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Biochemistry-Exam 2 > Amino acids > Flashcards

Amino acids Flashcards

0
Q

List the acidic AA

A

Aspartic acid, glutamic acid

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1
Q

List the basic AA

A

Lysine, Arginine, Histidine

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2
Q

List the uncharged polar AA

A

Serine, Threonine, Asparagine, Glutamine, Tyrosine, Cysteine

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3
Q

List the nonpolar AA

A

Glycine, Alanine, Valine, Leucine, Isoleucine, Methionine, Proline, Phenylalanine, Tryptophan

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4
Q

What AA are essential?

A

(Pvt Tim Hall)
Phenlyalanine, Valine, Threonine, Tryptophan, Isoleucine, Methionine, Histidine, Arginine (both essential and nonessential), Leucine, Lysine

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5
Q

What AA are made from glucose?

A

If you know essential and from essential you can deduce

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6
Q

What AA are made from essential AAs?

A

Tyrosine (Phenylalanine) and Cysteine (from methionine)

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7
Q

What is the biological value?

A

Determined by the extent to which it has the essential AAs

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8
Q

Where are most nonessential AA made?

A

Liver

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9
Q

When would a nonessential AA become an essential AA?

A

Loss of precursor or enzyme activity

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10
Q

3 Phosphoglycerate can be made into what AA?

A

Serine (then to glycine; to cysteine via methionine)

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11
Q

Pyruvate can be made into what AA? By what process?

A

Alanine, Transamination

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12
Q

Oxaloacetate can be made into what AA?

A

Asparate via transamination. Asparate combined with glutamine to yield asparagine

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13
Q

Alpha-ketoglutarate can be made into what AA?

A

Via transamination and glutamate dehydrogenase to glutamate. Glutamate can be made to glutamine or to glutamate semialdehyde. Glutamate semialdehyde to proline and arginine.

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14
Q

Where does N in AA come from?

A

Atmospheric N

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15
Q

90% of N is excreted as?

A

Urea

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16
Q

The C skeleton in AA comes from?

A

7 other intermediates from metabolism

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17
Q

Where is the major site of protein catabolism?

A

Muscle and Liver

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18
Q

What is the AA pool?

A

Sum of all free AA in our body; 90-100 g

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19
Q

T or F: Nitrogen is stored in the body

A

F

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20
Q

What is the healthy state of nitrogen balance?

A

No net change in amount of body N

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21
Q

A positive N balance would result from?

A

Net increase in protein. Pregnancy, lactation, recovery.

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22
Q

A negative nitrogen balance would result from? 3 Scenarios

A

Body protein breakdown (disease or trauma). Inadequate dietary protein. Lack of quality essential AA

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23
Q

What is kwashiorkor?

A

Inadequate dietary intake typified by growth failure, edema of liver and so on

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24
Q

What mediates protein degredation?

A

Ubiquitin

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25
Q

T or F: Protein digestion is highly regulated and very efficient

A

T

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26
Q

T or F: The digestive tract has a small reserve of digestive proteins

A

F (huge)

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27
Q

How much protein is consumed daily (average)?

A

70-100 g

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28
Q

What are the three phrases of digestive enzymes?

A

Gastric, Pancreatic, Intestinal

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29
Q

Describe the gastric phase of digestion

A

Protein digestion in stomach in HCl in stomach

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30
Q

Describe the pancreatic phase of digestion

A

In small intestine, pancreatic enzymes cleave the polypeptides to oligopeptides and AA (trypsin, chymotrypsin, elastase, and carboxypeptides)

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31
Q

What is the intestinal phase of digestion?

A

Cleave oligopeptides to AA. Aminopeptidases cleave the N-terminal. Di and tri peptidases cleave di and tripeptides to AA

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32
Q

Where do aminopeptidases cleave?

A

N-terminal

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33
Q

Where do carboxypeptidases cleave?

A

C terminal

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34
Q

Pepsin cleaves at what AA?

A

Phenylalanine, Tyrosine, Glutamine, Aspartate (aromatic and acidic AA)

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35
Q

Where does trypsin cleave?

A

Arginine and Lysine (basic AA)

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36
Q

Where does chymotrypsin cleave?

A

After aromatic AA (phenylalanine, tyrosine, tryptophan) and leucine (aromatic and hydrophobic AA)

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37
Q

Where does elastase cleave?

A

Alanine, glycine, serine (small AA)

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38
Q

Carboxypeptidase A cleaves?

A

Hydrophobic AA at C terminus

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39
Q

Carboxypeptidase B cleaves?

