Unit 4: Cell Communication and Cell Cycle (copy)

Taxis

Movement of an organism in response to a stimulus, which can be positive (toward the stimulus) or negative (away from the stimulus).

Chemotaxis

Movement in response to chemicals.

Signal transduction

The process by which an external signal is transmitted to the inside of a cell, usually involving binding of a signaling molecule to a receptor.

Ligands

Signaling molecules that bind to receptors and trigger a response by changing the shape of the receptor protein.

Signal transduction pathway

A series of molecular changes that result in a cellular response after a signaling molecule binds to a receptor.

Plasma membrane receptor

A type of receptor that transmits signals from the extracellular space into the cytoplasm.

Ligand-gated ion channels

Membrane receptors that open or close an ion channel upon binding a particular ligand.

Catalytic (enzyme-linked) receptors

Receptors with an enzymatic active site that is activated by ligand binding at the extracellular surface.

G-protein-linked receptor

A receptor that binds to a G-protein upon ligand binding, activating secondary messengers within the cell.

Cyclic AMP (cAMP)

An important second messenger that relays signals inside the cell.

Homeostasis

The set of conditions under which living things can successfully survive.

Negative feedback pathway

A control mechanism that turns itself off using the end product of the pathway, inhibiting the process from beginning.

Positive feedback pathway

A control mechanism where the end product stimulates the pathway further instead of inhibiting it.

Cell cycle

The period from the beginning of one cell division to the beginning of the next division.

Interphase

The growing phase of the cell cycle when the cell prepares for division.

S phase

The phase during interphase when the cell replicates its genetic material.

Sister chromatids

Identical strands of DNA held together by a centromere after DNA replication.

Centromere

The structure that holds sister chromatids together.

Cyclin-dependent kinases (CDKs)

Proteins that regulate the cell cycle progression in conjunction with cyclins.

Tumour suppressor genes

Genes that produce proteins preventing the conversion of normal cells into cancer cells.

Oncogenes

Mutated genes that can convert normal cells into cancerous cells.

Mitosis

The process of cellular division occurring in four stages: prophase, metaphase, anaphase, and telophase.

Cytokinesis

The final step in cell division where the cytoplasm and plasma membranes pinch off to form two distinct daughter cells.

Chromatin

The form of genetic material during interphase when chromosomes are decondensed.