Protein (Exam 2) Flashcards
Dietary proteins are polymers of ______.
amino acids
The amino acids of dietary proteins contain at least one ______ group and at least one _____ group.
carboxyl
amino
___ (number) different _ amino acids are commonly found in proteins.
20
L-amino acids
Amino acids differ from each other in the structure of ______.
side chains (R group)
_____ is a structurally exceptional amino acid not bound to dietary protein.
taurine
Taurine has an acidic group that is a ____ rather than carboxylic acid which is located on __ rather than __ carbon.
sulfonic
beta
alpha
__ to __ amino acids are nutritionally essential, varying by species.
9-11
3 reasons for needing nutritionally essential amino acids
- metabolites + synthesis of proteins
- carbon skeletons (carnitine)
- nitrogen + sulfur
(T/F) Half of amino acids in dietary proteins are classified as nutritionally essentially.
True
What makes an amino acid “essential”?
cannot be synthesized by animal OR not synthesized at sufficient rate
Arginine is essential in ______ but not in other species.
dogs/cats
Arginine is conditionally essential in _____ & during _____.
neonates
disease
Which amino acid is essential in cats and other “strict” carnivores?
taurine
Taurine is conditionally essential in ____ and ____.
neonates + adult dogs
Why is taurine conditionally essential in adult dogs? When is it necessary?
during dietary deficits
Two dietary deficiencies in which taurine is necessary/essential for dogs?
- low cysteine + methionine
- unexplained dietary interactions
(T/F) Using non-essential amino acids in the diet can increase the dietary need for essential amino acids.
False - can reduce need for some essential nutrients
What do “non-essential” amino acids provide which is essential for life?
provide amino nitrogen for protein synthesis
Non-protein and non-amino acid sources of nitrogen are used for low-cost substitution for protein in what kind of animals?
ruminants
To an extend, _______ make amino acids and protein from non-protein nitrogen sources.
rumen microbes
What are 2 common non-protein nitrogen sources?
ammonium salts
urea
3 limitations to using ammonium salts as a non-protein nitrogen source.
- forms ammonia
- acidifying
- excreted as urea
(T/F) Urea is a prominent source of non-protein in a horse’s diet.
False - toxic to horses!
2 limitations of urea as a non-protein nitrogen source
- produces ammonia
- toxic to horses
Nutritional value or “quality” of dietary protein varies with its amino acid ______ and _____.
composition
bioavailability
List the 4 methods to evaluate protein quality
- Protein Efficiency Ratio (PER)
- Net Protein Utilization (NPU)
- Biological Value (BC)
- Chemical Score
What is the “first-limiting” amino acid percentage that is a method used to evaluate protein quality?
chemical score
(T/F) Crude protein of proximate analysis measures nitrogen content but does not indicate protein content or quality.
True
Plant proteins are (higher/lower) quality than animal proteins.
lower
Which amino acid is the first-limiting amino acid in cereals like corn, wheat, and rice?
lysine