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NUTR 3210 > Exam - Proteins > Flashcards

Exam - Proteins Flashcards

1
Q

what does protein provide

A

amino acids for protein synthesis

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2
Q

is protein an energy source

A

only when needed

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3
Q

what is protein a substrate for

A

glucose synthesis

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4
Q

what is the recommended protein intake

A

10-30%

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5
Q

what is the average protein consumption in North America

A

16% of daily calories

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6
Q

how many proteinorganic amino acids are there in humans

A

20 standard - 21 including selenocysteine

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7
Q

what is a proteinorganic amino acid

A

an animo acid that is incorporated into a protein during translation

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8
Q

what proteinorganic amino acids are part of the standard genetic code

A

all but selenocysteine

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9
Q

how many amino acids are considered essential for humans

A

9

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10
Q

what was the last amino acid to be added to the essential list

A

Histidine

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11
Q

where is protein mainly found in the body

A

blood (RBC)
connective tissue
eye lens

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12
Q

what percentage of protein is found in the RBC

A

35%

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13
Q

what percentage of protein is found in connective tissue

A

37%

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14
Q

what percentage of protein is found in the eye lens

A

34%

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15
Q

is percent protein content higher in animal derived foods or plants

A

animal derived foods

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16
Q

what is the only amino acid that does not exist as an enantiomer

A

glycine

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17
Q

what is the naturally occurring configuration of amino acids

A

L

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18
Q

how are amino acids connected

A

peptide bonds (covalent chemical bond) - condensation rxn

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19
Q

how do you break a peptide bond

A

add H20 (hydrolysis)

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20
Q

how many amino acids in dipeptides

A

2

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21
Q

how many amino acids in tripeptides

A

3

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22
Q

how many amino acids in oligopeptides

A

~50

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23
Q

how many amino acids in polypeptides

A

> 50

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24
Q

what is a biologically active protein made of

A

1 or more polypeptides

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25
Q

what is correct polypeptide folding assisted by

A

chaperone proteins

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26
Q

what is the primary structure of proteins determined by

A

the DNA sequence

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27
Q

what does the primary structure of a protein refer to

A

a polypeptide chain of amino acids

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28
Q

what is the secondary structure of proteins determined by

A

the hydrogen bonds that create a more stabile structure

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29
Q

what do the hydrogen bonds in proteins involve

A

only backbone atoms - no side chains

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30
Q

what are the 2 types of stabilized structures to exist

A

B-pleated sheets and a-helix

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31
Q

how does an a-helix occur

A

amino group makes a hydrogen bond with a carboxyl group 4 AAs down the chain

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32
Q

how does a B-pleated sheet occur

A

amino group makes a hydrogen bond with a carboxyl group in the folded back peptide chain

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33
Q

what does the tertiary structure of proteins correspond to

A

the arrangement of the secondary structure in 3D space

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34
Q

what does a tertiary structure consist of

A

one polypeptide chain with interactions between AA side chains

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35
Q

what does is a quaternary structure of protein

A

a combination of 2 or more tertiary structures that are required to make a functional protein

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36
Q

what does a quaternary structure form

A

multi-subunit complex

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37
Q

do all proteins have a quaternary structure

A

no

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38
Q

what is a native protein

A

a protein in its normal 3D conformation

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39
Q

what does a protein lose when it is denatured

A

its bioactivity

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40
Q

what does denaturing a protein affect

A

secondary, tertiary and quaternary structure

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41
Q

what are essential amino acids

A

not made by the body or cannot be made quickly enough to meet demands

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42
Q

what are conditionally essential amino acids

A

not normally required in the diet in a healthy individual - become essential under specific contexts

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43
Q

reasons for conditionally essential amino acids

A

genetic problem
development of disease

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44
Q

example of a genetic problem that would result in a conditionally essential amino acids

A

phenylketonuria

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45
Q

what is phenylketonuria

A

an inborn error of metabolism where a person is unable to breakdown Phe into Tyr - build up of Phe causes intellectual disability

