nitrogen metabolism

Question 1

primary metabolites

Answer 1

needed for normal operation of metabolic pathways; amino acids, nucleotides, RNA, DNA, B vitamins

Question 2

secondary metabolites

Answer 2

those organic compounds not needed for cell growth, development, or reproduction

Question 3

alkaloids

Answer 3

plant-derived nitrogen-containing secondary metabolites; caffeine, morphine, taxol, LSD

Question 4

fungal metabolites

Answer 4

penicillin, streptomycin, cyclosporin

Question 5

nutritionally essential amino acids

Answer 5

PVT TIM HiLL ( phenylalanine, valine, tryptophan, threonine, isoleucine, methionine, histidine, leucine, lysine)

Question 6

conditionally essential amino acids

Answer 6

arginine, tyrosine, cysteine

Question 7

Arginine

Answer 7

humans make arginine, but more is needed for unimpaired growth during childhood and pregnancy

Question 8

tyrosine

Answer 8

becomes essential, whenver Phe is inadequate

Question 9

cysteine

Answer 9

becomes essential, whenever Met is inadequate

Question 10

why must diet be varied?

Answer 10

to get an adequate balance of AAs

Question 11

what is low in essential amino acids?

Answer 11

vegetables and even animal proteins

Question 12

how do omnivores gain advantage?

Answer 12

by eating both plant and animal protein

Question 13

what are the sources of amino acids?

Answer 13

intracellular proteolysis, digestion of proteins in foodstuffs, de novo AA synthesis

Question 14

intracellular proteolysis

Answer 14

removes misfolded as well as old and damaged proteins, supplies essential AAs when dietary intake is insufficient, controls cell-cycle transitions and cell disjunction

Question 15

digestion of proteins in foodstuffs

Answer 15

supplies both nutritionally essential and nutritionally nonessential AAs

Question 16

de novo AA synthesis

Answer 16

provides nutritionally nonessential AAs that are needed for protein synthesis; adjusts amino acid pools in different tissues, adjusts energy metabolism by controlling concentrations of central pathway metabolites; allows cells to adapt to metabolic stress; needed to make nucleotides, heme, hormones, as well as neurotransmitters

Question 17

Intracellular protein turnover

Answer 17

turnover rate depends on metabolic state; greater protein degradation occurs whenever nitrogen intake is low because cells need essential amino acids to make vitally needed proteins

Question 18

what are the three pathways for intracellular protein turnover?

Answer 18

lysosome pathway, proteasome pathway, autophagic pathway

Question 19

lysosome pathway

Answer 19

lysosome is an acidic compartment where proteins are protonated and undergo partial unfolding due to repulsion, making them more susceptible to proteolysis

Question 20

proteasome pathway

Answer 20

ubiquitin is a 8.6-kDa protein that is enzymatically joined to unfolded proteins, marking them for breakdown. only ubiquitinated proteins can enter proteasomes, barrel-like macromolecular structures that use on-board proteases to form small peptides and AAs

Question 21

autophagic pathway

Answer 21

uses ubiquitin system and lysosomes to remove old organelles that are first engulfed in an autophagic vacuole

Question 22

proteolysis

Answer 22

enzymatic cleavage of proteins

Question 23

saliva (proteins)

Answer 23

low levels of proteases

Question 24

stomach: low pH (proteins)

Answer 24

pepsin

Question 25

small intestine; neutral pH (protein fragments)

Answer 25

fragments can't refold at neutral pH; chymotrypsin, trypsin, carboxypeptidase, elastase

Question 26

after getting through the proteins and protein fragments what are we left with?

Answer 26

mainly amino acids and di- and tri- peptides

Question 27

zymogen activation

Answer 27

zymogen-> proteolytic cleavage-> active enzyme; inactive enzymes are safer to store; prevents autophagy and apoptosis

Question 28

what are the 4 major digestive proteases?

