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Biochem + Metabolism > Amino Acids & Proteins > Flashcards

Amino Acids & Proteins Flashcards

1
Q

Only __ are used as building blocks for protein

A

L- Amino Acids

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2
Q

The R group of an amino acid

A

Determines the unique and specific properties and functions
Does most of the buffering

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3
Q

How many pKa values do amino acids have?
(two answers)

A

at least 2
a 3rd occurs when the R group is ionizable, these are buffers

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4
Q

which amino acids are ionizable

A

glutamic acid (glutamate), aspartic acid (aspartate), lysine, arginine, histidine

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5
Q

which amino acids are hydrophobic?

A

Ala, Val, Leu, Ile, Pro, Met, Phe, Trp

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6
Q

which amino acids are hydrophilic

A

polar r-group: Ser, Cys, Thr, Tyr, Asp, Glu

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7
Q

Which amino acid is neither hydrophobic nor hydrophilic

A

glycine

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8
Q

Name the essential amino acids

A

Met, Thr, Arg, His, Val, Phe, Ile, Trp, Lys, Leu

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9
Q

When do amino acid modifications occur?

A

After the protein has already been made

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10
Q

Hydroxyproline and Hydroxylysine are essential for what?

A

Proper collagen structure

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11
Q

What vitamin is required for hydroxylation of lysine and proline to then later be used in collagen structures?

A

Vit. C (Absorbic avid )

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12
Q

What is the most abundant protein in mammalian organisms? at around 30%

A

Collagen

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13
Q

TRUE or FALSE: Ingested modified animo acids will be incorporated into their respective proteins?

A

FALSE

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14
Q

Desmosin and isodesmosine are formed from what animo acid? What protein are they prevalent in?

A

Lysine and they are prevalent in elastin (smooth muscle)

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15
Q

How does carboxylation of glutamic acid affect proteins? What important cascade is this involved in?

A

carboxyglutamate is a was of protein activation, this is essential in the clotting cascade.

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16
Q

What are the four levels of protein structure?

A

Primary: Amino acid sequence (peptide bonds)
Secondary: localized structural elements ( alpha helixes, beta pleated sheets)
Tertiary: Protein folding
Quaternary: Interaction of multiple subunits

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17
Q

Why is proper protein folding essential?

A

Structure is essential to proper function, misfolding can lead to pathologies

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18
Q

Define amyloid

A

term for a protein that misfolds and aggregates

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19
Q

Name 3 examples of misfolded protein pathologies:

A

Scrapie
Bovine spongiform encephalopathy
Chronic wasting disease

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20
Q

Define enzymes

A

biological catalysts that increase reaction rate by lowering the activation energy

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21
Q

Define coenzymes

A

organic or organometallic molecules that assists an enzyme and are REQUIRED for enzyme activity

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22
Q

List two types of enzyme activity control

A
  1. Feedback inhibition: increase of end products inhibits regulatory enzyme activity
    2.Proteolytic activation: cleavage of part of a protein resulting in activation
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23
Q

what does Km represent?

A

measures enzyme activity

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24
Q

what does a low Km signify? and a high Km?

A

low= enzyme has high affinity for substrate
high=enzyme has low affinity for substrate

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25
Q

Define a competitive inhibitor, how does it affect Km, is it reversible? if so how would you reverse it?

A

Competes with substrate for enzyme. The Km is the same. Is reversible by increase in substrate concentration.

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26
Q

Define noncompetitive inhibitors? How do they affect the Km and Vmax? are they reversible? if so how

A

Binding away from the active site causing a change in the structure thus affecting its ability to function. Km is increased and Vmax in decreased. It is reversible but only when the inhibiter is removed

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27
Q

What makes a “suicide inhibitor” irreversible?

A

They interact COVALENTLY (very stable bond) with the enzyme to form a stable complex that permanently inactivate the enzyme

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28
Q

Describe the stomach’s role in protein degredation

A

the acidic environment of the stomach begins protein denaturation. Hydrolysis of peptide bonds by pepsin into smaller polypeptides

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29
Q

what enzyme in the stomach hydrolyzes protein peptide bonds?

A

pepcin

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30
Q

Describe the role of the small intestine in protein digestion

A

-majority of protein digestion
-proteases breakdown polypeptides into amino acids

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31
Q

What enzyme breaks down polypeptides in the stomach?

A

proteases

32
Q

Where are proteases secreted? and into what part of the small intestine?

A

They are secreted from the pancreas into the duodenum

33
Q

Describe how the protease proenzymes are activated in the duodenum

A

enteropeptidase cleaves trypsinogen into trypsin, trypsin then activates the other enzymes

34
Q

List the two pathways for protein turnover

A
  1. Lysosomal degradation
  2. Ubiquitin-proteasome pathway
35
Q

Describe lysosomal degredation

A

proteins are transferred to lysosomes via macrophages or vesicles to be broken down. this mainly occurs via the highly acidic nature of the lumen. Lysosomes also have >40 digestive enzymes

36
Q

Describe Ubiquitin-Proteasome pathway protein degradation

A

Major pathway for intercellular protein degradation. ubiquitin is activated by E1 (ATP required), then ubiquitin is transferred to E2, the ubiquitin is added to the target protein by E3 catylization. Once there is a ubiquitin chain on the target protein it is then recognized by the proteasome for destruction.

