Cell Communication Part 1
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?
An increase in the ratio of the number of unsaturated to the number of saturated fatty acid tails of the membrane lipids
Antidiuretic hormone (ADH) is important in maintaining homeostasis in mammals. ADH is released from the hypothalamus in response to high tissue osmolarity. In response to ADH, the collecting duct and distal tubule in the kidney become more permeable to water, which increases water reabsorption into the capillaries. The amount of hormone released is controlled by a negative feedback loop. Based on the model presented, which of the following statements expresses the proper relationship between osmolarity, ADH release, and urine production?
As tissue osmolarity rises, more ADH is released, causing less water to be excreted as urine.
Previous experiments indicate that CDK5 is active only when attached to a protein called p35. Which of the following best predicts how p35 might play a role in regulating neuron function?
Degradation of p35 results in increased synaptic activity.
Based on the model, which of the following best explains how regulation of neurotransmitter release might increase the range of responses to a stimulus in the nervous system?
Different neurons in the same neural network can release different amounts of neurotransmitter.
Epinephrine is a protein hormone found in many animals. Epinephrine stimulates a signaling pathway that results in the breakdown of glycogen to glucose in the liver cells. Which of the following describes the initial steps in the process whereby epinephrine stimulates glycogen breakdown?
Epinephrine binds to a cell-surface receptor; the activated receptor stimulates production of the second messenger, cAMP .
Which of the following statements accurately uses the information presented to support the hypothesis that interruption of M function in a single body cell can result in cancer?
Growth-factor signaling can trigger mitosis in cells that are in direct contact with other cells.
Based on your understanding of the ways in which signal transmission mediates cell function, which of the following predictions is most consistent with the information given above?
In an environment with low fixed nitrogen, treating the Anabaena cells with a calcium-binding compound should prevent heterocyst differentiation.
Which of the following observations best supports the hypothesis that CDK5negatively 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.
A researcher examining a root tip observes a plant cell with condensed sister chromatids, kinetochores with attached microtubules, and individual chromosomes that are aligned at the equatorial plate of the cell. Which of the following best describes what the next process will be in the cell?
Paired chromatids will separate, and the new daughter chromosomes will move toward opposite poles of the cell.
During mitosis, which of the following normally occurs?
Replicated chromosomes line up on the equatorial plate.
Based on the experimental results, which of the following is the best evolutionary explanation for the occurrence of ARD in C. elegans ?
The ability to enter ARD provides a strong selective advantage because reproduction can occur despite periods of food scarcity.
If chemical signals in the cytoplasm control the progression of a cell to the M phase of the cell cycle, then fusion of a cell in G1 with a cell in early M phase would most likely result in the
condensation of chromatin in preparation of nuclear division in both cells
DNA replication occurs
during the S phase of the cell cycle
A human cell in prophase of mitosis can be distinguished from a human cell in prophase I of meiosis by the presence of
paired homologous chromosomes in the meiotic cell
The diagram above illustrates feedback control as exerted by the hormone thyroxine. Following surgical removal of the thyroid gland, the level of TSH in the blood will increase. Which of the following best explains this increase?
A decrease in thyroxine levels means a loss of inhibition to the hypothalamus and anterior pituitary, leading to increased TSH secretion.
The p53 protein regulates a cellular response to DNA damage. Based on the diagram above, which of the following best describes the role of p53 in the response to DNA damage?
Phosphorylated p53 stimulates transcription of p21 , and the resulting p21 protein suppresses cell division until the DNA damage is repaired.
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.