A

Arginine and Lysine at the C terminus

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40
Q

What are zymogens?

A

Precursor to enzymes

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41
Q

Zymogen of pepsin?

A

Pepsinogen (activated by acid)

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42
Q

Zymogen of Trypsin

A

Trypsinogen (enteropeptidase)

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43
Q

Zymogen of chymotrypsin

A

Chymotrypsinogen (trypsin)

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44
Q

Zymogen of elastase

A

Proelastase (trypsin)

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45
Q

Zymogen of carboxypeptidase

A

Procarboxypeptidase (trypsin)

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46
Q

How are AA transported from the lumen of small gut into the blood?

A

Via brush border membrane of intestinal and kidney cells (sodium cotransport of AA)

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47
Q

T or F: Brush border are rich in microvilli

A

T

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48
Q

What is cystinuria?

A

Defective cystine and other AA which lead to cystine AA in the urine

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49
Q

What is Hartnup disease?

A

Neutral amino aciduria (defective neutral AA transport). Excretion of neutral AA in urine. Tryptophan in the urine

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50
Q

-Uria relates to? -Emia relates to?

A

Urine levels, Blood levels

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51
Q

Describe the three processes involved in nitrogen disposal

A

Transamination, oxidative deamination, and urea cycle

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52
Q

alpha-AA is transaminated to?

A

alpha-Keto acid

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53
Q

Alpha-ketoglutarate is transaminated to?

A

Glutamate

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54
Q

Glutamate is oxidatively deaminated to?

A

Alpha-ketoglutarate

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55
Q

NAD is oxidatively deaminated to?

A

NADH and NH4+

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56
Q

What is the function of urea cycle?

A

Take NH4+ to Urea

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57
Q

What is transamination?

A

Transfer of amino from AA to alpha-keto acid

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58
Q

Alanine is transaminated to? Aspartate is transaminated to? Glutmate is transaminated to?

A

Pyruvate, Oxaloacetate, Alpha-ketoglutarate

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59
Q

Transamination is catalyzed by?

A

Aminotransferases

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60
Q

What is a keto acid?

A

Contain a carboxylic acid group adjacent to a ketone group

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61
Q

What is the usual acceptor of the amino group in an aminotransferase reaction?

A

Alpha-ketoglutarate

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62
Q

What is the cofactor of Aminotransferase?

A

Pyridoxal phosphate (PLP, from B6) via Ping Pong Mechanism

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63
Q

What is ALT?

A

Alanine aminotransferase (takes pyruvate to alanine)

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64
Q

What is AST?

A

Aspartate aminotransferase (Oxaloacetate to aspartate)

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65
Q

What do levels of ALT or AST imply?

A

Liver damage

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66
Q

AA groups (nitrogen) are typically collected via?

A

Glutamate and alpha-ketoglutarate

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67
Q

Where does transamination take place?

A

Muscle and Liver (usually in cytosol)

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68
Q

Describe oxidative deamination of glutamate?

A

Glutamate to alpha-ketoglutarate and ammonium (via NADP to NADPH or NAD to NADH)

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69
Q

Oxidative deamination prefers what cofactor?

A

NAD

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70
Q

Reductive deamination prefers what cofactor?

A

NADPH

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71
Q

What enzyme catalyzes glutamate to alpha-ketoglutarate?

A

Glutamate dehydrogenase

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72
Q

T or F: Oxidative deamination is fully reversible

A

T

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73
Q

Glutamate dehydrogenase is regulated by?

A

Negative (GTP) - lost of alpha-ketoglutarate so pushed away

Positive (ADP)

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74
Q

What is hyperammonemia?

A

High levels of ammonia in blood due to chronic liver disease or inherited metabolic disorder

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75
Q

Why is ammonia very toxic?

A

Depletes alpha-ketoglutarate, ATP, and NAD(P)H via back reaction. Glutamate is an excitatory NT leading to CNS defects

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76
Q

Where is the urea cycle fully perfomed?

A

Liver cells (partial in other cells)

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77
Q

High blood urea nitrogen is indicative of?

A

Kidney problems

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78
Q

Low blood urea nitrogen is indicative of?

A

Genetic defects in urea cycle

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79
Q

First step of Urea cycle

A

Carbamoyl Phosphate synthetase I (CPS I) takes CO2 and NH3 to Carbamoyl phosphate

80
Q

2nd step of urea cycle

A

Ornithine transcarbamoylase (OTC) takes L-ornithine and adds to L-citruline and out of mitochondria matrix to cytosol

81
Q

Step 3 or urea cycle?

