Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Biochem > Amino Acid Metabolism > Flashcards

Amino Acid Metabolism Flashcards

(62 cards)

Start Studying
1
Q

protein storage

A

no storage for proteins designated for energy metaboism
breakdown of body proteins only in times of great need -> the last resort

Cachexia; mm wasting, lipolysis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

input to amino acid pool

A
  1. the intracellular synthesis of non-essential aminoacids
  2. tissue proteins
  3. dietary as source of essentail aminoacids
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

out puts of amino acid pool

A
  1. biomolecules w/ special functions; biogenic amines, thyroid hormones, heme, purine/pyrimidines, NO, etc
  2. degradation to the;
    - ammonia / urea
    - carbon skeleton; alpha-ketoacid -> pyruvated, acetyl CoA
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

C skeletons produced by aa degradation can be…(3options)

A
  1. oxidized to CO2 and H2O
  2. converted to glucose (glucogenic aa)
  3. converted to ketone bodies (ketogenic aa)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

the NH3 produced by aa degradation can be (3 options)

A
  1. excreted in urine
  2. converted to urea then excreted
  3. used in synthesis rxns
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

first step of protein degradation

A

transamination - removal of alpha amino grp, freely reversible,
Aminotransferases (also syn non-essential aa from alpha-keto acid precursors)
PLP - B6

aa -> alpha-keto acid
alpha-ketoglutarate +NH2 grp -> glutamate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

ALT & AST

A

ALT - alanine aminotransferase
AST - aspartate aminotransferase

liver is rich in both, AST can be just from mm check creatinine to confirm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

second step of protein degradation

A

oxidative deamination - removal of aa group from glutamate

Glutamate Dehydrogenase (mito, liver, kidney)

glu -> alpha-ketoglutarate +NH3
special bc uses both;
NADP+ and NADPH depending on dir
forward rxn: +ADP, - GTP
reverse rxn: only when NH3 is high
anapleoritc rxn - another way to add intermediates to TCA cycle
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

transhydrogenation in mitochondria

A

ancillary rxn
NADH + NADP+ -> NAD+ + NADPH

mito need NADPH to reduced to keep glutathione in its functional form

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

transdeamination

A

combined process of transamination and oxidative deamination
most aa lose their alpha-NH2 this way
Thr & Lys are not substrates for PLP req aminotransferases -> req diff methods

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

transamination and the malate aspartate shuttle

A

in mito/cytosol OAA aspartate = transamination by AST

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

where does ammonia come from?

A

aa deamination
deamination of asn to asp, and gln-> glu
gut bacteria
etc

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

prob with ammonia

A

toxic to CNS. not sure why

perhaps due to dec in alpha-ketoglutarate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

how is ammonia kept low;

A
  1. transport as glutamine (gln), alanine (ala)

2. conversion to urea by the urea cyle of the liver

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

why is it that making too much glutamine could be bad

A

rxn Glutamine synthetase requires ATP
decreases available glutamate which is imp for the neurotransmitter GABA
gln is osmoticly active -> cause edema in the brain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Glutamin synthetase

A

deals w ammonia problem;
glutamate -> glutamine (25% all circulating aa)
req ATP
brain, mm, liver

(reverse dir; glutaminase in liver and kidney)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

most imp reason for low blood NH2 ?

A

rapid removal by the liver and conversion to urea

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

overall rxn of urea synthesis

A 
NH4 (imp source; ox deam of glu)
\+ HCO3(fr CO2) 
\+3ATP 
\+ NH2 (asp) 
-> urea

4 ATP ; 1 urea
5 rxns (2mito, 3cyto
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

carbamoyl phosphate synthetase 1

A

1st step of urea cycle; rate lim step
formation of carbamoyl phosphate
fr; CO2 and free ammonia
req N-acetylglutamate as an allosteric activator

*CPS 2 was in pyrimidine synthesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

ornithine transcarboamoylase (OTC)

A

2nd rxn of urea cycle
formation of citrulline from ornithine and carbamoyl phosphate
* only X-linked enzyme *

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

argininosuccinate synthetase (ASS)

