Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Metabolism > Amino Acid Metabolism > Flashcards

Amino Acid Metabolism Flashcards

1
Q

how many grams of protein do our bodies turn over a day?

A

300g

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

intake vs excretion

A

protein 100g/day

carbon dioxide, urea and ammonia 100g/day

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

what is the source of the amino acid pool?

A

diet and some body proteins if required

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

classifications of amino acid dependent on availability

A

essential, non-essential and semi-essential

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

essential amino acids

A

histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine

amino acids that cannot be synthesised de novo

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

conditionally essential

A

arginine, cysteine, glutamine, glycine, proline, serine, tyrosine

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

non essential

A

alanine, asparagine, aspartate and glutamate

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

enzymes involved in dietary absorption of amino acids

A

pepsin- non specific, maximally active at low stomach pH

proteolytic enzymes of the pancreas in the intestinal lumen

trypsin and chymotrypsin act in the duodenum

amino peptidases, digest proteins from the amino terminal end

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what do trypsin and chymotrypsin prefer cleaving?

A

chymotrypsin- peptides where the amino acid N terminal bond is bound to trypsin, tyrosine, phenylalanine or leucine

trypsin- cleaves peptide chains normally at the carboxyl end bound to arginine or lysine

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

how are di and tripeptides taken up into the intestinal cells?

A

transported in a hydrogen ion symporter called PepT1

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

another important transporter

A

active sodium linked transport, along with the sodium-potassium ATPase maintaining the sodium concentration gradient

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

why does protein turnover occur?

A

damaged/incorrectly produced/folded proteins need to be removed

signalling proteins need to be removed and produced as needed

enzymes are often up/down regulated as a part of regulatory mechanisms

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

how do we know which proteins to break down?

A

proteins are tagged with ubiquitin using ubiquitin ligase

the tased protein is then directed into the proteasome for degradation

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

ubiquitin ligase structure + function of different subunits

A

ligases are made from three components E1, E2, E3

E1 & E2 are responsible for activating the ubiquitin

E3 recognises the protein to be ubiquinated

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

How does E3 work?

A

able to recognise damaged/misfolded proteins

it can also recognise certain n-terminal residues which signal the half life of a protein

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

syndrome related to ubiquitination

A

Angelman’s syndrome

  • a genetic disease with features of severe motor and intellectual disability
  • caused by mutations in ubiquitin ligase
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

overall regulation of protein synthesis/breakdown

A

insulin

  • net anabolic effect by stimulating chain initiation; effects on transcription are protein specific
  • inhibition of protein breakdown

thyroid hormones, cortisol
- net catabolic effect

anabolic steroids- net anabolic effect, such as testosterone

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

how else can amino acids be classified?

A

unionised or zwitterions

side chain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

first two divisions of side chain

A

hydrophobic, non polar and hydrophilic, polar

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

further divisions of hydrophobic + amino acids

A

aromatic

  • glycine
  • alanine
  • valine
  • leucine
  • isoleucine
  • methionine
  • proline

alkyl

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

further divisions of hydrophilic + amino acids

A

neutral

  • tyrosine
  • serine
  • threonine
  • cysteine
  • glutamine
  • asparagine

acidic

  • glutamic acid
  • aspartic acid

basic

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

explain the concept of positive and negative nitrogen balance

A

positive nitrogen balance is associated with periods or growth and repair, when the mass intake of nitrogen is greater than the loss from the body, greater protein pool

negative nitrogen balance is associated with burns, fevers and periods of fasting, where the mass intake is lower than the loss from the body, decrease in protein pool

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

what stops catabolism for going forward with some amino acids?

A

presence of an alpha amino group prevents oxidative breakdown

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

how is this overcome?

A

alpha amino groups must be removed before catabolism can proceed, the nitrogen can be incorporated into other compounds or excreted

the process if called deamination and produced an alpha-veto acid and ammonia

25
Q

3 different types of deamination

A

oxidative

non-oxidative

hydrolytic

26
Q

explain oxidative deamination + which amino acids

A

amino acid becomes oxidised by NADP+ to form an alpha keto acid alpha ketoglutarate and NADPH + H+ and an ammonium ion

catalysed by glutamate dehydrogenase

glutamate

27
Q

profile on glutamate dehydrogenase

A

mostly used in the liver and kidney

NAD+ used as coenzyme in oxidative deamination

NADP+ in reductive amination

direction of reaction depends on substrate availability

28
Q

regulation of glutamate dehydrogenase

A

deamination allosterically modulated by high ADP and GDP

amination allosterically modulated by high ATP and GDP

29
Q

what is a process that happens to amino acids other than glutamate?

