Amino Acid Metabolism

Question 1

What must occur to proteins before they are absorbed in the intestines, and what enzyme faciliates this reaction?

Answer 1

proteolytic enzyms.

Question 2

Tripeptides and Dipeptides are broken down by what enzyme before they are released in the blood?

Answer 2

peptidases

Question 3

What are required for intracellular protein turnover?

Answer 3

proteasomes

Question 4

In the production of ammonia, an amino group is transferred to what other amino acid?

Answer 4

glutamate

Question 5

What enzyme transfers an amino acid to glutamate?

Answer 5

aminotransferase

Question 6

What enzyme involves glutamate and the production of NADH, as well as urea?

Answer 6

dehydrogenase

Question 7

Where does the urea cycle occur?

Answer 7

The liver

Question 8

What components of the urea cycle are found in the liver?

Answer 8

carbamoyl phosphate and citrulline

Question 9

What enzyme helps funnel nitrogens into the urea cycle?

Answer 9

aminotransferase

Question 10

In the brain, the conversion of alpha ketoglutarate to glutamate is facilitated by what enzyme?

Answer 10

glutamate dehydrogenase

Question 11

In the brain, the conversion of glutamate to glutamine synthetase is facilitated by what enzyme?

Answer 11

glutamine synthetase

Question 12

In the brain, alpha ketoglutarate must be converted into what amino acid before it can travel to the bloodstream?

Answer 12

Glutamine

Question 13

What does the liver convert glutamine into so that it can go into the urea cycle?

Answer 13

ammonium (NH4+)

Question 14

What enzyme in the liver converts glutamine into glutamate?

Answer 14

glutaminase

Question 15

What is the purpose of the glucose-alanine cycle?

Answer 15

To remove excess ammonia from the muscles.

It involves converting alanine and glutamate into ammonium.

Question 16

What are the two major types of reactions that remove nitrogen?

Answer 16

deamination

trans-amination

Question 17

True or false: only amino acids (di and tripeptides) get into the bloodstream.

Answer 17

true

Question 18

Does pepsinogen or pepsin break down things in the stomach?

Answer 18

pepsin

Question 19

What is the role of trypsinogen?

Answer 19

To break down proteins into amino acids.

Question 20

Proteins can be degraded via two methods. What are they?

Answer 20

lysosomal breakdown

proteosomes

Question 21

The carbon skeleton from proteins can bue used for what?

Answer 21

cellular respiration.

Question 22

The first step of the urea cycle is what type of reaction?

Answer 22

trans-amination (transfer of an amino group).

Glutamate is made.

Question 23

Once amino acids have formed glutamate, what happens to them?

Answer 23

They undergo dehydrogenation to become urea.

Question 24

What is the rate-limiting step of the urea cycle?

Answer 24

The production of carbamoyl phosphate from ammonium and carbon dioxide.

Question 25

How is ammonium toxic to the brain?

Answer 25

Because the brain is de-energized when there is an excess amount of ammonia.

Question 26

Protein breakdown in the muscles helps to regulate the balance of what?

Answer 26

nitrogen

Question 27

What enzyme converts carbon dioxide into carbamoyl phosphate?

Answer 27

carbamoyl phosphate synthetase I.

Question 28

What enzyme converts carbamoyl phosphate to citruline?

Answer 28

transcarbamoylase

Question 29

What enzyme converts citrulline to argininosuccinate?

Answer 29

argininosuccinate synthetase

Question 30

What enzym converts arginosuccinate into arginate?

Answer 30

arginosuccinate lyase

Question 31

What enzyme converts arginine to ornithine?

Answer 31

argininase I

Question 32

What is needed between ornithin and citruline?

Answer 32

An ornithine/citrulline transporter.

Question 33

What does glucogenic mean?

Answer 33

an amino acid that is capable of making glucose.

Question 34

What does ketogenic mean?

Answer 34

The ability to make ketones

Question 35

Where does citro-anemia occur?

Answer 35

Between citrulline and arginosuccinate.

Question 36

A deficiency in enzymes does what to BUN levels?

