Module 5- Protein metabolism Flashcards
what is protein
organic compound in feed that contains N
T or F: animals require amino acids, not proteins
T
how many amino acids are there
20
T or F: skeletal muscle is a storage for amino acids
F
what % of protein is found in skeletal muscle vs body organs, skin & blood
40, 25
T or F: all enzymes in our body are proteins
T
hydrolases
cleave compounds
isomerases
transfer atoms in a molecule
ligases
join compounds
oxidoreductases
transfer electrons
transferases
move functional groups
hormones
produced in endocrine glands
- transported through bloodstream to target tissues
T or F: all hormones are proteins
F
what 3 hormones are made of proteins
1) insulin
2) growth hormone
3) glucagon
2 contractile proteins
actin & myosin
fibrous proteins
keratin & collagen
2 groups of functional proteins
1) transporters
2) nutrient transporters
ceruloplasmin
transport copper
nutrient transporters function
expressed in cell membrane, responsible for uptake of nutrients into the cell
transporters function
transports different metabolites in the body
Na-dependent amino acid transporter
responsible for uptake of Na & AA
T or F: proteins can act as buffers
T
how do proteins act as acid-base buffers?
1) low pH -> AA accept H ions to increase pH
2) high pH -> AA release H ions = decrease pH
how does too much protein impact fertility?
ammonia can make acidic uterine environment
4 parts to an AA structure
1) central C atom
2) carboxylic group
3) amino group
4) side chain/R group -> what differs
physiological pH
7
at physiological pH, what form is the carboxylic group in?
dissociated
COO- + H
conditionally essential AA + example
requirement based on physiological state
- glycine in poultry
T or F: cysteine can reduce amount of dietary methionine required
T
phenylketonuria
elevation of phenylalanine in blood
aliphatic amino acids
have aliphatic side chains (methyl groups)
what are the 2 sulfur containing amino acids
cystenine & methionine
dicarboxylic AA
have 2 carboxylic acid groups = negatively charged
bibasic AA
have 2 amino groups
postive net charge
neutral AA
1 carboxylic + 1 amino group
negatively charged AA have an additional ( ) group while positively charged AA have additional ( ) group
carboxylic, amino
what 2 forms do AA exist in
L & D
what forms of AA are more abundant
L
monosaccharide enzymes recognize what form of AA
D
T or F: D isomers can be converted to L isomers but not vice versa
T
T or F: no enzymes available to convert L to D form of lysine
T
peptide bond links ( ) AA together
2
polypeptides vs proteins
polypeptides: less then 20 AA
proteins: more than 20 AA
T or F: no 2 proteins will be the same
T
how do proteins differ?
their sequence of AA
what is the sequence of AA determined by?
genetically by DNA
T or F: polypeptide backbones do not differ in AA
T
T or F: misfolded proteins are not functional
T
proteins in the ( ) structure are harder to digest
beta sheet
secondary structure of proteins
electrostatic attractions cause it to fold within itself
- alpha helix
- b sheets
tertiary structure of proteins have a ( ) bond
disulfide
quaternary structure of proteins
2+ polypeptide chains are interacting with each other
lactosynthase
synthesizes lactose in mammary gland
example of protein with a quaternary structure
hemoglobin
what 2 things does a primary protein structure determine?
1) AA profile
2) quantities of AA available
T or F: feather meal is not digestible due to beta sheets
T
how can feed with low digestibility be altered to improve it?
hydroylze
T or F: barley is very digestible bc it contains very little beta sheets
T
tertiary & quaternary structure of a protein are more involved with ( ) rather than nutrition
protein functionality
exogenous
derived in diet
example of a plant vs animal derived exogenous protein source
plant: soybean, canola meal
animals: fish meal
3 things that will decrease ability of GI tract to reclaim endogenous proteins
1) high fiber
2) anti-nutritional factors
3) tannins
protease enzymes perform
hydrolysis
T or F: protein digestion takes place in the monogastric mouth
F
chemical digestion in monogastric stomach
HCI + pepsin
pepsin is the ( ) form of pepsinogen
active
what do chief cells produce
gastric lipase
what is pepsinogen activated by
HCI
HCI function in stomach
denatures proteins = larger surface area
monogastric stomach pH
1-2
why does the pancreas not secrete enzymes instead of proenzymes?
bc they will break don the pancreas
T or F: proenzymes are active
F
what does acidic chyme in the proximal duodenum stimulate?
