AN SC 260 Ch. 3
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What is an amino acid? Do animals need them?
building blocks for proteins. Animals require AA not protein.
What is the basic chemical structure of AA
All have a common structure (except proline) has a carboxyl group (COO-) and amino group (NH2) and a functional group (R).
How many are naturally occuring? How many found in protein? How many are essential
300 naturally occuring. 20 found in protein. 10 are essential in the diet depeding on the species.
How are they chemically classified?
- Based on the properties of the R group.
- -charge (+, neutral, -)
- -hydrophobic vs hydrophillic (determine how proteins will fit in a membrane)
- -branched vs straight
The R groups have the following characteristics. Which are commonly limiting?
Aliphatic, Aromatic, Heterocyclic, sulfur containing (these are often limiting, methionne, and cysteine), acidic, and basic.
How are proteins classified nutritionally?
- Based on dietary requirement.
- -indespensible vs dispensible
- -conditionally indespensible
What does semi indespesible mean? Examples?
- can be synthesized from an indespesible precursor.
- Methionne comes from cysteine
- phenylalanine come from tyrosine
Examples of indispensible amino acids?
- Arginine - birds cant make it
Examples of conditionally essential. And when/who?
- - Arginine in poultry. Needed for maximum growth
- -Proline laying hens. Needed for producing a lot of eggs
- -Glycine in baby chicks
- -Glutamine. Intestinal mucosa during illness
Taurine is not in protein. How does it occur in cats? Who is it derived from?
occurs as a free amino acid in cats, and is derived from cysteine
Why is it required in the diet? What does it do?
Required in the diet because it is part of heart, skeletal muscles, brain and eyes.
It is also a major component of bile, antioxidant protection and cardiovascular protection
What configuration does Taurine naturally occur in? Which enatiomer is absorped? What are synthetic AA often?
- - Taurine is naturally in L configuration.
- - Only the L enantiomer can be absorbed
- -Often a mixture of D,L mixtures
Which amino acid can be absorped as a D enatiomer and how
Methionne. The body converts it from D to L enatntiomer
What are peptides? how are they joined? What are short chains called
- -chains of amino acids
- -peptide bonds
What are the four levels of protein organization? How is each different from the other?
- -Primary structure, relates to the amino acid order
- -secondary structure, alpha helices, b sheet domains
- -tertiary structure, relationships of domains within a chain, and protein folding (has to do with how the structure bonds to itself. How it folds will determine its function).
- -Quaternary structure, 2 or more polypeptide chains (oligomeric proteins have multiple polypeptide chains held together by non covalent forces)
Primary protein structure?
a squence of a chain of amino acids
secondary protein structure?
occurs when the squence of amino acids are linked by h bonds
tertiary protein structure?
occurs when certain attractions are present bewteen alpha helices and pleated sheets
quaternary protein structure?
is a protein consisting of more than one amino acid chain
What do prions do?
interfere with protein folding which affects protein function
Proteins vary widely in?
- -chemical compostion
- physical properties
- -biological functions
How are proteins classified?
- -other special characteristics
What are globular proteins? Functions?
- Soluble in water, dilute acids or bases, or alcohols
- – Hydrophobic core, hydrophilic external surface (over-simplistic)
- – Functions
- • Enzymes
- • Messengers
- • Transporters
What are fibrous proteins? Functions?
– Insoluble in H2O, susceptible to digestive enzymes
- – Muscle protein
- – Functions
- • Structural proteins in animals – Collagen – toughness in meat
- – Elastin – rubbery; ligaments and arteries
- – Keratins – hair, feathers, horns, hooves
What are Conjugated proteins?
- – Contain non-protein compounds
- • Lipoproteins
- • Glycoproteins
- • Mucus
What are the functions of proteins
- Transport and metabolism
How do proteins provide structure?
- -collagen ( toughness in meat)
- -elastin (rubbery and ligaments & arteries)
- -keratins (hooves, feathers, horns and hooves
How do proteins provide movement?
- - Myofibrillar proteins - sacroplasm of muscle
- - contractile proteins - actin, myosin, tyromyosin B
How do proteins help in transportation and metabolism?
- -Albumin in blood
- -Hormones (insulin, growth hormone, PTH)
- -Immune mediators
When is a time that the body can absorp protein?
