NURS 2100 Chapter 6: Proteins

Proteins

Large, complex molecules found in all living organism; its main functions include metabolism, immunity, fluid balance, and nutrient transport (in some cases provide energy)

Amino acids

Nitrogen-containing molecules that are the monomers to proteins

Side chain

The structure of the amino acids that affects the types of chemical bonds they form

Essential amino acid

A vital amino acid that the body cannot synthesize or produce in sufficient amounts

Nonessential amino acid

Amino acids that the body can produce

Transamination

The process in which the body transfers the amine group from another amino acids to a different acid group and side chain (this is the process nonessential amino acids are made)

Conditionally essential amino acid

A typically nonessential amino acids becomes essential when their requirement exceeds the ability to produce them

Example: Someone with PKU cannot metabolize phenylalanine (essential amino acids), and phenylalanine is required for the synthesis of tyrosine (nonessential amino acid), therefore, tyrosine becomes an essential amino acid

Peptide bond

Two or more amino acids join together—the amino group with the carboxylic acid—to form a polymer

Types of peptide

2 amino acids—dipeptide

3 amino acids—tripeptide

4-9 amino acids—oligopeptide

10 or more—polypeptide

Gene

A segment of DNA that serves as a template for the synthesis of a particular protein

Gene expression

the process by which cells use genes to make proteins

Nucleotide

Monomers of DNA composed of phosphate group and a deoxyribose (a pentose sugar); it includes adrenine, guanine, cytosine, and thymine

Complementary base

A to T; G to C (held by hydrogen bonds)

RNA

Similar structure to DNA; the difference being single strand molecules with uracil being a nucleotide instead of thymine and having a ribose sugar.

Transcription

Genetic material from DNA is transcribe onto the base of RNA in nucleus

Translation

Occurs within the ribosomes where mRNA translates the genetic information onto tRNA to amino acid (soon protein synthesis occurs)

Primary structure

Sequential order of the amino acids in a protein

Secondary structure

The structuring of polypeptide chains to form either spiral or pleated sheet achieved by hydrogen bonds

Tertiary proteins structure

Spiral or pleated sheet of secondary structure form three dimensional shape (achieved by hydrogen bonds, disulfide, salt bridges, or hydrophobic bonds)

Quaternary structure

Two or more identical or different polypeptides bonds to form larger protein (globular or fibrous)

Denaturation

The process by which proteins uncoils and loses its function when exposed to heat, acids, bases, heavy metals, alcohol, etc.

Example of denaturation

Example: stiffening of egg whites when whipped; curdling of milk when lemon juice or another acids is added

Limiting amino acid

The essential amino acid is missing or in small amounts, which can slow or halt protein synthesis

Incomplete proteins

Foods does not contain all nine essential amino acids in sufficient amounts

Complete proteins

Foods that contain sufficient amounts of all nine essential amino acids

Ex. foods derived from animals, egg whites, meat, poultry, fish, and milk

Also Soybeans and quinoa

Mutual supplementation

process of combining two or more incomplete protein sources to make a complete protein

Complementary proteins

Two or more foods that make a complete protein, containing all nine essential amino acids

Pepsin

An enzyme in the stomach that begins the breakdown of proteins into shorter polypeptide chains and single amino acids

Proteases

Enzymes that continue the breakdown of polypeptides in the small intestine

Gastrin

Controls the production of HCl and the release of pepsin