Question 1

The binding of a ligand to a G protein--coupled receptor will result in activation of adenylyl cyclase, which in turn will initiate which of the following pathways?&#10;A) Ca&#178;&#8314;-calmodulin&#10;B) cAMP&#10;C) cGMP&#10;D) MAP kinase&#10;E) Phospholipase C-Ca&#178;&#8314;

Accepted Answer

Activation of adenylyl cyclase by a ligand binding to a G protein-coupled receptor initiates the cAMP pathway.

Question 2

Which of the following is most likely to initiate apoptosis?&#10;A) Apaf-1&#10;B) Bcl-2&#10;C) Caspase 3&#10;D) Caspase 9&#10;E) DNA protein kinase

Accepted Answer

Caspase 9 is an initiator caspase that is activated in the intrinsic pathway of apoptosis, often in response to signals such as DNA damage. It is part of the apoptosome complex and plays a crucial role in the initiation of the caspase cascade leading to apoptosis.

Question 3

A ligand binding to a(n) _____ receptor directly results in phosphorylation&#10;A) Cytokine&#10;B) G protein-coupled&#10;C) Intracellular&#10;D) Threonine kinase&#10;E) Tyrosine kinase

Accepted Answer

Tyrosine kinases are a family of enzymes that add a phosphate group to the amino acid tyrosine in proteins. Ligand binding to a tyrosine kinase receptor results in auto-phosphorylation of the receptor, which initiates downstream signaling events.

Question 4

An action potential triggers the release of a(n)&#10;A) Eicosanoid&#10;B) Neurotransmitter&#10;C) Paracrine&#10;D) Peptide hormone&#10;E) Steroid hormone

Accepted Answer

An action potential triggers the release of a neurotransmitter. When an action potential reaches the axon terminal, it causes the release of neurotransmitters that then bind to receptors on postsynaptic cells, transmitting the signal across synapses.

Question 5

A secreted chemical messenger meant to act on an adjacent cell is called a(n)&#10;A) Autocrine&#10;B) Hormone&#10;C) Neurohormone&#10;D) Neurotransmitter&#10;E) Paracrine

Accepted Answer

A paracrine messenger is a secreted chemical that acts on nearby cells, but not on the cell that secreted it. Autocrine messengers act on the cell that secreted them, while hormones and neurohormones act on distant cells. Neurotransmitters are chemical messengers that transmit signals across chemical synapses between neurons and other cells.

Question 6

Which of the following functions by diffusing across the cell membrane to bind to intracellular protein receptors, resulting in gene activation or repression?&#10;A) Acetylcholine&#10;B) Insulin&#10;C) Nitric oxide&#10;D) Prostaglandin&#10;E) Testosterone

Accepted Answer

Testosterone is a steroid hormone that can diffuse across the cell membrane and bind to intracellular protein receptors, resulting in gene activation or repression. Acetylcholine, insulin, nitric oxide, and prostaglandin are all examples of signaling molecules that bind to extracellular receptors and activate signaling pathways through second messengers or other mechanisms.

Deck 3: Cell Signaling