Exam 7: Cell Communication and Multicellularity

Refer to the table below. The table lists four hormones and the human cell types that respond to them (yes) or do not respond to them (no).What must be true about the cells listed in the table?

You are studying a cell's response to a signal.After the cellular receptor binds the signal (ligand), you measure several responses.A transcription factor in one signal transduction pathway is inhibited, and an enzyme in a different signal transduction pathway is activated.This is an example of

Which molecule acts as a second messenger in the cascade by which epinephrine stimulates the activation of the enzyme glycogen phosphorylase in liver cells?

Refer to the figure below. It has been hypothesized that during development of the mammalian brain, neurons are first coupled through gap junctions to one another during the first few days after birth.These gap junctions provide a conduit for propagation of electrical activity as a flow of ions between neurons, as depicted in the figure on the left.However, it is thought that these gap junctions are replaced after this initial period with a chemical signaling system, as depicted in the figure on the right.This system involves one neuron secreting neurotransmitter compounds that carry the signal across the extracellular space to an adjacent neuron, where the electrical signal is continued.Design an experiment to test the hypothesis that gap junctions are replaced during the early days after birth.You may use rats and the compound halothane in your design.Halothane is a compound known to specifically bind to and block gap junctions.

Refer to the figure below. A biologist identifies a new signal transduction pathway in mouse cells that are stimulated by the compound L-alanine, represented above.Which statement makes a reasonable prediction about how D-alanine will interact with this pathway, and why?

If a signal transduction pathway involves amplification of the signal by a factor of 10 at each step, which set of numbers represents the sequence of molecules activated during a single signaling event?

Refer to the figure below. The figure shows a signal transduction pathway in a cell.How does the number of molecules change as the signal is carried in this pathway?

A single epinephrine molecule can cause the release of thousands of glucose molecules from glycogen in a liver cell.Why is this a useful feature of this signal transduction pathway?

Which statement regarding chemical signaling systems is false?

Nitric oxide (NO) participates in a signal transduction pathway that promotes relaxation of smooth muscle cells lining blood vessels and so increases blood flow.Nitric oxide accomplishes this by

Which statement about plasmodesmata is false?

Sketch a cell membrane receptor.Identify the parts of the receptor, and explain how each one functions.

A protein kinase can phosphorylate an enzyme and activate it by

Which statement about membrane receptors in a signal transduction pathway is true?

_______ are signaling molecules sent to distant cells and are usually transported via the circulatory system.

Refer to the figure below. Which action could the cell use to turn off the signal transduction pathway shown, as part of a regulatory mechanism?

The entry of a sperm into an egg causes a massive opening of _______ ion channels.

Gap junctions are a specialized component of cells that

Refer to the table below showing the observed characteristics of four species of algae. Which sequence of characteristics is consistent with the current thinking about the evolution of multicellularity?

Autocrine signals bind to