AP Bio Ch 11

In which of the following ways do plant hormones differ from hormones in animals?

• Plant hormones may travel in air or through vascular systems.
• Animal hormones are primarily for mating and embryonic development.
• Animal hormones are found in much greater concentration.
• Plant hormones interact primarily with intracellular receptors.

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.

What explains the increased concentration of Ca²⁺ in the ER?

• Calcium ions are actively imported from the cytoplasm into the ER.
• Calcium levels in the blood or other body fluids are extremely low.
• Calcium cannot enter the plasma membrane through ion channels.
• Calcium concentration is kept low in the cytoplasm because of its high usage level.

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

The human population's life expectancy has increased significantly but seems to have an upper limit. Which of the following might be described as an ecological consequence of passing that upper limit by regulating cell death?

• an increase in the relative frequency of deaths from cancer
• a decrease in the birth rate
• an increase in the total population of humans on the planet
• an increased need for gerontologists and other professionals to care for the elderly

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.