AP Biology - Cell Communication and Cell Cycle

Flashcards for Cell Communication and Cell Cycle based on lecture notes.

Signal Transduction Pathway

A series of molecular steps by which a signal on a cell’s surface is converted into a specific cellular response.

Ligand

A molecule that binds to a receptor.

Receptor

Protein on/in a cell that binds to a ligand and initiates a response.

Second Messenger

Small molecules (e.g., cAMP, Ca²⁺, IP₃) that help amplify and distribute signals inside the cell.

G Protein-Coupled Receptor (GPCR)

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

Protein Kinase

An enzyme that adds phosphate groups to proteins (phosphorylation).

Protein Phosphatase

An enzyme that removes phosphate groups from proteins.

Amplification

When one signal molecule activates many molecules inside the cell.

Autocrine

Signaling to the same cell that secreted the signal.

Paracrine

Signal acts on nearby cells.

Endocrine

Signal (often a hormone) travels through the bloodstream to distant cells.

Interphase

The phase where the cell grows and prepares to divide (G₁, S, G₂).

G₁ Phase

Cell grows and carries out normal functions.

S Phase

DNA is replicated.

G₂ Phase

Cell prepares for mitosis; checks for DNA errors.

Mitosis

Division of the nucleus into two identical nuclei.

Cytokinesis

Division of the cytoplasm into two daughter cells.

Checkpoints

Control points (G₁, G₂, M) where the cell decides whether to continue.

Cyclin

Protein that regulates the timing of the cell cycle.

CDK (Cyclin-Dependent Kinase)

Enzyme that is active only when bound to cyclin.

MPF (Maturation Promoting Factor)

A cyclin-CDK complex that triggers mitosis.

Apoptosis

Programmed cell death, important for development and damaged cells.

Prophase

Chromatin condenses into chromosomes; spindle forms.

Metaphase

Chromosomes line up at the metaphase plate.

Anaphase

Sister chromatids separate and move to opposite poles.

Telophase

Nuclear envelope re-forms; chromosomes decondense.

Centrosome/Centriole

Organizes spindle fibers in animal cells.

Spindle Fibers

Microtubules that help separate chromosomes.

Oncogene

A mutated gene that causes uncontrolled cell growth.

Tumor Suppressor Gene

A gene that prevents uncontrolled cell division; ex: p53.

Metastasis

Spread of cancer cells to other parts of the body.