Unit 4: Cell Communication and Cell Cycle

Vocabulary flashcards covering essential terms and concepts for Unit 4: Cell Communication and Cell Cycle.

Cell Communication

The generation, transmission, reception, and response to chemical signals between cells.

Signal Transduction Pathway

A series of molecular events that link signal reception to a specific cellular response.

Ligand

A molecule that specifically binds to a receptor protein to initiate signaling.

Receptor Protein

Cellular protein that recognizes and binds a ligand, triggering a signal inside the cell.

G Protein–Coupled Receptor (GPCR)

A membrane receptor in eukaryotes that activates a G protein upon ligand binding.

Second Messenger

Small intracellular molecule (e.g., cyclic AMP) that relays and amplifies a signal.

Phosphorylation Cascade

Sequential activation of protein kinases that amplify a signal in a pathway.

Amplification (in signaling)

Increase in the magnitude of a cellular response as the signal is relayed.

Quorum Sensing

Bacterial communication via chemical signals that depend on population density.

Neurotransmitter

Local regulator released by neurons to transmit signals across synapses.

Plasmodesmata

Cytoplasmic channels that connect plant cells, allowing direct cell–cell transport.

Antigen-Presenting Cell (APC)

Immune cell that displays antigens to T cells through direct contact.

Helper T Cell

T lymphocyte that coordinates immune responses by activating other immune cells.

Cytotoxic (Killer) T Cell

T cell that destroys infected or cancerous cells by direct contact.

Morphogen

Signaling molecule that forms a gradient and patterns tissues during development.

Endocrine Signal

Hormone that travels long distances through the bloodstream to target cells.

Insulin

Pancreatic hormone that lowers blood glucose; example of negative feedback.

Glucagon

Pancreatic hormone that raises blood glucose; counteracts insulin.

Feedback Mechanism

Loop by which a biological system self-regulates in response to internal or external change.

Negative Feedback

Regulatory process that counteracts a deviation from a set point to maintain homeostasis.

Positive Feedback

Regulatory process that amplifies a response, driving the system further from the set point.

Apoptosis

Programmed cell death resulting from specific signaling pathways.

Cell Cycle

Ordered series of events for eukaryotic cell growth, DNA replication, and division.

Interphase

Portion of the cell cycle consisting of G1, S, and G2 phases where the cell grows and duplicates DNA.

G1 Phase

First gap phase of interphase characterized by cell growth and normal functions.

S Phase

Synthesis phase of interphase in which DNA replication occurs.

G2 Phase

Second gap phase of interphase where the cell prepares for mitosis.

Mitosis

Process that divides the nucleus, ensuring each daughter cell receives an identical genome.

Cytokinesis

Division of the cytoplasm following mitosis, forming two separate daughter cells.

G0 Phase

Resting or quiescent stage where a cell is not actively dividing but can reenter the cycle.

Checkpoint

Control point in the cell cycle that verifies whether critical processes have been completed correctly.

Cyclin

Regulatory protein whose concentration fluctuates to control progression through the cell cycle.

Cyclin-Dependent Kinase (CdK)

Enzyme that, when bound to cyclin, phosphorylates target proteins to advance the cell cycle.

Disruption of Cell Cycle

Failure of normal checkpoints leading to uncontrolled division, cancer, or apoptosis.

Homeostasis

Maintenance of a stable internal environment in an organism.

Epinephrine

Hormone that initiates glycogen breakdown via signal transduction in mammals.

Cytokine

Secreted protein that regulates gene expression and cell division in immune responses.

Phosphorylation

Addition of a phosphate group to a protein, often regulating its activity.

Local Regulator

Signal molecule that affects target cells in the vicinity of the secreting cell.

Long-Distance Signal

Chemical messenger, such as a hormone, that travels far to reach its target cells.