Animal Nutrition Test 4 Flashcards
% molecular weight of atoms in protein
C: 53% H: 7% O: 22% N: 16% S and P: less than 1%
Range of MW of proteins
5,000- many millions
Average molecular weight of proteins
35,000-500,000
How many AAs naturally occur in nature?
200
How many AAs are commonly found in proteins and are required by the body?
20-22
How many major biochemical reactions and supportive reactions and ATP are needed to make a peptide bond?
20 major biochemical reactions
Hundreds of supportive reactions
7 ATP
Principal dry matter constituent of body organs?
Protein
When is the dietary requirement for protein highest? Lowest?
Highest in young growing animals (have to maintain all tissue AND make new tissue), lowest at maturity
2 things that determine the composition and function of a protein
Arrangement of AAs and length of chain
2 types of protein
Simple (yield a-AAs or their derivatives on hydrolysis) and conjugated (protein + nonprotein prosthetic group)
2 types of simple proteins
Globular and fibrous
Features of globular simple proteins
Smaller than fibrous proteins
Made of a compactly folded peptide chain(s)
Features of fibrous simple proteins
Insoluble animal proteins
Made of extended or cooked peptide chains
Very resistant to proteolytic enzymatic digestion (remember bc fiber is indigestible)
Other names for fibrous simple proteins
Scleroproteins or albuminoids
3 examples of fibrous simple proteins
Collagen, elastin, and keratin
3 examples of prosthetic groups on conjugated protein
Phosphoric acid, carb, or nucleic acid
Examples of conjugated proteins
Nucleoproteins, glycoproteins, mucoproteins, lipoproteins, chromoproteins, metalloproteins, and phosphoproteins
Basically ______proteins
3 functions of animal cell membrane proteins
Permeability barrier
Transport things between inside and outside of cell
Supports for catalytic functions
(Probably other important but less defined functions)
Myelin function
It is a lipoprotein that makes a sheath around nerve fibers
3 things that make up erythrocyte membranes
Mucolipids, phospholipids, and loosely bound proteins
Where to sugars attach to protein to make a glycoprotein?
Sugars are accepted by amino acid residues in the polypeptide chain
Function of chondroitin sulfate
It’s complexed with protein in cartilage, tendon, and skin so portably serves connective tissue purposes
3 types: A, B, and C
6 mucoproteins that were mentioned
Serum cholinesterase
Gonadotropin
Mucoproteins in mucous secretions (abundant)
Mucoproteins of submaxillary gland secretions
Ovalbumin
Ovomucoid?
Another name of essential amino acids
Indispensable amino acids
List of essential AAs
MATT HILL VP (remember it includes: Arg, Thr, TRP, Phe)
This list was made for rats during the mid 20th century but we still use it
Methionine can be partially replaced by:
Cysteine
Phenylalanine can be partially replaced by
Tyrosine
Proline is a dietary essential for
Laying hens
This means that the essential amino acids can vary with species! Also with production; genetics, age, environment, and sex
4 amino acids that are likely to be deficient in farm diets for monogastrics
Lys (usually the first limiting AA)
Trp
Thr
Met
(To remember: the lice tripped three times and met their match)
Nonessential amino acids
These are all metabolically essential but are made by the animal so they don’t need to be in diet
Weird ones: citrulline and hydroxyproline
Plus all the rest of the 20 amino acids that aren’t essential except glutamine and asparagine (probably because the acid version of these are on the nonessential list)
Is arginine required in the diet of all species for maximum growth?
No, most adults don’t need Arg except for cats and dogs.
When mature cats and dogs don’t get Arg in their diet, what deficiency symptoms arise?
Hyperammonemia, tremors, and high levels of urinary orotic acid
Citrullene can replace which amino acid in the diet of the cat and some other species?
Arg
Why should Gln be put on the essential amino acid list?
Needed to support the metabolic requirements of the intestinal mucosa during illness
May be important in normal GI tract immune function
May be important in normal metabolism of the pancreas and liver
Cats and sulfur-containing AAs?
Cats have a high sulfur AA requirement
Only species that requires taurine (a B-amino sulfonic acid that’s not in protein but occurs as a free AA in diet). When they don’t eat it their retinas degenerate
In which species do adults need dietary His?
humans
Is amino acid balance important to the ruminant? If not, what is?
