G-protein linked Plasma membrane receptor. Works with “G-protein”, an intracellular protein with GDP or GTP. Involved in yeast mating factors, epinephrine (adrenaline), many neurotransmitters, blood vessel development.

G-protein GDP and GTP acts as a switch. If GDP - inactive If GTP - active

G-protein When active (GTP), the protein binds to another protein (enzyme) and alters its activation. Active state is only temporary.

G-protein linked receptors Very widespread and diverse in functions. Ex - vision, smell,

G-protein linked receptors Many diseases work by affecting g-protein linked receptors. Ex - whooping cough, botulism, cholera, some cancers

G-protein linked receptors Up to 60% of all medicines exert their effects through G-protein linked receptors.

Signal-Transduction Pathways The further amplification and movement of a signal in the cytoplasm. Often has multiple steps using relay proteins such as Protein Kinases.

Protein Kinase General name for any enzyme that transfers Pi from ATP to a protein. About 1% of our genes are for Protein Kinases.

Protein Phosphorylation The addition of Pi to a protein, which activates the protein. Usually adds Pi to Serine or Threonine.

Amplification Protein Kinases often work in a cascade with each being able to activate several molecules. Result - from one signal, many molecules can be activated.

Proteins The molecular tools of the cell. Made of C,H,O,N, and sometimes S.

Functions of Proteins Structure Enzymes Antibodies Transport Movement Receptors Hormones

Proteins Polypeptide chains of Amino Acids linked by “peptide bonds”.

Amino Acids All have a Carbon with four attachments: -COOH (acid) -NH 2 (amine) -H -R (some other side group)

Amino Acids

R groups 20 different kinds: Nonpolar - 9 AA Polar - 6 AA Electrically Charged Acidic - 2 AA Basic - 3 AA

Amino Acids

Levels Of Protein Structure Organizing the polypeptide into its 3-D functional shape. Primary Secondary Tertiary Quaternary

Primary Sequence of amino acids in the polypeptide chain. Many different sequences are possible with 20 AAs.

Secondary 3-D structure formed by hydrogen bonding between parts of the peptide backbone. Two main secondary structures:  helix  β pleated sheets

Tertiary Bonding between the R groups. Examples: hydrophobic interactions ionic bonding Disulfide bridges (covalent bond) Can also include H bonds

Quaternary When two or more polypeptides unite to form a functional protein. Example: hemoglobin

Is Protein Structure Important?

Denaturing Of A Protein Events that cause a protein to lose structure (and function). Example: pH shifts high salt concentrations heat

Enzymes Biological catalysts made of protein. Cause the rate of a chemical reaction to increase.

Chemical Reaction AB + CD AC + BD AB and CD are “reactants” AC and BD are “products”

Enzymes Lower the activation energy for a chemical reaction to take place.

Enzyme Terms Substrate - the material and enzyme works on. Enzyme names: Ex. Sucrase - ase name of an enzyme 1st part tells what the substrate is. (Sucrose)

Enzyme Name Some older known enzymes don't fit this naming pattern. Examples: pepsin, trypsin

Active Site The area of an enzyme that binds to the substrate. Structure is designed to fit the molecular shape of the substrate. Therefore, each enzyme is substrate specific.

Environment Factors that change protein structure will affect an enzyme. Examples: pH shifts temperature salt concentrations

Enzyme Inhibitors Competitive - mimic the substrate and bind to the active site. Noncompetitive - bind to some other part of the enzyme.

Allosteric Regulation The control of an enzyme complex by the binding of a regulatory molecule. Regulatory molecule may stimulate or inhibit the enzyme complex.

Allosteric Regulation

Control of Metabolism Is necessary if life is to function. Controlled by switching enzyme activity "off" or "on” or separating the enzymes in time or space.