Amino acids Flashcards
(199 cards)
0
Q
List the acidic AA
A
Aspartic acid, glutamic acid
1
Q
List the basic AA
A
Lysine, Arginine, Histidine
2
Q
List the uncharged polar AA
A
Serine, Threonine, Asparagine, Glutamine, Tyrosine, Cysteine
3
Q
List the nonpolar AA
A
Glycine, Alanine, Valine, Leucine, Isoleucine, Methionine, Proline, Phenylalanine, Tryptophan
4
Q
What AA are essential?
A
(Pvt Tim Hall)
Phenlyalanine, Valine, Threonine, Tryptophan, Isoleucine, Methionine, Histidine, Arginine (both essential and nonessential), Leucine, Lysine
5
Q
What AA are made from glucose?
A
If you know essential and from essential you can deduce
6
Q
What AA are made from essential AAs?
A
Tyrosine (Phenylalanine) and Cysteine (from methionine)
7
Q
What is the biological value?
A
Determined by the extent to which it has the essential AAs
8
Q
Where are most nonessential AA made?
A
Liver
9
Q
When would a nonessential AA become an essential AA?
A
Loss of precursor or enzyme activity
10
Q
3 Phosphoglycerate can be made into what AA?
A
Serine (then to glycine; to cysteine via methionine)
11
Q
Pyruvate can be made into what AA? By what process?
A
Alanine, Transamination
12
Q
Oxaloacetate can be made into what AA?
A
Asparate via transamination. Asparate combined with glutamine to yield asparagine
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.
14
Q
Where does N in AA come from?
A
Atmospheric N
15
Q
90% of N is excreted as?
A
Urea
16
Q
The C skeleton in AA comes from?
A
7 other intermediates from metabolism
17
Q
Where is the major site of protein catabolism?
A
Muscle and Liver
18
Q
What is the AA pool?
A
Sum of all free AA in our body; 90-100 g
19
Q
T or F: Nitrogen is stored in the body
A
F
20
Q
What is the healthy state of nitrogen balance?
A
No net change in amount of body N
21
Q
A positive N balance would result from?
A
Net increase in protein. Pregnancy, lactation, recovery.
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
23
Q
What is kwashiorkor?
A
Inadequate dietary intake typified by growth failure, edema of liver and so on
24
What mediates protein degredation?
Ubiquitin
25
T or F: Protein digestion is highly regulated and very efficient
T
26
T or F: The digestive tract has a small reserve of digestive proteins
F (huge)
27
How much protein is consumed daily (average)?
70-100 g
28
What are the three phrases of digestive enzymes?
Gastric, Pancreatic, Intestinal
29
Describe the gastric phase of digestion
Protein digestion in stomach in HCl in stomach
30
Describe the pancreatic phase of digestion
In small intestine, pancreatic enzymes cleave the polypeptides to oligopeptides and AA (trypsin, chymotrypsin, elastase, and carboxypeptides)
31
What is the intestinal phase of digestion?
Cleave oligopeptides to AA. Aminopeptidases cleave the N-terminal. Di and tri peptidases cleave di and tripeptides to AA
32
Where do aminopeptidases cleave?
N-terminal
33
Where do carboxypeptidases cleave?
C terminal
34
Pepsin cleaves at what AA?
Phenylalanine, Tyrosine, Glutamine, Aspartate (aromatic and acidic AA)
35
Where does trypsin cleave?
Arginine and Lysine (basic AA)
36
Where does chymotrypsin cleave?
After aromatic AA (phenylalanine, tyrosine, tryptophan) and leucine (aromatic and hydrophobic AA)
37
Where does elastase cleave?
Alanine, glycine, serine (small AA)
38
Carboxypeptidase A cleaves?
Hydrophobic AA at C terminus
39
Carboxypeptidase B cleaves?
Arginine and Lysine at the C terminus
40
What are zymogens?
Precursor to enzymes
41
Zymogen of pepsin?