pancreatic juice which contains secretin & CCK to neutralize the chyme
endopeptidases vs exopeptidases
endo: digest polypeptide chain from the middle
exo: digest polypeptide chain from carboxylic end
3 examples of endopeptidases
1) pepsin
2) trypsin
3) chymotrypsin
2 examples of exopeptideases
1) carboxypeptidases A & B
2) aminopeptidases
aminopeptidases are ( ) enzymes
brush border
aminopeptidases
group of protease enzymes produced by enterocytes
enterocytes are ( ) enzymes
brush border
exopeptidase digestion end product
free AA
endopeptidase digestion end products
oligopeptides & small peptides
major absorption pathway for AA in monogastrics
facilitated by pept1
PEPT-1
hydrogen dependent transport system
passive diffusion of AA
via tight junctions
3 AA transporters
1) Na dependent
2) H dependent
3) Na independent
ionic gradients of H dependent transport is maintained by the
Na pump
4 steps of Na dependent AA transporter
1) Na binds to binding site on transporter
2) increases affinity for transporter for AA
3) AA binds to its binding site
4) both Na & AA are transported together into enterocyte & into the cell
why is AA transport through the Na K ATPase pump not the primary pathway?
it is an energy dependent process
what enzyme activates trypsinogen to trypsin
enteropeptidase
sodium hydrogen exchanger
removes H from cell in exchange for Na
what membrane does the Na K ATPase pump operate on?
basolateral membrane
why would there be more N in the duodenum than contained in the diet?
b/c of endogenous proteins
what N source is most abundant in feces
microbial N
microbial N
N from growth of microorganism in the hind gut + endogenous proteins
4 major sources of N in a monogastric diet
1) microbial N
2) sloughed off epithelial cells
3) enzymes
4) undigested feed nitrogen
what is the major source of N in monogastric diet
undigested feed N
why must all endogenous proteins not be lost
no growth / production bc losing more N than consuming
2 examples of anti-nutritional factors
1) trypsin inhibitor
2) tannins
what do trypsin inhibitors do
change shape of trypsin & chymotrypsin = unable to digest proteins
how to remove trypsin inhibitors and tannins from the feed
heat
tannins
phenolic compounds that bind proteins = reduce solubility of protein = reduced digestion
how are mallard products formed
when feed ingredients are heat treated = makes proteins less soluble = reduces digestibility
T or F: mallard reactions are undesirable in monogastrics
T
T or F: heat decreases protein solubility
T
3 AA used most extensively by small intestine during absorption
1) glutamate
2) glutamine
3) aspartate
T or F: lots of glucose is absorbed by small intestine for energy
F
glutamate -> a-ketoglutarate is a ( ) reaction
transamination
how does the small intestine get energy from glutamate, glutamine & aspartate
1) deamination reaction: glutamine -> glutamate
2) transamination reaction: glutamate -> a-ketoglutarate = can now enter TCA cycle for energy
what is used for ureagenesis
ammonia
glutamine, glutamate & aspartate are ( ) to produce energy
oxidized
glutathione is an
antioxidant
what organ is the major use of amino acids? for what function?
liver, energy
2 fates of AA
1) liver
2) other tissues
what % of amino acids in portal circulation absorbed from the small intestine are used by the liver?
50%
T or F: protein turnover is continual
T
rate of protein synthesis is ( ) than rate of protein degradation in animals that are growing
higher
Ks vs kd
Ks- protein synthesis
Kd- protein degradation
Ks > Kd =
protein accretion
when does catabolism of amino acids occur?
when carbohydrate intake is limited
what 2 catabolic states increase amino acid catabolism
sepsis & metabolic acidosis
ureagenesis
pathway to detoxify ammonia
ammonia is toxic to the ( ) system
central nervous system
how are non-essential amino acids synthesized?
