exam 3 objectives and notes

What is a signaling cell?

A cell that produces and releases a signaling molecule to communicate with other cells.

What defines endocrine signaling?

It involves long-distance signaling where hormones are secreted into the bloodstream and travel to distant target cells.

What is paracrine signaling?

Signaling where the signal molecule is released into the extracellular space and acts on nearby target cells.

Give an example of a growth factor in paracrine signaling.

Nerve growth factor.

What is a neuron in neuronal signaling?

The signaling cell that releases neurotransmitters at synapses.

What characterizes neuronal signaling?

A nerve impulse travels down an axon, leading to neurotransmitter release at synapses.

What are GPCRs and their function?

G-protein-coupled receptors are transmembrane proteins that bind extracellular ligands and activate G-proteins leading to intracellular signaling.

What are the components of a G-protein?

A heterotrimeric protein with three subunits: alpha (α), beta (β), and gamma (γ).

How is a G-protein activated?

A ligand binding to GPCR promotes the exchange of GDP for GTP on the α subunit.

What role do second messengers play?

They are intracellular signaling molecules that amplify and propagate the signal inside the cell.

What is the function of protein kinases in signaling pathways?

They add phosphate groups to proteins, activating or inactivating them.

What is positive feedback in signaling pathways?

A mechanism that amplifies the signal, like in blood clotting or childbirth.

What differentiates enzyme-coupled receptors from GPCRs?

Enzyme-coupled receptors have intrinsic enzymatic activity or associate with an enzyme, whereas GPCRs signal through G-proteins.

What characterizes receptor tyrosine kinases (RTKs)?

They have a single-pass transmembrane domain and possess kinase activity to phosphorylate tyrosine residues.

What is the Ras pathway activated by RTKs?

A signaling cascade that activates MAP kinases leading to changes in gene expression.

What is the PI-3-Kinase-Akt pathway's role in signaling?

It regulates cell survival and growth by preventing apoptosis.

What do ligands do in cell signaling?

They bind to receptors to initiate signaling pathways inside the cell.

What is the action of protein phosphatases?

They remove phosphate groups from proteins, reversing the action of kinases.

Why must cAMP be broken down rapidly?

To ensure precise, transient, and controlled signaling, allowing the cell to quickly reset for future signals.