Nitrogen Metabolism/Urea Cycle Flashcards Preview

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Flashcards in Nitrogen Metabolism/Urea Cycle Deck (64):
1

What are the dietary fuels

1. Carbohydrates - sugars and starches ( store glycogen in skeletal muscle and liver)
2. Lipids (store as triglycerides in adipose tissue)
3. Proteins - amino acids

2

We dont store amino acids ; we ____them down

break

3

No ____ in carbohydrates of lipids

nitrogen

4

Have to convert nitrogen to ____

urea

5

where does urea cycle occur

liver

6

When are aa oxidized for energy?

1. normal protein turnover
2. starvation/diabetes (uncontrolled)
3. protein rich diet (Atkins)

7

what is nitrogn balance

what you take in vs what you excrete; if intake and excretion are equal it is called N balance; healthy adults

8

What is + nitrogen balance

Holding all the nitrogen you take in (intake> loss); growing children, pregnancy, illness/trauma recovery

9

What is - nitrogen balance

loss is greater than your intake; excreting a lot of Nitrogen in urine; you get edema

10

What is kwashiorkor

The condition of the first born when the second child arrives. the first child who was on breast milk that had all the essential aa's is put on grain diet thats missing essential aa: muscle waisting metabolism!

11

what maintains fluid in bloodstream vs going into tissues

colloid osmotic pressure; proteins of blood maintain colloid osmotic pressure that draws water in but if your lose protein from your blood bc your using it for energy production the main protein you lose is albumin which prov bulk of colloidic osmotic pressureAs osmotic pressure dec fluid leaves blood and goes into tissues. You get edema.

12

What is ureotelic

excrete urea- terrestrial animals. 86%

13

what is ammonotelic

excrete ammonia directly - bony fishes. 2.8%

14

what is uricotelic

excrete uric acid- birds and reptiles. You dont want a bird with a big bladder; birds conserve water in this way. 1.5%

15

what does the other 4% nitrogen come from

Creatine. Which comes from muscle

16

What is peristalsis and stomach acid important for

open up proteins and dentature them; make them more accesible to proteases and cleave them into ind aa that can be asorpeed by brush border in intestine.

17

What do mucosal cells produce

Gastrin; hormone that binds to receptors on T cells that cause them to secrete pepsinogen (inactive precursor protein) and it also makes histamine which makes HCl via parietal cells.

18

What is the end result of the digestive system

liquid chyme

19

How does pepsinogen turn to pepsin

Pepsinogen-->pepsin-->active and auto cleaves itself which starts process of protein digestion slightly

20

Secretion initiated by CNS input is via

acetylcholine

21

What does atropine, probanthine do

blocks acetylcholine interaction with muscarinic receptors.

22

What does cimetidine or ranitidine block

histamine interaction with H2 receptors

23

What are the two hormones that the intestinal mucosa produces

cholecyskokinin: causes gall bladder to secrete bile salts to emulsify fats.
secretin: targets exocrine pancreas; secretes things into intestine which secretes zymogens and bicarbonate.

24

What is the enzyme that the intestinal mucosa produces:

enteropeptidase which activates trypsinogen-->trypsin--> pancreatic zymogens: pro carboxypeptidase

25

What are the enzymes involved in gall bladder and bile salts

chymotrypsinogen, procarboxypeptidase and proelastase

26

what do secretory cells secrete and what is the end result of it

zymogens and bicarbonate. End result is a single amino acids!

27

What are the different classes of aa that the intestine uses for active transport systems

1. neutral
2. basic and Cys
3. imino and Gly
4. acidic
5. beta amino acids: beta alanine, taurine

28

What is Hartnup's disease

similar to pellagra; niacine deficiency; bc this transporter transports tryptophan. you get dermatitis, diarrhea and dementia and inflammation of tongue and oral cavities.

29

how do you get amino acids

from intracellular protein or dietary proteins

30

what do the carbon skeletons do

Go into diff pathways: TCA cycle for energy production, ketone bodies which break down into acetyl coA for fatty acid synthesis, or glucose synthesis or glycogen storage

31

What are the 3 basic processes

1. Transport nitrogen to liver to synthesized into urea and excreted: transamination (moves nitrogen from aa to glutamate), glutamine synthase.
2. nitrogen removal in liver: glutaminase, glutamate dehydrogenase
3. Production of urea

32

what are peripheral tissues

center of universe is liver so peripheral tissues are everything else

33

what do peripheral tissues use in transamination

alpha keto gluturate --> funnel N to glutamate --> glutamine

34

How does skeletal muscle transaminate

doesnt want to give up alpha keto glutarate (bc in TCA cycle) instead it sacrifices pyruvate to form alanine. Glutamine and alanine then travel through bloodstream to liver.