A

3rd rxn of urea cycle
citrullin + asp -> arginosuccinate
driven by; hydrolysis of 3rd ATP
asp from transamination of glu by AST

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

lyase (ASL)

A

4th rxn of urea cycle;
cleavage of arginosuccinate to:
arginine (retains the N)
+ fumarate (carbon skel)

(recal purine ring synthesis)
fumarte = link to TCA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

arginase

A

5th rxn of urea cycle
form orthinine + urea via cleavage of argnine

virtually exclusive to liver
ornithine re-enters urea cycle
urea diffuses into cycle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

two amino acids you don’t find in protein. why?

A

citrullin and ornithine

no codons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
why no urea in kidney? what happens there?
kidney makes arginine (arg) from citrulline so, can generate Arginine here (thus arg is not really an essential aa) lacks arginase => no urea
26
liver and regulation of ammonia
1. UC enzymes in periportal hepatocytes glutaminase & GDH (generate NH3) there as well -> produce ammonia where it will be cleaned up into urea quickly 2. gln synthetase in perivenous hepatocytes (catch ammonia missed). Glu generated by reversal of GDH rx when NH3 is high so little ammonia escapes into blood (due to this structure) glutamine can escape, but thats ok
27
what happens to the fumarate?
converted to malate via fumarase malate - enters mito, malate dehydrogenase converts it to OAA generating NADH
28
regulation of urea cycle
substrate conce act of CPS 1 by N-acetyl glutamate made by NAG synthase change in enzyme conc; long term increase 20-30 fold in starvation
29
defect in ornithine transcarbamolyase
most common def in urea cycle X-linked recessive lethargy -> coma - > death ; encephalopathy
30
tx of x-linked OTC
1. severe protein restriction + supplementation w alpha-keto acid analogs of essental aa 2. N-scavenging drugs; bind up non-essentail aa for excretion 3. antibiotics - ammonia from bacteria 4. supp w arg in some cases
31
CPS 1 and CPS 2
both make carbamoyl phosphate 1 urea cycle, mito of liver, N from NH3, req NAG 2. de novo pyrimidine syn, cyto all nuc cells, N fr glutamine
32
orotic aciduria
deficiency of OTC due to increased syn of pyrimidine Orotic acid OTC: CP + ornithine -> citrulline; OTC deficient, CP increaes and is used to make OA
33
the three enzyems that fix NH3 into organic molecules;
Glutamate dehydrogenase Glutamine synthetase Carbamoyl phosphate synthetase 1
34
2 aa solely ketogenic
leucine lysine C appear in aceytl/aceto acetyle CoA
35
4(5) both keto and glucogenic
``` tryptophan isoleucine tyrosine phenylalanine (threonine) ```
36
solely glucogenic
alanine and rest of amino acids ``` metabolized to one of the following TCA intermediates: pyruvate OAA fumarate succinyl CoA alpha-ketoglutarate ``` (then, converted to PEP, to glucose)
37
the branched amino acids
leucine (leu) isoleucine (ile) valine (val) taken up preferentially by skel mm inc glucocorticoids and catecholamines -> aa released form mm -> skel mm initiates metabolism of BCAA (has the 1 aminotransferase)
38
metabolism of BCAA generates
energy; ATP glutamine alanine glucose ala and gln also produced to carry ammonia
39
branched chain amino acid aminotransferase
1 in muscle, plentiful here not in the liver | generates alpha keto acids from leu val ile
40
branch chain alpha-keto acid dehydrogenase
muscle and liver Coenzymes: TPP, CoA, lipoic acid, NAD, FAD) like PDH and alpha-KGD, common E3, all generate NADH also, like PDH, covalently reg; active if deP inhibited by NADH
41
Maple syrup urine disease
