Chapter 8- Proteins Flashcards
what is the proportion of proteins in body found in muscle ?
40%
what is the most widespread protein in the body?
actin and myosin (80-90%)
what are the three functions of proteins ?
structure, regulators of metabolism, energy
what are amino acids composed of , which elements ?
carbon, hydrogen, oxygen, nitrogen
how is it determined whether an aa is essential ?
you feed a diet w everything minus 1 aa. if the nitrogen balance becomes negative, the aa is considered essential/indispensable
what does aa lack limit ?
protein synthesis
what is the mnemonic for essential amino acids ?
PVT TIM HLL
what are the 9 essential aa ?
PVT TIM HLL
phenylalanine
valine
threonine
tryptophan
isoleucine
methionine
histidine
leucine
lysine
what are the 6 conditionally essential aa ?
CAT PGG
cysteine
arginine
tyrosine
proline
glutamine
glycine
what are proteins held with ?
peptide bonds
what chemical phenomenon leads to the formation of a peptide bond ?
condensation
what chemical process leads to the breakdown of peptide bonds ?
hydrolysis
how is aa transport executed simply put?
through transporters
what structure will a protein molecule have when put together ?
3D
what is another word for a high quality protein?
complete protein (all the essential aa)
which aa qualify as high quality protein ?
all of the essential aa
where are high quality protein usually derived from ?
animal protein
what are two non-animal sources of high quality protein?
quinoa and soy
what makes a protein low quality/incomplete ?
lacks one or more essential aa
what is the limiting aa?
the essential aa in short supply in the low quality protein
does a low quality protein necessarily mean that they are lacking an essential aa?
might have some but in small quantities
where in nature will you usually find low quality protein ?
plants
what are complementing proteins ?
incomplete proteins that, when put together, provide a full array of all essential aa
what are the 3 limiting aa in legumes ? what foods can complement well? 3 complementing meals ?
methionine, cysteine, tryptophan
complemented w grain and nuts/seeds
eg lentils and rice, beans and rice, hummus
what are the 3 limiting aa in grains ? what foods complement well?
lysine, isoleucine, threonine
legumes complement well
bread and peanut butter, barley and lentil soup
what are the 2 limiting aa in nuts ? what foods complement well?
lysine and isoleucine
just eat them w peanuts
what are the 3 limiting aa in vegetable? what 2 foods complement well?
lysine, methionine, cysteine
legumes and grains/nuts/seeds
what is protein energy malnutrition?
long term inadequate intake of protein, energy, or both, leading to wasting and infection
what is the percentage of ppl in world w PEM?
25%
in industrialized societies, what 3 ppl are at risk of PEM?
poor people
old people
hospital patients (AIDS, anorexia, cancer)
what is marasmus?
protein malnutrition due to inadequate energy intake
if untreated, body will not longer synthesize energy
what is kwashiorkor ?
protein malnutrition even if adequate energy intake, leads to edema and stomach swelling
when is the usual onset of kwashiorkor?
after breast feeding stops
what organs will be affected by too much protein intake ?
kidneys
what is the main risk w excessive protein diet ?
dehydration
what are 4 consequences of excess protein diet ?
dehydration (more urea)
fat deposition
calcium loss from bones (Ca2+ excreted in urine to treat its acidity)
risk of CVD due to increased fat especially if protein coming from high fat animal sources
what is the concentration gradient like for aa?
it is different for all aa
what are the aa transporters?
membrane bound proteins which recognize aa on shape and chemical properties
Na+ dependent or independent
what are the two inputs of AA?
intake and breakdown
does protein synthesis need a lot of energy?
yes !!!
what is the purpose of protein breakdown?
aa available for free aa pool
what are the three goals of protein breakdown?
degrade potentially damaged proteins to prevent a decline in their function
give energy when aa become either acetyl coa or TCA intermediates and are oxidized
synthesis of other compounds, eg NT, hormones, peptides and proteins
amino acids can be converted into which 3 energy sources ?
