Nitrogen 1

Question 1

What is nitrogen metabolism also known as?

Answer 1

Amino acid metabolism

Question 2

What kinds of molecules contain nitrogen?

Answer 2

Amino acids and nucleotides

Question 3

Where do we get our nitrogen from?

Answer 3

Our diet, not the air

Question 4

What are the 2 stages of the nitrogen cycle in organmisms?

Answer 4

Assimilation

Degradation

Question 5

Why is nitrogen very unreactive?

Answer 5

Nitrogen is bonded to another nitrogen with a triple bond

Question 6

What are 3 things that supply the massive amound of energy required to breakdown nitrogen?

Answer 6

Lighting

450^oC at 200atp with an iron catalyst

Bacteria

Question 7

What does bacteria perform to breakdown nitrogen?

Answer 7

Nitrogen fixation

Question 8

What does nitrogen fixation look like?

Question 9

What is nitrogen inactivated by?

Answer 9

O₂

Question 10

How does bacteria get around O₂ deactivating N₂?

Answer 10

Live anaerobically

Uncouple mitochondria to burn all O₂ in a cell

Question 11

What does the process of nitrogen after it is fixed look like?

Question 12

What does the flow of N₂ from NH₄⁺ to other biomolecules occur through?

Answer 12

Glutamate

Question 13

How does glutamate pass on the nitrogen?

Answer 13

By interconverting into other molecules

Question 14

What are the 4 amino acids in much higher concentrations in cells compared to others?

Answer 14

Alanine

Glutamine

Glutamate

Asparate

Question 15

What do most organisms do because they cannot fix N₂?

Answer 15

Conserve it by transamination

Question 16

What is transamination?

Answer 16

Transfering amino group between diferent molecules

Question 17

What does transamination look like?

Question 18

What is the basic reaction formula of transamination?

Question 19

Why is transamination involved in both the synthesis and degradation of nitrogen compounds?

Answer 19

The reactions of transamination are reversible

Question 20

What do all amino transferases rely on?

Answer 20

The pyruidoxal phosphate cofactor

Question 21

What is the typical molecule that accepts amino groups?

Answer 21

a-ketoglutamate

Question 22

What does L-glutamate act as?

Answer 22

A temporary storage of nitrogen

Question 23

What can L-glutamate do?

Answer 23

Donate amino groups when needed for amino acid biosynthesis

Question 24

What is pyridoxal phosphate (PLP)?

Answer 24

Cofactor made from vitamin B6 (essential vitamin)

Transfers the amino group during the reaction

Question 25

What does it mean if aminotransferases are found in the plasma?

Answer 25

There is tissue damage somewhere because aminotransferases are intracellular, this damage is usually in the liver

Question 26

When do amino acids undergo oxidative catabolism?

Answer 26

Left over amino acids (from normal protein turnover) Dietary amino acids Proteins in the body (are broken down when carbohydrates are short)

Question 27

What happens to dietary proteins?

Answer 27

They are enzymatically hydrolysed

Question 28

What is the process of dietary proteins being enzymatically hydrolysed?

Answer 28

1. Pepsin cuts protein into peptide in the stomach 2. Trypsin and chymotrypsin cut proteins and large peptides into smaller peptides in the small intestine 3. Aminopeptidase and carboxypeptidase A and B degrade peptides into amino acids in the small intestine

Question 29

Why is the stomach acidic?

Answer 29

To help breakdown proteins

Question 30

Where do the enzymes involved in the breakdown of dietary proteins come from?

Answer 30

Gastric glands in stomach lining Exocrine cells in pancreas Villi of small intestine

Question 31

What cellular proteins would be targeted for destruction?

Answer 31

Misfolded proteins Foreign proteins Unwanted proteins

Question 32

How are cellular proteins targeted for destruction?

Answer 32

Ubiquitin tags proteins that are to be degraded

Question 33

What are the fates of amino acids from broken down proteins?

Answer 33

Left intact for biosynthesis Broken down into amino groups and carbon skeleton, where the amino group is disposed of in the urea cycle

Question 34

What are the 3 fates of carbon skeletons from broken down amino acids?

Answer 34

Glucose or glycogen synthesis Cellular respiration Fatty acid synthesis