Unit 4: Cell Communication and Cell Cycle Part 1

Modules 20,23,21/22

Population

A group of organisms of the same species living in the same area.

Signaling molecule

A chemical released by a cell that affects other cells.

Target cell

A cell that has a receptor for a specific signaling molecule.

Ligand

A molecule that binds to a receptor.

Quorum sensing

A process where bacteria communicate using signaling molecules to sense population size.

Hormone

A chemical messenger released into the bloodstream that affects distant cells.

Plasmodesmata

Small channels between plant cells that allow materials to pass through.

Sensor

A receptor that detects a change in the environment.

Set point

The normal value the body tries to maintain.

Negative feedback

A process that reverses a change to bring conditions back to normal.

Positive feedback

A process that increases or strengthens a change.

Signal transduction

The process of converting an outside signal into a response inside the cell.

Amplification

When one signal causes many molecules to react, making the response stronger.

G protein-coupled receptor (GPCR)

A membrane receptor that activates a G protein when a ligand binds.

Second messenger

A small molecule inside the cell that spreads the signal.

Cyclic adenosine monophosphate (cAMP)

A second messenger that activates other proteins inside the cell.

Kinase

An enzyme that adds a phosphate group to a protein.

Signaling cascade

A chain reaction of proteins activating each other inside a cell.

Receptor-protein kinase

A receptor that adds phosphate groups to proteins when activated.

Ligand-gated channel

A channel that opens when a ligand binds, allowing ions to pass through.

Gene expression

The process of turning a gene into a protein.

Mutation

A change in DNA sequence.

Agonist

A molecule that binds to a receptor and activates it.

Antagonist

A molecule that binds to a receptor but blocks it from working.

Blood sugar regulation (negative feedback)

When blood sugar rises insulin lowers it and when it drops glucagon raises it to return to normal.

Labor/birth (positive feedback)

Oxytocin causes contractions which release more oxytocin until birth occurs.