Proteins Flashcards
what is protein
- organic compound in food or feed that contains N
- meat, fish, eggs and some plants
what do animals require
- they require amino acids not proteins
- proteins are made up of the essential amino acids
- if all the amino acids required for the synthesis of animal proteins are not present at the time of protin synthesis, no proteins are made
what is the importance of amino acids
40% of body protein in skeletal muscle = important for structure or locomotion
what are the major functions of amino acids
- catalysts
- messengers
- structural elements
- immunoprotectors
- transporters
- buffers
what are some major catalyst enzymes
- hydrolases - cleaves compounds
- isomerases - transfer atoms in a molecule
- ligases (synthases) - join compounds
- oxidoreductases - transfer electrons
- transferases - moves functional groups
whar do enzymes do
speed up the rate od reaction
what are messengers
- hormones
what are structural elements
- contractile proteins = skeletal muscel (actin/myosin)
- fibrous proteins - keretin, skin, hair, nail strength
what are immunoprotectors
- immunoproteins (antibiodies)
- identifying antigens and protect body
how do proteins act as buffers
- amino acids in proteins accept hydrogens when the pH is low
- hydrogen gets bind to amino group and goes from N2 -N3 and pH rises
- amino acids in proteins donate hydrogens when the pH is too high (H ions are released and pH goes down)
what do amino acids influence
- influence farm animal productivity (growth, production of milk and eggs)
- animal health and fertility ( immunoproteins = animals that are protein defficient will be immuno deficient and more succeptible to disease, ammonia toxicity
- infertility in dairy cows= over feed protein, excesssive ammonia is produced and abosorbed, creating toxic environment
- feeding cost and animal production
- environmental consequences = excretion of nitrogen into the environment (ammonia)
what is a basic structure of an amino acid
carboxlic
ride chain ( what makes amino acids Different from one another)
amino group (with accepted H atom)
central carbon
what is an essential amino acid
- body cannot synthesis in adequTE AMOUNTS, so it must be added to the diet
non essential amino acid
- building blocks are present in the body, can be made and doesnt need to be added in the diet
what type of amino acid isomers will be recognized by enzymes
L over D
- some D-AA can be converted to L AA (commercial DL - methionine produced by industrial process)
what D AA cannot be converted
- D - lysine
- lysine produced by fermentation so that only the L isomer is produced
what is peptide bonds
- AA link together to form peptides
what are polypeptides
less then or equal to 20
what are proteins
equal to or greater then 20
what is a primary structure
- AA sequence
- polypeptide backbones do not differ
what is a secondary structure
- folding of polypeptide chains into coiled or pleated structures
- determined by what AAs are involed in making protein
what is a tertiary structure
- 3- dimensional structure of the protein (electrostadic connections)
- strong covalent bonding between cysteine residues - disulfide bridges
what is a quaternary structure
- assembly of 2 or more different proteins by forces other than covalent bonds
what determines protein structure
- order of amino acids
- RNA creates genetic cross over that determines protein
- important factor in determining protein nutritional value
what does an a helix do for secondary structure
- straight chains of A.A determine the protein content
what do B sheets do
- major impact on digestibility
- the more beta sheets there are the more extensive attractions/ bonds limit the acess of enzymes as they are much more folded = making them less digestible
- most sheets are low b sheets except feather meal - feather meal needs to be hydrolysed first for better digestion
what are teriary and quaternary strutures more involved with
- more involved with protein functionality than animal nutrition
- keratin and collagen = elastic structure
- hemoglobin = blood oxygen transport
what are exogenous sources of proteins
- plant - derived ingredients = soybean, soybean meal, peas, canola meal* and cereal grains
what are endogenous proteins
- desquamated mucosal cells
- digestive enzymes, glycoproteins, mucins
- microbes = hind gut, most will be lost in the feces
what are the three objectives in protein digestion
