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MCBM Exam 4 Kat > Nitrogen Metabolism > Flashcards

Nitrogen Metabolism Flashcards

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1
Q

What are some dietary fuels?

A

Carbohydrates (sugars & starches)
Lipids (fats)
Proteins (amino acids)

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2
Q

When are amino acids oxidized for energy?

A

Normal protein turnover
Starvation
Uncontrolled diabetes mellitus
Protein Rich Diet (Atkin’s)

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3
Q

N Balance

A

Intake = Loss

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4
Q

(+) N Balance

A

Intake > Loss

Growing children, pregnancy, illness/trauma recovery

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5
Q

(-) N Balance

A

Loss > Intake

Starvation

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6
Q

What is kwashiorkor?

A

Muscle Wasting Metabolism

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7
Q

Define Ureotelic.

A

Beings that excrete Urea like terrestrial animals.

86%

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8
Q

Define Ammonotelic.

A

Beings that excrete Ammonia directly like bony fish

2.8%

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9
Q

Define Uricotelic.

A

Beings that excrete Uric Acid like birds & reptiles

1.5%

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10
Q

Where does the other 4.5% of excreted ammonia products come from?

A

Creatin

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11
Q

What do the mucosal cells of the stomach excrete?

A

Gastrin and Histamine

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12
Q

What do the parietal cells of the stomach excrete and what are they activated by?

A

Secretes HCl

Activated by Histamine from the Mucosal Cell

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13
Q

What does gastrin from the mucosal cells activate?

A

Chief cells which secrete Pepsinogen

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14
Q

What is the action of Atropine and probanthine on the digestive system?

A

Blocks ACh integration with muscarinic receptors

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15
Q

What is the action of Cimetidine (Tagamet) and ranitidine (Zantac) on the digestive system?

A

Block histamine interaction with H2 receptors

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16
Q

What CNS Neurotransmitter initiates secretion in the stomach?

A

Acetylcholine

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17
Q

What two hormones and one enzyme do the intestinal mucosa produce?

A

Cholesistokinin, Secretin, Enteropeptidase

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18
Q

What does the pancreas excrete?

A

The secretory cells secrete zymgens and HCO3-

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19
Q

What is the end result of pancreas excretion?

A

Single Amino Acids

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20
Q

What does a deficiency in Neutral amino acids result in?

A

Hartnup’s Disease (NAD def)

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21
Q

Can free amino acids be stored?

A

No, they are catabolized. There is no way to store them.

22
Q

What are the products of amino acid catabolism?

A

Ammonia (NH4+)

Alpha-keto acid carbon skeletons

23
Q

What is ammonia converted into?

A

To Urea for excretion

24
Q

What are alpha-keto acid carbon skeletons converted into?

A

Pyr, AcCoA or TCA cycle intermediates

25
Q

What are the 3 basic processes of nitrogen metabolism?

A

1) Transport nitrogen to liver
2) Nitrogen removal in liver
3) Production of urea

26
Q

How is nitrogen transported to the liver?

A

Transamination

Glutamine synthase

27
Q

How is nitrogen removed in the liver?

A

Glutaminase

Glutamate dehydrogenase

28
Q

What is the Glucose Alanine Cycle in a nutshell?

A

Pyruvate from skeletal muscle glucose metabolism converted to Ala, sent to liver & converted back to glucose & sent back to muscle

29
Q

What are some major Transaminases?

A

Glutamate-Oxaloacetate Transaminase (GOT)

Glutamate-Pyruvate Transaminase (GPT)

30
Q

What are some minor transaminases?

A

Branched chain aminotransferase
Tyrosine aminotransferase
Ornithine aminotransferase

31
Q

What forms of Vitamin B6 are involved in transamination reactions?

A

Pyridoxal phosphate

Pyridoxamine phosphate

32
Q

In what cases would serum levels of transaminases go from normally very low to elevated levels?

A

Heart Attack and Liver Damage

Damaged cells leak enzymes into bloodstream

33
Q

What serum levels should yo check if you think a heart attack may have occurred?

A 
SGOT
SGPT
CK
LDH
If both CK and LDH raised then 100% diagnostic
34
Q

What two intermediate steps are needed for nitrogen transport to the liver?

A

Transamination

Glutamine synthase

35
Q

What two intermediate steps are needed for nitrogen removal in the liver?

A

Glutaminase

Glutamate Dehydrogenase

36
Q

Why is the glutamine synthase step of nitrogen transport so important?

A

It commits the nitrogen to disposal and no other process and is thus highly regulated.

37
Q

What is glutamine important for?

A

Main repository for NH3

38
Q

What are the functions of glutaminase?

A

Hydrolytic deamination that uses water to exchange with NH2.

Also used in kidneys to supply ammonia for acid neutralization in urine.

39
Q

How much of the bodies nitrogen is excreted as Urea?

A

80%

40
Q

Where is more ammonia converted to Urea?

A

In the Liver

41
Q

How energy costly is the urea cycle?

A

Very

Uses 3 ATP’s and 4 high energy bonds

42
Q

What does to much urea in the body mean?

A

Gout

43
Q

What does increase BUN levels mean?

A

Kidney problem

44
Q

What does BUN stand for?

A

Blood urea nitrogen

45
Q

What does increase NH4+ levels mean?

A

Liver problem

46
Q

What is the committed step (rate limiting step) of the Urea Cycle?

A

Carbamoyl phosphate synthesis via carbamoyl phosphate synthetase I (an irreversible reaction)

47
Q

Which portion of the urea cycle occurs in the mitochondrial matrix?

A

The 1st portion

48
Q

What happens when NH4+ is in excess?

A

alpha-KG is removed from the TCA cycle for transamination to Glu for conversion to Gln for export to liver

49
Q

When would levels of NH4+ increase?

A

Cirrhosis caused by alcoholism, hepatitis or genetic defects

50
Q

Elevated ammonia levels affects which part of the body profoundly.

A

The brain

Problems include: decreased ATP, depleted Glu and GABA, and brain swelling due to osmotic imbalance.

51
Q

What are some effects of genetic defect in urea metabolism?

A

Life threatening

Usually cause mental retardation, seizures, and/or coma

52
Q

How are genetic defects in urea metabolism treated?

A

Requires careful control of diet and administration of detoxifying compounds

MCBM Exam 4 Kat (10 decks)

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