A

transamination

30
Q

explain transamination

A

amino acids are funnelled into glutamate to enable breakdown

amino transferase catalyses the conversion of one amino acid into an alpha keto acid and then another keto acid into an amino acid

31
Q

specific amino transferase examples

A

alanine transaminase
ala + alpha ketoglutarate to pyruvate and glutamate

aspartate transaminase

asp + alpha ketoglutarate to oxaloacetate and glutamate

32
Q

what do all transamination reactions require?

A

the cofactor pyridoxal phosphate, derived from pyridoxine vit B6

33
Q

how does pyridoxal phosphate work?

A

forms a Schiff base with a lys residue in the active site of the transaminase

34
Q

which amino acids under transamination + what do they produce and their relevance ?

A

alanine- pyruvate keto acid, can be added into glycolysis

aspartate- oxaloacetate- added to TCA cycle

leucine- 2-oxo-3-methyl valerate- oxidised in muscle

isoleucine- 2-oxo-4-methyl valerate- oxidised in muscle

valine- 2-oxo-3-methyl butyrate oxidised in muscle

35
Q

what ketoacid does the deamination of glutamate produce + function?

A

alpha ketoglutarate, which is a substrate in the TCA cycle

36
Q

2 examples of non oxidative deamination

A

serine to pyruvate and ammonium, catalysed by serine dehydratase

threonine to alpha ketobutyrate and ammonium, catalysed by threonine dehydratase

37
Q

why are the enzymes called dehydratases?

A

because the dehydration precedes deamination

38
Q

why are serine and threonine directly deaminated?

A

they have an OH group

39
Q

explain hydrolytic deamination + where this occurs

A

glutamine to glutamate, with water to ammonium catalysed by glutaminase

intestinal cells and renal cortex

40
Q

why is amino acid release from muscle important?

A

muscle has the largest store of protein in the body, typically 5-7kg

during starvation, glucose continues to be oxidised, so it must come from non-glucose sources

41
Q

what percentage of total free amino acids does skeletal muscle store?

A

50%

42
Q

stages of the Cahill cycle in muscle

A
  1. glucose to pyruvate in glycolysis

2. pyruvate to alanine and an alpha ketoacid in transamination

43
Q

stages of Cahill cycle in liver

A
  1. alanine transamination to pyruvate and release of ammonia

2. pyruvate to glucose via gluconeogenesis

44
Q

what is glutaminase + functions ?

A

mitochondrial tissue specific isozyme that converts glutamine to glutamate

helps generate urea
expressed in kidneys to generate ammonium ions to help in acid-base balance

expressed I neurones to assist neurotransmission

45
Q

reaction that form glutamine + where it occurs

A

glutamate to glutamine catalysed by glutamate synthetase

ammonium ion used

ATP to ADP and Pi

muscle

46
Q

what is waste nitrogen excreted as in humans?

A

90% urea, the rest 10% ammonia

47
Q

why is ammonia released in small amounts?

A

toxic so limited, however some still needed to maintain acid-base balance

48
Q

why is urea excreted instead?

A

safe, non toxic means to excrete nitrogen

49
Q

what is urea produced from?

A

ammonium ions

50
Q

urea cycle stages

A
  1. HCO3- + NH4+ to form carboxyl phosphate, catalysed by carboxyl phosphate synthesise-I along with 2ATP to form 2ADP and Pi. occurs in mitochondria
  2. carbomoyl phosphate to citrulline
  3. citrulline to argininosuccinate
  4. argininosuccinate to arginine
  5. arginine to urea and ornithine
  6. ornithine combined with carbamoyl phosphate to produce citrulline
51
Q

what is the urea cycle linked to + how?

A

TCA cycle through argininosuccinate

52
Q

regulation of urea cycle

A

enzymes are coordinately up regulated by glucagon and glucocorticoids

carboxyl phosphate synthesise is the controlling step

53
Q

how else can amino acids be classified

A

based on possible metabolic fates, such as glycogenic if enter TCA cycle or ketogenic via acetyl CoA or mixed

54
Q

glucogenic amino acids

A 
ala
gly
arg
his
met
asn
asp
cys
glu
gln
pro
ser
thr
val
55
Q

ketogenic

A

leu

lys

56
Q

both

A

ile
phe
trp
tyr

57
Q

how is ammonia transported to the liver?

A

in the form of glutamine

glutamate + ammonia forms glutamine

58
Q

three branched chain amino acids

A

leucine, isoleucine and valine

59
Q

explain stages of branched chain metabolism

A
  1. branched chain amino acids undergo transamination to form keto acids
  2. branched chain amino acid dehydrogenase complex converts the keto acids into acetyl CoA derivatives
  3. can then be converted into acetyl CoA or succinyl CoA to join the TCA cycle

Metabolism (13 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions