Brainscape's Knowledge GenomeTM

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


See full index

K1-MBOD Block 5 > Amino Acid Nitrogen > Flashcards

Amino Acid Nitrogen Flashcards

1
Q

What is a zymogen?

A

larger, inactive form of a protease that is cleaved to make its active form.

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

Where is pepsin most likely to be active?

A

Stomach

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

Where would trypsin, chymotrypsin, elastase, and carboxypeptidase most likely be active?

A

small instestine

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

Which digestive enzyme plays a key role in activating other protein-digesting enzymes?

A

trypsin

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

Where is pepsinogen secreted?

A

chief cells of stomach

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

Where is HCl in the stomach produced?

A

Gastric parietal cells

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

Which of these proteins are likely be denatured in low pH environments?

pepsin, trypsin, chymotrypsin, elastase, carboxypeptidase

A

All except pepsin, which is a stomach enzyme that remains active in acidic pH’s.

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

What mechanism raises the pH of the small intestine to ensure pancreatic digestive enzymes remain active?

A

bicarbonates are released into small intestine to raise pH.

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

Which enzyme cleaves pepsinogen to produce its active form, pepsin?

A

Pepsinogen is autocatalytic. HCl in the stomach changes its structural conformation and allows it to cleave and activate itself.

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

Where is bicarbonate secreted from?

A

exocrine pancreas

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

What cleaves trypsinogen to form active trypsin which then activates the other pancreatic proteases?

A

enteropeptidase (also called enterokinase)

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

Which of these enzymes is the most specific?

tyrpsin, chymotrypsin, elastase

A

trypsin is most specific, cleaving peptide bonds from lysine and arginine

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

What type of residues does chymotrypsin prefer?

A

Residues that contain hydrophobic or acidic AA’s

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

Which protease would likely cleave alanine, glycine, or serine (AAs with small side chains)?

A

Elastase. Also cleaves elastin

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

Which protease is commonly found in neutrophils?

A

Elastase

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

Define endopeptidase.

A

digestive proteases that hydrolyze peptide bonds within chains. Pepsin, trypsin, chymotrypsin, and elastase are all endopeptidases.

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

Define exopeptidase.

A

protease that removes either the amino acid at the N-terminus or C-terminus

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

What is an exopeptidase that works on the N-terminus called?

A

aminopeptidase

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

What is an exopeptidase that works on the C-terminus called?

A

carboxypeptidase

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

What might happen if the inhibitor for trypsinogen activation were defective?

A

Trypsin could activate the other pancreatic proteases while still in the pancreas, causing digestion of intracellular pancreatic proteins, leading to pancreatitis.

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

Which exopeptidase preferentially releases hydrophobic amino acids form the carboxy ends of peptide chains?

A

Carboxypeptidase A.

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

Where are exopeptidases produced?

A

intestinal epithelial cells

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

Where are exopeptidases most active?

A

In the brush border

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

What two transport methods allow absorption of AAs from intestinal lumen?

A

Secondary active Na+ depedent transport

Facilitated diffusion.

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

Which AA’s does carboxypeptidase B preferentially release form peptide chains?

A

Arginine and lysine (because they are basic AA’s) when they are on the C-terminus.

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

What is the primary method of AA absorption in the intestinal lumen?

A

Na+ dependent transport proteins in luminal membrane of intestinal cell brush border

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

Do intestinal epithelium cells have high or low cellular Na+?

A

Low. Na-K-ATPase pump forces them out of the cell continually, generating a gradient.

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

Which transport mechanism moves AAs from intestinal epithelium cells to the interstitial fluid? Is this transport uni or bidirectional?

A

Facilitated transporters in the serosal membrane. During fasting states, AAs are moved from the interstitial fluid back into the cells across the serosal membrane to provide energy to the cell (bidirectional)

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

Why do patients with cystinuria and Hartnup disease have hyperaminoaciduria but not hyperaminoacidemia?

A

Patients with Hartnup disease and cystinuria have defective transport proteins in both intestine and kidney. Patients do not absorb AAs at normal rate and also do not reabsorb AAs from the glomural filtrate back into blood at normal rate, causing low blood AA. Because the glomural filtrate AAs are not reabsorbed, the urine has high AA concentration (hyperaminoaciduria)

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

What is the primary method of transport for AA’s into body cells (not renal or intestinal)?

