AP Biology Unit 4

Cell Communication

Critical for the function and survival of cells, responsible for the growth and development of multicellular organisms.

Direct Contact

Communication through cell junctions where signaling substances pass between adjacent cells, e.g., gap junctions in animal cells and plasmodesmata in plant cells.

Paracrine Signaling

Local regulators released by secreting cells that cause a response in target cells at a short distance.

Synaptic Signaling

Occurs in animal nervous systems where neurons secrete neurotransmitters to diffuse across the synaptic cleft to target cells.

Hormones

Chemical messengers used for long distance signaling in animals and plants.

Signal Transduction Pathway

A series of molecular events and reactions that lead to a cellular response after ligand-receptor binding.

Phosphorylation

The addition of a phosphate group to a protein or other organic molecule, often modifying its activity.

Dephosphorylation

The removal of a phosphate group from a molecule, often reversing the effect of phosphorylation.

G Protein-Coupled Receptors (GPCRs)

A large family of cell surface receptors that play a role in sensory systems and signal transduction.

Cell Cycle

The life cycle of a cell from its formation until it divides, consisting of interphase and mitotic phase.

Mitosis

The process by which the nucleus of a cell divides, resulting in two identical diploid daughter cells.

Checkpoints in the Cell Cycle

Regulatory points in the cell cycle that ensure proper division and functioning of the cell.

Apoptosis

Programmed cell death, a process that is triggered when cells cannot repair damage.

Benign Tumor

A mass of abnormal cells that do not spread to other parts of the body.

Malignant Tumor

Cancerous cells that can spread to other parts of the body, often through metastasis.

Homeostasis

The state of relatively stable internal conditions maintained by biological systems.