AP cell signaling

Adjacent plant cells have narrow channels called plasmodesmata that pass through the cell walls of the connected cells and allow a cytoplasmic connection between the cells.

Which of the following statements best describes a primary function of plasmodesmata?

• They allow the movement of molecules from one cell to another, enabling communication between cells.

• They prevent the cell membrane from pulling away from the cell wall during periods of drought.

• They eliminate the need to produce signaling molecules and eliminate the need for cells to have receptors for signaling molecules.

• They increase the surface area available for attachment of ribosomes and thus increase protein synthesis.

A hydrophilic peptide hormone is produced in the anterior pituitary gland located at the base of the brain. The hormone targets specific cells in many parts of the body.

Which of the following best explains a possible mechanism that would enable the hormone to efficiently reach all of the target cells in the body?

• The hormone interacts with the nerves at the base of the brain and directs signals to the target cells through the nervous system.

• The hormone diffuses into target cells adjacent to the anterior pituitary gland, where the hormone is degraded.

• The hormone is released into the bloodstream where it can be transported to all cells with the correct receptors.

• The hormone moves through cytoplasmic connections between cells until it has reached all cells with the correct intracellular binding sites.

G proteins are a family of receptor proteins that are involved in transmitting signals from outside a cell to inside a cell. When a signaling molecule binds to a G protein, the G protein is activated. The G protein then activates an enzyme that produces a second messenger called cAMP.

Which of the following describes a critical role of cAMP during the transduction stage of a G protein signal transduction pathway?

• cAMP carries the signal to the nucleus of the cell and results in new sequences of nucleotides being added to the cell’s DNA.

• cAMP binds the extracellular signal molecule and carries it to the intracellular target specified by the signal.

• cAMP modifies a specific monomer so that it can be added to an elongating structural macromolecule.

• cAMP results in the activation of an enzyme that amplifies the signal by acting on many substrate molecules.

Which of the following steps in a signaling pathway typically occurs first once a chemical messenger reaches a target cell?

• Specific genes are activated.

• A second messenger molecule is produced.

• A ligand binds to a receptor.

• Specific proteins are synthesized.

A person’s blood glucose level fluctuates during the day, as represented in Figure 1. Two hormones, insulin and glucagon, are directly involved in regulating the blood glucose level to maintain a healthy level. Insulin acts to lower the blood glucose level, and glucagon acts to increase the blood glucose level.

Which of the following best predicts what will happen to the blood glucose level if the person has another meal at 5 p.m.?

• Immediately after the meal, the blood glucose level will decrease because of the increase in glucagon levels.

• Immediately after the meal, the blood glucose level will increase, and then insulin will be secreted to counter the increase.

• Several hours after the meal, the blood glucose level will increase sharply because of an increase in the amount of glucagon secreted.

• The blood glucose level will not change after the 5 p.m. meal because the person has already consumed two meals and the blood glucose level has been adjusted to a steady-state level.

What do you call it when two neurons communicate through neurotransmitters?

• Hormones
• Synapse
• Cholesterol
• Monty

What is an organic compound that is made by glands in the body (pituitary, thyroid, etc) that is used in long distance communication between cells?

• Hormones
• Neurotransmitters
• Synapse
• Carbohydrates

Which of the following can activate a protein by transferring a phosphate group to it?

• cAMP
• G Protein
• protein kinase
• protein phosphatase

What do second messengers do?

• transport a signal through the lipid bilayer
• relay a signal from the outside to the inside of the cell
• relay message from the inside of the mebrane throughout the cytoplasm
• dampen the message

The 3 steps of signal transduction in order are

• reception, transduction, response
• response, transduction, reception
• reception, response, transduction
• transduction, reception, response