transamination reactions
3 most active aminotransferases / 3 major players in transamination reactions
1) alanine
2) aspartate
3) glutamate
alanine gives up amino group to a-ketoglutarate to become
glutamate
aspartate becomes
oxaloacetate
alanine becomes
pyruvate
oxidative deamination
amino acid releases amino group to produce ammonia + a-ketoglutarate
transamination vs deamination reactions
T: no release of free ammonia, occur in lots of diff tissues
D: release of free ammonia, occur mostly in liver
2 causes of livestock ammonia toxicity
1) overfeed urea
2) genetic defects in urea cycle
primary site of catabolism of glutamine & glutamate
skeletal muscle
transamination of branched chain amino acids in skeletal muscle results in the production of
glutamine and glutamate
during transamination reaction, glutamine ( ) amino group and glutamate ( ) amino group
accepts, donates
mechanism that prevents releasing ammonia into the bloodstream
alanine glucose cycle
alanine glucose cycle
1) alanine transports the amino group from skeletal muscle to liver
2) glucose is released by liver -> skeletal muscle -> carbon skeleton of alanine
cost of urea synthesis
4 high energy phosphate bonds
where does the N in urea come from
catabolism of AA
arginine is important for the resynthesis of
orthinine
orthinine function
limits ability of urea cycle to operate
why do diets low in arginine impact the urea cycle?
reduces ability to regenerate orthonine which is needed for the urea cycle to operate
1 oxaloacetate is used to synthesize ( ) for the production of fumarate
aspartate
problem with urea excretion
urea is very rapidly degraded in the environment = ammonia production
ammonotelic refers to what species
aquatic species
ureotelic refers to what species
mammals
uricotelic refers to what species
birds/reptiles
what causes pasty form of bird poop
uric acid
T or F: there is little loss of water with uric acid excretion
T
T or F: uricogenic animals require more energy to excrete uric acid
T
how many ATP are hydrolyzed in ureagenesis
4
animal that secrete urea have a ( ) proportion of N b/c uric acid is higher in energy costs, therefore ( ) N content
higher
4 major sources of N in uric acid
1) glycine
2) glutamine
3) glutamate
4) aspartate
what is required in broiler diets for uric acid synthesis?
glycine
are plant or animal proteins higher in glycine
animal
urea is what % N
47
uric acid is what % N
33
uric acid synthesis has a ( ) energy cost
higher
ammonia -> uric acid vs uric acid -> ammonia on water requirements & energy cost
a->u : higher energy cost, lower water requirement
u->a: lower energy cost, higher water requirement
disposal of carbon skeleton occurs primary through
ureagenesis
T or F: carbon skeleton from any amino acid can be used to generate energy through the krebs cycle
T
T or F: some carbon skeletons are used exclusively for glucose synthesis
T
glucogenic carbon skeletons end up as? (5)
- a-ketoglutarate
- succinyl CoA
- fumarate
- oxaloacetate
- pyruvate
ketogenic carbon skeletons end up as? (2)
- acetyl CoA
- acetoacetyl CoA
phenylalanine is a ( )genic AA
glucogenic & ketogenic
why it it inefficient to catabolize AA for energy?
b/c have to dispose of amino group which costs energy & heat increment increases
heat increment definition
change in heat production after a meal
Kwashiorkor
protein deficiency with swelling
marasmus
protein and energy deficiency, no swelling
T or F: marasmus is more severe than kwashiorkor
T
T or F: protein synthesis is an all or nothing event
T
T or F: genetics determine an animal’s capacity for lean meat deposition
T
what is the 1st limiting amino acid in pigs vs poultry
pigs- lysine
poultry- methionine
2 major factors of protein quality
1) AA content determined by sequence/primary structure of AA sequence
2) digestibility of protein -> constituents being released
what 2 methods are amino acid requirements based on?
1) limiting amino acid requirements
2) ideal protein balance
what is a first limiting amino acid?
supplied in the least amount in diet relative to an animals requirement
- protein synthesis can only take place to the extent that lysine can support
what is the 1st limiting amino acid in monogastrics
lysine
why is methionine the 1st limiting amino acid in poultry?
bc feathers are very high in methionine
T or F: without synthetic AA, it is hard to formulate balanced diets for monogastrics
T
ideal protein balance concept
perfect balance of EAA that will meet requirements for maintenance & production but everything is expressed relative to the lysine or the limiting amino acid
- expressed as a % of lysine
5 advantages of using the ideal protein concept
1) balanced EAA composition
2) maximize growth
3) avoid under-feeding
4) reduces cost of diet
5) less N excretion bc proteins are in proper proportions
why is lysine set to 100 in ideal protein
only used for protein synthesize
T or F: age is a major factor that influences ideal protein ratios
T
T or F: only lysine is static in ideal protein ratios, the rest are all different
T
( ) requirements continues to increase to support protein accretion as the animal gets heavier
lysine
advantage & disadvantage of matching EAA content
A: save costs, less AA oxidation
D: difficult to manage
why is it called apparent digesibility?