- digest dietary protein
- absorb constituent AA
- reclaim digestive enzymes
overview of protein digestion
- no digestion in the mouth
- starts in the stomach
- absorbed mostly in the SI - duodenum and jejunum
what
breaks protein down in the stomach
acid (HCL) and pepsin when it gets activated
- the inactive form of pepsin is pepsinogen
- muscular contractions (peristalsis ) also assist with mechanical break down
what happens to the proteins in the stomach
- the proteins need to be denatured to increase the surface area
- HCL does that
- proteins unfold
the stomach pH is 1-2
how is protein digested in the small intestine
- acidic chyme enters the small intestine - stimulating enterocytes
- release of pancreatic juice - secretin and CCK
- pro-enzymes, bicarbonate, water and electrolytes are released
pancreatic enzymes are released - trypsinogen(trypsin) chymotrypsinogen (chymotrypsin) procarboxypeptidases A and B (carboxypeptidases A B) proelastase, collagenase
what is the difference between endopeptidases and exopeptidases
endopeptidases - digestive polypeptide from the middle
exopeptidases - digestive polypeetide from the ends
how are AA and peptides absorbed
- across intestinal brush border memebrane
- AA absorbtion ( through passive diffusion, transporter-dependent absorbtion)
- peptide transport ( >60% of AA absorbed by peptides
Pept 1
H dependent
how do endogenous protein losses occur
- mostly enzyme secretion (20-70%) of protein from the diet
- if lost in excess, negative N balance even through dietart protein is adequate
- protease reclamation to reabsorb AA
what is a trypsin inhibitor
- changes the shape of trypsin
- protein inhibitor present in many plant products
- causes a significant decrease of protein digestion in monogastrics
- heat labile
what is a Tannins
- phenolic compounds that bind, precipitate protein, reduce digestibility
- they are heat labile - destroyed by heat
- reduce solubility and reduce digestion in the small intestine
what is a maillard reaction
- free sugars, lysine react in presence of heat, moisture = makes protein less soluable, reduces digestibility
lysine becomes unavailable - heat decreases protein soluability
what are the most used amino acids in the small intestine
- glutamine, glutamate and aspartate
how are amino acids absorbed into the extra intestinal tissues
- amino acids enter portal vein to liver
- used by liver ( 50% AA released from portal vein) can be used by other tissues
what is the post absorbtion of AA
- plasma AA rise after the meal
- AA pool available for metabolism
- more non essential amino acid in pool
what happens during protein takeoever
- continous process of synthesis, degradation (liver, skeletal muscles)
- ks = protein synthesis kd = protein degration
- is ks> kd then protein accretion occurs
- rapidly growing broilers
if kd >ks animals will loose weight
why does catabolism of amino acids occur
- normal part of tissue turnover - 20-25% of AA from tissue proteolysis
- disposal of excess(has to be degraded) AA from dietary protein - AA imbalance
- starvation or inadequate CHO, energy intake ( limited CHO - increases AA but lipids are going to be targeted first)
- catabolism states
what is a transamination reaction
- amino acids are synthesized
- disposal of access amino acid by taking amonia and turning it into a amino group
what is oxidative deamination
- always have the release of free ammonia (always takes place in the liver)
- complete release of amino group as amonia
what is ammonia toxicity in famr animals
- extremely toxic to CNS
- ruminants - excessive absorbtion of ammonia from rumen
- non ruminants - excessive protein intake, low arginine diets in monogastrics
-genetic defects in urea cycle
what is the urea cycle
- NH3 combines with CO2 or HCO3 to form carbamoyl phosphate
- reacts with ornithine to form citrulline
- aspartate reacts with citrulline to form argininosuccinate
- is cleaved to form fumarate and arginine
- urea is formed and ornithine is reformed from cleavage of arginine
what is the fate of urea
- urinary excretion - major form of N secretion
- secretion into the GIT - urea recycling in ruminants
- milk secretion (milk urea- nitrogen)
what are the 4 ways the carbon skeleton is used
- the C skeleton from any AA can be used to generate energy for the Kreb Cycle
- for some AA their carbon skeleton can exclusively be used for glucose synthesis through glucogenesis