glucose, ketones, and fat
what is transamination?
a reversible reaction in which amino group is transferred to a keto-acid, resulting in formation of different aa
when you transaminate glutamate, you get…
a-ketoglutarate
what is oxidative deamination?
amino group removed from aa to form free ammonia (NH3)
what happens to the free ammonia after oxidative deamination ?
excreted as urea, or transferred to alpha-ketoglutarate to make glutamate and then glutamine
which aa can undergo transamination with glutamate ?
leucine valine isoleucine alanine aspartate glutamine
(LIVAAG)
what are the most abundant aa in muscle ?
glutamate and glutamine
what are the only essential aa that can undergo transamination?
branched chain amino acids
leucine, isoleucine, and valine
what is the main limiting factor in transamination?
processes sometimes take place in different tissues, and aa have to be transported by circulation
out of 20, how many aa are significantly oxidized by muscle ?
6
what are the 6 aa that are significantly oxidized by muscle ?
isoleucine
leucine
valine
aspartate
glutamate
asparagine
how does synthesis of essential aa work ?
it doesnt bc we cant synthesize it
how does synthesis of non essential aa work ?
glutamate donates nitrogen in transamination to give to carbon skeleton of keto acid (from TCA, or a non-essential or essential aa), so it becomes amino acid
why is synthesis of aa by transamination rarely limited ?
ample availability of substrates (NH3 and carbon skeletons)
why is synthesis of aa from other aa limited ?
limited dietary supply
what two aa are special cases in aa synthesis, especially dependent on adequate aa intake ?
cysteine and tyrosine: they are synthesized from essential aa
how does protein turnover depend on function?
regulatory or signalling: minutes, hours, days
structures: days, weeks, months
why is it that you don’t have to eat large amount of protein?
protein turnover is magic
in a normal diet, the intake of protein provides only _____% of amino acids entering amino acid pool
25%
what organs are involved in protein turnover ?
gut, kidneys, liver
also a bit of muscle
what is creatine synthesized from ? (3)
arginine, glycine, methionine
what is glutathione (antioxidant) synthesized from? (3)
cysteine, taurine, glutamine
what are NT synthesized from? (3)
glutamate
tyrosine
tryptophan
what are purines synthesized from? (3)
aspartate, glutamine, glycine
what are pyrimidines synthesized from? (2)
aspartate and glutamine
what is histamine synthesized from
histidine
what is carnitine synthesized from
lysine
what are choline and serine synthesized from
methionine
what are T3, T4, epinephrine synthesized from
tyrosine
tryptophan is the precursor of what
serotonin
protein synthesis- what % blood proteins, viscera, and muscle ?
20% blood, 50% viscera, 30% muscle
what is urea concentration in urine an indicator of ?
whole body protein breakdown
what is nitrogen balance an indicator of?
protein diet, since protein is our only diet source of nitrogen
when calculating nitrogen balance in exercise, what precaution must we take ?
measure sweat
what is positive nitrogen balance ?
when N intake > excretion
what is negative nitrogen balance
when N excretion > intake
what are disadvantages of nitrogen balance measures ?
time consuming, trained staff, underestimate nitrogen excretion (doesnt usually measure sweat or feces) and doesn’t give insight on metabolic pathways
what is 3-methylhistidine excretion?
measure of contractile protein breakdown, found in urine
however, diet with meat and fish can confound the results
how can one measure net uptake and release of aa by tissue ?
