Chapter Three: Cell structure and Function

The cardiac drug digitalis enhances myocardial contraction because it A. Increases intracellular calcium level in cardiac cells B. Inhibits sodium from entering cardiac cells C. Enhances the sodium-potassium pump D. Increases the sodium gradient across the cell membrane

A. Increases intracellular calcium level in cardiac cells

The organelle that contains enzymes necessary for oxidative phosphorylation to produce ATP is the A. Mitochondria B. Ribosome C. Lysosome D. Nucleus

A. Mitochondria

GTP-binding proteins function to A. Activate receptors on the extracellular surface B. Degrade second-messenger molecules C. Activate intracellular enzyme systems D. Synthesize ATP

C. Activate intracellular enzyme systems

Repolarization of a neuron after a depolarizing action potential is because of A. Activation of the Na K pump B. Influx of calcium C. Efflux of potassium D. Influx of sodium

C. Efflux of potassium

Cell-to-cell communication through secretion of chemical signals into the bloodstream to target cells throughout the body is called ______ signaling A. Synaptic B. Paracrine C. Endocrine D. Autocrine

C. Endocrine

An increase in extracellular potassium ion from 4.0 to 6.0 mEq/L would A. Hyperpolarize the resting membrane potential B. Make it more difficult to reach threshold and produce an action potential C. Hypopolarize the resting membrane potential D. Alter the threshold potential

C. Hypopolarize the resting membrane potential

Phospholipids spontaneously form lipid bilayers because they are A. Polar B. Charged C. Insoluble D. Amphipathic

D. Amphipathic

Ion channels open and close in response to all the following except A. Mechanical pressure B. Ligand binding C. Voltage changes D. Temperature changes

D. Temperature changes

Excitable cells are able to conduct action potentials because they have A. Receptors for neurotransmitters B. Tight junctions C. Ligand-gated channels D. Voltage-gated channels

D. Voltage-gated channels

Glycolysis is the metabolic process of breaking down a glucose molecule to form A. CO2 and H2O B. 2 ATP and 2 pyruvate C. 30 ATP D. Oxygen

B. 2 ATP and 2 pyruvate

The benefit of glycolysis is that this second stage of catabolism supplies A. ATP to meet energy needs of the body B. Pyruvate to the citric acid cycle C. Energy for oxidative phosphorylation D. Lactate during anaerobic conditions

B. Pyruvate to the citric acid cycle

Ribosomes are very important organelles within the cell that have the function of A. Detoxifying substances B. Synthesizing proteins C. Converting energy to forms that can be used D. Coding for protein synthesis

B. Synthesizing proteins

The resting membrane potential in nerve and skeletal muscle is determined primarily by A. Extracellular sodium ion concentration B. The ratio of intracellular to extracellular potassium ions C. Activation of voltage-gated sodium channels D. Activity of energy-dependent membrane pumps

B. The ratio of intracellular to extracellular potassium ions

Gap junctions are connecting channels that allow passage of small molecules from one cell to the next and are especially important for A. Distance signaling B. Tissues requiring synchronized function C. Communication within a cell D. Passage of large molecules

B. Tissues requiring synchronized function