Pepsinogen (activated by acid)
42
Zymogen of Trypsin
Trypsinogen (enteropeptidase)
43
Zymogen of chymotrypsin
Chymotrypsinogen (trypsin)
44
Zymogen of elastase
Proelastase (trypsin)
45
Zymogen of carboxypeptidase
Procarboxypeptidase (trypsin)
46
How are AA transported from the lumen of small gut into the blood?
Via brush border membrane of intestinal and kidney cells (sodium cotransport of AA)
47
T or F: Brush border are rich in microvilli
T
48
What is cystinuria?
Defective cystine and other AA which lead to cystine AA in the urine
49
What is Hartnup disease?
Neutral amino aciduria (defective neutral AA transport). Excretion of neutral AA in urine. Tryptophan in the urine
50
-Uria relates to? -Emia relates to?
Urine levels, Blood levels
51
Describe the three processes involved in nitrogen disposal
Transamination, oxidative deamination, and urea cycle
52
alpha-AA is transaminated to?
alpha-Keto acid
53
Alpha-ketoglutarate is transaminated to?
Glutamate
54
Glutamate is oxidatively deaminated to?
Alpha-ketoglutarate
55
NAD is oxidatively deaminated to?
NADH and NH4+
56
What is the function of urea cycle?
Take NH4+ to Urea
57
What is transamination?
Transfer of amino from AA to alpha-keto acid
58
Alanine is transaminated to? Aspartate is transaminated to? Glutmate is transaminated to?
Pyruvate, Oxaloacetate, Alpha-ketoglutarate
59
Transamination is catalyzed by?
Aminotransferases
60
What is a keto acid?
Contain a carboxylic acid group adjacent to a ketone group
61
What is the usual acceptor of the amino group in an aminotransferase reaction?
Alpha-ketoglutarate
62
What is the cofactor of Aminotransferase?
Pyridoxal phosphate (PLP, from B6) via Ping Pong Mechanism
63
What is ALT?
Alanine aminotransferase (takes pyruvate to alanine)
64
What is AST?
Aspartate aminotransferase (Oxaloacetate to aspartate)
65
What do levels of ALT or AST imply?
Liver damage
66
AA groups (nitrogen) are typically collected via?
Glutamate and alpha-ketoglutarate
67
Where does transamination take place?
Muscle and Liver (usually in cytosol)
68
Describe oxidative deamination of glutamate?
Glutamate to alpha-ketoglutarate and ammonium (via NADP to NADPH or NAD to NADH)
69
Oxidative deamination prefers what cofactor?
NAD
70
Reductive deamination prefers what cofactor?
NADPH
71
What enzyme catalyzes glutamate to alpha-ketoglutarate?
Glutamate dehydrogenase
72
T or F: Oxidative deamination is fully reversible
T
73
Glutamate dehydrogenase is regulated by?
Negative (GTP) - lost of alpha-ketoglutarate so pushed away
| Positive (ADP)
74
What is hyperammonemia?
High levels of ammonia in blood due to chronic liver disease or inherited metabolic disorder
75
Why is ammonia very toxic?
Depletes alpha-ketoglutarate, ATP, and NAD(P)H via back reaction. Glutamate is an excitatory NT leading to CNS defects
76
Where is the urea cycle fully perfomed?
Liver cells (partial in other cells)
77
High blood urea nitrogen is indicative of?
Kidney problems
78
Low blood urea nitrogen is indicative of?
Genetic defects in urea cycle
79
First step of Urea cycle
Carbamoyl Phosphate synthetase I (CPS I) takes CO2 and NH3 to Carbamoyl phosphate
80
2nd step of urea cycle
Ornithine transcarbamoylase (OTC) takes L-ornithine and adds to L-citruline and out of mitochondria matrix to cytosol
81
Step 3 or urea cycle?