No, amount of N and readily available carbs
What is the nearly perfect protein for meeting animal needs? Why?
Albumin in eggs
It has an ideal AA composition and it’s easy to digest
Nutritive value
The balance among the AAs in the protein
Nutritive value is variable bc no 2 proteins have an identical AA composition
Where are most body proteins found?
Cell membranes
Muscle
Skin, hair, and hooves
8 Specialized functions of proteins in the body
Gene expression Enzyme catalyzed reactions Muscle contraction Hormone mediated effects Metabolic regulation Immune function (protection) Cell structure Storage and transport of nutrients and O2
Categories of tissue proteins
Collagen Elastin Myofibrilar proteins Contractile proteins Keratins Blood proteins Enzymes Hormones Metabolically active peptides and polypeptides Immune antibodies
Why is cooked meat from older animals often tough?
Because collagen content increases with aging of the animal. So old animals have lots of collagen and collagen is known to shrink when heated bc of its high Pro and Hyp content
How is elastin different from collagen?
Elastin resembles denatured collagen
Elastin consists of long, randomly ordered polypeptide chains
Elastin breaks more easily than collagen
They are both insoluble in water and resistant to digestive enzymes
Often found associated with collagen
Lots of collagen in muscle, only a little of elastin
Myofibrilar proteins
More than 20 enzymes found in sarcoplasm involved in muscle metabolism
Where is keratin found? Why is it of little value as a protein supplement?
hair, wool, feathers, hooves, horns, claws, and beak
It’s resistant to acid, base, heat, and digestive enzymes so obviously you can’t use it as a supplement
What are the major blood proteins and where are they made?
Albumin and a series of globulin (a,B,y) Thromboplastin Fibrinogen Hemoglobin Apoproteins A, B, and E
They’re mostly made in the liver
Enzymes are also called:
Organic catalysts
Major jobs of enzymes
Hydrolysis (digestion)
Degradation metabolic reactions
Synthetic processes
How many enzymes are found in animal cells?
Hundreds
Net protein accretion
The balance between protein synthesis or degredation
How much energy is needed to keep the net protein accretion balance?
15-22% of total energy expenditure
Some examples of important protein hormones
Insulin Growth hormone Gonadotrophic hormone Parathyroid hormone Calcitonin
Active vs passive immunity
Active= actually come in contact with antigen (pathogen) and body makes antibodies
Passive= get antibodies against antigen without exposure to actual antigen. Usually comes from mother to baby
Vaccines can be either!
Define prion
Infectious particles with no nucleic acids that are made of an abnormal form of a normal cellular protein
Diseases caused by prions
Scrapie
Creutzfelst-Jakob
Mad cow (BSE)
Chronic wasting disease
Other prion diseases are known to occur in mink, cats, and humans
Which body tissues are prions found in?
Brain and other nervous tissue
Why have slaughter house meat byproducts been banned from the diets of ruminants?
Because consumption of feed products containing nervous tissue from prion-infected animals can transmit the prions to the ruminant
4 steps in the conversion of dietary protein to tissue protein
1) intact dietary protein hydrolysis in GI tract
2) amino acids in intestinal lumen absorption from GI tract
3) amino acids in blood synthesis in tissues
4) now we have intact tissue proteins
Where do proteolytic enzymes come from?
Epithelial cells lining the GI tract lumen
Pancreas
2 factors that determine nutritive value of dietary value?
Hydrolysis efficiency (which determines the degree of absorption of individual amino acids)
Balance of absorbable essential amino acids
Proteins can be characterized nutritionally on the basis of…
Digestibility
Absorbability
Degree of utilization of the AAs after absorption
These are also the 3 factors affecting the degree of utilization of feed proteins
What is digestible protein?
Protein that disappears from the ingesta as it passes down the GI tract
Apparent protein digestibility
(I-F)/I ( where I= N intake, F= N in feces)
DOESNT MEASURE QUALITY, JUST QUANTITY
Problem: F includes metabolic N too (that from metabolic processes, cell turnover, and enzymes)
Where does metabolic fecal N come from?
Normal metabolism of tissue protein
When is the only time that whole proteins are absorbed across intestinal epithelium? How?
Postnatal (first 24 hours), pinocytosis
Usually proteins have to be hydrolyzed to AAs to be absorbed, but antibodies in the colostrum of the mom can be absorbed whole by pinocytosis
AAs are absorbed from the gut by:
Active transport
Why can lots of one AA increase the requirement for another AA?
