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MCBM Exam 4 Kat > Nitrogen Metabolism > Flashcards

Flashcards in Nitrogen Metabolism Deck (52):
1

What are some dietary fuels?

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

2

When are amino acids oxidized for energy?

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

3

N Balance

Intake = Loss

4

(+) N Balance

Intake > Loss
Growing children, pregnancy, illness/trauma recovery

5

(-) N Balance

Loss > Intake
Starvation

6

What is kwashiorkor?

Muscle Wasting Metabolism

7

Define Ureotelic.

Beings that excrete Urea like terrestrial animals.
86%

8

Define Ammonotelic.

Beings that excrete Ammonia directly like bony fish
2.8%

9

Define Uricotelic.

Beings that excrete Uric Acid like birds & reptiles
1.5%

10

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

Creatin

11

What do the mucosal cells of the stomach excrete?

Gastrin and Histamine

12

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

Secretes HCl
Activated by Histamine from the Mucosal Cell

13

What does gastrin from the mucosal cells activate?

Chief cells which secrete Pepsinogen

14

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

Blocks ACh integration with muscarinic receptors

15

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

Block histamine interaction with H2 receptors

16

What CNS Neurotransmitter initiates secretion in the stomach?

Acetylcholine

17

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

Cholesistokinin, Secretin, Enteropeptidase

18

What does the pancreas excrete?

The secretory cells secrete zymgens and HCO3-

19

What is the end result of pancreas excretion?

Single Amino Acids

20

What does a deficiency in Neutral amino acids result in?

Hartnup's Disease (NAD def)

21

Can free amino acids be stored?

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

22

What are the products of amino acid catabolism?

Ammonia (NH4+)
Alpha-keto acid carbon skeletons

23

What is ammonia converted into?

To Urea for excretion

24

What are alpha-keto acid carbon skeletons converted into?

Pyr, AcCoA or TCA cycle intermediates

25

What are the 3 basic processes of nitrogen metabolism?

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

26

How is nitrogen transported to the liver?

Transamination
Glutamine synthase

27

How is nitrogen removed in the liver?

Glutaminase
Glutamate dehydrogenase

28

What is the Glucose Alanine Cycle in a nutshell?

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

29

What are some major Transaminases?

Glutamate-Oxaloacetate Transaminase (GOT)
Glutamate-Pyruvate Transaminase (GPT)

30

What are some minor transaminases?

Branched chain aminotransferase
Tyrosine aminotransferase
Ornithine aminotransferase

31

What forms of Vitamin B6 are involved in transamination reactions?

Pyridoxal phosphate
Pyridoxamine phosphate

32

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

Heart Attack and Liver Damage
Damaged cells leak enzymes into bloodstream

33

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

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

34

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

Transamination
Glutamine synthase

35

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

Glutaminase
Glutamate Dehydrogenase

36

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

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

37

What is glutamine important for?

Main repository for NH3

38

What are the functions of glutaminase?

Hydrolytic deamination that uses water to exchange with NH2.

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

39

How much of the bodies nitrogen is excreted as Urea?

80%

40

Where is more ammonia converted to Urea?

In the Liver

41

How energy costly is the urea cycle?

Very
Uses 3 ATP's and 4 high energy bonds

42

What does to much urea in the body mean?

Gout

43

What does increase BUN levels mean?

Kidney problem

44

What does BUN stand for?

Blood urea nitrogen

45

What does increase NH4+ levels mean?

Liver problem

46

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

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

47

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

The 1st portion

48

What happens when NH4+ is in excess?

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

49

When would levels of NH4+ increase?

Cirrhosis caused by alcoholism, hepatitis or genetic defects

50

Elevated ammonia levels affects which part of the body profoundly.

The brain

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

51

What are some effects of genetic defect in urea metabolism?

Life threatening
Usually cause mental retardation, seizures, and/or coma

52

How are genetic defects in urea metabolism treated?

Requires careful control of diet and administration of detoxifying compounds