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46
Q

what is the solution of phenylketonuria

A

limit Phe intake and supplement with Tyr

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47
Q

example of a disease that would result in a conditionally essential amino acid

A

liver disease (cirrhosis)

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48
Q

what does liver disease do

A

impairs Phe and Met catabolism - Tyr and Cys are synthesized from Phe and Met… impairment makes Tyr and Cys essential

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49
Q

what are non-essential amino acids

A

can be synthesized and are not essential to obtain from diet

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50
Q

for protein digestion - what occurs in the mouth

A

mechanical breakdown - no enzymatic digestion

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51
Q

for protein digestion what occurs in the stomach

A

enzymatic digestion:
HCl in gastric juice
pepsin (endopeptidase)

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52
Q

for protein digestion what is in the pancreas

A

pancreatic juice containing zymogens

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53
Q

what are zymogens

A

inactive digestive proenzymes

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54
Q

for protein digestion what occurs in the small intestine

A

zymogens are activated
enzymes break down peptides
absorption of AA

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55
Q

what are the 4 main components of protein digestion

A

mouth
stomach
pancreas
small intestine

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56
Q

what does the stomach produce

A

gastric juice

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57
Q

where is HCl secreted from

A

parietal cells

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58
Q

what is HCl release triggered by

A

gastrin
acetylcholine
histamine

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59
Q

what are the 2 functions of HCl

A

denatures protein (disrupts hydrogen and electrostatic bonds)
activates pepsin

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60
Q

what is pepsin secreted as

A

pepsinogen

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61
Q

what is pepsinogen

A

an inactive zymogen

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62
Q

when is pepsinogen/pepsin active

A

in an acidic pH

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63
Q

when is pepsinogen/pepsin inactive

A

at a neutral pH

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64
Q

what causes a conformational change in pepsinogen

A

HCl - allows it to autoactivate itself

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65
Q

what does pepsin do

A

cleaves peptide bonds within polypeptide chain (endopeptidase)

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66
Q

what does pepsin mostly generate

A

oligopeptides and some free AAs

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67
Q

where are most amino acids absorbed

A

upper small intestine

68
Q

what are the 2 ways amino acids are absorbed

A

facilitated diffusion
active transport

69
Q

what percentage of amino acids are absorbed through active transport

A

> 60%

70
Q

what does active transport entail

A

sodium-dependent transporters

71
Q

do essential AAs absorb faster or slower than non-essential AAs

A

faster

72
Q

is there any advantage in taking supplements in terms of absorption

A

no - the free amino acids don’t have an advantage over amino acids in food

73
Q

qualities of facilitated diffusion

A

does not require sodium or ATO
does not concentrate against the gradient

74
Q

qualities of active transport

A

sodium dependent
requires ATP
concentrates against gradient

75
Q

what is PEPT1

A

peptide transporter 1 (active transport)

76
Q

2 fates of amino acids used in small intestine

A

either transported out of intestinal cell or used directly within enterocyte

77
Q

what are amino acids used directly in enterocyte used for

A

energy
synthesis of new protein

78
Q

what percentage of essential amino acids are estimated to be used in the small intestine

A

30-40%

79
Q

example of an amino acid that is highly used in intestinal enterocytes

A

glutamine

80
Q

what does glutamine do in intestinal enterocytes

A
  1. generates energy for the cell
  2. stimulate cell proliferation
  3. increase synthesis of heat shock proteins
  4. drive mucus production to help prevent bacterial translocation
81
Q

which organ is effective at taking up amino acids from circulation

A

the liver

82
Q

what percentage of amino acids does the liver use

A

20%

83
Q

what does the liver use amino acids for

A

making new proteins/enzymes
making peptide hormones

84
Q

example of proteins made in liver

A

albumin and other transport proteins

85
Q

what does the liver do with the remaining 80% of amino acids

A

catabolizes them

86
Q

where does the liver send NH3

A

the urea cycle

87
Q

where does the liver send carbon skeleton

A

the Krebs cycle
gluconeogenesis
lipogenesis

88
Q

are BCAAs taken up by the liver

A

no

89
Q

what are BCAAs used for

A

they are anabolic signals for tissues like muscle

90
Q

what are the 4 aspects to consider when determining protein quality

A
  1. AA composition
  2. Digestibility
  3. Presence of toxic factors
  4. Species consuming the protein
91
Q

