Brainscape's Knowledge GenomeTM

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


See full index

Biochemistry - Sarah > Protein Breakdown (Catabolism) > Flashcards

Protein Breakdown (Catabolism) Flashcards

1
Q

Amino acid catabolism creates ____.

A

Urea, carbon dioxide, and water

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

The amino acid pool can be used to make ___.

A

porphyrins, purines and pyrimidines, nitric oxide, mealnin, creatine, hormones and neurotransmitters

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

The stomach secretes ____.

A

HCl and Pepsinogen

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

HCl is secreted by ___.

A

parietal cells in the stomach

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

Acholrhydria can cause ____.

A

Iron deficiency

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

Pepsinogen is secreted by ___.

A

Chief cells in the stomach.

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

How does pepsinogen function?

A

Autocatalytic activation occurs by a conformational change at lower pH. (Goes from pepsinogen to pepsin.) Pepsinogen acts as an endopeptidase, cleaving peptide bonds (prefers CO group provided by an aromatic or acidic amino acid).
Smaller peptides and some free amino acids are produced.

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

The pancreas produces ___.

A

Trypsinogen, chymotripsinogen, proelastase, procaboxypeptidase

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

What zymogens are activated by trypsin?

A

Chymotripsinogen –> chymotrypsin,
Preoelastase —> elastase,
Procarboxypeptidases –> carboxypeptidase A or B (exopeptidase)

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

What enzyme activates trypsinogen?

A

Enteropeptidase activates trypsinogen by proteolysis into trypsin

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

Zymogens are activated by ___.

A

proteolysis

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

Amino acids are absorbed by semi-specific ___ transport proteins

A

sodium

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

There are at least ___ types of carriers for amino acids.

A

Six

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

Hartnup and cystinuria are caused by ___.

A

defects of sodium transport proteins (for amino acid transport)

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

Hartnup diease

A

Autosomal recessive gene that presents with ataxia, emotional instability and pellagra rash caused by a mutation in the sodium-dependent and chloride-independent neutral amino acid transporter, expressed predominately in the intestine and kidneys.

Also called amidoaciduria?
Urine levels of neutral aa are high due to failure to reabsorb amino acids in kidney.
Tryptophan is a precursor for niacin synthesis and most symptoms of hartnup are believed to be niacin deficiency related

Affects Neutral amino acid transport

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

Cystinuria

A

It affect dibasic amino acid transport and the transport of cytstine. Cystine stones appear in the bladder and kidney

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

What carries out intracellular proteolysis?

A

Lysosomes (acid hydrolases, pH 5 is optimal) and the 26S proteasome in the cytosol (for poly-ubiquitin-tagged proteins)

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

What carries out extracellular proteolysis?

A

Serine proteases (elastase from neutrophils contributes to lung damage in chronic obstructive pulmonary disease) and matrix metalloproteases (collagenases)

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

What is a byproduct of amino acid breakdown?

A

Ammonium (NH4+)

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

What amino acids are used to transport nitrogen in the blood?

A

Alanine and glutamine

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

Where does ammonium detoxification occur?

A

In the liver. (It is the only organ with all the enzymes for urea synthesis.)

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

Ammonium is converted to ___ because of these properties: ___.

A

urea,

It is soluble and not charged

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

____ should be obtained for any chile with unexplained vomiting, lethargy, or other evidence of an encephalopathy.

A

A plasma ammonia level

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

Ammonia is very toxic to the ___. It is converted to two nontoxic compounds: _____ and ____.

A

CNS,

Urea and glutamine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What reactions are involved in the first step of amino acid catabolism?

A

Removal of the amino groups through transamination or deamination

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Transamination

A

moves amino groups into glutamate (either use or deaminate, releasing ammonium ion)
carried out by aminotransferase

Aminotransferase reactions require pyridoxal phosphate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Deamination

A

Direct release of ammonium ion, different methods for different amino acids:
glutamate dehydrogenase, hydrolytic deamination (e.g. glutaminase), non-oxidative (PLP dependent)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What does aminotransferase do?

