Amino Acid catabolism and urea production

Question 1

when does amino acids catabolism occur?

Answer 1

1. Normal protein degradation and synthesis inside the cell
   2.Carnivore animals
2. Excess of amino acids in diet
3. Starvation and uncontrolled diabetes

Question 2

Main steps of digestion of proteins

Question 3

Enzymes

Question 4

Gastrin stimulates secretion of ___ by parietal cells and secretion of ___ by chief cells

Answer 4

HCl, pepsinogen (zymogen)

Question 5

pepsinogen self-cleaves at __ pH to generate active pepsin

Answer 5

low

Question 6

___ cuts protein into peptides in the stomach

Answer 6

pepsin

Question 7

___ and ___ cut proteins and larger peptides into smaller peptides in the small intestine

Answer 7

trypsin, chymotrypsin

Question 8

____ and ________ in the small intestine degrade peptides into amino acids which are absorbed

Answer 8

aminopeptidase, carboxypeptidases A and B

Question 9

1st step of amino acid catabolism

Answer 9

amino acid is converted to NH4+ and a-keto acids

Question 10

Glutamate (Glu) and Glutamine(Gln) is converted to

Answer 10

a-ketoglutarate

Question 11

Alanine (Ala) is converted to

Answer 11

pyruvate

Question 11

Aspartate (Asp) is converted to

Answer 11

oxaloacetate

Question 12

nitrogen metabolism is played by what amino acids?

Answer 12

Alanine,Aspartate,Glutamate,Glutamine

Question 13

T/F Many aquatic vertebrates release ammonia to their environment through passive diffusion from epithelial cells and active transport via gills

Answer 13

T

Question 14

Plants conserve ___

Answer 14

nitrogen

Question 15

Many terrestrial vertebrates and sharks excrete nitrogen in the form of __

Answer 15

urea

Question 16

why many terrestrial vertebrates and sharks excrete nitrogen in the form of Urea?

Answer 16

1. it is less toxic than ammonia
2. it has a high solubility in water

Question 17

Birds and reptiles excrete nitrogen as _____

Answer 17

uric acid

Question 18

why birds and reptiles excrete uric acid?

Answer 18

it is insoluble (excretion as “paste” allows the animals to conserve water

Question 19

Humans and great apes excrete both __ (from amino acids) and __ (purines)

Answer 19

urea, uric acid

Question 20

step 1: removal of the amino group

Answer 20

free ammonia is captured by a series of transamination reactions and transamination allow transfer of an amine to a metabolite (e.g. a-ketoglutarate) and generate glutamate

Question 21

enzymatic transamination is catalyzed by ____

Answer 21

aminotransferases

Question 22

what cofactor enzymatic transamination uses ?

Answer 22

pyridoxal phosphate cofactor (PLP, vitamin B6)

Question 23

what molecule accepts amino groups, generating L- glutamate?

Answer 23

a-ketoglutarate

Question 24

what molecule acts as a temporary storage of nitrogen?

Answer 24

L-glutamate

Question 25

___ can donate back the amino group when needed for amino acid biosynthesis

Answer 25

L-glutamate

Question 26

elevated levels of ALT and AST indicate ....

Answer 26

liver dysfunctions (cirrhosis, hepatitis)

Question 27

what enzymes are measured in the serum to assess liver function?

Answer 27

Alanine transaminase (ALT) and aspartate transaminase (AST)

Question 28

excess ammonia is transported to the liver and even lower extent of the kidneys via ___ to be transformed into urea

Answer 28

glutamine

Question 29

Oxidative deamination occurs when ....

Answer 29

ammonia collected in glutamate is further removed by glutamate dehydrogenase in mitochondria matrix

Question 30

Oxidative deamination use __ as electron acceptor

Answer 30

NAD+ and NADP+

Question 31

Ammonia is processed into __ for excretion

Answer 31

urea

Question 32

pathway for ammonia excretion is called ...