bc not accounting for sloughed off epithelial cells & enzymes
T or F: apparent digestibility is used to formulate diets
F- it is very misleading bc it does not account for endogenous protein losses
T or F: microorganisms have lysine requirements
T
problem with measuring endogenous losses
digestive function
T or F: apparent fecal & ileal AA digestibility is used to calculate diets
F
what digestibility calculation is used to formulate diets
true ileal AA digestibility
2 methods to measure amino acid requirements
1) broken line model
2) quadratic model
broken line model
add more AA until weight gain plateaus
- not biologically correct
quadratic model
add more AA until find peak in weight gain curve
- decreases are due to toxic effects
what is the major source of AA in ruminants vs monogastrics
ruminants- microbial protein
monogastrics- dietary protein
true proteins + example
AA linked by peptide bonds to form large polypeptides
- canola meal
2 major sources of NPN in ruminant diet
1) urea in diet
2) ammonia in fermented forages
urea makes up to (%) of DM in ruminant rations
2%
major NPN in forages is
ammonia
degradation of NPN produces
ammonia
RUP is digested in ( ) to provide ( )
small intestine, AA
RDP are degraded in the ( ) to provide ()
rumen, nitrogenous compounds
T or F: microbial proteins require ATP to synthesize microbial proteins
T
metabolizable protein =
microbial protein + RUP
3 fates of ammonia in rumen
1) absorbed by rumen wall
2) go to bloodstream for excretion as urea
3) recycled back in saliva
2 components of dietary protein
RUP + RDP
true proteins are degraded to
AA & small peptides
T or F: protein degradation is initially an extracellular process
T
carbon skeletons from AA are degraded to produce ( ) in ruminants
VFAs
the process of dietary protein -> amino acid occurs ( ) and small peptides -> VFAs occur ( )
extracellularly, intracellularly
what % of rumen bacteria are proteolytic
30-50
difference between bacteria & protozoa
bacteria: use ammonia as N source for bacterial protein synthesis
protozoa: major source of N is the bacteria they consume
T or F: there is high urease activity in the rumen
T
T or F: urease is expressed everywhere in the rumen
T
what is required for microorganisms to use ammonia to synthesize AA?
carbon skeleton from VFAs
fiber digesting microorganisms prefer( ) as an N source for microbial protein synthesis
ammonia
coupled fermentation
nitrogenous compounds are available at the same time as ATP that drives microbial protein synthesis
protozoa preferred source of N is
bacteria
what is the most efficient protein synthesis in the rumen?
coupled fermentation
energy sources are fermented to produce
ATP
sugars are ( ) rapidly fermented than steam flaked corn / ground barley
more
why add sugars in diet to help with microbial protein synthesis?
sugars ferment rapidly like urea so they will ferment together = efficient microbial protein synthesis
T or F: rumen ammonia concentration is more stable when ammonia & ATP release are matched
T
what occurs with uncoupled fermentation
protein source is fermented faster than carb source = no ATP available = ammonia is absorbed into bloodstream = wasted N
what happens when you maximize microbial protein production
minimize RUP
3 factors that affect rumen microbial protein production
1) rumen NH3 levels
2) available energy
3) AA/peptides
How does an acidic rumen affect microbial protein synthesis?
suppresses it
SF22 effect on microbial N
b/c of rapid production of VFA = decrease in rumen pH
T or F: rumen NH3 concentration is very dynamic
T
T or F: forages are quite high in ammonia
T
T or F: a more fermentable carb = more stable ammonia production in rumen
T
rumen dilution rate
proportion of total volume leaving the rumen per hour
faster rumen dilution rate = ( ) outflow of microbial protein
more efficient
2 reasons why a faster rumen dilution rate causes a greater rate of outflow of microbial protein
1) protozoa
- faster = less opportunity to eat bacteria = more will reach small intestine
2) keep more bugs in rumen = can support growth of new organisms
protozoa make up (%) of rumen microbial mass
20-70%
protozoa make up (%) of total rumen N
10-40%
what % of rumen protozoa wash out to lower gut
20-40%
T or F: protozoa have small contribution to metabolizable protein
T
2 main microorganisms responsible for protein degradation
1) protozoa
2) bacteria
how often do bacteria double their numbers in the rumen?
every 60 mins
how often do protozoa double their numbers in the rumen?