Right after birth when drinking colostrum
What does cooking do to protein? Is it necessary?
It denatures protein by disrupting the tertiary structure. It is not necessary for the digestion of protein.
What does the stomach due in digestion?
- Very acidic environment.
- - disrupts tertiary structure (protein folding)
- -Allows access to peptide bonds by pepsin in stomach'
- -endopeptidase, cleaves peptide bonds within the main structure
- -peptide chain broken into smaller chains
What does the SI do in digestion and absorption?
- - PH is buffered to neutral
- -Activity of pancreatic proteases
- -peptidases secreted as zymogens ( they are inactive precursors and help prevent self digestion)
- -Entrokinase - secreted by intestinal mucosa and cleaves trypsinogen to trypsin
See chart page 6
Examples of endopeptidases - from within chain.
- Make lots of smaller chains
Exopeptidases example? Where do they come from?
They come from the end of chains, example is carboxypeptidase
What do active enzymes in the SI do? Examples?
- they cleave specific bonds.
- -Chymotrypsin - basic amino acids
- -Elastase - small amino acids
- -carboxypeptidase - works at the carboxyl end
What is the action of proteases?
- - release of tri and dipeptides, free amino acids in the lumen of the small intestine
- - brush border membrane reduces di and tri-peptides to AA
- -AA absorped
- - Must be heat treated to prevent trypsin inhibition
- - very good animal feed has lots of amino acids
- -has a trypsin inhibitor which will stop trypsin which will leave lots of long polypeptides lead to digestion ineffeciency
Protein Requirements in mongastrics?
No protein requirements but needs esssential AA and Nitrogen usaully in the form of protein)
Protein Requirements in ruminants?
- - Can depend totally on microbial protein synthesis
- - high producing animals may need pre-formed dietary AA
When are protein requirement the highest
Highest at birth and decline with age. This is related to the growth rate
What are some factors that affect protein requirements
- -Higher in stages of growth then maintenace
- -Sex dependent usually higher for males
- -Affected by physiological state (gestation, lactation, growth work ect...
Is calorie to protien ratio imprtant?
yes! Most animals will eat to meet energy requirements so it is important to have protein balanced depending on that
Defeciency signs of protein?
- – Anorexia
- – Reduced growth
- – Negative N balance
- – Decreased feed efficiency
- – Reduced serum protein
- – Anemia
- – Fatty liver
- – Reduced birth weight
- – Reduced milk production
- – Reduced synthesis of enzymes, hormones
What is a sign of protein defency in humans?
Kwashiorkor- Edema will cause ppl to have extended belly because of fluid buildup in belly.
Liebig’s Law of the Minimum
• "A crop ́s yield is restricted by the lack of a single element, even though there may be sufficient quantities of all other essential nutrients.”
What is protein synthesis limited by?
Protein synthesis can only occur untill the limiting AA is used up. Doesnt matter if all other AA acids are in excess. If protein synthesis is defiecent in one AA then the other AA are oxidized leads to fat desposition. Once that limiting AA is replace protein synthesis can continual at optimal level
What are signs of AA defeciencies (similiar to protein synthesis)?
- - specific lesions.
- - trypotophan leads to cataracts
- -thereonone or methionine leads to fatty livers.
Why do you have combos of feed stuffs in rations?
Because most feedstuffs are deffecient in at least one amino acid. Example Corn is low in Lys and Trp and Soy is high in Lys and Trp. Thus they will make a good combo
What is a viable option if you are low on a certain AA in a diet?
- - Supplement with synthetic amino acids.
- - D,L-Met, L-Lys, L-Thr, L-Trp available
- - L-Arg, L-Ile on the way
Amino acid interactions. Antagonism?
- – Reduction in performance that can be overcome by supplementation of a structurally similar amino acid
- • Effects of lysine excess overcome by supplementation by arginine
- • AA need not be limiting
AA interactions. Toxicity?
- – Adverse effects of an AA in excess can not be overcome by supplementation of other AA
- - you have to reformulate the diet
AA interactions. Imbalance
- – The dietary proportions of indispensible AA do not meet the needs of the animal
- • 1 or more AA are limiting
- • Can be overcome by relatively small supplementation of the limiting amino acid or acids
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