Protein Metabolism Flashcards

1
Q

What is a peptide?

A

short chain of AA (less than 50)

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2
Q

What is a protein?

A

a long chain of AA
-sequence will determine shape and function

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3
Q

What is an essential AA?

A

-cant be synthesize by the body of cant be synthesized at a high enough rate to support the need
-required in diet

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4
Q

What is a nonessential AA?

A

cant be synthesized at a high enough rate to support the body’s needs
-does not need to be included in diet

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5
Q

What are conditionally essential AA?

A

non essential AA may become essential if the rate of synthesis is not high enough to meet the demand

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6
Q

What is a semi essential AA?

A

synthesized from essential AA
-if there is not enough of the essential AA precursor in the diet, these AA become essential

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7
Q

What are the essential AA?

A
  1. Phenylalanine
  2. Valine
  3. Threonine
  4. Tryptophan
  5. Isoleucine
  6. Methionine
  7. Histidine
  8. Arginine
  9. Lysine
  10. Leucine
    (PVT TIM HALL)
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8
Q

What are the non essential AAs?

A
  1. Cysteine
  2. Alanine
  3. Asparagine
  4. Aspartate
  5. Tyrosine
  6. Serine
  7. Glycine
  8. Glutamine
  9. Glutamate
  10. Proline
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9
Q

What are the semi essential AAs?

A

Cysteine and Tyrosine

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10
Q

What is cysteine synthesized from?

A

methionine
-need to include enough methionine in diet to meet the requirement for methionine needs + the synthesis of cysteine
-if include cysteine in the diet, this will have a sparing effect on methionine and decrease methionine requirement

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11
Q

What is tyrosine synthesized from?

A

phenylalanine
-need enough in diet to meet needs + synthesis
-sparing effect

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12
Q

Protein digestion in the stomach deals with?

A

-HCl
-Pepsin

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13
Q

What does the HCL do?

A

denatures protein

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14
Q

What does the pepsin do?

A

pepsinogen is activated by HCL to be pepsin
then pepsin breaks down protein into long peptide chains

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15
Q

How does protein digestion work in the small intestine?

A

-cholecystokinin is secreted when chyme enters the duodenum
-CCK acts on pancreas to secrete digestive enzymes
etc

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16
Q

What digestive enzymes does the pancreas secrete after CCK acts on it?

A

-trypsinogen
-chymotrypsin
-procarboxypeptidase

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17
Q

What is secreted by the brush border?

A

enterokinase
-activates trypsinogen to trypsin

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18
Q

What does trypsin activate?

A

chymotrypsinogen to chymotrypsin & procarboxypeptide to carboxypeptide

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19
Q

What breaks down large peptides into oligopeptides? (<10AA)

A

trypsin, chymotrypsin, & carboxypeptidase

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20
Q

What does aminopeptidase (secreted by brush border) do?

A

breaks down oligopeptides into tripeptides, dipeptides, and free AAs

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21
Q

What do microbes synthesize?

A

microbial protein from dietary protein and AA

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22
Q

Microbial protein leaves rumen for

A

digestion in abomasum and s.i.