10-60 hours
T or F: population density of protozoa are lower than bacteria
T
2 main problems with protozoa
1) not providing AA to the animal by staying in the rumen
2) using up rumen energy
2 ways protozoa remain in the rumen
1) stick to feed particles
2) attach to rumen epithelium
defaunation of protozoa ( ) rumen N efficiency
improves
what is the universal response to when protozoa are not present in the rumen?
rumen ammonia & N concentration decreases
what will happen to fiber digestion if there is no protozoa in the rumen?
it will decrease bc they are important for fiber digestion
2 functions of protozoa in the rumen
1) fiber digestion
2) energy
how do young ruminants establish a protozoa population?
cross inoculation from staying on dam
why do feedlot animals not have protozoa in their rumens?
high concentrate diet makes protozoa eat too much start and then they explode
T or F: unsaturated fats are toxic to protozoa
T
T or F: ruminants have requirement for microbial protein
T
3 factors that influence the extent of rumen degradation
1) protein structure
2) rumen passage rate
3) rumen pH & diet type
how do denatured proteins impact digestibility in monogastrics vs ruminants
monogastrics: uncoils & makes more accessible to enzymes
ruminants: reduce solubility in rumen fluid = reduces degradation
what makes good sources of RUP?
proteins coiled amongst themselves = lowers solubility
animal proteins are ( ) undergradable in the rumen compared to plant proteins
more
why are animal proteins less degradable in the rumen?
high in disulfide linkages = less soluble in rumen = less degradable
4 factors that limit the use of animal proteins in the diet
1) cost
2) availability
3) consumer perceptions
4) CFIA regulations
why can meat/bone meal not be fed to ruminants
bc of mad cow disease
a reduction in particle size = ( ) degradation
improved b/c increases surface area
optimal pH for proteases
5.5-7
acidic rumen conditions ( ) protein degradation/ why?
decrease, microorganisms responsible for protein degradation are sensitive to acidic conditions
2 advantages of lowering protein degradation in the rumen
1) lower ammonia production
2) increase rumen by pass protein
fermentation is slowed when protein degradation is
decreased
T or F: mature cows on pasture have no requirement for RUP
T
low protein diets depend on ( ) to provide N for microbial protein synthesis
urea recycling
2 methods of ammonia absorption
- do they use NH3 or NH4
1) passive diffusion (NH3)
- across rumen wall into bloodstream
2) potassium channels (NH4)
- cannot freely diffuse so must use potassium channels
NH3 vs NH4
NH3- ammonia
NH4- ammonium
3 factors that impact ammonia absorption from the rumen
1) rumen ammonia levels
- higher levels = more absorbed
2) ATP supply
- more ATP = lower ammonia concentration
3) rumen pH
- more alkaline pH = more absorption bc ammonia exists in NH3 form = passive diffusion is more rapid
3 fates of blood urea
1) urine
2) milk
3) liver
4) saliva
a high fiber diet will ( ) the amount of urea recycled via saliva
increase
2 transporters that secrete urea directly into rumen via rumen wall
1) urea transporters
2) aquaporins
why is ATP required for urea use in the rumen
protozoa cannot use urea as a source of N so bacteria need ATP to drive this process
as CP increases, the amount of urea that is recycled ( )
decreases
what % of protein is in a ruminant diet
14-16%
T or F: more N in the diet will decrease urea recycling
T
T or F: high ammonia concentration in the rumen has inhibitory effects on urea recyling
T
impacts on urea recycling in high vs low blood urea concentrations
high= facilitate movement of urea into the blood
low= less urea moved
T or F: any microbial protein production in large intestine will not provide energy
T
what animals will benefit from microbial protein production in the large intestine
rabbits -> coprophagy
2 disadvantages to rumen protein degradation
1) rumen microbes are proteolytic = degrade any N compounds = waste
2) most dietary N is absorbed as NH3, not as AA = not useful to animal
- also need to detoxify via ureagenesis which costs ATP
monogastric vs ruminant source of essential AA
monogastrics: dietary protein
ruminants: microbial protein + RUP
a-ketoglutarate is the alpha-keto acid of
glutamate
T or F: ruminants do not have dietary requirement for essential amino acids
T- required but do not have to be supplied in the diet