Argininosuccinate synthetase takes L-citrulline to L-aspartate
82
Step 4 of urea cycle
L-aspartate to argininosuccinate
83
Step 5 of urea cycle?
Arginosuccinate to L-arginine via arginnosuccinate lyase
84
6th step of urea cycle?
L-arginine to L-orninthine releasing Urea via arginase
85
What is sum of reaction of urea cycle?
Aspartate + NH3 + CO2 + 3 ATP + H2O > Urea + Fumarate + 2 ADP + AMP + 2 Pi + 2PPi
86
N in urea cycle comes from?
Glutamate
87
How much ATP is used in urea cycle?
3 ATPs (4 high energy bonds)
88
What are the two major ways urea cycle is regulated?
Amount of enzymes and CPS I activity
89
What is the rate limiting step of urea cycle?
CPS I activity
90
What cofactor is required for CPS I activity?
N-acetylglutamate from acetyl-CoA and glutamate via N-acetylglutamate synthase
91
Urea cycle is initiated by the presence of what two AA?
Glutamate and Arginine
92
T or F: Urea cycle requires energy
T (3ATP)
93
Urea cycle deficiency presents as?
Lethargy, vomiting, hypotonia, respiratory failure, seizure, coma. Biochemical findings of hyperammonemia, low BUN, and elevated glutamine and glycine levels
94
Hyperammonemia is caused by what three enzyme diseases?
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
CPSI: Location? Pathway? Source of nitrogen? Allosteric regulator?
Mitochondria, urea cycle, ammonia, n-acetylglutamate
96
CPS II: Location, Pathway, Source of nitrogen, allosteric regulator?
Cytosol, pyrmidine synthesis, amide group of glutamine, ATP, PRPP and UTP
97
Why does OTC deficiency cause accumulation of orotic acid and uracil?
Carbamoyl Phosphate builds up and spills into cytosol for pyrimidine synthesis
98
What is citrullinemia?
Argininosuccinate synthetase deficiency. Citrulline is excreted
99
What is argininosuccinic aciduria (ASA)?
Argininosuccinate lyase deficiecny. Argininosuccine is excreted
100
What is argininemia?
Arginase deficiency. Arginine can be excreted
101
Alpha amino acids are taken to what by aminotransferases?
Alpha keto acids
102
Aminotransferases take alpha-ketoglutarate to?
Glutamate
103
What cofactor is required for transamination?
Pyridoxal Phosphate (PLP, from B6)
104
What would NAGS deficiency cause?
Hyperammonemia
105
What would CPS I deficiency cause?
Hyeperammonemia
106
What would OTC deficiency cause?
Hyperammonemia
107
What is the most common malady with the urea cycle?
OTC deficiency
108
Accumulation of orotic acid and uracil can relate to the urea cycle by?
Excess CP due to OTC deficiency. Spills over into the cytosol and encourages pyrimidine synthesis
109
Supplementing diet with benzoate or with phenylacetate does what?
Alternative means to remove nitrogen
110
T or F: Arginine supplementation can stimulate the urea cycle?
T (allosteric activator of CPSI)
111
Glutamine is deaminated to? Via?
Glutaminase to glutamate
112
Why would antibiotics lead to hyperammonemia?
Kill bacteria in intestines leading to loss of hydrolysis of ammonia
113
Asparagine is deaminated to?
Aspartate via asparaginase
114
Most of ammonia is transported in the blood as?
Glutamine (~50 percent)
115
Nitrogen is transported from muscle to the liver in the form of?
Alanine
116
Aminotransferases in the muscle convert what to what?
Pyruvate to Alanine
117
Pyruvate and alanine differ in?
Alanine has nitrogen group, pyruvate does not
118
What happens to the N on alanine when transported from the muscle to the liver?
N is excreted as urea and resulting pyruvate is used in glycolysis
119
Glutamate dehydrogenase takes glutamate to?