A

Na+-dependent cotransporters. This allows cells from other tissues to concentrate AAs from blood.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Where is the N system for glutamine uptake present in the body?

A

the liver. not present in other tissues

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Describe autophagy.

A

Intracellular components are surrounded by membranes that then fuse with lysosomes for degredation. This is triggered by cell starvation, and recycles old proteins to generate AAs for synthesis of new AAs and temporary fasting survival.

33
Q

Which AA does ubiquitin bind to on peptide chains

A

Lysine

34
Q

What happens to a protein that has been bound by ubiquitin?

A

Ubiquitin marks a protein for proteosome degradation.

35
Q

A region of a protein rich in what AAs would cause it to have a short half-life? What system is it likely to be degraded by?

A

PEST - proline, glutamate (E), serine, and threonine

These sequences make an AA likely to be degraded by the ubiquitin-proteosome system rather rapidly, causing short half-lives.

36
Q

Would you expect decreased plasma AA levels in a patient who had a defect in the intestinal and renal transporter for cystine and other basic AAs?

A

No, even though there will be decreased digestive absorption and increased excretion, these are non-essential AAs and will be synthesized from other sources to maintain plasma levels.

37
Q

Describe Hartnup disease.

A

Defect to intestinal and renal AA transport that involves neutral, essential AAs (isoleucine, leucine, phenylalanine, threonine, tryptophan and valine) as well as nonessential alanine, serine and tyrosine. Usually patients develop photosesnsitive rash and pellagra (lack of Vitamin B3/Niacin) as well as hyperaminoacidurea. Treatment by administering megadoses of niacin and other vitamins.

38
Q

What cycle is necessary for the production of glutathione? What does glutathione do?

A

gamma-glutamyl cycle.

Protects cells from oxidative damage

39
Q

What enzyme reacts with an extracellular AA to transport it across the membrane and form a gamma-glutamyl amino acid?

A

gamma-glutamyl transpeptidase

40
Q

What AA is the gamma-glutamyl cycle involved in salvaging?

A

cysteine. The cycle uses this to form Glutathione

41
Q

What AAs are used to form Glutathione?

A

glutamate, cysteine and glycine

42
Q

Describe Kwashiorkor.

A

Wasting disease. Deficiency of protein in diet that is adequate in calories causes muscle wasting and decreased plasma proteins (especially albumin). This causes edema, distended abdomens. Digestive enzymes can no longer be formed due to lack of essential AAs, leading to further nutritional problems.

43
Q

List the essential AAs.

A

PVT TIM HALL.

Phenylalanine-Valine-Tryptophan, Threonine-Isoleucine-Methionine, Histidine-Arginine-Lysine-Leucine

44
Q

List the ketogenic AAs.

A

LL - leucine and lysine

45
Q

List the AAs that are both ketogenic and glucogenic.

A

PITTT (Pitt with three T’s) - Pheynylalanine, Isoleucine, Threonine, Tyrosine, Tryptophan

46
Q

What happens to excess digested protein?

A

Protein is broken down to AAs. If these AAs are not used for protein synthesis, they will be converted to glucose or triacylglycerols

47
Q

Where is amino acid nitrogen converted to urea?

A

Liver

48
Q

Where do the two nitrogens in urea come from?

A

NH4+ and nitrogen of aspartate

49
Q

What two major AA’s are formed from muscle breakdown during fasting? Where is each of these processed for energy production?

A

Glutamine and Alanine.
Glutamine is converted to alanine in the kidney.
Alanine is processed in the liver to form glucose, ketone bodies, and urea.

Note, there are other AAs formed and they enter bloodstream to be processed by liver.

50
Q

What happens to the triacylglycerides formed from excess protein digestion?

A

They are packed and secreted from the liver as VLDLs.

51
Q

What is transamination concerning AA’s?

A

removal of nitrogen from AA’s

52
Q

What happens to the nitrogen lost from an AA in transamination?

A

N is transfered to alpha-ketoglutarate to form glutamate

53
Q

What does an AA become after it loses a Nitrogen in transamination?

A

the corresponding alpha-keto-acid.

for aspartate this is OAA

54
Q

Which AAs undergo transamination?

A

all except threonine and lysine

55
Q

Which is the dominant form at physiological pH: NH3 or NH4+?