A

It catalyzes the transfer of an alpha-amino group from an amino acid to an alpha-ketoacid (uses PLP)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What is an example of an aminotransferase?

A

Aspartate aminotranferase (converts aspartate and alpha-ketoglutarate to oxaloacetate and glutamate) or alanine aminotransferase (converts alanine and alpha-ketolglutarate to pyruvate and glutamate) are listed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

True or false: Transamination reactions are irreversible.

A

False (They are reversible)

31
Q

What is used to evaluate liver damage?

A

Serum ALT and AST

32
Q

___ is required for aminotransferase reactions.

A 
Pyridoxal phosphate (derived from vitamin B6)
The aldehyde carbon forms and Schiff base (C=N)
33
Q

In the liver, most amino acids transer the ___ amino group to ____ to form ___.

A

alpha,
alpha ketoglutarate,
glutamate

34
Q

Glutamate releases ___ via ____.

A

ammonia,

glutamate dehydrogenase

35
Q

Glutamate dehydrogenase is located in ___.

A

liver mitochondria

36
Q

Glutamate dehydrogenase can use ___ or ___ to convert glutamate to alpha-ketoglutarate.

A

NAD or NADPH

37
Q

What regulates glutamate dehydrogenase?

A

GTP and ATP are allosteric inhibitors of glutamate dehydrogenase.
GDP and ADP activate glutamate dehydrogenase

38
Q

True or false: Glutamate dehydrogenase catalyzes a reversible reaction.

A

True

39
Q

Hydrolytic deamination occurs on the ____.

A

side chain amide groups of asparagine and glutamine

40
Q

Deamination reaction of glutamine

A

Glutamine and water are converted to glutamate and ammonium by glutaminase

(Asparagine is the same but with asapar- prefix instead of gluta-prefix)

41
Q

Nonoxidative deamination occurs with what amino acids?

A

Serine and Threonine

42
Q

What is the deamination process starting with serine?

A

Serine is converted to pyruvate and ammonium using serine dehydratase. Pyridoxal phosphate is required.

43
Q

What is the deamination process starting with threonine?

A

Threonine is converted to alpha-ketobutyrate and ammonium using threonine dehydratase. Pyridoxal phosphate is required.

44
Q

A mutation in glutamine synthetase can cause ___.

A

buildup of glutamate in the brain, which leads to newborns with sever brain malformations

45
Q

What does glutamine synthetase do?

A

It fixes ammonium in a carbon compound.

It converts glutamate and ammonium to glutamine (using ATP).

46
Q

When does positive-nitrogen balance occur (in nitrogen homeostasis)?

A

During physical trauma or for a growing child, nitrogen is needed to increase protein synthesis and excreted nitrogen is less than consumed nitrogen

47
Q

When does negative-nitrogen balance occur?

A

During protein malnutrition or starvation. The body degrades protein to synthesize essential proteins and the excreted nitrogen is greater than consumed nitrogen.

48
Q

What is the nitrogen balance in a normal healthy adult?

A

The protein content exceeds requirement and excreted nitrogen is equivalent to consumed nitrogen.

49
Q

What is the overall reaction for the urea cycle?

A

NH4+ + CO2 + aspartate + 3 ATP + 2 H2O —> Urea + fumarate + 2 ADP + AMP + PPi + 2 Pi

50
Q

# high energy bonds are used for each molecule of ureas

A

4

51
Q

True or false: The urea cycle is reversible.

A

False (There is a large, negative delta G)

52
Q

Ammonia toxicity is called ___.

A

Hyperammonemia

53
Q

Ammonia is toxic especially to the ___.

A

Brain and CNS

54
Q

Draw Urea Cycle

A

See slide 20

55
Q

Where is carbamoyl phosphate synthase I located and what is its function?

A

In mitochondria, urea synthesis

56
Q

Where is carbamoyl phosphate synthase II located and what is its main function?

A

In the cytosol, pyrimidine synthesis

57
Q

What does carbamoyl phosphate synthase require?

A

N-acetylglutamate (NAG). It is an allosteric activator.

