lecture quiz 4: proteins

Question 1

common commercially available synthetic antioxidants & functions

Answer 1

BHA & BHT: extend shelf life of food (prevent oxidation & rancidity that PUFA are prone to)

Question 2

examples of natural antioxidants

Answer 2

blueberries & vitamin E

Question 3

fat sources in animal diets

Answer 3

• most feedstuffs (grain, forages, & some animal products) contain low levels of fat (<5%)
• fatt suppliments (processed animal & vegitable fats) sometimes used to ↑ energy-density of animal diets

Question 4

typical fat contents of animal diets

Answer 4

• swine & poultry: ~5-6% (can tolerate higher levels but it would make feed sticky & cause practical issues by clogging feeding system)
• ruminants (3-6%): too much fat (>6%) reduces fiber digestion in rumen → fat covers feed particles so microbial enzymes cannot access interferes w/ nutrient exchange in the membrane of those microbes ➞ overall reduces microbial activity so the diet cannot be digested
• horses <5% ➞ no need for added fat, can usually meet energy requirements
• dogs & cats vary depending on stage, envir, behaviors, as long as diet is balanced for all nutrients

Question 5

proteins

Answer 5

• contain C, H, O, N, & sometimes S
• can come from anything that has DNA (encodes for proteins)
• found in both plant & animal sources
• made of AA (monomers)
• AA linked by peptide bonds via condensation rxn of amino group (NH3+) + carboxyl group (-COOH)
• in diet: typically have ≥100 AA

Question 6

fxns of dietary protein

Answer 6

1. provide AA for body to make its own proteins (meet requirements for AA)
2. in excess: energy supply (as long as structural needs are met)

Question 7

essential AA (EAA)

Answer 7

required in diet b/c cannot be synthesized by animal or in adequate amounts

• “the tiny little monkey and violet lion in her photo”
• threonine, tyrosine, leucine, methionine, arginine, valine, lysine, isoleucine, histidine, phenylalanine
• cats also require taurine ➞ only found in animal tissues = 2nd reason cats considered obligate carnivores
  
  • most mammals can synthesize taurine from other S-containing AA (met & cys)

Question 8

non-essential AA

Answer 8

made by animals in adequate amounts

Question 9

D & L AA

Answer 9

• AA can exist as isomers (specifically D or L = same chem formula but differ in chem orientation (stereochemistry) = mirror images (enantiomers)
• L-AA exist in nature
• animals can only use L form of AA (except Met)
• D form = synthetic

Question 10

limiting AA

Answer 10

EAA in a feedstuff that is in lowest amount relative to required amount

• for essentail AA only
• to synthesize a protein: all required AA must be present at time of synthesis ➞ if an AA is in short supply it will limit the process ∴ = limiting AA
• when one AA is deficient, proteins can only be synthesized to the level of availablity of that AA
• limiting AA dictates protein synthesis
• can hve 1st, 2nd, 3rd limiting AA
• lysine = 1st limiting AA for most animals (dogs, pigs, & many non-ruminants) in common feed
• for poultry: because of connective tissue in feathers (that contains a lot of Met that contains S) Met is the 1st limiting AA

Question 11

2nd reason cats considered obligate carnivores

Answer 11

cats require taurine ➞ only found in animal tissues

• most mammals can synthesize taurine from other S-containing AA (met & cys)