CELL SIGNALLING and TRANSDUCTION
1. Small charged molecules, often biogenic amines function as
A. hormones
B. neurotransmitters
C. both (a) and (b)
D. none of these
Answer: C
2. SH2 domains specifically bind to
A. phosphorylated serine residues
B. phosphorylated tyrosine residues
C. GDP
D. Ca2+
Answer: B
3. In paracrine signaling, the signaling molecules affects only
A. target cells close to the cell from which it was secreted
B. target cells distant from its site of synthesis in cells of an endocrine organ
C. both (a) and (b)
D. none of the above
Answer: A
4. Simple nerve reflexes use signaling molecules called
A. neurotransmitters
B. nitric oxides
C. G proteins
D. proteases
Answer: A
5. Which of the following is not a type of signaling molecule?
A. Testosterone
B. Insulin
C. Thyroxin
D. Adenylate cyclase
Answer: D
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
Answer: A
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
Answer: C
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
Answer: C
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
Answer: C
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
Answer: D
11. Which of the following is true about a hydrophilic signaling molecule?
A. Its receptor is located in the cytosol of the target cell
B. It might trigger a signal cascade that causes some effect in a cell
C. Since it can enter the cell, it directly affects some specific cell process
D. It is a steroid
Answer: B
12. cAMP and cGMP are derived from
A. ATP and GTP by the actions of adenylate cyclase and guanylate cyclase respectively
B. GTP and ATP by the actions of adenylate cyclase and guanylate cyclase respectively
C. ATP and GTP by the actions of guanylate cyclase and adenylate cyclase respectively
D. none of the above
Answer: A
13. Nitroglycerin has long been administered to human patients suffering from chronic chest pain (angina). This medication works because it
A. mimics the action of signal receptors
B. is broken down into hormones that affect the heart
C. interferes with chemical cascades that trigger contraction of heart muscle
D. breaks down into nitric oxide, which increases blood flow to the heart
Answer: D
14. If a disease of the blood vessels caused the endothelial cells of the vessel to die, what effect would that have on the cellular activities associated with vasodilation?
A. Nitric oxide would no longer be produced
B. Smooth muscle cells could not be made to relax
C. It would be more difficult to increase blood flow and reduce blood pressure
D. All of the above
Answer: D
15. In terms of cell communication, what do bacterial pathogens such as cholera and anthrax have in common?
A. They destroy the receptors for key signaling molecules
B. They prevent the production of key signaling molecules
C. They alter the chemical structure of key signaling molecules
D. They block the normal functioning of signal transduction mechanisms
Answer: D
16. What is the name of the protein signaling molecule that alters glucose uptake, and where would its receptors be located?
A. Insulin; many different cell types that use glucose for fuel
B. Insulin; beta cells of the pancreas
C. PDGF; the blood
D. NGF; the nerves involved in simple reflexes
Answer: A
17. In the signal transduction mechanism known as protein phosphorylation
A. the signaling molecule binds to a surface receptor
B. receptor kinases play a key role in triggering the signal cascade
C. phosphorylated proteins act with enzymes to trigger the signal cascade
D. All of the above
Answer: D
18. Cell signaling can be classified into
A. three distinct types based on the distance over which the signaling molecules act
B. two distinct types based on the distance over which the signaling molecules act
C. three distinct types based on the signaling molecules
D. none of the above
Answer: A
19. Which of the following statement is correct?
A. Cell communicate with one another in multicellular organisms using extracellular signaling molecules or hormones
B. Cell communicate with one another in unicellular organisms using extracellular signaling antigen and antibody
C. Cell communicate with one another in multicellular organisms using intracellular signaling molecules only
D. Cell communicate with one another in unicellular organisms using intracellular signaling antigen and antibody
Answer: A
20. In vasodilation, proper nerve signals sent to blood vessels cause
A. the release of nitric oxide from endothelial cells
B. relaxation of smooth muscle cells
C. reduced blood pressure
D. All of the above
Answer: D
21. A cell is known to respond to a particular signaling molecule. Which of the following must be true of this cell?
A. It is in the heart muscle
B. It is also the site of production for the signaling molecule
C. It contains the receptor for the signaling molecule
D. It is incapable of signal transduction
Answer: C
22. The enzyme that catalyzes the splitting of PIP2 into two molecules of inositol triphosphate (IP3) and diacylglycerol in cell signaling, is
A. phosphokinase C
B. phospholipase C
C. phosphodiesterase C
D. lipokinase
Answer: B
23. The binding of ligands to many G-proteins linked receptors leads to shortlived
A. increase in the concentration of certain intracellular signaling molecules called second messenger
B. decrease in the concentration of certain intracellular signaling molecules called second messenger
C. increase in the concentration of certain extracellular signaling molecules called first messenger
D. decrease in the concentration of certain extracellular signaling molecules called first messenger
Answer: A
24. Which of the following processes involve the combining of a message from one signaling molecule with that of another to either enhance or inhibit a cellular effect?
A. Signal transduction
B. Signal reception
C. Signal integration
D. Signal amplification
Answer: C
25. A signal cascade induced by adrenaline or thyroxine
A. must begin with receipt of the signal molecule by a surface receptor
B. involves the activation of a G protein
C. results in the activation of a sequence of enzymes needed for the cell effect
D. all of the above
Answer: D
26. Which of the following is a second messenger?
A. lnositol 1,4,5-triphosphate
B. Diacyl glycerol
C. Phospholipase C
D. Both (a) and (b)
Answer: D
27. Which of the following statement is incorrect?
A. The principal lipophilic hormones that binds to receptors located in the plasma membranes are prostaglandins
B. Prostaglandins are synthesized from arachidonic acid
C. Prostaglandins act as paracrine signaling molecules
D. None of the above
Answer: D
28. Two key organizing principles for large multicellular organisms are
A. prokaryotic cell structure and cell specialization
B. cell specialization and communication between cells
C. communication between cells and simple nerve reflexes
D. simple nerve reflexes and cell specialization
Answer: B
29. Which of the following is a hormone whose action requires a cell surface receptor?
A. Nitric oxide
B. Progesterone
C. Adrenaline
D. Growth factors
Answer: C
30. The hormone or ligand can be considered as
A. first messenger
B. second messenger
C. both (a) and (b)
D. none of these
Answer: A
31. The major second messengers are
A. cAMP
B. cGMP
C. DAG
D. All of these
Answer: D
32. The signaling molecules called steroid hormones
A. are made in one location of the body but have their effects some distance away
B. are hydrophilic and so cannot penetrate the plasma membrane
C. bind to cell surface receptors to trigger chemical cascades
D. never enter the blood of humans
Answer: A
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