They compete with each other for transport
3 main sources of the amino acids in the digestive tract
Dietary ingestion
Recycled with other N and returned to the lumen
Made by microbes
What raw ingredients do microbes need for amino acid manufacture?
Ammonia, sulfur, and a carbon source
They can make all amino acids with these things
What tissues are capable of making the nonessential AAs?
Skeletal muscle Liver Brain Adipose Intestine Kidney Lung Placenta Lactating mammary gland Other tissues
What do microbes degrade AAs to?
Ammonia, S, fatty acids (acetate, propionate, butyrate, and branched chain fatty acids), and CO2
Where in the body are AAs degraded?
Liver is the principle organ degrading all AAs except branched chain amino acids (BCAA) and Gln.
Degradation of many essential and nonessential AAs also occurs extensively in small intestinal cells
Are AAs made from recycled N of any consequence to animals?
Yes, a high proportion of intestinal mucosal cell AA supply for enterocyte growth and maintenance is derived from endogenously supplied AAs rather than those absorbed directly from the lumen of the intestine
Why is feeding excessive protein to a ruminant a bad idea?
It results in ammonia release, which is absorbed and wasted as urea lost in the urine
A low protein diet can be supplemented by microbial protein derived from endogenous recycling of urea
Where does the protein found in the lower gut of the ruminant come from?
Protein that escaped fermentation in the rumen and microbes that washed out from the rumen
What does the rumen escape of protein depend on?
Type of protein
Rate of degradation (this depends on whether it’s soluble and moves with liquid or insoluble and moves with particles)
What does the concentration of RUP depend on?
The dietary protein concentration and level of intake
3 major things that happen to amino acids after absorption?
- Tissue protein synthesis (AAs move into the cell and are used for protein synthesis within 5-10 minutes after absorption from the gut)
- Synthesis of enzymes, hormones, and other metabolites (these participate in digestion, metabolism, immunity, heredity, and endocrine synthesis)
- Deamination or transamination and use of the carbon skeleton for energy
Each organ or tissue in the body has its own rate of protein ____
Turnover
Constant turnover of protein in body and all cells require protein which is why there’s a protein maintenance requirement
What do polypeptide growth factors (PGF) do in the body?
They influence protein metabolism and animal development and maintenance (at the cell, tissue, and organ levels)
Not well understood though
Transamination
Transfer of an amino group from one amino acid to the carbon skeleton of a keto acid
MAKING AMINO ACIDS BY DEGRADING ANOTHER ONE
Deamination
Removal of an amino group and lone H from the carbon skeleton to make ammonia (NH3), which then enters the urea (ornithine) cycle. The carbon skeleton enters the TCA and is used to make ATP.
DEGRADING AMINO ACID NOT MAKING THEM
Where do the AA for body protein synthesis come from?
Absorption by GI tract or synthesis by transamination in tissues
Basis for classifying AA as essential or nonessential? How do we know?
The carbon skeleton
If it’s an essential AA, the animal can’t make the carbon skeleton
We know this because several of the 10 essential amino acids can be replaced by their corresponding a-hydroxy or a-ketoanalogs
How is it that some dietary nonessential AAs can replace some of the need for dietary essential AAs?
Essential AAs can make some of the nonessential AAs!
Ex: Cys is made from Met and can replace about half of the dietary Met
Describe the urea cycle using x+y+2=Q+B=urea
Ammonia+CO2+ATP=carbamyl phosphate + ornithine = urea
Ammonia comes from deamination, just use P from ATP, and urea should really be citrulline, which then undergoes a series of reactions to make urea
Where does the urea cycle take place?
Liver and to a lesser degree enterocytes
Same places that degrade amino acids! This makes sense because deamination is part of degradation
Cost of protein supplements?
Expensive, so we try to get all absorbed dietary AAs into proteins to save $$, but this is a tricky process because many factors come together to turn dietary AAs into animal protein
Nonessential amino acids comprise what percent of tissue protein?
