Chapter 11 Vocabulary

etiolation

Plant morphological adaptations for growing in darkness.

tropism

A growth response that results in the curvature of whole plant organs toward or away from stimuli due to differential rates of cell elongation.

Phototropism

Growth of a plant shoot toward or away from light.

Photomorphogenesis

Effects of light on plant morphology.

Epinephrine

A catecholamine that, when secreted as a hormone by the adrenal medulla, mediates "fight-or-flight" responses to short-term stresses; also released by some neurons as a neurotransmitter; also called adrenaline.

Phytochrome

A type of light receptor in plants that mostly absorbs red light and regulates many plant responses, such as seed germination and shade avoidance.

Expansin

Plant enzyme that breaks the cross-links (hydrogen bonds) between cellulose microfibrils and other cell wall constituents, loosening the wall's fabric.

reception

In cellular communication, the first step of a signaling pathway in which a signaling molecule is detected by a receptor molecule on or in the cell

receptor tyrosine kinase (RTK)

A receptor protein spanning the plasma membrane, the cytoplasmic (intracellular) part of which can catalyze the transfer of a phosphate group from ATP to a tyrosine on another protein.

Response

In cellular communication, the change in a specific cellular activity brought about by a transduced signal from outside the cell.

second messenger

A small, nonprotein, water-soluble molecule or ion, such as a calcium ion (Ca2+) or cyclic AMP, that relays a signal to a cell's interior in response to a signaling molecule bound by a signal receptor protein.

signal transduction pathway

A series of steps linking a mechanical, chemical, or electrical stimulus to a specific cellular response.

transduction

In cellular communication, the conversion of a signal from outside the cell to a form that can bring about a specific cellular response

scaffolding protein

A type of large relay protein to which several other relay proteins are simultaneously attached, increasing the efficiency of signal transduction.

phosphorylation cascade

A series of protein phosphorylations occurring sequentially in which each protein kinase phosphorylates the next, activating it; often found in signaling pathways.

protein kinase

An enzyme that transfers phosphate groups from ATP to a protein, thus phosphorylating the protein.

protein phosphatase

An enzyme that removes phosphate groups from (de- phosphorylates) proteins

inositol trisphosphate (IP3)

A second messenger that functions as an intermediate between certain signaling molecules and a subsequent second messenger, Ca2+, by causing a rise in cytoplasmic Ca2+ concentration.

ligand-gated ion channel

A transmembrane protein containing a pore that opens or closes as it changes shape in response to a signaling molecule (ligand), allowing or blocking the flow of specific ions

adenylyl cyclase

An enzyme that converts ATP to cyclic AMP in response to an extracellular signal.

Apoptosis

A type of programmed cell death, which is brought about by activation of enzymes that break down many chemical components in the cell.

Cyclic AMP (cAMP)

a ring-shaped molecule made from ATP that is a common intracellular signaling molecule (second messenger) in eukaryotic cells.

diacylglycerol (DAG)

A second messenger produced by the cleavage of the phospholipid PIP2 in the plasma membrane.

G protein

A GTP-binding protein that relays signals from a plasma membrane signal receptor, known as a G protein-coupled receptor, to other signal transduction proteins inside the cell.

G protein-coupled receptor (GPCR)

A signal receptor protein in the plasma membrane that responds to the binding of a signaling molecule by activating a G protein.

hormone

In multicellular organisms, one of many types of secreted chemicals that are formed in specialized cells, travel in body fluids, and act on specific target cells in other parts of the organism, changing the target cells' functioning.