A

Argininosuccinate synthetase takes L-citrulline to L-aspartate

82
Q

Step 4 of urea cycle

A

L-aspartate to argininosuccinate

83
Q

Step 5 of urea cycle?

A

Arginosuccinate to L-arginine via arginnosuccinate lyase

84
Q

6th step of urea cycle?

A

L-arginine to L-orninthine releasing Urea via arginase

85
Q

What is sum of reaction of urea cycle?

A

Aspartate + NH3 + CO2 + 3 ATP + H2O > Urea + Fumarate + 2 ADP + AMP + 2 Pi + 2PPi

86
Q

N in urea cycle comes from?

87
Q

How much ATP is used in urea cycle?

A

3 ATPs (4 high energy bonds)

88
Q

What are the two major ways urea cycle is regulated?

A

Amount of enzymes and CPS I activity

89
Q

What is the rate limiting step of urea cycle?

A

CPS I activity

90
Q

What cofactor is required for CPS I activity?

A

N-acetylglutamate from acetyl-CoA and glutamate via N-acetylglutamate synthase

91
Q

Urea cycle is initiated by the presence of what two AA?

A

Glutamate and Arginine

92
Q

T or F: Urea cycle requires energy

93
Q

Urea cycle deficiency presents as?

A

Lethargy, vomiting, hypotonia, respiratory failure, seizure, coma. Biochemical findings of hyperammonemia, low BUN, and elevated glutamine and glycine levels

94
Q

Hyperammonemia is caused by what three enzyme diseases?

A

NAGS deficiency (N-acetylglutamate synthase) and CPSI deficiency and OTC (ornithine transcarbamoylase) deficiency (leads to increased uracil and orotic acid in blood and urine)

95
Q

CPSI: Location? Pathway? Source of nitrogen? Allosteric regulator?

A

Mitochondria, urea cycle, ammonia, n-acetylglutamate

96
Q

CPS II: Location, Pathway, Source of nitrogen, allosteric regulator?

A

Cytosol, pyrmidine synthesis, amide group of glutamine, ATP, PRPP and UTP

97
Q

Why does OTC deficiency cause accumulation of orotic acid and uracil?

A

Carbamoyl Phosphate builds up and spills into cytosol for pyrimidine synthesis

98
Q

What is citrullinemia?

A

Argininosuccinate synthetase deficiency. Citrulline is excreted

99
Q

What is argininosuccinic aciduria (ASA)?

A

Argininosuccinate lyase deficiecny. Argininosuccine is excreted

100
Q

What is argininemia?

A

Arginase deficiency. Arginine can be excreted

101
Q

Alpha amino acids are taken to what by aminotransferases?

A

Alpha keto acids

102
Q

Aminotransferases take alpha-ketoglutarate to?

103
Q

What cofactor is required for transamination?

A

Pyridoxal Phosphate (PLP, from B6)

104
Q

What would NAGS deficiency cause?

A

Hyperammonemia

105
Q

What would CPS I deficiency cause?

A

Hyeperammonemia

106
Q

What would OTC deficiency cause?

A

Hyperammonemia

107
Q

What is the most common malady with the urea cycle?

A

OTC deficiency

108
Q

Accumulation of orotic acid and uracil can relate to the urea cycle by?

A

Excess CP due to OTC deficiency. Spills over into the cytosol and encourages pyrimidine synthesis

109
Q

Supplementing diet with benzoate or with phenylacetate does what?

A

Alternative means to remove nitrogen

110
Q

T or F: Arginine supplementation can stimulate the urea cycle?

A

T (allosteric activator of CPSI)

111
Q

Glutamine is deaminated to? Via?

A

Glutaminase to glutamate

112
Q

Why would antibiotics lead to hyperammonemia?

A

Kill bacteria in intestines leading to loss of hydrolysis of ammonia

113
Q

Asparagine is deaminated to?

A

Aspartate via asparaginase

114
Q

Most of ammonia is transported in the blood as?

A

Glutamine (~50 percent)

115
Q

Nitrogen is transported from muscle to the liver in the form of?

116
Q

Aminotransferases in the muscle convert what to what?

A

Pyruvate to Alanine

117
Q

Pyruvate and alanine differ in?

A

Alanine has nitrogen group, pyruvate does not

118
Q

What happens to the N on alanine when transported from the muscle to the liver?

A

N is excreted as urea and resulting pyruvate is used in glycolysis

119
Q

Glutamate dehydrogenase takes glutamate to?

