Unit 4: Cell Communication & The Cell Cycle Review

Receptors for signal molecules __________.

• can be found in the plasma membrane & in cytoplasm/nucleus

• all work via protein kinases

• all work by opening ion channels

• are only found associated with the plasma membrane

A G protein is active when __________.

• GDP replaces GTP

• it is phosphorylated by protein kinase

• GTP is bound to it

• it is bound by its ligand and transported to the nucleus

What is the general name for an enzyme that transfers phosphate groups from ATP to a protein?

• protein dehydrogenase

• protein kinase

• protein cyclase

• protein phosphatase

The source of phosphate for a phosphorylation cascade is __________.

• ATP

• GTP

• protein kinase

• protein phosphatase

Why are phosphorylation cascades involving a series of protein kinases useful?

• they always lead to the same cellular response

• the number of molecules used is small and fixed

• cAMP is not always readily available

• they amplify the original signal

A process in which an initial change will bring about more change in the same direction.

• negative feedback

• positive feedback

• homeostasis

• neutral feedback

Which of the following is not true about homeostasis?

• it is how the body maintains a constant environment

• it is controlled by positive feedback loops

• it is controlled by negative feedback loops

• it is a characteristic of all living organisms

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Which of the following is not an example of a negative feedback loop?

• body maintaining a temperature of about 37°C

• release of ADH to increase H₂O reabsorption when dehydrated

• a ripe apple releasing ethylene, which causes more ripening

• heart rate increasing when exercising to deliver more O₂ to cells

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What do cells have in order to respond to a particular hormone?

• a receptor for the hormone

• nothing as any hormone can affect any cell at any time

• an effector for the hormone

• a plasma membrane

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Through a microscope, you can see a cell plate developing between two nuclei. What's going on?

• a plant cell is in the process of cytokinesis

• an animal cell is in the process of cytokinesis

• an animal cell is in the S phase of the cell cycle

• a bacterial cell is diving via binary fission

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