module 12

Question 1

nitrogen fixation

Answer 1

carried out by cyanobacteria, converts N2 to ammonia

higher organisms get nitrogen in form of NH3, which is incorporated into several carbon skeletons

Question 2

what can be formed from NH3

Answer 2

alpha keto glutarate. glutamate, aspartate, CO2, ATP

form glutamate, glutamine, and asparagine, reactions are reversible

Question 3

protein turnover

Answer 3

allows for replacement of damaged proteins, rate of breakdown is important for controlling enzyme levels

important for nucleotides, non protein amino acids, and other nitrogen containing compounds

Question 4

types of non protein amino acids

Answer 4

ornithine, citrulline, sarcosine

Question 5

nitrogen excretion

Answer 5

most vertebrates excrete it as urea which is water soluble, uric acid and ammonia are also ways to excrete it

Question 6

transamination -

Answer 6

transfer of amino group from one molecule to another, alpha keto acid generates an amino acid. They are pyridoxal phosphate and transaminase dependent.

Question 7

oxidative deamination -

Answer 7

amine is removed from ammonia, catalyzed by glutamate dehydrogenase, NADH, NH4+ are generated

alpha ketoglutarate formed enters citric acid cycle, NADH goes into ETC or cellular respiration

Question 8

where is glutamate dehydrogenase found

Answer 8

mitochondrial membrane

Question 9

glutamine deamination -

Answer 9

one ammmonium freed by glutaminase to yield glutamate.

Question 10

glutamine synthetase

Answer 10

found in liver, allows it to sequester ammonia as glutamine as urea biosynthesis becomes overwhelmed, allows liver to detoxify amines

Question 11

glutamate dehydrogrenase -

Answer 11

passes extra nitrogen to urea cycle in liver.

Question 12

glucose alanine shuttle -

Answer 12

transfers ammonia to liver for conversion to urea.

Question 13

how do most tissues use glutamate

Answer 13

most tissues convert glutamate to glutamine using ammonia and atp. This glutamine is then moved into the liver

Question 14

what happens to glutamine in the liver

Answer 14

glutaminase releases nitrogen from glutamine, regenerating glutamate and moving NH4 to urea cycle

Question 15

glucose alanine shuttle muscle step 1

Answer 15

ammonium passed to alpha ketoglutarate, converting it to glutamate, which transaminates pyruvate to form alanine that moves into the liver.

Question 16

glucose alanine muscle shuttle step 2

Answer 16

Alanine is then converted to pyruvate, reforming glutamate. Pyruvate produces glucose through gluconeogeneis. This glucose goes through glycolysis in the muscle to produce pyruvate.

Question 17

advantage of uric acid

Answer 17

It is not water soluble, allowing it to be excreted by uricotelic organisms

Question 18

what does oxidative deamination need in order to take place

Answer 18

pyridoxal phosphate

Question 19

importance of urea

Answer 19

it helps maintain pH balance in mammals

Question 20

carbamoyl phosphate

Answer 20

created by reaction of NH4 and HCO3, requires 2 ATP. N-acetylglutamate is also required

Question 21

formation of N-acetylglutamate

Answer 21

produced in the presence of extra acetyl CoA and glutamic acid, signaling molecule for carbamoyl phosphate synthetase

Question 22

Urea Cycle reactants and products

Answer 22

requires 3 ATP (energy expensive), produces urea and fumarate, requires 5 enzymes