Introductory Animal Nutrition - Protein and Amino Acids

A comprehensive set of vocabulary flashcards covering protein composition, analysis methods, structures, amino acid classification, and nitrogen metabolism as detailed in the lecture notes.

Crude protein (CP)

Total nitrogen $\times 6.25$, representing both true protein and non-protein nitrogen compounds.

Kjeldahl digestion

A method to determine nitrogen where a sample is treated with $H_2SO_4$ to produce $(NH_4)_2SO_4$, $CO_2$, $SO_2$, and $H_2O$.

Dumas method

A technique for nitrogen determination involving high temperature combustion to release $N_2$ gas.

True protein

Protein that is composed exclusively of amino acids.

Non-protein nitrogen (NPN)

Compounds that are not protein in nature but contain nitrogen that can be converted into amino acids by microbes, such as Urea.

Amino acids

The monomer units of protein composed of carbon, hydrogen, oxygen, nitrogen, and sulfur, containing an amino group ($-NH_2$), a carboxylic group ($-COOH$), and a side group ($-R$).

Imino group

A specific nitrogen-containing group connected to a carboxylic acid at a shared carbon atom, characteristic of amino acids like proline.

Peptide bond

The chemical bond formed between the carboxyl group of one amino acid and the amino group of another, releasing $H_2O$.

Primary Structure

The genetically determined sequence of amino acids in a protein chain.

Secondary Structure

The local spatial arrangement of the protein backbone, typically in the form of an alpha-helix or beta sheet.

Tertiary Structure

The specific coiling or folding of the alpha-helix or beta sheet into a three-dimensional shape.

Quaternary Structure

The structure formed by the assembly of several tertiary protein structures together.

Denaturation

The loss of secondary, tertiary, and quaternary protein structures caused by heat, UV light, or chemical damage.

Maillard reaction

A browning reaction between the carbonyl group of reducing sugars and the terminal amino group of amino acids that reduces nutrient digestibility.

Essential (Indispensable) Amino Acids

Amino acids that cannot be synthesized by the animal at a rate adequate to meet requirements and must be supplied in the diet.

PVT TIM HALL

A mnemonic for the ten essential amino acids: Phenylalanine, Valine, Threonine, Tryptophan, Isoleucine, Methionine, Histidine, Arginine, Leucine, and Lysine.

Conditionally essential amino acids

Amino acids that are normally non-essential but must be supplied in the diet under specific conditions, such as Cysteine (from Methionine) and Tyrosine (from Phenylalanine).

Taurine

A sulfur amino acid essential for cats, abundant in fish and rodents, which is critical for vision, cardiac function, and bile acids.

Ideal Protein concept

The nutritional approach of supplying the optimal amount and proportion of all essential amino acids, usually expressed as a ratio to lysine.

Limiting Essential Amino Acid

The essential amino acid present in a dietary protein in the least amount relative to the animal's requirement.

Apparent Ileal Amino Acid Digestibility (AIAAD)

A measurement of amino acid digestibility determined at the end of the small intestine, used to avoid the influence of hindgut microorganisms.

Dietary markers

Recognizable, indigestible, and non-absorbable substances like $Cr_2O_3$, Acid insoluble ash (AIA), or $TiO_2$ used in the index method to measure digestibility.

Metabolic Fecal Nitrogen (MFN)

The nitrogen in feces originating from endogenous sources such as epithelial cells, enzymes, and mucus, rather than undigested food.

Endogenous Urinary Nitrogen (EUN)

The nitrogen excreted in urine that results from the body's mandatory metabolic processes, independent of dietary nitrogen intake.

Maintenance Nitrogen Requirement (MNR)

The amount of nitrogen required to balance all obligatory losses, achieved when nitrogen intake equals nitrogen output.

Uric acid-nitrogen recycling

A nitrogen-conserving mechanism in birds and reptiles where uric acid is refluxed from the cloaca to the ceca for microbial degradation into ammonia or amino acids.