Alpha-ketoglutarate
120
List the seven common produces of AA carbon skeleton
Alpha-ketoglutarate, pyruvate, oxaloacetate, fumarate, succinyl CoA, Acetyl CoA, and Acetoacetyl CoA (PAK SOFA)
121
What are the carbon skeletons of AA used for?
Gluconeogenesis, FA, ketone bodies, metabolized
122
What are glucogenic amino acids?
Make Pyruvate or TCA cycle intermediates
123
What are ketogenic amino acids?
Give rise to acetyl-CoA or Acetoacetyl CoA which are taken to ketone bodies
124
T or F: Acetyl CoA can be converted to OAA in humans?
False
125
What are the two modes of AA degredation?
Transamination and one carbon transfer
126
Transamination requires what cofactors?
Pyridoxal Phosphate (B6)
127
One-Carbon transfer requires what cofactors?
Biotin, B12, THF, and SAM
128
Glycine is taken to what two products?
Serine or broken down to CO2 and NH4
129
Glycine is most commonly broken down to?
CO2 and Ammonia
130
Glycine to Ammonia and CO2 donates a carbon to?
THF
131
Nonketotic hyperglycemia is?
Glycine encephalopathy which is a defect in glycine cleavage complex leading to excess glycine in blood. Leads to brain issues
132
Asparagine is taken to?
Asparatate via asparaginase
133
Asparatate is deaminated to?
Oxaloacetate
134
Histidine is catabolized to?
Glutamate (then to alpha-ketoglutarate)
135
What is histidinemia?
Excess histidine due to deficiency in histidase
136
What intermediate in histidine catabolism is often measured?
FIGlu (N-formimino glutamate). Low THF leads to accumulation of FIGlu in administration of histitine
137
What are the branched amino acids?
Valine, isoleucine, leucine
138
Branched amino acids are taken to?
Succinyl CoA and Acetyl CoA
139
Branch chain amino acid catabolism enzyme is?
Branched chain alpha keto acid dehydrogenase (need TPP...remember this cofactor for alpha-ketoglutarate dehydrogenase?)
140
Branched amino acids are broken down primarily where?
Muscle
141
Maple syrup disease is caused by?
Defective or missing branched-chain alpha keto acid dehydrogenase enzymes
142
Hydroxylation of phenylalanine leads to?
Tyrosine
143
Tyrosinase activity on tyrosine leads to production of?
Melanin
144
Tyrosine is transaminated by?
Tyrosine aminotransferase (deficiency is called tyrosinemia II)
145
Tyrosine can be metabolised to what compounds?
Fumarate and Acetoacetate
146
What is alcaptonuria?
Absence of homogentisate oxidase leading to accumulation of homogentisate (recall tyrosine to hydroxyphenylpyruvate to homogentisate). Black urine and cartilidge
147
Albinism is caused by?
Defect in melanin production from tyrosine and tyrosinase enzyme
148
T of F: Patients with PKU tend to be lighter in complexion
T (deficiency in melanin production)
149
What is phenylketonuria?
Defect in Phenylalanine conversion to tyrosin
150
Phenylalanine conversion to tyrosine requires?
Phenylalanine hydroxylase, molecular oxygen, Biopterin (tetrahydrobiopterin)
151
What is the function of BH4?
Used in phe to tyr conversion. BH4 is oxidized to BH2 and then regenerated by NAD(H). Biopterin
152
What are the two causes of PKU?
Loss of phenylalanine hydroxlase (Classical) or loss of biopterin (non-classical)
153
What is maternal PKU?
High Phe in mom leads to potential issues with baby
154
T or F: Phe restriction relieves ALL issues in Non-classical PKU
False, BH4 is used in synthesis of several neurotransmitters
155
Describe serotonin and catecholamine production
Tyrptophan to serotonin
| Tyrsoine to Phenylalanine to Dopa to Dopamine to Norephinephrine to epinephrine
156
Methionie accepts a methyl group and adenosine and is made into?