when is an a protein considered high quality in aa composition

A

any protein that provides all essential AA

92
Q

when is a protein considered high quality with digestibility

A

when they are more digestible

93
Q

when is a protein considered high quality with toxic factors

A

the lesser the amount of toxic factors, the higher the quality

94
Q

why is there protein quality differences for different species

A

differing protein needs (i.e ruminants don’t have any essential amino acids, so they can utilize lesser quality proteins compared to humans)

95
Q

pros of using Protein Efficiency Ratio to assess protein quality

A

simple
cheap
sensitive to AA balance, digestibility and toxic factors

96
Q

cons of using Protein Efficiency Ratio to assess protein quality

A

rats are not humans
growth, not maintenance
do not know why a protein has poor quality

97
Q

pros of using chemical score to assess protein quality

A

simple and cheap
identifies limiting AA in food
used to optimize feeds by mixing different sources of proteins

98
Q

cons of using chemical score to assess protein quality

A

does not account for digestibility or toxins
assumes whole egg is an ideal protein

99
Q

what does measuring nitrogen balance do

A

determines protein quanitity

100
Q

when is nitrogen balance > 0

A

during growth, pregnancy, and times of tissue repair

101
Q

when is nitrogen balance <0

A

when you do not have enough protein

102
Q

who is usually seen with a nitrogen balance < 0

A

serious tissue injuries
wasting diseases (sarcopenia)
long term fasting

103
Q

what is the nitrogen balance for most adults

A

NB = 0

104
Q

when are protein requirements higher

A

infancy
childhood
teenagers
pregnancy
lactation

105
Q

2 types of abnormal protein intake

A

excessive intake
deficient intake

106
Q

when might someone have excessive protein intake

A
  1. high protein diet
  2. protein supplementation
107
Q

when might someone have deficient intake

A
  1. deficient in both protein quantity and energy (overall malnutrition)
  2. deficient in only protein quantity
108
Q

what are high protein diets typically low in

A

carbs

109
Q

2 common high protein diets

A

Atkins Diet
South Beach diet

110
Q

what is the most criticized high protein diet

A

Atkins Diet

111
Q

ratio of carbs, fats, and proteins in the Atkins Diet

A

C:F:P = 3:64:33

112
Q

why is the Atkins Diet Criticized

A

no attention to the type of carbs or fats consumed

113
Q

what is the ratio carbs, fats and proteins in the South Beach diet

A

C:F:P = 30:40:30

114
Q

what is the emphasis on for carb intake in the South Beach diet

A

low glycemic index foods

115
Q

are all high protein diets created equal

A

no - big differences in macronutrient content and types consumed

116
Q

who should avoid high protein diets

A

people with kidney disease

117
Q

what do most protein supplements deliver high levels of

A

BCAAs - rapidly absorbed and delivered to muscle

118
Q

when does anabolic muscle response to a protein meal start to diminish

A

after 40 years of age - improve with protein supplements

119
Q

what is marasmus

A

protein/calorie malnutrition - low intake of a balanced diet

120
Q

what happens with marasmus

A

because everything is in balance - body starts to starve

121
Q

how is marasmus characterized

A

complete loss of body fat and muscle, peeling skin, uneven pigmentation

122
Q

what is kwashiorkor

A

protein deficiency - sufficient calories but deficient in proteins

123
Q

what is the protein percentage in kwashiorkor

A

1-2%

124
Q

what are kwashiorkor patients characterized by

A

enlarged abdomen
burns on skin
diarrhea

125
Q

why do kwashiorkor patients have an enlarged abdomen

A

decreased plasma proteins causes osmotic imbalance in gut (edema) - osmotic fluid leaks leading to gut swelling

