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Flashcards in Urea Cycle Deck (39):
1

What does glutamate synthase transfer to a-ketoglutarate?

Nitrogen

2

Glutamine is the ____ carrier.

Nitrogen

3

What are the three fates of ammonium?

Glutamate dehydrogenase
Glutamine synthase
Carbamoyl-phosphate synthase I

4

What happens in the reactions containing glutamate dehydrogenase and glutamate synthase?

Reductive amination of a-ketoglutarate to form glutamate

5

What happens in the reaction containing glutamine synthetase?

ATP-dependent amidation of gamma-carboxyl of glutamate

6

What happens in the reactions containing carbamoyl-phosphate synthase I?

2 ATP are required
1 activates bicarbonatem which the other phosphorylates carbamate

7

Why would the body want to have NH3 when it could be the more relevant NH4+?

NH3 is the form that can cross cell membranes

8

What is the breakdown of animo acids from food called and how does it work?

Transamination
Swap NH3 group for a different keto-acid

9

What is transamination?

Transfer of an amino group from an a-amino acid to an a-keto-acid

10

In amino acid biosynthesis, the amino acid glutamate is transferred to various _____ which generates _____.

a-keto acids, a-amino acids

11

What two amino acids are generated in mino acid catabolism?

Glutamate or aspartate

12

What are the essential amino acids?

Histidine, Isoleucine, Leucine, Methionine, Phenylalanine, Threonina, Tryptophan, Valine, Lysine

13

What is nitric oxide?

NO is a gas hormone which can diffuse into cells and is a messenger that activates guanylyl cyclase (cGMP synth)

14

What is NO synthesized from?

Arginine

15

What are the actions of NO?

Relaxes blood vessels, lowers blood pressure and is a neurotransmitter in the brain

16

What is converted into NO to dilate coronary arteries?

Nitroglycerin

17

When the body is in starvation, what are degraded to amino acids for glucose?

Proteins

18

What are the glucogenic animo acids?

Ala, Ser, Cys, Thr, Trp, Asp, Arg, Phe, Ile, Met, Val

19

What are the ketogenic amino acids?

Ile, Leu, Thr, Trp, Leu, Lys, Phe, Tyr

20

What process does the muscle eliminate nitrogen to replenish energy?

Indirectly due to the exchange of glucose and alanine

21

Which types of animo acids are the first to be catalyzed for these pathways?

Branched-chain (Leucine, Valine and Isoleucine)

22

Which intermediate of amino acid breakdown also is used in the formation of ketone bodies?

HMG-CoA

23

In the study of branched-chain amino acids, what is the key to understanding the relationship between dietary protein and carbohydrates?

Understnading the relationship between branched-amino acids, insulin and glucose metabolism

24

What is a major gluconeogenic amino acid and what happens to it when it enters the liver?

Alanine and it becomes urea

25

When a transamination reactions happen what is used as the enzyme and cofactor in the reverse reactions?

Transaminases/ aminotransferases and pyridoxal phospahte (PLP)

26

Which is the only reversible step of the urea cycle?

Glutamate dehydrogenase (GDH)

27

What is the link between the TCA and Urea cycle?

Fumarate

28

What is the role of glutamate in urea production?

Collects nitrogen from other amino acids by transamination reactions and is released as NH4+ by glutamate dehydrogenase

29

What is the first step of the urea cycle?

NH4+, bicarbonate and ATP react to form carbamoyl phosphate catalyzed by carbamoyl phosphate synthase I (CPSI)

30

Where would you find carbamoyl phosphate synthase II and what does it do?

In the cytosol and produced carbamoyl phosphate for pyrimidine biosynthesis, using nitrogen from glutamine

31

When you combine citrulline and aspartate via arginosuccinate synthase what do you get?

Arginosuccinate

32

What gets release by arginosuccinate lyase to make arginine?

Fumarate

33

The higher the rate of ammonia production, the _____ the rate of urea formation.

Higher

34

What type of regulation is the urea cycle?

Feed forward

35

What are the other two types of regulation that can control the urea cycle?

Allosteric activation of CPSI by N-acetylglutamate (NAG)
Induction/repression of the synthesis of urea cycle enzyme

36

During fasting is urea excretion high or low?

High

37

When the something happen to the urea cycle and it stop working correctly, what is the key factor in ammonia build up?

a-ketoglutarate cannot be regenerated ledaing to an inc in glutamine and thus cannot fix free ammonia

38

Which drugs can be used to form conjugates with amino acids in the case of urea cycle deficits?

Benzoic acid and phenylbutyrate

39

Which enzyme deficiency of the urea cycle is thought to be genetically linked?

Ornithine transcarbamoylase