Unit 4: Cell Communication and Cell Cycle (anjeline's version)

Cell communication

Mechanisms cells use to detect signals and change behavior accordingly.

Signal

A detectable cue that triggers a biological response.

Ligand

A signal molecule that binds to a receptor to initiate cell signaling.

Receptor

A protein that binds a ligand, initiating signal transduction.

Reception

Stage where a ligand binds its receptor.

Transduction

Activation of the receptor triggers intracellular events.

Response

Final effect of signaling, such as changes in gene expression.

Signal specificity

Same ligand can produce different responses in different cell types.

Target cell

Cell that responds to a signal due to having a specific receptor.

Amplification

One activated molecule triggers a large response by activating many downstream molecules.

Desensitization/resetting (signal termination)

Shutting down a signaling pathway through various mechanisms.

Paracrine signaling

Local signaling affecting nearby cells via secreted regulators.

Synaptic signaling

Neuron releases neurotransmitters into a synapse to signal a specific cell.

Endocrine signaling

Long-distance signaling where hormones are released into the bloodstream.

Hormone

A long-distance signaling molecule affecting cells with the correct receptor.

Autocrine signaling

Cell signals itself by releasing a molecule that binds its own receptors.

Cell-surface receptor

Receptor that binds extracellular ligands and transmits signals into the cell.

Intracellular receptor

Receptor in the cytoplasm or nucleus that binds ligands that cross the membrane.

Ligand-gated ion channel

Membrane receptor that opens or closes in response to ligand binding.

Receptor tyrosine kinase (RTK)

Membrane receptor that phosphorylates tyrosine residues upon ligand binding.

G protein-coupled receptor (GPCR)

Membrane receptor that activates an intracellular G protein upon ligand binding.

G protein

An intracellular relay protein activated by GPCRs that switches between active and inactive states.

Second messenger

A small molecule that relays and amplifies signals inside the cell.

Cyclic AMP (cAMP)

A common second messenger that activates protein kinases and amplifies responses.

Protein kinase

Enzyme that transfers a phosphate group from ATP to a target protein.

Protein phosphatase

Enzyme that removes phosphate groups from proteins.

Phosphorylation cascade

A series of protein kinases activating one another by phosphorylation.

Apoptosis

Programmed cell death that dismantles the cell without causing inflammation.

Negative feedback

Regulation where response reduces the initial stimulus.

Positive feedback

Regulation where response amplifies the initial stimulus.

Cell cycle

Ordered sequence of events from one cell division to the next.

Interphase

Phase of the cell cycle when the cell grows and replicates DNA.

G1 phase

Stage of cell growth where nutrients and signals are assessed.

S phase

Stage when DNA replication occurs, producing sister chromatids.

G2 phase

Stage of further growth and preparation for division.

Mitosis

Nuclear division ensuring each daughter nucleus receives identical chromosomes.

Cytokinesis

Division of the cytoplasm to form two separate daughter cells.

Sister chromatids

Identical copies of a duplicated chromosome joined together.

Centromere

Region that holds sister chromatids together.

Cell cycle checkpoint

Control point evaluating conditions and completion of key events.

Cyclin

Regulatory protein whose concentration rises and falls during the cell cycle.

Cyclin-dependent kinase (CDK)

Kinase that drives cell cycle events when activated by cyclins.

Growth factor

Protein signal that stimulates cell division.

Density-dependent inhibition

Normal cells stop dividing when crowded.

Anchorage dependence

Requirement for normal cells to be attached to a surface to divide.

Cancer

Breakdown of signaling and control leading to inappropriate cell division.

Proto-oncogene

Gene that promotes cell division or survival; can contribute to cancer if altered.

Oncogene

Mutated form of a proto-oncogene that drives excessive cell division.

Tumor suppressor gene

Gene that inhibits cell cycle progression or triggers apoptosis.

p53

Tumor suppressor protein that can cause cell cycle arrest or promote apoptosis.