- any AA whos carbon skeleton end up as Acetly CoA are ketogenic products of a ketone body and fatty acids
- Fourth group of AA that are both glucogenic and ketogenic. their pathways are dependent on animal requirement
what is a heat increment
energy lost through evaporation
what type of diet is poor in finishing animals
high protein
- want high carbs or high lipids
what are amino acid and protein requirements
- common nutrient deficiency ( inadequate protein/AA, energy intake = forces body to catabolize AA) imbalanced AA profile - AA deficiency
- reduces performance = poor growth, poor feed efficiency, negative N balance, low birth weight, low milk production, low egg production
what happens to humans with a protein deficiency
energy is adequate
- serum protein is severly decreased (swollen abdomne is present because of the low protein osmotic pressure pulls water out of blood into the tissue
- often occurs in children after weaning in famine areas
what is marasmus
- protein and energy malnutrition
- more severe then kwashiorkor
- tissue protein loss is serum protein, liver, then muscle = extremely low body weight
what are amino acid requirements of monogastrics
- adequate AA intake for protein accretion, milk production and growing fetus
- maximize lean meat deposition
- protein synthesis is an “all or nothing” event = need correct amounts of proportions to take place
- specicies, genotype, age, level of production, environmental factors
- genetics determine animals capacity for lean meat deposition
- nutrition determines if the genetic capacity is reached
- different genetics have different requirements for AA
what are the two major facotrs that effect protein quality
- AA content of protein relative to the requirement of an animal (primary protein structure)
- digestibility of the protein
what are the concepts of the first limiting amino acid
- AA supplied in dietary protein in the lowest amount relative to animal requirement
- feed amino acid composition
- animal requirements
- limiting AA determines level of production
what is the barrel analogy
- only fill the barrel to the minimum requirement of wine without it spilling
what do pigs require for AA
- lysine
why does poultry require methionine
- poultry feathers are hight in methionine = they require a larger requirement
what are problems with first limiting AA
- takes account of deficiencies but no excesses (excess protein costs energy to metabolize)
- supplimenting first limiting AA may not give optimal growth ( second third are also important)
what is the ideal protein concept
- perfect balance of EAA that will meet the requirements for maintenance, production
- lysine is always set at 100% (other EAA expressed as a % of lysine)
- allows for the calculation of the requirement of all AA if lysine requirement is kown
advantages of using ideal protein concept
- balanced EAA composition can be fed
- maximum protein accretion and synthesis is supported (maximize growth, reduce days on feed, faster turnover)
- avoid under feeding of AA (maximize growth)
- avoid over feeding of AA (lower cost and less nitrogen excretion)
- can reduce dietary CP requirement
- only need to know the requirement for lysine (everything else you can calculate)
- reduce feed costs, increase profitability
why is lysine set to 100 in ideal protein
- usually limiting EAA in cereal - based diets
- no metabolic function other then as a component of protein (lysine requirements can be easily determined (exclusively used for protein synthesis)
- lysine is easy to analyze
- lysine contents of most feeds are well known
what are ideal protein ratios
- changes because EAA requirements change
- species, genotype, age, production level, environmental factors
- as pigs grow, EAA req for maintenance, protein deposit changes
amino acid requirements
in a growing pig - maintenance requirement is less then production requirement
- EAA requirement mainly determined by the requirement for production (lean deposition)
what is total AA vs digestible AA
- % of AA abosorbed in gut differs amount feed ingredients
- diet formulation based on total levels of dietary AA are inaccurate
- practical, usually AA composition of feed ingredients available
how do you determine lysine requirement
- provide a basal diet that is adequate for all nutrients other then lysine (basal diet deficienct in lysine)
- add lys-HCl to the basal diet to give different levels of lysine