S-adenosylmethionine (SAM) by S-adenosylmethionine synthase
157
What is the function of SAM?
methyl transfer.
158
Methionine is converted to?
SAM
159
SAM is converted to?
Homocysteine
160
Homocysteine can be converted to what two products?
Back to methionine or to Cystathione (eventually cysteine or to propionyl CoA to Succinyl CoA)
161
Homocysteine back to methionine requires what cofactors?
THF and B12
162
Homocysteine to Cystathionine requires what cofactors?
B6
163
Cysteine is synthisized from what AAs?
Serine and Methionine
164
What is homocystineuria?
Defects in the cystathionine pathway or reduced B6 affinity. Resembles Marfan.
165
Biotin is a cofactor for?
Carboxylation
166
What two cofactors are required for conversion of propinoyl CoA to succinyl CoA
Biotin and B12
167
What is methylmalonic acidemia (MMA)?
Deficiency in methylmalonyl CoA mutase. Accumulation of methylmalonyl CoA from propionyl CoA
168
MMA leads to the accumulation of what AA?
Met, Val, Ile, and Threonine
169
MMA is treated with?
B12
170
Methylmalonyl-CoA to Succinyl CoA requires what cofactor?
B12
171
What are the 4 major causes for homocystinuria?
Cystathinonine synthase deficiency; B6; B12, methinonine synthase; or deficiency in THF component
172
Biotin carries?
CO2
173
THF carries?
-CH=, -CHO-, -CHNH-, -CH2- (Methenyl, formyl, formimino, methylene),
174
THF and SAM both carry?
Methyl
175
What connects THF, B12, and SAM?
Methionine metabolism
176
MethylTHF can regenerate THF by?
Homocysteine to Methionine (to SAM)
177
Methyl-THF is activated only by?
Methionine salvage pathway
178
THF is derived from?
Folic acid
179
Folic acid deficiency can lead to?
Defective homocysteine to methionine conversion (hyperhomocysteinemia), defective gylcine cleavage, defect in purine/thymidine synthesis (hematopoietic defect)
180
B12 carrier
Intrinsic factor (from stomach parietal cells)
181
What is pernicious anemia?
Deficiency in IF leading to imparied absorption of B12, lead to megaloblastic anemia
182
What two processes is B12 involved in?
Homocysteine to Methionine recovery as well as methylmalonyl CoA to Succinyl CoA
183
MMA can be caused by what deficiency?
B12
184
Hyperhomocysteinemia can be caused by what deficiency?
B12
185
Defective THF regeneration is caused by what deficeit?
B12, leads to hematopoetic effect
186
Why does B12 deficiency lead lead to purine and thymidine defects?
B12 is required to alleviate the methylTHF trap. B12 takes homocysteine to methionine and regenerates THF
187
What are the functions of heme?
Binds oxygen, electron carriers, active site contributors
188
Where does heme biosynthesis occur?
Mitochondria and cytosol
189
What are the ingredients for heme production?
8 gylcine, 8 succinyl CoA, and iron
190
What is the rate limiting step of heme biosynthesis?
ALA synthetase. Feedback inhibition of end product
191
What is the cause of neuropsychiatric porphyria?
Accumulation of ALA and PBG in the early steps of synthesis
192
Accumulation of ALA and PBG lead to?
Neuropsychiatric porphyria
193
Cutaneous porphyria is caused by?
Accumulation of porphyrinogens at end of biosynth. Leads to photosensitvity
194
What is acute intermittent porphyria?
Deficency in PBG deaminase leading to PBG and ALA accumulation. Most common porphyria
195
What is porphyria cutaneous tarda (PCT)?
Defect in uroporphyrinogen decarboxylase which converts uroporphyrinogen III to coproporphyrinogen III
196
PCT is treated with what two supplements?
Chloroquine and beta-carotene
197
Map out heme degredation
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
Where is conjugated bilirubin present? Unconjugated?
Bile; blood