58
Q

What is NAG?

A

N-acetylglutamate is an allosteric activator that is synthesized in the mitochondria by N-Acetylglutamate synthase. (Glutamine and acetyl CoA form NAG). It is positively regulated by the presence of arginine.

59
Q

A CPS-1 dimer is composed of ___.

A

Two CPS-1-NAG monomers. The monomer is catalytically active.

60
Q

What regulates the urea cycle?

A

In the short term (minutes) CPS-1 is regulated.
It is allosterically activated by NAG. A protein-rich meal results in increased NAG synthesis.

In the long term (days)
Dietary protein levels regulate the synthesis of urea cycle enzymes. Starvation raises protein degradation in tissues and synthesis of urea cycle enzymes, where as regular dietary protein leads to increased urea enzyme synthesis and increase urea excretion.

61
Q

The Km of NAG synthase for glumatate is ___ and it is ____ under physiological conditions.

A

high,

not saturated

62
Q

The equivalent of __ ATPs are consumed to synthesize one molecule of urea.

A

4 (The extra ATP comes from where aspartate would have entered the TCA cycle)

63
Q

Connect the urea cycle to the TCA cycle in a drawing

A

See slide 27. Basically show how argininosuccinate converts aspartate to fumarate, and how oxaloacetate is converted to aspartate using glutamate and aminotransferase (which produces alpha-keto-glutarate).

64
Q

What is the defective enzyme and the products accumulated in Hyperammonemia type I?

A

The enzyme is CPS-1, the products accumulated are ammonium (NH4+), glutamine, and alanine

65
Q

What is the defective enzyme and the products accumulated in Hyperammonemia type II?

A

The enzyme is ornithine transcarbamoylase,

The products accumulated are ammonium, glutamine, and orotic acid

66
Q

What is the defective enzyme and the products accumulated in Citrullinemia?

A

Argininosuccinate synthetase is the enzyme.

Citrulline accumulates

67
Q

What is the defective enzyme and the products accumulated in Argininosuccinic aciduria?

A

Argininosuccintate lyase is the enzyme,

argininosuccinate accumulates

68
Q

What is the defective enzyme and the products accumulated in Argininemia?

A

Arginase is the defective enzyme.

Arginine builds up.

69
Q

What are the mechanisms of ammonium toxicity?

A

A shift in the equilibrium of glutamate dehydrogenase reaction toward the direction of glutamate formation could deplete alpha-ketoglutarate (essential for TCA) resulting in decreased oxidation and ATP production (which makes the brain particularly vulnerable to hyperammonemia)

high levels of glutamine in the brain lead to brain swelling because of an osmotic increase in water in astrocytes. It also causes a decrease in neurotransmitters glutamate and GABA

70
Q

How can defects in the urea cycle be treated?

A

Acute hyperammonemia can be treated using hemodialysis or exchange transfusion to reapidly lower ammonia.

Diet: limit protein intake. A low protein, high carbohydrate diet with frequent meals

Removing excess ammonia using levulose, avoid and treat infections, kill intestinal ammonia producing bacteria with antibiotics, and administer benzoate and phenylacetate or phenylbutyrate (use this one now) to reduce glycine and glutamine levels

Replace missing intermediates
Supllement with arginine or citrulline

71
Q

Other ways nitrogen could be excreted

A

Amino groups can be removed by scavenging amino acids for excretion. Benzoic acid removes glycine, phenylbutyrate removes glutamine

72
Q

What is ornithine transcarbamylase deficiency?

A

It is an x-linked trait that acts like a dominant trait in heterozygous females, so abnormal OTC gene is more visible than others.
Not as noticeable in females as in males

73
Q

Gene therapy for OTC facts (Probably not high-yield)

A

Jesse Gelsinger
Partial gene deletion
Patients with partial enzyme production have done well under dietary and drug treatment
adenovirus vector
final patient of Phase I clinical trial
got infection from treatment/catheter that caused RBC breakdown and protein degredation and increased nitrogen load, blood clots, fever. Not good. (died)

Biochemistry - Sarah (12 decks)

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