L39 Protien as Macronutrient Flashcards
Difference between essential, non essential and conditionally essential AA
Essential: Not synthesized by humans, MUST be consumed
Non essential AA: can be synthesized in sufficient quantities, to satisfy normal requirements assuming adequate source of nitrogen available
conditionally essential: cannot be syth at required rate under some circ
- glutamine met, accelerated during stress
- argenine exceeds rate of synthesis during infance due to high demand in growth
- DEF of AA precursor can lead to new cond essential
(PKU) phynylalanine must be kept low, but its a precursor to tyrosine: cond essential
Protien quality considerations; complete vs incomplete and complimentary
Complete: all the essential AA in correct amounts -typically animal: meat fish eggs (not gelatin) Dairy: milk yogurt whey plant: quinoa, buckwheat....
incompleteL one or more of the essentials
- nuts and seeds, legumes, grains, veg
- most plants
- SOY an exception
- cannot be SOLE source of prot
complimentary: paired to make complete:
grains; high methionine, low lysine
legumes: high in lysine, low in methionine
not EVERY meal this balanced…just throughout day
Eval of Dietary protein PER, nitrogen balance
Protein efficiency ratio:
not used anymore, set for animals, VERY different
-weight of growing animals and protein source: 10% protein for 10 days
Nitrogen Balance: -asses protein quality -nitrogen into body, excreted as urea, ammonia and other. -can show dietary protein reqs nitrogen intake-nitrogen loss
can be NEG nitrogen status or POS nitrogen status
protein turnover
short lived: minutes to hours
N’ aspartate, N PEST proline glutamate seriene and threonine
longl ivedL n serine: half life of one day
structural protein months to years
Amino Acid pool and nitrogen balance
AA pool stays in constant balance
sources: degradation of body protiens
- digestion of dietary protein
- synthesis of NEAA
Three depletion events
- sunthesis of body protein
- syn of nitrogen containing molecules
- conversion of AA to glucose, glycogen, FA, ketone…ec
Two methods for protein degradation
Ubiquition: degradation of endogenous proteins and ATP dependent and in cytoplasm
- covalent attachment of ub to protein , chain of polyuB
- proteasome recognizes tag, unfolds and cuts into peptide fragments (ub recycled)`
- fragsdegrated into AA pool
- Where is the ATP??
lysosomal proteolysis system
- acidic organelles, single membrane NOT in RBC
- more than 50 enzymes,
- acid stable proteases
- mostly for EXTRA CELLULAR PROTEINS, endo cytosed then autophagy
biological value for protein quality
USE NITROGEN
how much N is retained in teh body following a protien diet
-diet witout known amount of N is fed and uring and fecal collections are assesed
BV= nitrogen returned/absorbed x100
-inherent value in certain foods
BV100: all protiens absorbed
PDCAAS
Protien Digestibility Corrected AA score
gold standard by WHO
uses N balance and essential AA requirement
complete protien has PDCAAS # greater than or equal to 1
peanuts : 0.52
Leucine content
protien quality (studies show)
leucine rich protien sources much better at stimulating muscle growth.
-activation of mTOR pathway- increase muscle synthesis
-whey has more leucine than soy
protein synthesis for athletes (and AA sup)
MAY benefit from increased protien intake
-normal RDA: 0.8 athlete 1.2-2.4
AA supplements as well
- leucine: stim protein synthesis via mTOR path
- BCAA: E source, prevent muscle fatigue
- Arg/citruline: increased NO for increased Blood flow
- glutamine, beta alanine, creatine
Risk of increased protien diet
greater than 2 g/kg daily
- hydration- increased urinary output to expel nitrogen
- kidney disease: elderly or sick cannot handle increased phosphorous as a result
- bone health: protein diet leads to increased ca loss in urine
- fatty protien sources lead to increased CV risk
- lack of carbs/fiber/vitamins
Digestion of protien
ingestion digestion (gastric) digestion (pancreatic) digestion by si enzymes absorbtion of AA and peptides transport of AA into cells
action of digestive enzymes in general: exo and endo peptidases
peptidases: hydrolyze peptide bonds
endo: middle/inside (smaller frags)
exo: cleaves only peptide bond that links the C or N term amino acid (one free AA and chain)
protien digestion in stomach
HCl and pepsinogen
HCL
- stomach acid too dilute to hydrolyze protiens
- from parietal cells
- kills some bacteria
- denatures protiens to prep them for proteases
Pepsin
- acid stable
- ENDO peptidase
- secreted by cheif cells as pepsinogen (hcl activates)
release and activation of Panc enzymes
Release controlled by CCK and Secretin
-zymogen activation-
enteropeptidase/kinase: enzyme synthesized and presend on luminal surface of intestinal mucosa BB
-makes trypsinogen into trypsin, then trypsin will continue to cleave other trypsinogen molecueles as well as activate chymotrypsin, elastase and carboxypeptidase
Four main enzymes and all details
Trypsin (panc)
- serine endopeptidase (serine at its active site)
- cleaves pepetide chain at CARBOXY side of AA
- only at Lysine or Argenine (EXCEPT WHEN FOLLOED BY A PROLINE)
Chymotrypsin (panc)
- serine endopeptidase
- trypsin cleaves it into two fragments
- larger fragment cleaves inself into 2 parts
- all linked together to form active enzyme
- cleaves peptide amids bonds at CARBOXY side or large hydrophobic AA (Ty, Tryp, Phen)
- can do others too but slowly
Elsastase (panc)
- serine endopeptidase
- cleaves peptide amide bonds at CARBOXY side
- small hydrophobic AA (ala, gly, Ser)
- has additional fxns in body (break down elastin)
Carboxypeptidase A&B
-proteases that hydrolize a peptide bond at the CARBOXY end C’ EXOPEPTIDASE
-either serine OR cystein proteaes
A-cleaves pep aminde bond at AMINE side of - ala, iso, leu, val
B-cleaves peptide amide bond at amine side of arg, lys
peptide digestion and absorbtion in SI
enterocytes have aminoexopetidases (repeat cleave at amino end)
- Na+ transforters for Free AA on luminal surface
- several AA transporters exist
- also di and tri peptide transporters also Na linked
- more peptidases inside enterocyte
-cleaved to free AA, exit cell basally (on carriers) or some free, then to portal vein
Celiac Disease
immune mediated intestical inflammation 1/120-300
- damage to microvilli of si
- unable to absorb nutrients
- due to respone to gluten (wheat, barley, rye)
- transglutaminase crosslinked gluten initiates immune response
- diarrhea, vomit, no nutrition
- irona nd folate deficiency lead to anemia
-G free diet
Cysteinuria
most common genetic AA transporter disease
- defective transport of dibasic AA (Cystein Ornothine Argenine Lysine)
- transporter located on apical membrane of Si and renal proximal tubule
- excessive urinary secretion of cystein and dibasic amino acids
- cystein stones and kidney, ureter and bladder
- lots of fluids and plant based protiens proscribed (decreased cystein content)
Hartnup Disease
autosomal recessive
defect in intestinal renal AA carrer for large neutral AA (trp, tyr, val, leu, ile)
- def in ESS especially tryp is noticed
- niacin (vit B fam) deficiency also occurs leading to dermatitis and diarrhea (pellagra like)
- tryptophan is a precursor to niacin and seritonin
must take niacin supplements and seritonin (CNS defects)
Bacterial fermentation of unabsorbed tryp makes indols with foul smelling stool
besign amino aciduria-kindey unable to reabsorb the fil Large AA
asymptomatic of high protein diet
-by di and tri AA absorbed and hydrolized within the enterocyes will yeild random assortment of AA including the large neutral AAs
