Cell Signaling & Homeostasis: Key Concepts and Processes

Homeostasis

Maintaining internal stability

Receptor

Detects stimulus

Stimulus

Change in environment

Effector

Responds to restore balance

Response

The body's action to a change

Feedback inhibition

Process that uses feedback to regulate systems

Passive transport

Movement without energy

Active transport

Movement requiring ATP

Hypertonic

Water leaves cell - Shrinks

Hypotonic

Water enters cell - Swells

Isotonic

Equal movement of water

Ligand

Molecule that binds to receptor

Signal transduction

The process where a cell converts an external signal (like a hormone binding) into an internal response.

Pathway

The series of molecular steps inside the cell that carry the signal to produce a specific response.

Inhibitor

Molecule that blocks a reaction or signal

Transduction

Step-by-step relay of signal inside cell

Phosphorylation

Adding phosphate → activates protein

Dephosphorylation

Removing phosphate → deactivates protein

Second messenger

Internal molecules that amplify