A

Alpha-ketoglutarate

120
Q

List the seven common produces of AA carbon skeleton

A

Alpha-ketoglutarate, pyruvate, oxaloacetate, fumarate, succinyl CoA, Acetyl CoA, and Acetoacetyl CoA (PAK SOFA)

121
Q

What are the carbon skeletons of AA used for?

A

Gluconeogenesis, FA, ketone bodies, metabolized

122
Q

What are glucogenic amino acids?

A

Make Pyruvate or TCA cycle intermediates

123
Q

What are ketogenic amino acids?

A

Give rise to acetyl-CoA or Acetoacetyl CoA which are taken to ketone bodies

124
Q

T or F: Acetyl CoA can be converted to OAA in humans?

125
Q

What are the two modes of AA degredation?

A

Transamination and one carbon transfer

126
Q

Transamination requires what cofactors?

A

Pyridoxal Phosphate (B6)

127
Q

One-Carbon transfer requires what cofactors?

A

Biotin, B12, THF, and SAM

128
Q

Glycine is taken to what two products?

A

Serine or broken down to CO2 and NH4

129
Q

Glycine is most commonly broken down to?

A

CO2 and Ammonia

130
Q

Glycine to Ammonia and CO2 donates a carbon to?

131
Q

Nonketotic hyperglycemia is?

A

Glycine encephalopathy which is a defect in glycine cleavage complex leading to excess glycine in blood. Leads to brain issues

132
Q

Asparagine is taken to?

A

Asparatate via asparaginase

133
Q

Asparatate is deaminated to?

A

Oxaloacetate

134
Q

Histidine is catabolized to?

A

Glutamate (then to alpha-ketoglutarate)

135
Q

What is histidinemia?

A

Excess histidine due to deficiency in histidase

136
Q

What intermediate in histidine catabolism is often measured?

A

FIGlu (N-formimino glutamate). Low THF leads to accumulation of FIGlu in administration of histitine

137
Q

What are the branched amino acids?

A

Valine, isoleucine, leucine

138
Q

Branched amino acids are taken to?

A

Succinyl CoA and Acetyl CoA

139
Q

Branch chain amino acid catabolism enzyme is?

A

Branched chain alpha keto acid dehydrogenase (need TPP…remember this cofactor for alpha-ketoglutarate dehydrogenase?)

140
Q

Branched amino acids are broken down primarily where?

141
Q

Maple syrup disease is caused by?

A

Defective or missing branched-chain alpha keto acid dehydrogenase enzymes

142
Q

Hydroxylation of phenylalanine leads to?

143
Q

Tyrosinase activity on tyrosine leads to production of?

144
Q

Tyrosine is transaminated by?

A

Tyrosine aminotransferase (deficiency is called tyrosinemia II)

145
Q

Tyrosine can be metabolised to what compounds?

A

Fumarate and Acetoacetate

146
Q

What is alcaptonuria?

A

Absence of homogentisate oxidase leading to accumulation of homogentisate (recall tyrosine to hydroxyphenylpyruvate to homogentisate). Black urine and cartilidge

147
Q

Albinism is caused by?

A

Defect in melanin production from tyrosine and tyrosinase enzyme

148
Q

T of F: Patients with PKU tend to be lighter in complexion

A

T (deficiency in melanin production)

149
Q

What is phenylketonuria?

A

Defect in Phenylalanine conversion to tyrosin

150
Q

Phenylalanine conversion to tyrosine requires?

A

Phenylalanine hydroxylase, molecular oxygen, Biopterin (tetrahydrobiopterin)

151
Q

What is the function of BH4?

A

Used in phe to tyr conversion. BH4 is oxidized to BH2 and then regenerated by NAD(H). Biopterin

152
Q

What are the two causes of PKU?

A

Loss of phenylalanine hydroxlase (Classical) or loss of biopterin (non-classical)

153
Q

What is maternal PKU?

A

High Phe in mom leads to potential issues with baby

154
Q

T or F: Phe restriction relieves ALL issues in Non-classical PKU

A

False, BH4 is used in synthesis of several neurotransmitters

155
Q

Describe serotonin and catecholamine production

A

Tyrptophan to serotonin

Tyrsoine to Phenylalanine to Dopa to Dopamine to Norephinephrine to epinephrine

156
Q

Methionie accepts a methyl group and adenosine and is made into?

A

S-adenosylmethionine (SAM) by S-adenosylmethionine synthase

157
Q

What is the function of SAM?

A

methyl transfer.

158
Q

Methionine is converted to?

