1. Hormones are chemical signals that A. affect adjacent cells. B. work in proka
ID: 13221 • Letter: 1
Question
1. Hormones are chemical signals thatA.
affect adjacent cells.
B.
work in prokaryotes.
C.
are autocrine signals.
D.
travel through circulatory systems.
E.
are paracrine signals.
Answer choice C
2. A universal feature of receptors is that they
A.
undergo structural (shape) changes when the signal molecule is bound.
B.
are protein kinases.
C.
are present in the plasma membrane.
D.
are ion channel proteins.
E.
do not undergo structural (shape) changes when the signal molecule is bound.
Answer choice A
3. Which of the following statements about receptors and enzymes is true?
A.
Most receptors and enzymes are nucleic acids.
B.
Both receptors and enzymes may be integral membrane proteins.
C.
Receptor ligands, like enzyme substrates, are altered during signal transduction.
D.
Both receptors and enzymes are not specific for the molecules they bind.
E.
Receptors generally have enzymatic activity, whereas enzymes do not.
Answer choice B
4. Chemical signal transduction pathways
A.
use non-specific receptors.
B.
involve binding of the signal molecule to receptors.
C.
use receptors that are located only on the plasma membrane.
D.
use receptors that change the ligands they bind.
E.
all use G proteins.
Answer C
5. Adenylyl cyclase
A.
is located such that cAMP is made outside of cells.
B.
makes cAMP from ATP with the liberation of phosphate (Pi).
C.
is inactivated by activated G proteins.
D.
makes cAMP from ATP with the liberation of pyrophosphate (PPi).
E.
is directly activated by receptors.
Answer choice D
6. Which of the following statements is true?
A.
Glycogen phosphorylase in liver cells is always active.
B.
cAMP is referred to as a “first messenger.”
C.
Epinephrine directly activates adenylyl cyclase.
D.
cAMP is referred to as a “second messenger.”
E.
Adenylyl cyclase is a protein kinase.
Answer choice C
7. Which step of the signal transduction cascade that results in glucose release during the “fight-or-flight” response does not directly involve a nucleotide?
A.
Phosphorylation of glycogen phosphorylase
B.
Activation of adenylyl cyclase
C.
Epinephrine binding to its receptor
D.
Activation of a G protein
E.
Inactivation of glycogen synthase
Answer choice A
8. The phosphorylation of proteins by ATP
A.
is catalyzed by enzymes known as “protein kinases.”
B.
always stimulates the activity of an enzyme.
C.
is catalyzed by adenylyl cyclase.
D.
is catalyzed by the epinephrine receptor.
E.
is catalyzed by G proteins.
Answer choice A
9. Suppose the concentration of epinephrine in the blood stream of an animal drops. The cyclic AMP concentration in liver cells would be expected to _______ because _______ activity would _______.
A.
increase; adenylyl cyclase; increase
B.
decrease; protein kinase; decrease
C.
decrease; phoshodiesterase; decrease
D.
increase; protein kinase; increase
E.
decrease; adenylyl cyclase; decrease
Answer choice B
Explanation / Answer
1. Hormones are chemical signals that
A. affect adjacent cells.
B.work in prokaryotes.
C.are autocrine signals.
D.travel through circulatory systems.
E.are paracrine signals.
Answer choice C
2. A universal feature of receptors is that they
A.undergo structural (shape) changes when the signal molecule is bound.
B.are protein kinases.
C.are present in the plasma membrane.
D.are ion channel proteins.
E.do not undergo structural (shape) changes when the signal molecule is bound.
Answer choice A
3. Which of the following statements about receptors and enzymes is true?
A.Most receptors and enzymes are nucleic acids.
B.Both receptors and enzymes may be integral membrane proteins.
C.Receptor ligands, like enzyme substrates, are altered during signal transduction.
D.Both receptors and enzymes are not specific for the molecules they bind.
E.Receptors generally have enzymatic activity, whereas enzymes do not.
Answer choice B
4. Chemical signal transduction pathways
A.use non-specific receptors.
B.involve binding of the signal molecule to receptors.
C.use receptors that are located only on the plasma membrane.
D.use receptors that change the ligands they bind.
E.all use G proteins.
Answer C
5. Adenylyl cyclase
A.is located such that cAMP is made outside of cells.
B.makes cAMP from ATP with the liberation of phosphate (Pi).
C.is inactivated by activated G proteins.
D.makes cAMP from ATP with the liberation of pyrophosphate (PPi).
E.is directly activated by receptors.
Answer choice D
6. Which of the following statements is true?
A.Glycogen phosphorylase in liver cells is always active.
B.cAMP is referred to as a “first messenger.”
C.Epinephrine directly activates adenylyl cyclase.
D.cAMP is referred to as a “second messenger.”
E.Adenylyl cyclase is a protein kinase.
Answer choice C
7. Which step of the signal transduction cascade that results in glucose release during the “fight-or-flight” response does not directly involve a nucleotide?
A.
Phosphorylation of glycogen phosphorylase
B.
Activation of adenylyl cyclase
C.
Epinephrine binding to its receptor
D.
Activation of a G protein
E.
Inactivation of glycogen synthase
Answer choice A
8. The phosphorylation of proteins by ATP
A.is catalyzed by enzymes known as “protein kinases.”
B.always stimulates the activity of an enzyme.
C.is catalyzed by adenylyl cyclase.
D.is catalyzed by the epinephrine receptor.
E.is catalyzed by G proteins.
Answer choice A
9. Suppose the concentration of epinephrine in the blood stream of an animal drops. The cyclic AMP concentration in liver cells would be expected to _______ because _______ activity would _______.
A.increase; adenylyl cyclase; increase
B.decrease; protein kinase; decrease
C.decrease; phoshodiesterase; decrease
D.increase; protein kinase; increase
E.decrease; adenylyl cyclase; decrease
Answer choice B
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