Proteins and Amino Acids

Proteins are made up of

Amino acids

Sequence determines structure and structure determines

Function

Proximate analysis determines

Crude protein

Kjeldahl methology measures

Nitrogen content, assuming it is all protein

Kjedahl methology assumes average N content of protein is

16%

100/16= 6.25

Kjedahl methology equation

N% x 6.25 = % Crude protein

Crude protein limitations

Assumes all N is protein

no info on amino acid composition or digestibility

Leco protein analysis

Measures crude protein by igniting sample to 1050 C, collecting the gas and measuring N

Leco protein analysis limitations

Faster, safer, easier than kjedahl BUT is much more expensive

R side chain is

Different for each amino acid

How many commonly found amino acids in most proteins?

20

How many essential amino acids in humans?

9, arginine is considered essential for the young but not adults

Simplest amino acid

Glycine

Semi essential amino acid

Arginine

Aromatics and characteristics

Phenylalaine - Cyclic ring

Aliphatic and characteristics

Valine

Icoleucine

Threonine

Leucine

BRANCHED AMINO ACIDS

Heterocyclic and characteristics

Tryptophan - Eye cataracts deficient, can lead to blindness

Sulfur containing

Methionine - Important in poultry

Basic class

Histidine

Arginine

Lysine (First limiting in swine and humans)

Leucine helps regulate

Glucose uptake by cells

Required amino acid in poultry

Proline

Required amino acids in cats

Taurine

What happens to cats deficient in taurine

Degeneration of the retina

Amino acids are linked by

Peptide bonds

Primary structure

Linear sequence of amino acids

Secondary structure

Arranged in helix formation

Tertiary structure

Helix folds on to itself, 3D

Quarternary structure 

Two or more polypeptide chains united by non-covalent bonds

Quarternary structure example

Hemoglobin → oxygen binds to iron

A proteins amino acid sequence will

Determine its structure and if its functional

Proteins are denatured by

Heat, heavy metals, and mechanical forces

Name the 5 functions of proteins

1. Tissue or structural

2. Blood proteins

3. Enzymes

4. Hormones

5. Antibodies

Absorption of intact proteins are limited to

The first 24 hours after animal is born

After 24 hours only _____ and small _____ can be absorbed

free amino acids; di and tri-peptides

Absorption of di and tripeptides take place via

Active transport

L form isomer

Biologically active

D form isomer

Rarely biologically active

Amino acid isomer forms are based on the

Position of amine groups relative to its carbon molecule

Digestion of amino acids

Intact dietary proteins → amino acids in small intestine → amino acids in bloodstream → Tissue proteins

After absorption:

1. Tissue synthesis

2. Enzyme synthesis

3. Excess amino acids are deaminated and carbon skeletons are used for energy

What happens when proteins escape rumen fermentation?

They are hydrolyzed in the small intestine - similar to monogastric

What type of species have a greater need for amino acids and why?

Dairy cattle because they have higher requirements for protein synthesis than what can be provided by microbial cell proteins

What needs to be provided to help meet the increased requirement for certain amino acids

Bypass amino acids

UIP: Undegraded intake protein

Bypass or escape protein

NPN _____ - urea NH2-Co-NH2,_______

Urea; Biuret

Most common commercial source of NPN

Urea - 287% crude protein

Microbes can synthesize amino acids if they have

Adequate N

Must provide ______ to form amino acids

Ample dietary carbohydrate

Microbes must convert NH3 into

Microbial cell proteins

What can cause ammonia toxicity

Lack of carbon skeletons used to synthesize microbial protein

Ammonia toxicity is a practical problem in

Ruminants