Answer 28

pepsinogen, chymotrypsinogen, trypsinogen, procarboxypeptidase

Question 29

pepsinogen

Answer 29

active enzyme=pepsin, optimally active at pH 1-3

Question 30

chymotrypsinogen

Answer 30

active enzyme=chymotrypsin, optimally active at pH 7

Question 31

trypsinogen

Answer 31

active enzyme: trypsin, optimally active at pH 7

Question 32

procarboxypeptidase

Answer 32

active enzyme: carboxypeptidase, optimally active at pH 7

Question 33

autocatalysis

Answer 33

any process in which a reaction product is capable of catalyzing its own formation

Question 34

pepsinogen is formed in and released by ____________ cells, which store pepsinogen in ___________

Answer 34

gastric chief cells; secretory granules

Question 35

once a few pepsin molecules are formed by acid catalysis...

Answer 35

they rapidly cleave many pepsinogen molecules, each forming considerably more molecules of catalytically active pepsin

Question 36

what mediate catalysis at low pH for pepsin?

Answer 36

two active-site aspartyl residues

Question 37

chymosin

Answer 37

acid protease that curds milk to hasten pepsin cleavage

Question 38

what is NOT absorbed by healthy intestine?

Answer 38

dietary proteins; foreign proteins are immunogenic; must be proteolyzed to amino acids, di- &tri-peptides

Question 39

proteolysis of protein foodstuffs process begins by making what?

Answer 39

zymogens; synthesized and stored in pancreas; secreted into small intestine-> only then converted to active catalysts

Question 40

trysinogen activation

Answer 40

pancreas makes & stores trypsinogen in vesicles; secretory vesicles contain trysin inhibitor; prevents unwanted proteolysis of host cells; enterokinase converts trysinogen into trypsin; trypsin activates chymotrypsinogen to chymotrypsin

Question 41

enterokinase

Answer 41

an ectoprotease on intestinal mucosal wall

Question 42

pro-carboxypeptidase

Answer 42

activated to carboxypeptidase in a cleavage reaction that is catalyzed by trypsin

Question 43

AAs and small peptides are...

Answer 43

actively transported (against the concentration gradient) into intenstinal brush border cells

Question 44

amino acids and sodium ions are transported in the same direction, and transport is driven by...

Answer 44

transmembrane ion gradient (high na+ in intestinal lumen & low na+ in brush border)

Question 45

cells use _____________ to drive Na+ outward and K+ inward

Answer 45

ATP-hydrolysis dependent pumps

Question 46

what drives AA uptake?

Answer 46

cell's chemiosmotic gradient

Question 47

organs selectively import AAs they need thru...

Answer 47

organ-specific expression of AA-selective transporters

Question 48

true nitrogen balance

Answer 48

intake=excretion

Question 49

positive nitrogen balance

Answer 49

intake>excretion

Question 50

negative nitrogen balance

Answer 50

intake

Question 51

positive nitrogen balance is required for...

Answer 51

growth in childhood, growth in pregnancy, healing of wounds, convalescence

Question 52

negative nitrogen balance occurs during...

Answer 52

starvation, malnutrition, disease (burns, trauma, surgery)

Question 53

marasmus

Answer 53

malnutrition associated with extensive tissue and muscle wasting, with little/no edema features: loose folds of skin hanging over buttocks severe deficiency of nearly all nutrients, especially protein, carbohydrates, and lipids

Question 54

protein-energy malfunction

Answer 54

resulting from inadequate intake of protein and calories

Question 55

Kwashiorkor

Answer 55

translation: sickness last baby gets when the new baby arrives acute childhood protein malnutrition inadequate protein intake but adequate caloric intake

Question 56

characteristics of kwashiorkor

Answer 56

irritability (neurotransmitter deficit), big belly (liver enlarged with fatty infiltrates) kids are always hungry & eat too much cassava (excess carbohydrate is stored as fat in liver), edema hypoalbuminemia causes osmotic imbalance within ankles, feet, and belly