35

What aa are most in blood

1. glutamine
2. alanine (these two bc they use N groups to transport to liver)
3. all others are pretty low

36

How does the glucose alanine cycle work in skeletal muscle

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

37

What is first step of nitrogen cycle

Transamination: Peripheral tissues will send nitrogen to liver via glutamine or alanine

38

What are the major transaminases

1. Glutamate Oxaloacetate Transaminase (GOT) which makes aspartate aminotransferase (AAT)
2. Glutamate Pyruvate Transaminase (GPT): makes alanine amino transferase (ALT)

39

How do transamination reactions occur?

swap positions of nitrogen group and keto group.

40

Reactions occur in pairs. All aa can transaminate with alpha KG except:

Lysine, Thr, and Proline

41

Which cofactor does it require

B6. (pyridoxal phosphate and pyridoxamine phosphate)

42

What is second step

Alpha Ketoacid (usally alpha KG) picks up nitrogen group and comes off as glutamate.

43

What if you used something else other than alpha KG

Pyruvate; goes off as alanine.

44

Heart and liver has, but liver also has a lot of :

GOT; GPT. Both elevated it points to liver disease.

45

What enzyme converts glutamate to glutamine synthase.

Glutamine synthase. Highly regulated! Bc once you make glutamine it gets transported out and goes to liver. When this happens it converts to urea and then gets excreted out forever.

46

What are the allosteric modifiers in glutamine synthase regulation

amino acids, nucleotides, N compounds

47

If glycine and alanine levels drop then

inhibition would be lost. Make glutamine for protein synthesis.

48

Once in the liver, the nitrogens will be removed to be converted to _____. Alanine from muscle will transaminate with alpha KG to make _____. Glutamine will have side chain nitrogen removed via glutaminase and become _____

urea. Glutamate. Glutamate.

49

What are the two things that glutamate does

1. Transaminate with OAA to make Asp which will be used in the urea cycle
2. Undergo oxidative deamination via glutamate dehydrogenase to regenerate alpha KG and NH4 which be used in the urea cycle.

50

Hydrolytic deamination uses ____to exchange with NH2

water

51

What is step 3 of the nitrogen cycle

1. most ammonia is converted to urea in the LIVER
2. You get 1 N from NH4, and 1 N from Asp
3. You get 3 ATPs, and 4 high energy bonds

52

Portions of the cycle occur in cytosol, other parts occur in:

mitochondria

53

What are the nitrogen excretion products

86% urea, 2.8% ammonia, 1.5% uric acid

54

What are normal BUN levels

8-25 mg% or 2.9 -8.9 mM

55

What does high urea or BUN indicate

kidney problem; liver does its job of making urea

56

What does high NH4+ indicate

liver problem; cause the liver doesnt convert ammonia to urea and some ammonia is escaping into bloodstream

57

Oxaloacetate makes aps. Puruvate makes____

alanine

58

What is the Urea Cycle

Starts in mitochondria matrix bc of free amonia. Take CO2 + free amonia and hook them together to make carbamoyl phosphate which condenses with citrulline which leaves mitochondria to transaminate to aspartate. It makes argeninosuccinate which gets transferred to fumerate which goes to TCA cycle. This also releases argenine wthic gets cleaved with water, regenerates to ornithine and releases UREA.

59

What is the committed step of the urea cycle

carbamoyl phosphate synthesis; occurs in mitochondira

60

What enzyme is responsbile for carbamoyl phosphate

carbamoyl phosphate synthetase I. This reaction is irreversible.

61

What are non standard aa

no codon in genetic code for ornithine and citrulline

62

Krebs Bicycle refers to oxaloacetate giving off aspartate which gets turned to :

fumerate

63

why is ammonia so toxic

1. depletes the TCA cycle intermediate alpha KG and thus NADH production which results in dec ATP production. Bran in highly ATP dependent.
2. Depletes Glu and gammy aminobutyrate (GABA) both are neurotransmitters
3. Build up of Gln inc. intracellular osmotic balance; water enters astrocytes; brain swells.

64

What are genetic defects in urea metabolism

1. usually cause mental retardation, seizures/coma
2. treatment requires careful control of diet and admin of detoxifying compounds.