37
Q

Which organ generates over half of free amino acid pool

A

Muscle

38
Q

What organ is the major site of amino acid catabolism?

A

Liver

39
Q

What type of amino acids does the liver prefer to metabolize?

A

aromatic amino acids

40
Q

Describe the interorgan exchange of amino acids in the fed state

A

Meal- gut releases all but glutamine + asparagine - BCAAs will go to the muscles- most other amino acids go to the liver for catabolism

41
Q

Describe the interorgan exchange of amino acids in the postabsorptive state (fasting/starvation)

A

Muscle releases glutamine, alanine, and valine- glutamine goes to the kidney/gut- alanine goes to the liver- valine goes to the brain

42
Q

How do amino acids get to the liver?

A

through portal circulation ( the portal vein)

43
Q

List two ways to catabolize amino acids

A

1.Transamination
2.Deamination

44
Q

Describe the process of transamination

A

the amino group of the amino acid is interchanges with the keto (C=O) of a keto acid

45
Q

What cells does transamination amino acid catabolism occur?

A

the liver (hepatocytes)

46
Q

What coezyme does transaminases require?

A

active vit.B6

47
Q

Name two hepatic transaminases

A

Alanine aminotransferase (ALT)
Aspartate aminotransferase (AST)

48
Q

After transamination where does aminated glutamine go?

A

the liver for oxidative deamination

49
Q

Describe oxidative deamination

A

The amino group gets removed from glutamine, then it is converted to NH4+, a keto group replaces amino group. products are NH4+ (then to be used in the urea cycle) and alpha ketoglutarate ( to later be used in TCA cycle)

50
Q

What enzyme catalyzes oxidative deamination in the liver

A

glutamate dehydrogenase (GLDH)

51
Q

Why is oxidative deamination favored in the liver as compared to other cells?

A

Because one of the end products is ammonia ion, which is highly toxic

52
Q

What is the purpose of the urea cycle? and where does it mainly occur?

A

to detoxify ammonia. the cycle take place mainly in the liver

53
Q

How many ATP are required to complete the urea cycle? Where do they enter?

A

3 total. 2 enter at the rate limiting step with N-acetylglutamate and carbamoyl phosphate synthetase I to form carbamoyl phosphate. The other enters with L-aspartate ( this step provides the second nitrogen)

54
Q

What 5 enzymes are required by the urea cycle?

A

carbamoyl phosphate synthetase I, orrithine carbamoyl transferase, arginosuccinate synthetase, arginosuccitate lyase, arginase

55
Q

What 5 amino acids are required by the urea cycle?

A

N-acetylglutamate, L-Ornithine, L-Citrulline, L-Aspartate, L-Arginine

56
Q

Which enzyme required by the urea cycle is liver specific?

A

Arginase

57
Q

What is the rate limiting step of the urea cycle?

A

The activation of carbamoyl phosphate synthetase I

58
Q

What amino acid provides the second nitrogen to the urea cycle?

A

L- aspartate

59
Q

Where does the urea cycle take place in hepatocytes?

A

The mitochondria and the cytosol

60
Q

What nonprotein amino acid is essential in cats?

A

Taurine

61
Q

From what amino acid is Taurine derived?

A

Methionine

62
Q

What three derivatives are produced from Tyrosine?

A

Catecholamines (Dopamine, norepinephrine, epinephrine)
Melanin
Thyroid hormones

63
Q

What two derivatives are produced from Tryptophan (Trp,W)?

A

Serotonin
Melatonin

64
Q

What derivative is produced from Histidine (His, H)?

A

Histamine

65
Q

What derivatives are produced from Glutamate (Glu, G)?

A

GABA
+cysteine = glutathione

66
Q

Name the important features of glutathione

A

Glutamine + cysteine
-An abundant sulfur containing molecule in the cells
-Antioxidant

67
Q

What type of neurotransmitter is glutamate in the CNS?

A

Excitatory

68
Q

What type of neurotransmitter is Glycine in the CNS?

A

inhibitory

69
Q

What derivatives are produced from Glycine?

A

-Purine
+ methionine+arginine = creatine

70
Q

What derivative is produced from Arginine?

A

NO (vasodilator and neurotransmitter)

71
Q

What derivatives are produced from Serine?

A

Ethanolamine + choline formation which is important in phospholipid formation

72
Q

What derivatives are produced from Methionine?

A

+ lysine = carnitine (shuttles long fatty acids across mitochondrial membranes)
- S-adenosyl methionine (SAMe) = used in practive as methyl group transferases (denamarin)

73
Q

What amino acids are BOTH glucogenic and ketogenic?

A

WIFTY
Tryptophan
Isoleuicine
Phenylalanine
Threonine
Tyrosine

74
Q

What amino acids are ONLY ketogenic?

A

Leucine
Lysine

75
Q

What Amino Acids are ONLY Glucogenic?

A

Alanine, Valine, Proline, Methionine, Serine, Cystine, Glycine, Arginine,
Histidine, Aspartate, Glutamate, Asparagine, Glutamine

Biochem + Metabolism (15 decks)

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