Answer 36

Causes BUN levels to decrease.

Question 37

What is a positive NB?

Answer 37

Amount of nitrogen intake is higher than nitrogen excretion.

Question 38

What is negative NB?

Answer 38

nitrogen excretion is higher than intake Is the case in starvation/malnutrition

Question 39

Where do the amino groups in urea come from?

Answer 39

glutamate and aspartate

Question 40

What urea cycle intermediate is shuttled into the mitochondria?

Answer 40

ornithine

Question 41

What enzyme catalyzes the rate-limiting step of the urea cycle?

Answer 41

carbamoyl phosphate synthetase

Question 42

Heme is a ___ containing compound

Answer 42

Nitrogen

Question 43

What is the rate determining step of heme synthesis?

Answer 43

the reaction of succinyl CoA and glycine.

Question 44

What vitamin is required in the first reaction of heme synthesis?

Answer 44

vitamin B6

Question 45

What is the enzyme used in the rate-determing step?

Answer 45

allosynthase

Question 46

What organ is affected by acute intermittent porphyria?

Answer 46

The liver

Question 47

Congenital erythropoietic porphyria has an effect on what?

Answer 47

red blood cells

Question 48

What protein carries bilirubin in the blood?

Answer 48

albumin

Question 49

Conjugated bilirubin is associated with what sugar?

Answer 49

diglucuronide

Question 50

What distinguishes the conjugated and nonconjungated (indirect) bilirubins?

Answer 50

``` The conjugate rubin is solubule and can be tested in a blood sample. Th nonconjugated (indirect) has to be separated from albumin. ``` Conjugated bilirubin has the diglucuronide

Question 51

Histamine is derived from what amino acid?

Answer 51

Histidine

Question 52

Sphingosine is derived from what amino acid?

Answer 52

serine

Question 53

Thyroxine is derived from what amino acid?

Answer 53

tyrosine

Question 54

Epinephrine is derived from what amino acid?

Answer 54

tyrosine

Question 55

Serotonin is derived from what amino acid?

Answer 55

tryptophan

Question 56

NAD is derived from what amino acid?

Answer 56

tryptophan

Question 57

Nitric oxide is derived from what amino acid?

Answer 57

arginine

Question 58

What cofactor dos nitric oxide need?

Answer 58

BH4

Question 59

What is nNOS?

Answer 59

neuronal nitric oxide synthase. IT is expressed in neurons and produces nitric oxide as a neurotransmitter.

Question 60

What is iNOS?

Answer 60

inducable nitric oxide synthase. It is found in the immune system and is a killer compound to bacteria and microorganisms.

Question 61

What is eNOS?

Answer 61

endothelial-derived nitric oxide synthse. It acts as a vasodilator and is produced in endothelium. It moves through the surrounding muscle and relaxes.

Question 62

What are porphyrins synthesized from?

Answer 62

glycine and succinyl CoA

Question 63

What enzyme converts delta-amino levullinate into porphobillnogen?

Answer 63

ALA dehydratase. It is associated with lead poisoning.

Question 64

What enzyme converts porphobillnogen into a linear tetrapyrrole?

Answer 64

prophobilinogen deaminase It is associated with acute intermittent porphyria

Question 65

What enzme converts a linear tetrapyrrole into uroporphyrinogen III?

Answer 65

uroporphyrinogen III synthase It is associated with congenital erythropoetic porphyria

Question 66

What enzyme converts urophyrinogen III into corproporphyrinogen III?

Answer 66

uroporphyrinogen decarboxylase

Question 67

The heme degradation products (billverdin and Billrubin) are responsible for what?

Answer 67

the color of bruises

Question 68

What are the degradation products of heme?

Answer 68

billiverdin and billirubin

Question 69

Glutathione reacts with hydrogen peroxide and organic peroxides. What does this indicate that glutathione is?

Answer 69

an antioxidant

Question 70

Selenium is important in what system?

Answer 70

The glutathoine system

Question 71

Protein digestion leads to absorption of what?

Answer 71

amino acids and di (tri) peptides.