How many naturally occuring AAs are there?
How many are found in proteins?
How many are essential?
What is the common structure of an AA (except proline)?
How are AAs chemically classified?
- Based on R group
- Hydro -phobic vs -philic
- Branched vs straight
How are AAs nutritionally classified?
- Based on dietary requirement
- Indispensible vs dispensible
- Conditionally indispensible
What does semi-indispensible mean?
Can be sythesized from indispensible precursors
- Methionine => Cysteine
- Phenylalanine => Tyrosine
What are 3 examples of indispensible AAs?
What are 3 examples of dispensible AAs?
What are some examples of conditionally essential AAs?
Arginine - poultry, max growth for some species (dogs, cats, pigs)
Proline - hens
Glycine - chicks
Glutamine - intestinal mucosa during illness
What is Taurine derived from?
Except in cats, they cannot derive Taruine due to shorter digestive tract
What is special about Taurine?
- Not in protein
- Occurs as free AA in cats
What configuration do AAs naturally occur in?
Only L enantiomer absorbed for most AAs except...
D methianine - the body can absorb and convert to L methianine
What are the levels of organization in proteins?
Primary structure - AA chain order
Secondary structure - alpha helix or beta sheet domains
Tertiary structure - relationships of domains within a chain, protein folding
Quaternary structure - 2+ polypeptide chains, oligomeric proteins
Proteins are classified on the basis of...
What are the properties of globular proteins?
- Soluble in water
- Dilute acids and bases
- Hydrophobic core
- Hyphilic surface
What are the functions of globular proteins?
What are the properties of fibrous proteins?
- Insoluble in water
- Resistant to digestive enzymes
What are the functions of fibrous proteins?
Structural - collagen, elastin, keratins
What are conjugated proteins?
Contain non-protein compounds
The body cannot absorb intact proteins. What is the one exception to this?
Collostrum from breast milk for a short period after birth
What are the different forms of protein digestion and absorption?
- Stomach acid
- Small intestine pH, pancreatic proteases, zymogens, cleaving enzymes, active enzymes
What are zymogens?
Inactive precursors of active enzymes so that intestinal wall is not digested.
What are the different cleaving enzyme classifications?
- Active Enzymes
What does enterokinase do?
Cleaves trypsinogen to trypsin
What are some examples of endopeptidases?
What is an example of an exopeptidase?
What are some examples of active enzymes that cleave specific peptide bonds?
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What are some signs of protein deficiency?
- Reduced growth
- Decreased feed efficiency
- Kwashiorkor - Edema
Pregnant - Reduced birth weight, milk production
How do AAs regulate protein synthesis?
Protein synthesis can only occur until the first "limiting" AA is used up, the other AAs are broken down (oxidized)
What are 3 AA interactions?
Antagonism - reduction in performance that can be overcome by supplementation of a structurally similar AA, ex. lysine and arginine
Toxicity - adverse reactions of an AA can not be overcome by suplementation of other AA
Imbalance - dietary proportions of indispensible AA do not meet needs of animal, can be overcome by supplementation