Answer 32

transdemamination

Question 33

transdemamination consists of

Answer 33

transamination and oxidative deamination

Question 34

BUN

Answer 34

blood urea nitrogen

Question 35

BUN measures ___

Answer 35

total nitrogen

Question 36

Azotemia

Answer 36

Excess of nitrogenous waste products in the blood (high BUN); uremia usually due to kidney failure

Question 37

If NH4+ can't permeate through the membrane, what molecule can?

Answer 37

NH3 (since it is neutral)

Question 38

Brain is very sensitive to what molecule?

Answer 38

NH3

Question 39

what makes the brain sensitive to NH3?

Answer 39

excess NH3 is converted to glutamate (excitatory neurotransmitter) via glutamate dehydrogenase In the case of liver failure, excess glutamate builds up in neurons and some it is converted to GABA (inhibitory neurotransmitter, modulates muscle tone) and can cause Asterixis (flapping tremor, liver flap) and coma

Question 40

Asterixis (liver flap) is directly related to high concentrations of ___ in the brain

Answer 40

glutamate

Question 41

treatment of asterixis

Answer 41

administration of lactulose

Question 42

Urea cycle (mnemonic: come on sally lets act)

Answer 42

1. ammonium is converted to carbamoyl via CPS1 2. carbamoyl PO4 and Ornithine is converted to citrulline via OTC 3. aspartate and citrulline is converted to argininosuccinate via synthetase 4. argininosuccinate is converted to arginine and fumarate via lyase 5. arginine is converted to urea and ornithine via arginase

Question 43

Essential or non essential: amino acids must be obtained as dietary protein

Answer 43

essential

Question 44

Essential or non essential: amino acids easily made from central metabolites

Answer 44

non essential

Question 45

9 essential amino acids ( harry is loving lauren miller pink thong that vibrate)

Answer 45

histidine isoleucine leucine lysine methionine phenylalanine threonine tryptophan valine

Question 46

5 non essential AA (mnemonic: triple A Sexy Girl)

Answer 46

alanine asparagine aspartate glutamate serine

Question 47

5 essential AA that are both glucogenic and ketogenic (mnemonic: triple T P.I)

Answer 47

isoleucine phenylalanine tryptophan threonine tyrosine

Question 48

2 essential AA that are ketogenic ONLY (2 Ls)

Answer 48

leucine lysine

Question 49

which substance is NOT involved in the production of urea from NH4+ via the urea cycle?

Answer 49

Acetyl CoA

Question 50

In AA catabolism, the 1st rxn for many AA is:

Answer 50

transamination requiring PLP

Question 51

which enzyme can access liver function

Answer 51

alanine transaminase

Question 52

in muscles, pyruvate is combined with glutamate to yield alpha ketoglutarate and ____

Answer 52

alanine

Question 53

how many ATP are used to generate one molecule of urea within urea cycle?

Answer 53

4

Question 54

urea contains 2 nitrogen atoms. one nitrogen comes from ammonia while the other comes from _________

Answer 54

aspartate

Question 55

N-acetylglutamate acts as an allosteric activator of _____

Answer 55

CPS1

Question 56

in the urea cycle, arginase catalyzes ...

Answer 56

formation of urea from arginine

Question 57

cofactors in AA catabolism

Answer 57

biotin SAM folic acid plp or vitamin b6

Question 58

sulfonamide antibiotics are PABA analogs and acts as competitive inhibitors of ....

Answer 58

dihydropteroate synthase and bacterial folic acid synthesis

Question 59

folate is a vitamin ...

Answer 59

B9

Question 60

Bactrim consists

Answer 60

sulfamethoxazole and trimethoprim

Question 61

sulfamethoxazole does what?

Answer 61

inhibit folate synthesis

Question 62

trimethoprim does what?

Answer 62

inhibit bacterial dihydrofolate reductase 50,000x more than human enzyme

Question 63

symptoms of PKU

Answer 63

Heart problems, microcephaly, low birth weight, intellectual disabilities, mental disorders, seizures, newborns genotyped at birth for PAH mutations

Question 64

treatment of PKU

Answer 64

- reduce Phe in diet - synthetic BH4 ( Sapropterin)