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23
Q

Na+ dependent AA transport system

A

transports Na+ into cell w/ the amino acid

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24
Q

Na+ independent AA transport system

A

transports AA into the cell

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25
Peptide transport (Tri and Di-peptide)
-transport di- or tri- peptide w/ a H+ into the cell -cellular aminopeptidases breakdown di- and tri- peptides into free AA -free AA leave the cell via AA transporters and enter the hepatic portal system
26
Functions?
-maintain body structure -facilitate mobility -transport -metabolism -regulation -immune regulation
27
What is nitrogen balance?
measure N intake & excretion
28
What is positive nitrogen balance?
N intake exceeds N excretion
29
What is nitrogen equilibrium?
N intake = N excretion -indicates maintenance
30
What is negative nitrogen balance?
N intake less than N excretion -geriatric animals/ disease states
31
What is dynamic protein turnover?
continual degradation and resynthesis of body protein
32
What is involved in protein synthesis?
transcription/ translation
33
Amino acids can be used for
protein synthesis, oxidized, or used for the synthesis of non protein metabolites
34
Transcription
DNA to RNA
35
Translation
RNA to protein
36
What is transcription/translation activated by?
insulin
37
What is involved in protein degradation?
intracellular proteases
38
What is intracellular proteases?
-lysosomal -ubiquitin
39
What activates intracellular proteases?
high concentrations of glucagon (severe starvation)
40
What does amino acid oxidation take place?
liver
41
What are AA considered?
either glucogenic or ketogenic
42
Glucogenic AA
oxidized to glycolytic or citric acid cycle intermediates -can be used for gluconeogenesis
43
Ketogenic AA
oxidized to acetyl CoA -can be used for ketone body synthesis, FA synthesis
44
Which AA are ketogenic?
-lysine -leucine
45
Which AA are glucogenic?
-valine -threonine -histidine -arginine -methionine -cysteine -alanine -aspartate -asparagine -serine -glycine -glutamine -glutamate -proline
46
Which AA are both?
-phenylalanine -tyrosine -isoleucine -tryptophan
47
Various forms of nitrogen excretion?
-ammonia (aquatic invertebrates) -uric acid (birds, insects) -urea (mammals)
48
What is nitric oxide synthesized from?
arginine
49
What is creatine synthesized from?
arginine
50
What is choline synthesized from?
serine
51
What is histamine synthesized from?
histidine
52
What is taurine synthesized from?
cysteine -cant be synthesized by cats
53
What is glutathione synthesized from?
cysteine
54
What is Coenzyme A synthesized from?
cysteine
55
What is the thyroid hormone synthesized from?
tyrosine
56
What is NAD synthesized from?
tryptophan
57
What is Melatonin synthesized from?
tryptophan
58
What is Carnitine synthesized from?
lysine
59
What does a protein concentrate have to have?
at least 20% CP
60
What are oilseed meals?
-by products of vegetable oil production -meal remains after oil extraction
61
What is the most important protein supplement for livestock feeding?
soybean meal
62
What is the downside with soybean meal?
deleterious factors (protease inhibitors, lectins, goitrogens)
63
Protease inhibitors
-inhibit protein digestion -decrease growth
64
Lectins
bind carbohydrates & cause digestive disturbances (diarrhea)
65
Goitrogens
inhibit production of thyroid hormone -causes goiter
66
What is the nutritional content of soybean meal?
CP = 44-50% -low fiber, high quality protein -high phytate
67
What is the second most important plant protein supplement?
cottonseed meal
68
What deleterious factors does cottonseed meal have?
Gossypol
69
Gossypol
-reduced feed intake & growth -damage to lungs, liver, heart, anemia -green yolks in birds
70
What is the nutritional content of cottonseed?
whole cottonseed -23% CP, 23% fat, 17% fiber cottonseed meal -41% CP, 12% fiber cottonseed oil -contains cyclopropene fatty acids
71
Cyclopropene fatty acids
-inhibits desaturases -hard fat in the meat due to saturated FAs -pink egg albumin
72
Animal protein sources examples
-meat meal -meat + bone meal -blood meal
73
Content of animal protein sources
-contains vitamin B12 -high quality protein -concerns with safety (e coli, mad cow disease)
74
What happens to Nonprotein Nitrogen in the rumen?
NPN sources are converted to ammonia in rumen -used by microbes for amino acid synthesis
75
What is the most common NPN source?
Urea -must be careful of urea toxicity -use at less than 2% of diet
76
Urea toxicity
labored breathing, slobbering, bloating, incoordination
77
Other NPN sources
-biuret -dried poultry waste
78
Biuret
2 ureas -brokendown to ammonia more slowly then urea -takes up to 6 weeks for the microbes to produce enzyme to breakdown