Nitrogen Metabolism: Urea Cycle Flashcards Preview

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Flashcards in Nitrogen Metabolism: Urea Cycle Deck (14):
1

Biological Molecules that require Nitrogen

  • Amino Acids
  • Nucleotides
  • Amino Sugars
  • Coenzymes
  • Porphyrins
  • Proteins
  • DNA
  • RNA
  • Complex Polysaccharides
  • Phospholipids

2

Describe the aminotransferase reactions

  • The first step in amino acid degradation
  • Using Pyroxidal phosphate (B6) as a cofactor, they remove the amino group and give it to the corresponding alpha-keto acid.

3

Glutamate + alpha-keto acid

alpha-ketoglutarate + Glutamate

4

Aspartate + A-ketoglutarate 

Oxaloacetate + Glutamate

5

Alanine + A-ketoglutarate

Pyruvate + Glutamate

6

Name this molecule:

Q image thumb

Vitamin B6 (pyroxidal)

7

Name this Molecule:

Q image thumb

Pyroxidal Phosphate

8

For which types of reactions is pyroxidal phosphate a prosthetic group?

  • Transamination reactions
  • Chemical change at alpha, beta, or gamma carbons of common amino acids
  • Some decarboxylation reactions
  • Deamination (Ser ---> pyruvate + NH3)

9

Excrete ammonia into water because it is water soluble

Aquatic Animals

10

Ammonia is converted to urea in the liver by the urea cycle

Mammals

11

Convert ammonia to uric acid; precipitates and can be excreted without water

Birds and Reptiles

12

Describe how nitrogen can travel through the blood to the liver

  • In most tissues, ammonia is convered to glutamine using glutamine synthetase, then transported through the blood to the liver.
  • Muscle uses the glucose-alanine cycle, wherein pyruvate undergoes transamination w/glutamate to form alanine and A-ketoglutarate. Alanine is then transported to the liver. 

13

Describe the Glucose-Alanine Cycle

Pyruvate undergoes transamination with glutamate, which forms alanine and A-ketoglutarate. Alanine is then transported to the liver. 

14