Nitrogen Metabolism

Question 1

Name the essential amino acids.

Answer 1

Threonine, lycine, histidine, methionine, phenylalanine, leucine, isoleucine, valine, arginine, tryptophan, tyrosine

Question 2

Which enzyme removes ammonia from circulation?

Answer 2

Glutamate dehydrogenase

Question 3

What does glutamine synthetase do?

Answer 3

Detoxifies ammonia (Especially in the CNS) for transport to the liver

Question 4

What does glutaminase do?

Answer 4

Releases ammonia for use in urea cycle (In liver)

Question 5

What reaction is present in synthesis and degradation of all amino acids?

Answer 5

Transaminase reactions

Question 6

What are commonly used as donors/acceptors for animo acids?

Answer 6

Glutamate and alpha-ketoglutarate (Aspartate and oxaloacetate can also be used)

Question 7

What is produced when amino groups are added to ketoacids?

Answer 7

Amino acids

Question 8

What is the precursor to glutamate and glutamine?

Answer 8

alpha-ketoglutarate

Question 9

What is the precursor to aspartate and asparagine?

Answer 9

Oxaloacetate

Question 10

What is the precursor to serine, cysteine, glycine, and proline?

Answer 10

3-phosphoglycerate

Question 11

What is the precursor to alanine?

Answer 11

Pyruvate

Question 12

How is excess nitrogen removed from the system?

Answer 12

Urea cycle

Question 13

Can amino acids form glucose?

Answer 13

Glucogenic amino acids can enter gluconeogenesis to produce glucose

Question 14

What do ketogenic amino acids become?

Answer 14

Acetyl CoA or ketones

Question 15

What are some effects of ammonium toxicity?

Answer 15

Neurological disease, ineffective neurotransmission, inhibited TCA cycle (So less ATP), CNS decline (Coma or death)

Question 16

How can ammonia be transferred from the CNS to the liver?

Answer 16

Glutamate, can cross BBB

Question 17

What are the three ways ammonia can be removed from the systems of different species?

Answer 17

Ammonotelic: Free ammonia released into environment (Fish)
Uricotelic: Low solubility, no need for water, high crystallization (Birds)
Ureotelic: Urea soluble, water lost along with urea

Question 18

In which organ does the urea cycle take place?

Answer 18

Liver

Question 19

Does the urea cycle require energy or produce energy?

Answer 19

Requires ATP

Question 20

What are the precursors to the urea cycle?

Answer 20

NH4+, COOH-, aspartate

Question 21

Where does urea go once it is produced?

Answer 21

Kidney for excretion