40%
3 major reactions to make the nonessential AAs
Amination
Transamination
Dehydration
3 requirements for protein synthesis
Amino acids
Energy (ATP)
Nucleic acids (made by cells)
How fast is protein synthesis? Use hemoglobin as an example
Fast. Hemoglobin is 146 AAs long and is made in 1.5 minutes
Amount of amino acids in the diet
No diet has exactly the right amount of AAs, usually we feed excess bc it’s cheaper than buying expensive protein supplements or using crystalline AAs to perfectly balance an animals diet for AAs.
Not a problem bc usually excess AAs can be deamination and used for energy or transaminated to make another AA
Is protein a metabolic requirement?
No
Why do nonruminant omnivores have stricter AA requirements than some nonruminat herbivores?
Bc some nonruminant herbivores can use NPN to make AAs in the lower digestive tract
Can adult ruminants live with no protein at all in the diet?
Yes, they can use the protein made by the microbes from NPN and also from the microbes themselves
Why is protein deficiency so common?
Most energy sources are low in protein (not a lot of protein in plants) and protein supplements are expensive
Factors that influence protein requirements
Growth increases requirements
Sex (males usually need more than females)
Species
Genetic makeup within species
Why is protein:calorie important in the diet?
Even if the animal eats a lot of protein, it can still be made protein deficient if it’s fed a high calorie diet (lots of fat). This happens because animals only eat to satisfy energy requirements, so they’ll eat less of the high calorie feed and consequently eat less protein –> protein deficiency
we have little ability to balance protein intake with requirements
When will the body use protein for energy?
When it’s provided in excess of the metabolic requirement
When calorie intake is insufficient
Signs of protein deficiency
Anorexia Reduced growth rate Reduced or negative N balance Reduced efficiency of feed utilization Reduced serum protein concentration Anemia Fatty liver Edema (in severe cases) Reduced birth weight of young Reduced milk production Reduced synthesis of certain enzymes and hormones
AA deficiency usually causes these same symptoms, but there are some symptoms associated with certain AA deficiencies
What happens to other AAs if one is deficient?
Deamination of the remaining amino acids (which results in loss of the ammonia as urea and use of the carbon chain for energy)
This is a big waste of good AAs!
Trp deficiency causes:
Eye cataracts
Thr or Met deficiency causes:
Fatty liver
Lys deficiency in birds causes:
Abnormal feathering
How has recombinant DNA technology changed the way we balance rations for their AA needs?
We’ve used recombinant DNA technology to make microbes mass produce certain AAs. We can now use these in feed (before, Trp, Thr, and other AAs were only available for $$$$$). Now we can use lower protein diets to provide adequate protein and AAs for growth and other productive functions.
Ideal protein diet
Formulate AA mixtures that exactly match the AA requirement of the animal in a given state of growth and with a particular genotype
What is kwashiorkor?
It’s protein deficiency in young human children who are weaned from their mothers milk when the next child comes along
Translates to “first-second”, and is a problem in 3rd world countries bc their food doesn’t have a lot of protein in it
Symptoms of kwashiorkor
Decrease in blood protein, which causes bloated bellies and thin limbs
The better the _____________ the better the protein
Amino acid balance (this goes along with nutritive value)
Also, the closer the dietary protein to the proportions required by the animal, the better the protein will be used by the body for the manufacture of new protein
Example of AA that is toxic when fed at high levels
Met
Note: you can also feed too much protein!
Which isomer of amino acid is the natural one used most by the body?
L
Can D isomers of AAs be used by animals?
Yes, the D isomers of some essential AAs can be used for growth by most animals. Some D AAs can be converted to the L form by D-AA oxidase and transaminase
Can alpha-keto acids be used by animals? How?
Yes, they can form the corresponding L amino acid by transamination
Coprophagy vs cecotrophy
Coprophagy= the animal eats its poop bc it’s suffering a dietary deficiency of protein (also some vitamins). Ex: horse
Cecotrophy= organized eating of poop directly from the anus with the intent of taking advantage of cecal fermentation. They don’t just eat any feces but rather those referred to as cecotrophs.
Beyond cecotrophy, there’s no reason to feed NPN to a nonruminant (also NPN can be toxic in small quantities to them)
What are proteins degraded to in the rumen?
Peptides and AAs, most of which are further degraded to ammonia, organic acids, and CO2
What happens to ammonia released when microbes digest feed protein or NPN?
It’s either removed from the rumen by absorption (at a basic pH) and much of it is recycled back to the rumen as urea via the blood and saliva
…or used by the microbes along with carbs to make protein
