Madura - Nitrogen Elimination And Carbon Chain Elimination

Question 1

Once the AAs get to the liver, what is the first reaction that occurs?

Answer 1

A transaminatioon reaction occurs in which the alpha amino group is relocated onto alpha-ketoglutarate, yielding glutamate.

• This is accomplish through a aminotransferase enzyme
• the AA is then left as a keto acid

Question 2

In muscle cells, what is the primary NH3 acceptor?

Answer 2

It is pyruvate, thus causing pyruvate to be converted into alanine. Alanine is then brought to the liver where it gives up the NH3 to alpha-ketoglutarate to make glutamine.
- This recycles the pyruvate back to the muscles.

Question 3

Following a High protein meal, which AAs will be elevated in the blood? Why

Answer 3

Glutamine (Glutamate + NH3)
Asparagine (Aspartate + NH3)
Alanine (pyruvate + NH3)

• they provide a safe way to transport NH3 to the liver.

Question 4

Glutamate dehydrogenase

Answer 4

Does oxidative deamination.

Will take the NH3 off of glutamate and give it to alpha-ketoglutarate

Question 5

Aspartate aminotransferase

Answer 5

Will take a NH3 off of glutamate and put it on oxaloacetate to make Aspartate.

Question 6

Glutamine synthase

Answer 6

Will add a NH3 to glutamate.
This increases the capture and transport of nitrogen from peripheral tissues to the liver.
This process usually only occurs when there is excess NH3 lying around because NH3 is toxic and the body will do anything to not have it lying around.
- This requires ATP

Question 7

Asparagine synthase

Answer 7

Can add an NH3 from Aspartate to make asparagine

Question 8

Glucose-alanine pathway

Answer 8

This is the whole thing where. In skeletal muscle NH3 is added onto pyruvate in order to make alanine, which can safely be transported to the liver.

Question 9

Arginase

Answer 9

An enzyme produced only in the liver than converts arginine into ornithine and creates Urea as a byproduct.

Question 10

What three enzymes are only made in the liver?

Answer 10

Arginase, Glutaminase, asparaginase

Question 11

Where. Does. The addition of NH3 happen?

Answer 11

In the mitochondria and in The cytosol.

Question 12

What role does N-acetylglutamate play? What upregulates it?

Answer 12

It is responsible for activating CPS1, which activates the co-factor for the conversion of ornithine to citrulline.
- Arginine upregulates this

Question 13

What is the cofactor of the aminotransferase reaction And how does It occur?

Answer 13

Pyridoxyl phosphate (B6). 
- Basically the NH3 will go from the AA to the co-factor and then From the co-factor to alpha-ketoglutarate to make glutamate

Question 14

What are the two AAs that come from other AAs?

Answer 14

Cysteine requires methionine

Tyrosine comes from phenylalanine

Question 15

WHat AA Is SAM made from?

Answer 15

Methionine

Question 16

PKU — phenylketonuria

Answer 16

It is a buildup up of phenylalanine due to a mutation either in Phenylalanine Hydroxylase (PAH) or in the co-factor tetrahydrobioterin. Therefore, none of the downstream products will be made such as Tyrosine, L-DOPA, Dopamine, Norepi, or Epi.
- will have mental retardation

Question 17

Blue-Diaper syndrome

Answer 17

If there is a absorption problem in which tryptophan can not be absorbed in the intestine, it will stay and be converted into indole. This can be converted into indigo blue, a blue byproduct and be excreted in the urine as blue.

Question 18

Polycystic Kidney Disease

Answer 18

Associated with formation of fluid filled cysts. Cysts interfere with normal function. Can cause UTI, hypertension, fatigue etc.

Question 19

How do proteins get broken down starting from the mouth??

Answer 19

1) mouth. Masticates food so that it is easily transferred to the stomach.
2) Gastric - extreme acidity of the stomach begins protein unfolding and desaturation. This is important because ATP is not necessary to denature food.
3) Pancreatic - there are a number of zymogens that are stored and released into the small intestine. Enteropeptidase, which is made by the intestinal mucosal cells converts trypsinogen into trypsin. Trypsin then activates the rest of the digestive enzymes.
4) Intestinal - amino acids/peptides are taken into intestinal cells where complete hydrolysis of peptides occur. Then the free AAs are transferred to the portal vein onto the liver.