AV-difference
what are labeled tracers?
follow aa in body
what are the 2 arguments saying that exercise increases protein requirement ?
amino acids may be oxidized during exercise
increased protein synthesis needed to repair damage and form training adaptations
what are the answers to arguments saying exercise increases protein requirement bc aa used in metabolism?
even if aa oxidized, contribute less than 5% to metabolism.
also, oxidized aa not derived from muscle !
what are the answers to arguments saying exercise increases protein requirement bc increased protein synthesis needed to repair tissues?
training causes a protein sparing effect
what is the research discussing increase in aa oxidation in acute exercise ?
usually based on leucine oxidation, BUT leucine oxidation is diff from other proteins, overestimates protein oxidation
what is the research discussing increase in protein degradation in exercise ?
resistance exercise may accelerate protein turnover (synthesis and degradation) BUT nitrogen balance studies found no diff or more positive balance after exercise
what is the argument for increasing or maintaining protein for endurance athletes ?
endurance increases protein oxidation but also it works to spare protein interestingly, less breakdown.. and also no trouble meeting increased needs
for resistance athletes, does training increase rate of leucine oxidation
no (unlike endurance)
for resistance athletes, what justifies need for increased aa in diet ?
aa as precursors for proteins synthesized
if there is an increased need, what are the recommendations for protein?
- 2-1.4/1.8 g/kg BW endurance
1. 6-1.7 g/kg BW strength athletes
most uni students eat how much protein?
1-1.5 g/kg BW
what is the relationship between protein and energy intake? what does this mean
linear relationship so supplementation not needed
which athletes at risk of PEM?
those who eat not a lot
eg wrestlers, gymnasts
are vegetarian athletes at risk of PEM ?
nah
what type of exercise increases protein synthesis
both strength and endurance !!!
how does strength training increase protein synthesis
hypertrophy, muscle mass, mitochondria MASS
myofibrillar protein synthesis
how does endurance training increase protein synthesis
increase mitochondrial DENSITY, no mass increase
mitochondrial protein synthesis
what are the 4 factors that affect protein synthesis after exercise protein intake ?
coingestion
amount
timing
type
how does co-ingestion impact protein synthesis in post workout meal
measured phenylalanine uptake
control CHO diet, AA diet, mix diet
mixed diet had significantly more uptake and synthesis: carb intake creates favorable encironment
what did IV studies show when it comes to protein synthesis after exercise ?
more aa available for synthesis
however IV study can’t be applied bc neglects liver, which normally extracts 20-90% aa after gut absorption
explain research concerning timing of protein food after exercise
Tipton et al: 6g EAA + 35g CHO
before and after acute resistance bout
uptake and synthesis greater when nutrients ingested before
then, replicated study w 20g whey protein, and found no difference in aa uptake
does it really matter if you eat protein 1h or 3h before ?
nah
what protein is fast to be absorbed ?
whey
what protein is slow to be absorbed?
casein
milk protein is composed of what and what ?
80% casein, 20% whey
why is casein slow ?
clots in stomach, slowing gastric emptying
how does milk protein compare to soy when it comes to protein synthesis and muscle mass ?
milk better
what do ppl claim is the benefit of free AA?
improve exercise performance, hormone release, immune function
do free AA help as supplements ?
no benefit
what is the downside of free AA supplements ?
toxic or lead to deficiencies in other AA
can free AA increase GH?
injection maybe, orally no
how is glutamine made ?
from glutamate (Krebs) by glutamine synthetase
what is the most abundant AA in plasma and muscle ?
glutamine
what is the biggest danger for healthy ppl w high protein intake ?
it comes at the cost of carb intake
do glutamine supplements help ?
no
what are the three BCAA ?
valine, leucine, isoleucine
BCAA constitute what % of muscle protein
33%
what serves as nitrogen source for glutamine synthesis
BCAA
what is the central fatigue hypothesis ? how would BCAA help ?
FA mobilized from fat used as fuel, meaning tryptophan can’t bind to albumin. more free Trp (fTrp) means there is an increase in fTrp:BCAA ratio, increased fTrp transport in BBB, converted to serotonin, local increase of that NT
serotonin brings fatigue
therefore BCAA would prevent that from happening bc BCAA counter fatigue, reduce transport of fTrp to brain
does BCAA intake change time to fatigue according to research?
no !
is BCAA good for muscle soreness ?
yes but not function
what is considered excess protein intake ?
3g/kg BW
does tryptophan help release GH?
no
