Protein Regulation and Cell Signaling Flashcards

Comprehensive vocabulary flashcards generated from lecture notes covering protein regulation, cell signaling mechanisms, signaling functions, and drug interactions.

Negative feedback

A regulatory mechanism where a later product of a pathway inhibits an earlier step, decreasing pathway activity or shutting the pathway off.

Feedback inhibition

Occurs when a later product of a pathway inhibits an earlier step to prevent wasting energy and building blocks.

Conformation

The specific shape of a protein.

Stabilizing a conformation

Keeping a protein held more often in one particular shape needed for its activity through ligand binding.

Relay

A function of a signaling cascade where the signal is passed along sequentially from one protein to the next.

Amplify

A function of a signaling cascade where one activated molecule activates hundreds or thousands of molecules at the next step to turn a small initial signal into a large response.

Integrate

A function of a signaling cascade where several incoming signals or pieces of information are combined into one cellular decision.

Distribute

A function of a signaling cascade where the signal is sent to different effector proteins to produce cellular responses like survival, growth, division, or differentiation.

Exogenous

Originating or coming from outside the body, such as a drug taken into the body.

Endogenous

Produced inside the body, such as endorphins or enkephalins made by the body.

Therapeutic effect

The desired effect of a drug.

Side effect

An additional, unintended effect produced when a drug affects a pathway that influences multiple processes.

Apoptosis

Programmed cell death that can be triggered by specific signals or by the loss of necessary survival signals.

Fast signaling response

A cellular response that regulates existing proteins without needing gene expression in the nucleus, taking fractions of a second.

Slow signaling response

A cellular response involving the nucleus that changes gene expression and protein synthesis, taking hours, days, or longer.

Cell signaling

Communication between cells that coordinates their activities and determines cellular responses.

Receptor

A protein that receives information by binding a specific signaling molecule outside or inside the cell.

Signaling cascade

A sequence of activations where proteins inside the cell activate other proteins in turn following receptor binding.

Effector protein

A protein in a signaling cascade that executes the final cellular response, such as altering enzyme activity, cell shape, or gene expression.

Paracrine signaling

Local signaling where signaling molecules act on nearby target cells within the same tissue rather than traveling through the bloodstream.

cGMP (cyclic GMP)

A signaling molecule produced by guanylyl cyclase in response to nitric oxide that causes smooth muscle relaxation and blood vessel widening.

PDE5 (phosphodiesterase type 5)

An enzyme that breaks down cGMP, terminating its signaling response.

Sildenafil

The generic drug name for Viagra; a PDE5 inhibitor that reduces cGMP breakdown, prolonging smooth muscle relaxation and vessel dilation.

Endocrine signaling

Long-distance signaling where a cell releases hormones into the bloodstream to reach distant target cells throughout the body.

Neuronal signaling

Very fast, targeted signaling where an electrical signal travels along a neuron to release neurotransmitters to target cells.

Contact-dependent signaling

Signaling requiring physical cell-to-cell contact because the signaling molecule remains attached to the membrane of the signaling cell.

Delta and Notch

In developing brain contact-dependent signaling, Delta is the membrane-bound signaling molecule on a neuron-forming cell and Notch is the receptor on a physically touching cell.

Ligand

A molecule that binds to a specific site on a protein.

Binding site

The specific region of a protein where a ligand binds.

Orthosteric binding

Competitive binding of a molecule at the main active site where the natural ligand or substrate normally binds.

Allosteric binding

Noncompetitive binding of a molecule somewhere other than the active site, inducing a conformational change in the protein.

Phosphorylation

The addition of a phosphate group to a protein, which changes the protein's conformation and function.

Kinase

An enzyme that adds a phosphate group to a protein.

Dephosphorylation

The removal of a phosphate group from a protein, altering its shape and function.

Phosphatase

An enzyme that removes a phosphate group from a protein.

Post-translational modification

A chemical or structural modification made to a protein after it has been translated, such as phosphorylation, acetylation, or ubiquitination.

Quaternary structure

The structural arrangement of multiple polypeptide chains coming together to form a functional complex or protein machine.

G protein

A GTP-binding protein that acts as an ON/OFF switch depending on whether it is bound to GTP (active/ON) or GDP (inactive/OFF).

Motor proteins

Proteins that use energy from ATP binding and hydrolysis to undergo repeated conformational changes and walk along the cytoskeleton.