Intro to Nitrogen Metabolism exam 3

What are essential amino acids?

cannot be synthesized by the body must be obtained by diet

What are non essential amino acids?

can be synthesized by the body

What are the essential amino acids?

tryptophan, valine, phenylalanine, methionine, threonine, leucine, histidine, isoleucine, lysine

What is selenocysteine?

the only animo acid that contains selenium

In the presence of selenium what happens?

The stop codon UGA is ignored and a selenorpeotin will be made

What is a selenoprotein?

a protein that plays a role in the redox reactions. Like preventing oxidative damage from RBCs

What amino acids are conditionally essential for tissue repair or healing?

glycine and proline

What animo acid is conditionally essential during periods of growth?

arginine

What two amino acids are conditionally essential because they are made from an essential amino acid?

tyrosine and cysteine

What is a conditionally amino acid that is a fuel source for rapidly dividing cells?

glutamine

What is proteostasis?

Protein turnover is regulated by several tightly controlled processes that help facilitate protein homoeostasis, also known as proteostasis.

What do proteostatic mechanisms do?

ensure functional proteins are maintained at their correct concentrations and in the proper locations

What are the three proteolytic mechanism that protein degradation occurs via?

lysosome, proteasome, and autophagic pathway

What is ubiquitination?

a post translational modification in which a ubiquitin polypeptide attaches to a protein to make it a target for many cellular processes.

What are the three enzymes that the ubiquitination taging occurs by?

1. intiating enzyme

2. conjuegating enzyme

3. protein lygase

Once a protein is tagged with multiple ubiquitins what happens?

it enters a proteasome barrel to break down the protein in an acidic enviroment mabye?

What is proteolysis?

breakdown of proteins by enzymes that cleave peptide bonds

What are the two main locations of protein digestion?

stomach and small intestine

What are the final products of protein digestion?

amino acids, dipeptides, and tripeptides

What is a zymogen?

inactive precursor that must be activated before it can function

Why are proteases released as zymogens?

to prevent premature protein digestion and self digestion of the tissues that produce them.

How are digestive protease zymogens activated?

by proteolytic cleavage

What is the protease activation cascade?

a aequence in which one activated protease activates other protease zymogens

What is the inactive prexursor of pepsin?

pepsinogen

Q: How is pepsinogen activated?

A: Low stomach pH initiates activation, and active pepsin can activate additional pepsinogen through autocatalysis.

What is autocatalysis in pepsin activation?

Active pepsin helps convert more pepsinogen into pepsin.

What is the inactive precursor of trypsin?

Trypsinogen

Where is trypsinogen activated?

In the small intestine, within the intestinal lumen.

Which enzyme initially activates trypsinogen in the small intestine?

Enteropeptidase (also called enterokinase), located on the intestinal brush border.

How is chymotrypsinogen activated?

Trypsin cleaves chymotrypsinogen to initiate its conversion into active chymotrypsin.

Where does absorption occur?

small intestine

How are amino acids absorbed?

via transporters

How are di/tri peptides absorbed?

peptide transporters

How is AAs/Di/Tri peptides brought into the intesintal cells?

through secondary active transport with the intake of NA+ down its concentration gradient.

How does amino acids/di/tri peptides enter the bloodstream?

through facilitated passive diffusion with a transporter

Once in the bloodstream what is the fat of amino acids?

oxidative degration when they are not needed for new protein synthesis, excess animo acids. They are then excreted.