Proteins

  • Make up gelatin, hair, antibodies, spider webs, blood clots, etc…

  • Made up of amino acids

  • At the atomic level, all proteins are made up of carbon, hydrogen, oxygen, nitrogen, and sometimes sulphur

  • Proteins can be obtained from both animal and plant sources

Protein and DNA

  • The genetic info in DNA codes for producing specific proteins and nothing else

  • These proteins then go on to accomplish all life processes

Functions of Proteins

  • Enzymes

    • are biological catalysts that speed up chemical rxns in the body

    • can function to break molecular bonds, rearrange bonds, or form new bonds

  • Hormones

    • regulate physiological processes, such as growth and development, metabolism, and reproduction

    • chemical signaling molecules, usually proteins or steroids, secreted by an endocrine gland or group of endocrine cells that act to control or regulate specific physiological processes, like growth, development, metabolism, and reproduction

  • Antibodies

    • Proteins that bind like a lock-and-key to the body’s foreign invaders - whether they are viruses, bacteria, fungi, or parasites

  • Protein Carriers

    • Transport materials through cell membranes and through the body

  • Structural

    • Keratin found in hair and fingernails, fibrin helps blood clot, and collagen forms the protein portion of bones, skin, ligaments, and tendons

Amino Acids

  • Shape determines protein function

  • Every amino acid has the same structure

    • Consists of a central carbon atom bonded to an amino group (-NH2), carboxyl group (-COOH), and a hydrogen atom.

  • The difference lies in the R group - R group gives the amino acid distinct properties.

Proteins

  • There are 20 diff amino acid R groups

    • 9 amino acids are essential (consume in our diets)

    • 11 amino acids are non-essential (our bodies create them)

  • R groups determine the properties of the amino acid and the protein

  • Side groups may be polar or nonpolar, acid or base

  • Sequence and # of amino acids ultimately determines a protein’s shape, size, and function

Acidic and Basic Amino Acids

  • Acidic amino acids possess a carboxyl group on their R-group

  • Basic amino acids possess an amino group on their R-group

Protein Structure

  • Amino acids are the monomers that make up proteins

  • The bonds that hold amino acids together are called peptide bonds

    • Formed by a dehydration synthesis reaction

  • Occurs between an amino group of one amino acid and the carboxyl group of an adjacent amino acid

  • As more amino acids are added, it becomes a polypeptide

    • A peptide that is greater than 50 amino acids in length

  • A protein consists of one or more polypeptides that are folded into a precise 3-dimensional shape

  • Only after the folding occurs is the protein able to function

  • The unique amino acid sequence of a protein is reflected in its unique folded structure

    • This structure determines protein’s function

  • Proteins have up to 4 levels of structures, each giving them diff characeristics to the overall protein:

    • Primary structure

    • Secondary structure

    • Tertiary Structure

    • Quaternary Structure

Primary Structure

  • Primary structure of a protein is the unique linear sequence of its amino acid in each polypeptide chain

  • Changing even a single amino acid in the primary structure will alter the overall structure of the protein or destroy its biological function

Secondary Structure

  • Secondary structure folds and coils as the polypeptide chain grows

  • Formed by H- bonds between O atoms of a carboxyl group (partially +)

  • There are two types:

    • α helix

    • β pleated sheets

Tertiary Structure

  • In the tertiary structure, the polypeptide chain undergoes additional folding due to side chain (R-group) interactions

Quaternary Structure

  • Two or more polypeptide chains come together to form a functional protein, like collagen and hemoglobin

  • Hemoglobin is the combination of four polypeptides

Denaturation

  • Involves the breaking of many of the weak bonds (hydrogen bonds) within a protein molecule that are responsible for the highly ordered structure of the protein

Denature

  • Heat, pH and salt [ ] can break hydrogen bonds, which changes the structure of the protein

  • Change in structure = change in function