Cell Communication and Cell Cycle Cheat Sheet

The core ideas of Cell Communication and Cell Cycle distilled into a single, scannable reference — perfect for review or quick lookup.

PiqCue — piqcue.com/cell-communication-cell-cycle/cheatsheet

Quick Reference

Signal Transduction

The process by which a cell converts an extracellular signal into a specific intracellular response through receptor activation, relay molecules, and second messengers.

G Protein-Coupled Receptors (GPCRs)

A large family of cell-surface receptors with seven transmembrane domains that activate G proteins when a ligand binds, which then activate downstream enzymes or ion channels.

Receptor Tyrosine Kinases (RTKs)

Cell-surface receptors that dimerize and autophosphorylate tyrosine residues upon ligand binding, creating docking sites for relay proteins.

Second Messengers

Small molecules (cAMP, Ca2+, IP3) that relay and amplify signals from receptors to targets inside the cell.

Cell Cycle Checkpoints

Regulatory points (G1, G2, metaphase) where the cell checks DNA integrity, replication, and spindle attachment before proceeding.

Cyclins and CDKs

Cyclins fluctuate during the cell cycle; CDKs, when cyclin-bound, phosphorylate targets to drive cell cycle progression.

Apoptosis

Programmed cell death via caspase activation, DNA fragmentation, and membrane blebbing without inflammation.

Key Terms at a Glance

Signal Transduction:The process of converting an extracellular signal into an intracellular response through a cascade of molecular interactions including receptor activation, relay proteins, and second messengers.

G Protein-Coupled Receptor (GPCR):A seven-transmembrane-domain cell-surface receptor that activates intracellular G proteins upon ligand binding, initiating signaling cascades via second messengers like cAMP.

Receptor Tyrosine Kinase (RTK):A cell-surface receptor that dimerizes and autophosphorylates tyrosine residues upon ligand binding, creating docking sites for intracellular relay proteins.

Cyclin-Dependent Kinase (CDK):A protein kinase that is active only when bound to its cyclin partner. Different cyclin-CDK complexes drive transitions between cell cycle phases by phosphorylating specific target proteins.

Tumor Suppressor Gene:A gene whose protein product inhibits cell division, promotes DNA repair, or triggers apoptosis. Loss-of-function mutations remove growth-inhibiting controls, contributing to cancer.

Oncogene:A mutated form of a proto-oncogene that is constitutively active, promoting uncontrolled cell growth and division. Oncogenes act as gain-of-function mutations that drive cancer.

Apoptosis:Programmed cell death executed by caspases, characterized by cell shrinkage, DNA fragmentation, and formation of apoptotic bodies. Unlike necrosis, it occurs without inflammation.

Aneuploidy:An abnormal number of chromosomes resulting from errors in chromosome segregation during cell division. Aneuploidy is a hallmark of many cancer cells.

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