A

equilibrium favors NH4+ by a factor of 100 at physiological pH

(Note, NH3 is present in the body though because it is able to pass through membranes)

56
Q

What is pyridoxal phosphate (PLP)?

A

A cofactor in transamination reaction

57
Q

What enzyme is used to form NH4+ from glutamate? What is used as a cofactor? Where does the reaction occur?

A

glutamate dehydrogenase.
Either NAD+ or NADP+ is used as a cofactor.
Reaction occurs in mitochondria of most cells.

58
Q

What enzyme catalyzes the deamination of serine and threonine?

A

serine dehydratase

59
Q

What AAs have R group amides that can be released as NH4+?

A

Glutamine and Asparagine-

60
Q

What enzyme catalyzes the deamination of Asn? What is formed?

A

asparaginase. Yields aspartate and NH4+

61
Q

What reaction does glutaminase catalyze and what are the products?

A

Deamination of glutamine to form glutamate and NH4+

62
Q

How is glutamine synthesized?

A

Glutamane synthetase fixes ammonia to glutamate using ATP. This occurs in the cytoplasm of cells.

63
Q

What two AAs carry the NH4+ before they it is used to form urea?

A

Glutamate and Aspartate

64
Q

What are the two major carriers of NH4+ in blood?

A

Glutamine and Alanine

65
Q

Where is glutamine synthatase located?

A

In the cytoplasm of most cells

66
Q

If ammonia levels are high and start to leave the liver before they can be converted to urea, what happens to keep ammonia levels from becoming toxic?

A

Excess ammonia is converted to glutamine by glutamine synthatase to prevent free ammonia buildup in circulation

67
Q

What do NH4+, bicarbonate, and 2 ATP react together to form? What enzyme is involved in catalyzing the reaction and where is it found?

A

carbomoyl phosphate.

carbamoyl phosphate synthatase I (CPS1) found in the mitochondria of liver and intestine

68
Q

What does carbamoyl phosphate react with in the urea cycle and what does it form?

A

carbamoyl phosphate reacts with ornithine to form citrulline. This occurs in the mitochondria

69
Q

How does citrulline get across the mitochondrial membrane?

A

It is exchanged for cytoplasmic ornithine.

70
Q

What does citrulline react with in the cytoplasm and what does it form?

A

Citrulline reacts with aspartate to produce arginosuccinate.
Catalyzed by argininosuccinate synthetase and powerd by ATP–> AMP

71
Q

What does argininosuccinate lyase do?

A

Argininosuccinate lyase cleaves argininosuccinate to form fumarate and arginine

72
Q

In the urea cycle, what happens to the fumarate after arginosuccinate is cleaved to form arginine and fumarate?

A

Fumarate is converted to malate using fumarase. The malate is then put into the TCA cycle to form OAA, which can be transaminated to aspartate (recycled)

73
Q

What happens to the arginine formed by the cleavage of argininosuccinate?

A

Arginine is cleaved by arginase to produce urea and regenerate ornithine

74
Q

What type of regulation does the urea cycle have (what is it called)?

A

Feedfoward regulation (as more substrate ammonia appears, more urea is formed)

75
Q

What does NAG do?

A

it allosterically activates CPSI to upregulate the urea cycle by producing more carbomoyl phosphate

76
Q

What two reactions would high levels of arginine in the liver stimulate?

A

Synthesis of NAG

Produces more onithine

77
Q

Why is ammonia toxic to the brain?

A

It depletes TCA cycle intermediates and ATP in the CNS by binding with ketoglutarates to form glutamate and glutamine.

GABA levels increase

78
Q

<p>

| Why is ammonia toxic to the brain?</p>

A

<p>
It depletes TCA cycle intermediates and ATP in the CNS by binding with ketoglutarates to form glutamate, which is rapidly consumed to form glutamine. This leads to low ATP, low glutamate, and high glutamine.</p>

<p>
In addition, high ammonia levels increase GABA (a neuro inhibitor) ligand binding properties and concentration in brain.</p>

79
Q

<p>

| What treatment would be given to a patient with a urea cycle enzyme defect?</p>

A

<p>
massive arginine supplementation to counteract the inability to regenerate urea cycle intermediates and form argininosuccinate</p>

K1-MBOD Block 5 (2 decks)

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