``` definciency in BCKAD accumulation of BCKA and BCAA AR, mennonites encephalopathy missence E1 tx; dietary restriction of BCAA, balance thiamine tx, effective in rar leu most toxic of BCAA challenge; provid suff calories so don't force them into catabolism ```
42
leu BCAA metabolism
acetoacetate + acetyl CoA so leu; ketogenic biotin dependent carboxylation required
43
val BCAA metabolism
propionyl CoA -> succinyl CoA -> glucose val: glucogenic
44
ile BCAA metabolism
acetyl CoA and proprionyl CoA so both ketogenic and glucogenic
45
source of ala from muscle:
Muscle: val/ile ->succinyl CoA -(TCA)-> OAA -PEPCK-> PEP -> Pyruvate -(ALT)-> ala glu -ALT-> alpha-KG Liver: ala transported to liver where glu and pyurvate form; ALT; ala->pyruvate & alpha-KG -> glu pyruvate can be used as substrate for gluconeogenesis
46
glucose-alanin intertissue cycle
mucle produces pyruvate from glc & BCAA -> ala liver: ala -(transamination)> pyruvate -(gluconeogenesis)> glucose
47
source of gln sent out by mm
glu produced by transmaination rxn BCAA -> BC alphaketo acids, while alpha-KG -> glutamate then glu -> gln via Glutamine sythetase gln used by gut, liver, kidney
48
what happens to gln in gut
glutaminase; gln -> glu + NH3 glu -> citrulline -> arginine (in kidney only) or glu + pyruvate -> alpha-KG + ala (via ALT) ala -> glucose (in liver + kidney)
49
what happens gln/glu in liver and kidney
glutaminase; gln -> glu + ammonia GDH; glu -> alpha KG + ammonia alpha-KG -> glucose use of ammonia tissue dep; liver -> urea or gln
50
ammonia produced in kidney
used in excretion of H+ in acidosis especially imp in ketoacidosis remember use of ammonia tissue dep
51
which does the gut prefer KB or gln
KB, uses them of gln; sparing gln | gln goes to kidney and liver
52
what amino acids have a special metabolism scheme?
aromatic aa: trp phe & tyr
53
trp metabolism
an essential aa, keto&glucogenic trp oxygenase, contains heme ox cleavage of pyrrole ring = N-formylkurenine hyrolytic removal -> kynurenine & formate -> 3-hydroxykynurenine -> 3 Products 1. alanine (glucogenic) 2. quinolinate (-> NAD/NADP synthesis) 3. acetoacetyl CoA (ketogenic)
54
kenurenine can be
1. catabolized to alanine & acetyle CoA (primary pathway) | 2. met to quinolinate (minor, but phys sig pathway)
55
quinolinate
from trp metabolism quinolinate or niacin (frm diet) -> NAD & NADP
56
Hartnup disorder
AR defect in intestinal and renal abosorption of trp symptoms; similar to niacin def (pellagra) NT serotonin made from trp via hydroxylation (THB) and decarboxylation (PLP)
57
metabolism of phe and tyr
phe & tyr - gluc and keto genic Phenylalanine hydroxylase (liver) - Tetrahydrobiopterin (THB / BH2) gets ox - hydroxylates C4 phe (essential) -> tyr - Irreversible complete def; Phenylketonuria (PKU)
58
phenylketonuria (PKU)
``` most common disease of enzyme deficiency Phenylalanine hydroxylase (phe->tyr) AR phenylpyruvate (ketone) appears in urine mousy musty odor trp-> melanin (light skin/hair) sev mental retaradation Tx; diet low in phe + tyr supp Phe = teratogen Hyperphenylalanemia -> could be a def in synth of BH4 too ```
59
BH4 / THB
Tetrahydrobiopterin (THB / BH4) involved in met of phe & tyr phenylalanin hydroxylase gets ox def in this, or inab to reduce dihydrobiopterin back to tetra -> hyperphenylalaninemia
60
degradation of tyr
noteworthy bc virtually every step has a known clinical conseq if enzyme is deficient; focus on 2: alcaptonuria tyrosinemia 1
61
alcaptonuria
trp degradation prob, AR = historical 1st def; Homogentisate oxidase homogentisate accumulates ox to dark pigment-like polymer -> urine, bone, CT joint destruction, deterioration of cardiac valves
62
glucogenic amino acids
all but leu and lys

Biochem (13 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions