Cell Signalling and Transduction – Section 1

6. Self-phosphorylation is an excellent mechanism for triggering specific catalytic function of the proteins involved in signal cascades because it

A. changes the shape and thus the enzymatic activity of the proteins involved
B. makes the receptor more likely to capture the signaling, molecule
C. allows hydrophilic signaling molecules to cross the plasma membrane
D. None of the above

Correct Answer: A. changes the shape and thus the enzymatic activity of the proteins involved

7. Which of the following statements about G proteins is false?

A. They are involved in signal cascades
B. They bind to and are regulated by guanine nucleotides
C. They become activated when bound to GDP
D. They must be active before the cell can make needed cAMP

Correct Answer: C. They become activated when bound to GDP

8. When a __________ reaches its __________ , there is a specific means of receiving it and acting on the message. This task is the responsibility of specialized proteins called __________ .

A. signaling molecule; receptor; G proteins
B. signaling molecule; target cell; G proteins
C. signaling molecule; target cell; receptors
D. kinase; receptor; proteases

Correct Answer: C. signaling molecule; target cell; receptors

9. Why is it that inhaling nitric oxide reduces blood pressure only in the lung tissue and not elsewhere in the body*?

A. Because other body tissues use a different signaling molecule
B. Because nitric oxide cannot cross cell membranes and enter the blood
C. Because nitric oxide breaks down quickly and thus cannot travel far
D. None of the above

Correct Answer: C. Because nitric oxide breaks down quickly and thus cannot travel far

10. Which of the following comes under the category of cell surface receptor?

A. Enzyme linked receptors
B. Ion-channel linked receptors
C. G protein linked receptors
D. All of these

Correct Answer: D. All of these

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