159
Q

SAM is converted to?

A

Homocysteine

160
Q

Homocysteine can be converted to what two products?

A

Back to methionine or to Cystathione (eventually cysteine or to propionyl CoA to Succinyl CoA)

161
Q

Homocysteine back to methionine requires what cofactors?

A

THF and B12

162
Q

Homocysteine to Cystathionine requires what cofactors?

163
Q

Cysteine is synthisized from what AAs?

A

Serine and Methionine

164
Q

What is homocystineuria?

A

Defects in the cystathionine pathway or reduced B6 affinity. Resembles Marfan.

165
Q

Biotin is a cofactor for?

A

Carboxylation

166
Q

What two cofactors are required for conversion of propinoyl CoA to succinyl CoA

A

Biotin and B12

167
Q

What is methylmalonic acidemia (MMA)?

A

Deficiency in methylmalonyl CoA mutase. Accumulation of methylmalonyl CoA from propionyl CoA

168
Q

MMA leads to the accumulation of what AA?

A

Met, Val, Ile, and Threonine

169
Q

MMA is treated with?

170
Q

Methylmalonyl-CoA to Succinyl CoA requires what cofactor?

171
Q

What are the 4 major causes for homocystinuria?

A

Cystathinonine synthase deficiency; B6; B12, methinonine synthase; or deficiency in THF component

172
Q

Biotin carries?

173
Q

THF carries?

A

-CH=, -CHO-, -CHNH-, -CH2- (Methenyl, formyl, formimino, methylene),

174
Q

THF and SAM both carry?

175
Q

What connects THF, B12, and SAM?

A

Methionine metabolism

176
Q

MethylTHF can regenerate THF by?

A

Homocysteine to Methionine (to SAM)

177
Q

Methyl-THF is activated only by?

A

Methionine salvage pathway

178
Q

THF is derived from?

A

Folic acid

179
Q

Folic acid deficiency can lead to?

A

Defective homocysteine to methionine conversion (hyperhomocysteinemia), defective gylcine cleavage, defect in purine/thymidine synthesis (hematopoietic defect)

180
Q

B12 carrier

A

Intrinsic factor (from stomach parietal cells)

181
Q

What is pernicious anemia?

A

Deficiency in IF leading to imparied absorption of B12, lead to megaloblastic anemia

182
Q

What two processes is B12 involved in?

A

Homocysteine to Methionine recovery as well as methylmalonyl CoA to Succinyl CoA

183
Q

MMA can be caused by what deficiency?

184
Q

Hyperhomocysteinemia can be caused by what deficiency?

185
Q

Defective THF regeneration is caused by what deficeit?

A

B12, leads to hematopoetic effect

186
Q

Why does B12 deficiency lead lead to purine and thymidine defects?

A

B12 is required to alleviate the methylTHF trap. B12 takes homocysteine to methionine and regenerates THF

187
Q

What are the functions of heme?

A

Binds oxygen, electron carriers, active site contributors

188
Q

Where does heme biosynthesis occur?

A

Mitochondria and cytosol

189
Q

What are the ingredients for heme production?

A

8 gylcine, 8 succinyl CoA, and iron

190
Q

What is the rate limiting step of heme biosynthesis?

A

ALA synthetase. Feedback inhibition of end product

191
Q

What is the cause of neuropsychiatric porphyria?

A

Accumulation of ALA and PBG in the early steps of synthesis

192
Q

Accumulation of ALA and PBG lead to?

A

Neuropsychiatric porphyria

193
Q

Cutaneous porphyria is caused by?

A

Accumulation of porphyrinogens at end of biosynth. Leads to photosensitvity

194
Q

What is acute intermittent porphyria?

A

Deficency in PBG deaminase leading to PBG and ALA accumulation. Most common porphyria

195
Q

What is porphyria cutaneous tarda (PCT)?

A

Defect in uroporphyrinogen decarboxylase which converts uroporphyrinogen III to coproporphyrinogen III

196
Q

PCT is treated with what two supplements?

A

Chloroquine and beta-carotene

197
Q

Map out heme degredation

A

Heme to billiverdin to bilirubin to (in macrophate) to bilirubin-albumin complex in blood to bilirubin in liver to bilirubin diglucuronide to intestines where converted back to bilirubin then oxidized to urobilinogen then to stercobiligin. Some urobilinogen into blood and turned to urobilin by kindney

198
Q

Where is conjugated bilirubin present? Unconjugated?

A

Bile; blood

Biochemistry-Exam 2 (14 decks)

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