Week 3 Amino Acid Metabolism Nitrogen Balance Module

Question 1

of the 20 AA how many can be generated by the bodY

Answer 1

11

Question 2

protein accounts for what % of nitrogen in body?

Answer 2

95%

Question 3

how are lipids stored int he body?

Answer 3

adipose tissue

Question 4

how is glucose stored in the body?

Answer 4

glycogen (liver, muscle)

Question 5

how is protein stored in the body?

Answer 5

its not!

Question 6

what are the three states of nitrogen balance?

Answer 6

negative, positive, equilibrium

Question 7

what is a negative nitrogen balance?

Answer 7

inadequate nitrogen intake or hyper-catabolic state

Question 8

what is positive nitrogen balance?

Answer 8

a person is accumulating protein in the body over what is needed to maintain lean body mass (ideal for growing children)

Question 9

what is the free amino acid pool?

Answer 9

ALL free amino acids of the body. those present in all tissues including blood.

Question 10

what are the pathways that deplete the free amino acid pool (3)?

Answer 10

protein translation, nitrogenous compound biosynthesis, amino acid catabolism

Question 11

what are the pathways that maintain the amino acid pool?

Answer 11

degradation of body proteins, dietary amino acids, biosynthesis of non-essential AA

Question 12

what is the largest compartment of amino acids?

Answer 12

body proteins

Question 13

what is protein turn over?

Answer 13

refers to the total flux (in and out) of proteins through protein synthesis and protein degradation pathways

Question 14

how does lean tissue deposition occur?

Answer 14

protein synthesis>protein degradation

Question 15

how does lean tissue wasting occur?

Answer 15

protein degradation>protein synthesis

Question 16

which amino acids can be converted to purines and pyrimidines? 3

Answer 16

Gly, Asp, Gln

Question 17

Along with Pur and Pyr, Gly is also a precursor for what to molecules?

Answer 17

heme and creatine

Question 18

what neurotransmitters origanate from the free AA pool?

Answer 18

serotonin (Trp), GABA (Gln), histamine (His), EP, NE (Tyr)

Question 19

NO is made from what AA

Answer 19

Arg

Question 20

when the body degrades amino acids, what occurs to the N?

Answer 20

excreted in urine

Question 21

what is the significance of N being excreted in the urine?

Answer 21

gives us a window to body protein homeostasis

Question 22

nitrogen equilibrium exists when

Answer 22

nitrogen intake= excretion

Question 23

when we have a positive nitrogen balance?…what state is the body in

Answer 23

intake>excretion and the protein compartment grows. anabolic state

Question 24

when is positive nitrogen balance required?

Answer 24

in normal growth, (supports gains in lean body mass)

Question 25

what is a negative nitrogen balance? what state?

Answer 25

excretion>intake. catabolic state

Question 26

when the body is in a negative nitrogen balance how is free amino acid pool maintained?

Answer 26

proteins are degraded

Question 27

which compartment (amino acid pool or body protein) is maintained within a narrow compartment

Answer 27

amino acid pool! the pathways that add to it and take from it are narrowly regulated

Question 28

nitrogen balance is measured by....

Answer 28

nitrogen ingested-nitrogen excreted

Question 29

what is a non-nutritional cause of negative nitrogen balance

Answer 29

cachexia

Question 30

what is cachexia? cause? seen in? treatment?

Answer 30

a hyper-catabolic state. results in profound weight loss. seen in cancer, chronic renal disease, severe burns. Treat: stimulate anabolism (steroids)

Question 31

anabolism:

Answer 31

building

Question 32

catbolism

Answer 32

breaking down

Question 33

what do anabolic steroids do to nitrogen balance?

Answer 33

lead to a large increase in nitrogen balance where less nitrogen is being excreted. build protein (and muscle)

Question 34

most of the body protein is in...

Answer 34

skeletal muscle (40%)

Question 35

if a decrease in dietary protein does not explain cachexia, what does?

Answer 35

the inflammatory response. cytokines catabolize skeletal muscle causing an influx in the AA pool and a correlated increase in AA breakdown

Question 36

why are some AA 'essential'?

