chapter 21 cell signaling and homeostasis

Protein Kinases

Enzymes that add phosphate groups to proteins

Negative feedback

A regulatory mechanism where a deviation from a set point triggers a response to restore the set point.

Endocrine signaling

Long-distance signaling where hormones are secreted into the bloodstream and travel to target cells throughout the body.

Paracrine signaling

A type of cell signaling where a cell releases a signal that affects nearby target cells.

Glucose homeostasis

The maintenance of stable blood glucose levels through the action of hormones like insulin and glucagon.

Electrogenic pumps

Membrane proteins that generate voltage across the membrane by transporting ions against their electrochemical gradients.

Simple diffusion

Movement across a membrane without the help of membrane proteins; molecules directly cross the phospholipid bilayer.

Intracellular receptors

Proteins located inside the cell that bind to lipid-soluble ligands

Synaptic signaling

A type of cell signaling that occurs between neurons

Facilitated diffusion

Movement across a membrane with the assistance of membrane proteins (e.g.

Primary active transport

A transport process that directly uses ATP to move substances against their concentration gradients.

Osmosis

The movement of water across a semipermeable membrane from an area of high water concentration to an area of low water concentration.

Positive feedback

A regulatory mechanism where a change is reinforced

Reception (in signal transduction)

The initial step in signal transduction where a ligand binds to its receptor

Electrochemical gradient

The combination of a chemical concentration gradient and an electrical potential gradient that drives the movement of charged ions across a membrane.

Phosphorylation cascade

A series of sequential activations of kinases

Glucagon

A hormone that raises blood glucose levels by stimulating glycogen breakdown.

Peptide hormones

Signaling molecules composed of chains of amino acids and are water-soluble

Diffusion

The spontaneous movement of particles from an area of high concentration to an area of low concentration until equilibrium is reached.

Cell-surface receptors

Proteins on the cell membrane that bind to lipid-insoluble ligands

Na⁺/K⁺‑ATPase

An enzyme that uses ATP to transport sodium ions (Na⁺) out of the cell and potassium ions (K⁺) into the cell

Response (in signal transduction)

The cellular activity that changes due to a signal

Amine hormones

Signaling molecules derived from amino acids

Insulin

A hormone that lowers blood glucose levels by promoting cellular uptake and glycogen storage.

Termination (in signal transduction)

The cessation of a signal when the ligand dissociates or receptors are deactivated.

Second Messengers

Small

Insulin signaling pathway

A complex network of proteins triggered by insulin that regulates glucose uptake and gene expression.

Transduction (in signal transduction)

The stage in cell signaling where intracellular relay molecules propagate the signal.

Secondary active transport

A transport process that uses the energy stored in the electrochemical gradient of one molecule to drive the transport of another molecule against its concentration gradient.

Membrane permeability

The extent to which a substance can pass through a cell membrane.

Homeostasis

The maintenance of stable internal conditions in an organism despite external changes.

Hormone amplification

The process by which downstream signaling cascades magnify the effect of hormones

Ligand

A molecule that binds to a receptor

Aquaporins

Membrane proteins that facilitate the rapid transport of water across the cell membrane.

Co-transport

A form of secondary active transport where the downhill movement of one solute is coupled with the uphill movement of another solute across the cell membrane.

Receptor

A protein that binds to a specific ligand

Amplification (in signal transduction)

The process by which one activated receptor can trigger many downstream molecules

Steroid hormones

Signaling molecules composed of four fused rings