nitrogen metabolism (deev- only one question)

Question 1

What is one of the most abundant porphyrin rings in the body?

Answer 1

Heme

Question 2

____________ is most abundant but is too inert for use in most biochemical reactions.

Answer 2

Atmospheric nitrogen (N2)

Question 3

True/False: Humans store nitrogen in the Liver.

Answer 3

False, we have no storage from of Nitrogen!

Question 4

True/False: Nitrogen is a reactive compound.

Answer 4

True, most explosives contain nitrogen, so the body needs to get rid of any nitrogen that is above the needs.

Question 5

Most nitrogen leaves the body via the _______ cycle.

Answer 5

Urea, clears body of excess nitrogen, but also retains carbon skeltons

Question 6

How does nitrogen enter the body?

Answer 6

Most nitrogen enters in amino acids by digestion

Question 7

What are 3 ways to input AAs?

Answer 7

Dietary protein (Digestion)
Protein turnover
amino acid synthesis de novo (from scratch)

Question 8

What are 3 ways to output AAs?

Answer 8

Synthesis of proteins- Transcription, translation
Synthesis of other nitrogen containing compounds (nucleotides, heme)
Use of Carbon skeleton of AA for other compounds (i.e. glucose, lipids, ketone bodies) or for energy.

Question 9

Input and output of AA is always balanced, why?

Answer 9

If you don’t have a certain amino acid in the body, certain proteins can’t be made…

Question 10

What selectively degrade damaged or short-lived proteins, uses ubiquitin to target proteins for degradation? What energy does it use?

Answer 10

Proteasomes

Energy dependent mechanism—uses ATP

Question 11

What non-selectively degrades intracellular proteins (autophagy) and extracellular (heterophagy)?

Answer 11

Lysosomes

use acid hydrolases to brake down peptide bonds to short peptides and AA

Question 12

Enzyme in stomach?

Answer 12

Pepsin

Question 13

Small intestine enzymes?

Answer 13

Pancreatic enzymes- trypsin, chymotrypsin, elastase, Carboxypeptidase
Aminopeptidases, Di- and Tripeptidases

Question 14

All enzymes cleave specific sequences of amino acids via 2 enzymes.

Answer 14

Endopeptidases - inside a peptide sequence

Exopeptidases- from the ends (exo) of a peptide sequence

Question 15

Peptides are hydrolyzed to amino acids in the ______.

Answer 15

Cytosol

Question 16

Only free amino acids are found in the ________ after a meal containing protein.

Answer 16

portal vein

Question 17

Branched chain amino acids are not metabolized by the liver, instead sent from liver primarily to _____ via blood.

Answer 17

Muscle

Question 18

What is the first step and what enzymes are involved in the removal of Nitrogen from Amino Acids? What is the name of the step?

Answer 18

Step 1: Transamination, aminotransferase

transfers AA to alpha ketogluterate producing alpha keto acid.

Question 19

What is the 2nd step and what enzymes are involved in the removal of nitrogen from amino acids? Where does this occur?

Answer 19

Step 2: Oxidative deamination, Glutamate dehydrogenase

Occur in Liver and Kidney

Question 20

What are the sources of ammonia?

Answer 20

Dietary AA
Glutamine
Bacterial action
Amines
Catabolism of purines and pyrimidines

Question 21

Ammonia is constantly produced in the ________ but is present at very low levels in blood.

Answer 21

tissues

Question 22

_________ is highly neurotoxic and must be kept at low levels in the blood

Answer 22

Ammonia

Question 23

Any free ammonia present in the circulation will be removed by the ______, and used for synthesis of ___.

Answer 23

Liver

Urea

Question 24

Free ammonia is released in the _____ and contributes to the acid-base balance of the body by excreting protons.

Answer 24

urine

Question 25

What is a general term for elevated levels of ammonia in the blood, which can be due to many different conditions.

Answer 25

Hyperammonemia

Question 26

Elevated ______, above 1000 micromol/l, ________ intoxication is a medical emergency and can have effects on the CNS/ blurring of vision

Answer 26

ammonia

ammonia

Question 27

A disease that is due to a deficiency in cystathionine synthase. Promotes damaging of LDLs and dislocation of the lens can occur.

Answer 27

Homocystinuria in the urine

Question 28

A defect in enzymes involved in the conversion of tyrosine to melanin will cause _______.

Answer 28

Albinism

Question 29

Most severe form of albinism is the deficiency in the enzyme ______ and results in a complete lack of pigment.

Answer 29

tyrosinase