126
Q

why do kwashiorkor patients have enlarged liver

A

inability to export fat from liver - cannot make VLDL

127
Q

what is there a constant turnover between

A

protein synthesis and breakdown

128
Q

what is the body very efficient at during protein breakdown

A

recycling amino acids - most reused to make a new protein (only a little bit is catabolized)

129
Q

overall gist of urea cycle

A

NH4+ is toxic - needs to be converted to urea (safe molecule)

130
Q

1st main difference between fed and fasted states

A

fasted - formation of both glutamine and alanine
fed - primarily involves glutamine

131
Q

2nd main difference between fed and fasted states

A

fed state involves both liver and kidneys
fasted state involves just kidney

132
Q

3rd main difference between fed and fasted states

A

fed - involves excretion of amino group as urea
fasted - involves excretion of amino group as ammonium directly

133
Q

what does catabolizing an a-ketoacid (carbon skeleton) lead to

A

production of bicarbonate (HCO3-)

134
Q

what is bicarbonate

A

weak base that reacts with an H+ (no pH change)

135
Q

what does the fed state encourage

A

alkalosis (increase pH)

136
Q

response to high protein diets intake (fed state)

A
  1. liver converts amino group to urea in a process that consumes HCO3-
  2. catabolism of sulfur containing amino acid produces a bit pf sulphuric acid to neutralize pH
137
Q

what happens during a long term fast/starvation

A

minor amounts of protein are catabolized to release glycogenic acids for gluconeogenesis

138
Q

during long term fast/starvation, what does the breakdown of TAG lead to

A

production of acidic ketone bodies

139
Q

what does long term fasting encourage

A

slight acidosis - pH drops to ~7.0 (nutritional ketosis)

140
Q

what does liver do to products of TAG breakdown (not water soluble)

A

converts long hydrocarbons into small soluble ketone bodies

141
Q

how can the brain use ketone bodies

A

use for energy during starvation

142
Q

4 important amino acids in nitrogen metabolism

A

glutamate
aspartate
alanine
glutamine

143
Q

what are the 4 reactions that move nitrogen from catabolized protein between organs for excretion

A

transamination
oxidative deamination
glutamine production/glutamate regeneration
urea cycle

144
Q

what are the types of reactions in transamination

A

bi-directionaly reactions

145
Q

where is transamination active

A

all tissues

146
Q

why is glutamate the main amino acid to undergo oxidative deamination

A

it is the main product of transamination

147
Q

how is free NH4+ handled in extrahepatic tissue

A

used for synthesis of glutamine

148
Q

how is free NH4+ handled in liver

A

for urea synthesis

149
Q

how is free NH4+ handled in kidneys

A

excreted directly as is into urine

150
Q

what is the primary inter-organ nitrogen carrier

A

glutamine

151
Q

what percentage of glutamine in the body does muscle produce

A

90%

152
Q

where does glutamine primarily travel to in the fed state

A

liver

153
Q

where does glutamine primarily travel to in the fasted state

A

kidney

154
Q

what is the most abundant amino acid in blood

A

glutamine

155
Q

overall difference between glutamine synthesis and glutamate regeneration

A

same reaction - opposite
different enzymes are required

156
Q

when is glutamate regeneration active in the liver

A

fed state

157
Q

when is glutamate regeneration active in kidney

A

during fasting

158
Q

what does the urea cycle do

A

toxic NH4+ is converted to less toxic urea in liver
urea transported to kidney for excretion

159
Q

when is 80-90% of urinary N in the form of NH4+

A

fasted state

160
Q

when is 80-90% of urinary N in the form of urea

A

fed state

161
Q

what is deamination

A

remove of amino group from AA

162
Q

what is the a-ketoacid

A

the remaining carbon skeleton after deamination

163
Q

what is transamination

A

transfer of an amino group from an amino acid to an a-ketoacid

164
Q

what function groups does an a-ketoacid contain

A

ketone and carboxylic acid

165
Q

ketogenic

A

degraded AA that can be converted into Acetyl CoA

166
Q

glucogenic

A

degraded AA that can be converted into glucose

NUTR 3210 (29 decks)

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