terminal peptide bonds (i.e. process releases a single AA or dipeptide from the carboxyl acid side of a peptide chain)
38
name 2 proteolytic exopeptidases
carboxypeptidase A & B
39
precursor to carboxypeptidase
procarboxypeptidase
40
precursor to trypsin and chymotrypsin
trypsinogen chymotrypsinogen
41
Trypsin has autocatalytic properties meaning
it can activate: – new molecules of trypsin – other proteolytic enzymes This makes it the most important proteolytic enzyme.
42
name the main amylolytic pancreatic enzyme
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
how does pancreatic amylase differ between species?
It’s active in monogastric animals, but lacks in herbivores (small amount + low activity).
44
Main lipolytic pancreatic enzyme
alfa-lipase
45
describe lipases' cleaving action
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
Name 4 lesser lipolytic pancreatic enzymes
Phospholipases (A1, A2, C etc.) cholesterol esterase tocopherol esterases retinyl esterases
47
what degrades cholesterides
cholesterol esterase (specificity is low) ▪ produces cholesterol and FA
48
what releases α-tocopherol from tocopherol esters
tocopherol esterases
49
what hydrolyses retinol esters
retinyl esterases ▪ produces retinol and free FAs
50
Key moment in lipid digestion is their
emulsification The main fat emulsifying agents are the bile acids and their salts.
51
Lipids are also emulsified by some proteins such as
casein.
52
Lipids are also emulsified by some salts of
free FAs (and monoglycerides which were liberated during digestion)
53
another name for enteropeptidase and what is its function
enterokinase activates pancreatic juice proteolytic enzymes
54
aminopeptidase does what
breaks peptide bonds from the amino terminus (NH2) side of oligopeptides (as does exopeptidase)
55
dipeptidase does what
breaks dipeptides
56
Nucleoprotein degrading enzymes: (3)
– nucleases – nucleotidase – nucleosidase
57
name 2 nucleases
RNA → ribonuclease DNA → deoxyribonuclease ▪ occurs in oligo- and mononucleotides
58
nucleosidase cleaves
nucleosides for example: adenosine into ribose + adenine
59
name 4 saccharolytic enzymes produced by small intestinal mucosa
* sucrase * lactase * maltase * isomaltase
60
sucrase splits
sucrose into fructose and glucose
61
lactase splits
lactose into galactose and glucose
62
maltase splits
maltose into two glucose
63
isomaltase splits
the bonds which cannot be broken by amylase or maltase due to α-1,6 linkages
64
isomaltose and dextrins are hydrolysed into
respectively into glucose and maltose
65
All saccharolytic enzymes are located, and act, in
the brush border of the small intestine
66
Final hydrolysis of proteins and carbohydrates in the small intestine takes place at
the top of the microvilli (brush border) membrane (glycocalyx), where the active site of the enzymes is positioned into the gut lumen
67
Protein digestion in the small intestine results in
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
Carbohydrate digestion in the small intestine results in
monosaccharides – undigestable remaining carbohydrates contain β-type links (hemicellulose, cellulose), and lignin
69
there are no enzymes synthesized in what part of GI tract
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
name the final products of microbial digestion of polysaccharides (3)
the volatile fatty acids (VFA) ▪ acetic acid ▪ propionic acid ▪ butyric acid Note that simple sugars are not produced!
71
Microorganisms synthesize what type of vitamins
B-group vitamins, which are used by the host animal (but extent of absorption is questionable via the large intestine) + vit K
72
salivary amylase begins the break down of?
starch and glycogen mono-, di-, oligo- and polysaccharides are produced via cleavage
73
Where does carbohydrate digestion not take place?
in the stomach but it does take place in the mouth and duodenum
74
disaccharides are digested in?
disaccharides into maltose, sucrose, lactose in the duodenum
75
disaccharides are digested where by what?
disaccharides are digested in the later parts of the small intestine, into glucose, fructose, galactose, by disaccharidase (maltase, sucrase) isomaltase
76
cruded protein digestion in a monogastric animal begins where by what to produce what?
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
crude protein digestion after the stomach in monogastrics:
activator enteropeptidase in the duodenum is required to activate proteolytic pancreatic enzymes: trypsin chymotrypsin carboxypeptidase to produce di- & tripeptides, and amino acids
78
crude protein digestion in monogastrics after the duodenum use what to produce what
aminopeptidase dipeptidase to produce dipeptides, amino acids (which can be absorbed into the intestinal wall and partially excreted with feces)
79
Salivary α-amylase is produced more in ... A. cattle B. dogs C. pigs D. goats
C. pigs actually not very active in dogs
80
Protein is digested in the stomach into ...
A. polypeptides
81
The enzymes trypsin and chymotrypsin are ... A. exopeptidases –> split terminal peptide bonds B. endopeptidases –> break peptide bonds inside the molecule
B. endopeptidases –> break peptide bonds inside the molecule
82
Enzyme α-lipase digests ...
C. fats
83
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
D. all the above mentioned enzymes
84
The end product of carbohydrate digestion in the large intestine is...
A. volatile fatty acids

Animal nutrition (19 decks)

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