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Which of the following statements best describes how a growth factor stimulates cell division from outside a cell?

The growth factor binds to receptors on the cell surface, initiating a signal transduction pathway that activates specific target genes.

When the concentration of GAl is highest, the average height of the control seedlings is approximately

10 cm

Based on the information presented, which of the following describes the most likely role of ADH in maintaining blood osmolarity?

ADH promotes an increase in the movement of water into the bloodstream.

Which of the following explains how a mutation that removes a portion of each cytoplasmic domain of EPoR most likely affects differentiation of the cells?

STAT 5 will not be activated because it will not be phosphorylated by the kinases.

Cell communication is critical for the function of both unicellular and multicellular eukaryotes. Which of the following is likely true of cell signaling?

Similar cell signaling pathways in diverse eukaryotes are evidence of conserved evolutionary processes.

In flowering plants, plasmodesmata are narrow channels through cell walls that connect the cytoplasms of adjacent cells. An explanation of how plant cells communicate across cell walls will most likely refer to the diffusion through plasmodesmata of which of the following?

Small, water-soluble molecules

The mechanism of action of many common medications involves interfering with the normal pathways that cells use to respond to hormone signals. Which of the following best describes a drug interaction that directly interferes with a signal transduction pathway?

A medication enters the target cell and inhibits an enzyme that normally synthesizes a second messenger.

The figure above shows a model of a ligand precursor being cleaved to produce an active ligand that binds to a specific receptor. Which of the following is most likely to reduce the binding of the active ligand to its receptor?

A mutation in the receptor gene that causes a substitution of a charged amino acid for a nonpolar amino acid in the ligand binding site of the receptor

Which of the following research questions would best guide an investigation of the link between the structure of the signaling molecules and the evolution of quorum sensing?

Did these species evolve from a common ancestor that used a similar signaling molecule?

Based on the experimental results, which of the following describes the most likely defect in muscle cells of patients with type 2 diabetes?

IRS-1 activation is reduced at high insulin concentrations.

Based on Figure 1, which of the following statements best describes the epinephrine signaling pathway?

In involves enzymes activating other enzymes.

Cortisol is a hormone produced in response to stress, including starvation, in humans. Which of the following is most likely an immediate effect of a starvation-induced increase in cortisol secretion?

Increased mobilization of fatty acids from fat cells

Which of the following observations best supports the hypothesis that CDK5 negatively regulates neurotransmitter release?

Inhibition of CDK5 activity in neurons increases the movement of synaptic vesicles to the plasma membrane in response to a specific stimulus.

Based on the information provided, which of the following best describes the role of insulin in this liver cell signal transduction pathway?

It acts as a ligand.

Which of the following statements best describes the role of cyclic in the signal transduction pathway?

It acts as a second messenger that helps relay and amplify the signal within the cell.

A mutation changes the shape of the extracellular domain of transmembrane receptor protein produced by the cell. Which of the following predictions is the most likely consequence of the mutation?

The molecule that normally binds to protein will no longer attach, deactivating the cellular response.

Vertebrate immune responses involve communication over short and long distances. Which of the following statements best helps explain how cell surface proteins, such as proteins and T cell receptors, mediate cell communication over short distances?

The proteins interact directly with proteins on the surfaces of other cells.

Which of the following best explains the observation that the drugs can effectively control blood cholesterol levels in individuals who are heterozygous but are not effective in individuals homozygous for the mutant allele?

There must be at least one copy of the wild-type LDL receptor allele to produce functional LDL receptors.

One approach to treating patients with pancreatic cancer and other cancers in which the Hedgehog protein is detected is to modify the Hedgehog signaling pathway. Which of the following is the most useful approach?

Treating patients with a membrane-soluble compound that can bind to Smo and block its activity