Cell Communication and the Cell Cycle

Vocabulary terms and definitions from the lecture notes on cell signaling (4.1-4.3), feedback (4.4), and the eukaryotic cell cycle and its regulation (4.5-4.6).

Direct contact

A type of cell signaling where cells transmit information to adjacent cells.

Local signaling

Cell communication involving the emission of molecules that target cells in the immediate area, such as neurotransmitters or quorum sensing.

Long distance signaling (endocrine)

Signaling where molecules called hormones travel through the blood or lymph in animals to reach target cells.

Reception

The first step of cell communication where a chemical signal binds to a specific receptor protein in a target cell.

Ligand

A chemical signal, such as a small protein (peptide) or a small molecule, that binds to a specific receptor protein.

Intracellular Receptor

Receptor proteins located inside the cell; the ligands must pass through the membrane to reach them.

Membrane Receptor

Receptor proteins that are bound to the cell membrane, such as G-Protein coupled Receptors.

G-Protein coupled Receptors

A type of receptor where a ligand binds and changes the receptor's shape, which activates a g-protein by phosphorylation.

Signal Transduction

The intermediate stage between reception and the cellular response.

Kinases

Enzymes that relay a signal by transferring phosphates from ATP (or GTP) to other molecules to activate them.

Phosphorylation Cascades

A process during transduction where phosphates are transferred between several kinases in a sequence.

Second Messengers

Small molecules, such as cAMP, that can activate many different signal pathways.

Adenylate Cyclase

An enzyme that converts ATP to the second messenger cAMP.

Ligand-Gated Ion Channels

Ion channels that open or close specifically when a ligand binds to them.

Apoptosis

A signal that triggers programmed cell death.

Epinephrine

A signaling molecule that triggers the Flight or Flight response.

Cytokines

Signaling molecules released by immune cells when an infection is detected to trigger an inflammatory response.

Pheromones

Signaling molecules released by yeast that cause cells to express genes required for mating.

Ethylene

A gas released by ripening fruit that triggers enzymes in nearby fruits to ripen as well.

Homeostasis

The maintenance of a stable internal environment, including temperature, pH, solute concentrations, and water.

Negative Feedback

A feedback mechanism where the cellular response is opposite or counteracting the original stimulus.

Positive Feedback

A feedback mechanism where a stimulus is amplified by the cellular response.

Cell Cycle

The growth and reproductive cycle of a eukaryotic cell, which is highly regulated by signals.

Interphase

The phase of the cell cycle consisting of G1, S, and G2, where the cell grows and prepares for division.

G1 Phase

The first part of Interphase where the cell is active, duplicating organelles, and growing.

S Phase

The part of Interphase where DNA is copied or replicated to form sister chromatids.

G2 Phase

The final part of Interphase where proteins are synthesized, ATP is produced, and centrosomes are copied.

Mitosis

The process of eukaryotic cell division that transfers all DNA to two genetically identical daughter cells.

G0 Phase

A nondividing stage of the cell cycle that can be exited to reenter G1 in response to a signal.

Chromatin

The uncondensed form of DNA present during interphase.

Sister Chromatids

Two identical chromosomes connected by a centromere.

Prophase

The mitotic stage where sister chromatids condense, spindle fibers form, and the nuclear envelope begins to breakdown.

Metaphase

The mitotic stage where spindle fibers align the chromosomes along the equator of the cell.

Anaphase

The mitotic stage where sister chromatids are split and pulled in opposite directions toward the poles.

Telophase

The mitotic stage where the spindle breaks down, new nuclear envelopes reform, and the cytoplasm begins to divide.

Cytokinesis

The final dividing of the cell membrane to form two distinct daughter cells.

Cyclins

Proteins that build up as a cell proceeds through the cycle; they must reach a specific concentration to advance to the next phase.

Cyclin-dependent kinases

Enzymes activated by cyclins that trigger the transduction pathways allowing a cell to advance through checkpoints.

Cancer

A condition resulting from uncontrollable cell division, often occurring when checkpoints and apoptosis fail.