Answer 36

out body doesnt have the machinery to produce them. Probably an evolutionary thing that resulted in us conserving energy by eliminating the need to synthesize some of the more metabolically complex AA

Question 37

compared to essential AA, the number of proteins needed to make non-essential AA is....

Answer 37

far less. Essential AA would require an average of 6.6 additional enzymes per AA

Question 38

why are Tyr and Cys conditionally non-essential?

Answer 38

they can be synthesized from the essential Phe and Met

Question 39

the N equilibrium is determined mainly by...

Answer 39

the most limiting AA (essential), the N equilibrium point will differ for protein sources of different quality

Question 40

what is an incomplete protien?

Answer 40

protein that does not provide all the essential AA

Question 41

what does a nitrogen balance curve look like for incomplete proteins?

Answer 41

smaller slope and larger x-intercept

Question 42

where is nitrogen equilibrium on a nitrogen balance curve?

Answer 42

the x-intercept

Question 43

all non-essential AA except Tyr and Cys can be synthesize by...

Answer 43

transamination from Glutamate

Question 44

Phe+Phe hydroxylase-->

Answer 44

Tyr

Question 45

a deficiency in Phenylalanine hydroxylase results in...

Answer 45

phenylketonuria (PKU)

Question 46

what is the cofactor of Phe hydroxylase?

Answer 46

tetrahydrobiopterin

Question 47

co factor

Answer 47

a molecule essential of enzyme function

Question 48

Phe hydroxylase deficiency can be caused by which two things?

Answer 48

mutation in gene encoding Phe hydroxylase or an inability to regenerate tetrahydrobiopterin

Question 49

why is Phe hydroxylase deficiency a problem? (2)

Answer 49

its product (Tyr) becomes an essential AA along with its downstream metabolites. Also, an increase in the reactant (Phe) leads to the accumulation of neurotoxic metabolites of phenyllactate and phenylacetate

Question 50

what is the therapy for PKU?

Answer 50

suppmlment Tyr and avoid Phe (things that contain aspartame such as artificial sweeteners)

Question 51

how is the (conditionally) non-essential AA Cys produced?

Answer 51

in two steps from the non-essential AA Ser with the help of the essential AA Met

Question 52

How does Met contribute to Cys synthesis

Answer 52

donates its sulfur, through its metabolite homocysteine (these are the only two sulfur containing AA)

Question 53

what is homocystinuria? cause?

Answer 53

rare recessive disorder caused by a mutation in the gene coding for cystathionine synthase (CBS)

Question 54

what is the role of CBS?

Answer 54

role in producing Cys from Met and Ser

Question 55

what accumulates in people with homocystinuria? why is this bad?

Answer 55

Met, homocysteine. homocysteine disrupts collagen cross-linking and leads to premature atherosclerosis, strokes, heart attacks, and mental retardation

Question 56

how is homocystinuria treated?

Answer 56

diet: limit Met and supplement Cys

Question 57

what is cystathioninuria?

Answer 57

a disorder in which cystathionine (metabolite of homocystein) accumulates. relatively benign because this intermediate doesnt feed into many pathways

Question 58

how is Asn (non-essential) asparagine produced? enzyme

Answer 58

in a single step from aspartate (Asp) with the enzyme asparagine synthetase (requires ATP)

Question 59

what is the cause of acute lympahtic leukemia?

Answer 59

Asparagine snythetase deficiency in WBCs. Asn can't be produced and becomes essential AA

Question 60

what is the treatment for acute lymphatic leukemia?

Answer 60

administration of L-asparaginase (enzyme in prokaryotes that converts Asn TO Asp) that depletes Asn and kills cancerous leukocytes

Question 61

how is glutamine (Gln) produced?

Answer 61

in a single step from Glu and ammonia by the enzyme glutamine synthetase (requires ATP)

Question 62

what is the most abundant AA

Answer 62

Gln

Question 63

What can be said about Gln transfer among organs

Answer 63

it is the FASTEST making Gln a major vehicle in N transfer among tissues

Question 64

Cachexia also depletes what AA (along with protein)?

Answer 64

Gln, therefore supplementing Gln is used to treat Cachexia

Question 65

what are important conditions that require a positive nitrogen balance?

Answer 65

pregnancy and childhood growth

Question 66

what are two causes of a negative nitrogen balance?

Answer 66

malnutrition, cachexia