AP Bio - Ch. 11

When a neuron responds to a particular neurotransmitter by opening gated ion channels, the neurotransmitter is serving as which part of the signal pathway?

• relay molecule
• endocrine molecule
• signal molecule
• receptor

Which of the following is true for the signaling system in an animal cell that lacks the ability to produce GTP?

• It could activate only the epinephrine system.
• It would be able to carry out reception and transduction but would not be able to respond to a signal.
• It would not be able to activate and inactivate the G protein on the cytoplasmic side of the plasma membrane.
• It would employ a transduction pathway directly from an external messenger.

Receptor tyrosine kinases (RTKs) are found at high levels on various cancer cells. A protein, Herceptin, has been found to bind to an RTK known as HER2. This information can now be utilized in breast cancer treatment if which of the following is true?

• If Herceptin is found in the breast lymph nodes of the patient.
• If the patient's cancer cells have detectable HER2.
• If the patient's genome codes for the HER2 receptor.
• If HER2, administered by injection, is in sufficient concentration.

At puberty, an adolescent female body changes in both structure and function of several organ systems, primarily under the influence of changing concentrations of estrogens and other steroid hormones. How can one hormone, such as estrogen, mediate so many effects?

• Estrogen is produced in very large concentration and therefore diffuses widely.
• Estrogen binds to specific receptors inside many kinds of cells, each of which have different responses to its binding.
• The subcomponents of estrogen, when metabolized, can influence cell response.
• Estrogen is kept away from the surface of any cells not able to bind it at the surface.

What are scaffolding proteins?

• ladderlike proteins that allow receptor–ligand complexes to climb through cells from one position to another
• proteins that can reach into the nucleus of a cell to affect transcription
• microtubular protein arrays that allow lipid–soluble hormones to get from the cell membrane to the nuclear pores
• large molecules to which several relay proteins attach to facilitate cascade effects

Which of the following describes the events of apoptosis?

• The cell dies and the presence of its fragmented contents stimulates nearby cells to divide.
• Its DNA and organelles are fragmented, the cell shrinks and forms blebs, and then is phagocytized.
• Its DNA and organelles shrink then it dies.
• Its nucleus and organelles are lysed, then the cell enlarges and bursts.

Phosphorylation cascades involving a series of protein kinases are useful for cellular signal transduction because

• they amplify the original signal manyfold.
• they always lead to the same cellular response.
• they are species specific.
• the number of molecules used is small and fixed.

Of the following, a receptor protein in a membrane that recognizes a chemical signal is most similar to

• a metabolic pathway operating within a specific organelle.
• an enzyme having an optimum pH and temperature for activity.
• the active site of an allosteric enzyme that binds to a specific substrate.
• tRNA specifying which amino acids are in a polypeptide.

The termination phase of cell signaling requires which of the following?

• incompatibility of the binding of the signal molecule to the receptor
• converting ATP to cAMP
• activation of a different set of relay molecules
• apoptosis

Lipid–soluble signaling molecules, such as testosterone, cross the membranes of all cells but affect only target cells because

• intracellular receptors are present only in target cells.
• only target cells retain the appropriate DNA segments.
• only target cells possess the cytosolic enzymes that transduce the testosterone.
• most cells lack the Y chromosome required.