What is the correct order for the following events that follow a nerve impulse along a sympathetic
neuron, and which innervates the heart?
1) G protein activates adenylyl cyclase
2) Neuron releases norepinephrine
3) Cyclic AMP activates protein kinase
4) Receptor activates G protein
5) Protein kinase phosphorylates Ca2+ channels
6) Receptors activated on the membrane of the cardiac muscle
a. 1, 3, 4, 5, 2, 6
b. 5, 3, 4, 1, 2, 6
c. 6, 2, 4, 1, 3, 5
d. 2, 6, 4, 1, 3, 5
e. 2, 3, 4, 1, 6, 5
D
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In the sliding filament model of muscle contraction, I bands contain
A) thick filaments. B) thin filaments. C) myosin. D) sacrcomeres. E) both thick and thin filaments.
If Meselson and Stahl let replication proceed for one more round of replication (3 rounds) what fraction of the daughter DNA molecules would be of intermediate density?
A: None B: ½ C: ¼ D: 1/8
Which of the following best describes an advantage that eukaryote organisms have over prokaryote organisms?
(A) Prokaryotes lack a cell membrane and therefore are unable to control what enters or exits the cell. (B) Eukaryotes have a nuclear envelope separating their DNA from the rest of the cell, which increases the likelihood of advantageous mutations. (C) Eukaryotes have mitochondria and chloroplasts that contain their own genome, which allows the cells to reproduce more rapidly. (D) Eukaryotes have organelles that allow for compartmentalization of cellular processes, which increases the efficiency of those processes.
Digestion is the
A) absorption of nutrients suspended in water. B) conversion of glycogen to glucose. C) breakdown of food into molecules small enough for the body to absorb. D) churning of food in the stomach and intestine.