QUIZ 5

In biological membranes, the phospholipids are arranged in a _______, with the ___. A.bilayer; fatty acids pointing toward each other B.bilayer; fatty acids facing outward C.single layer; fatty acids facing the interior of the cell D.single layer; phosphorus-containing region facing the interior of the cell E.bilayer; phosphorus groups in the interior of the membrane

A.bilayer; fatty acids pointing toward each other

If a G protein were unable to release its bound nucleotide but could hydrolyze it, signal transduction would A.cease B.be continuous. C.be unaffected. D.be constantly switching on and off. E.be unpredictable.

A.cease

Increased synthesis of phosphodiesterase would lead to A.decreased concentration of cyclic AMP. B.increased concentration of cyclic AMP. C.increased concentration of epinephrine. D.decreased concentration of G proteins. E.inhibition of adenylyl cyclase.

A.decreased concentration of cyclic AMP.

Osmosis is a specific form of A.diffusion. B.pinocytosis. C.active transport. D.secondary active transport. E.movement of water by carrier proteins

A.diffusion.

The existence of a concentration gradient of glucose across a membrane means that : A. there is a high concentration of glucose on both sides of the membrane. B.the glucose molecules are more crowded on one side of the membrane than on the other. C.there is a high concentration of water on both sides of the membrane. D.the glucose molecules are chemically more tightly bonded on one side than on the other. E.there are more glucose molecules within the membrane than outside of the membrane.

B. the glucose molecules are more crowded on one side of the membrane than on the other.

Houseplants adapted to indoor temperatures may die if they are left outdoors, because in a cold environment their A.DNA cannot function. B.membranes lack adequate fluidity C.photosynthesis is impaired. D.membranes contain too many unsaturated fatty acids. E.membranes need more cholesterol.

B.membranes lack adequate fluidity

The LDL receptor is an integral protein that crosses the plasma membrane, with portions of the protein extending both outside and into the interior of the cell. The amino acid side chains (R groups) in the region of the protein that crosses the membrane are most likely A.charged. B.hydrophilic. C.hydrophobic D.carbohydrates. E.lipids.

C.hydrophobic.

The compounds in biological membranes that form a barrier to the movement of hydrophilic materials across the membrane are A.integral membrane proteins. B.carbohydrates. C.lipids. D.nucleic acids. E.peripheral membrane proteins.

C.lipids.

Which of the following is the driving force for simple diffusion? A.Concentration gradient B.ATP hydrolysis C.ADP hydrolysis D.Phosphorylation E.GTP-GDP exchange

Concentration gradient

Which molecule acts as a second messenger in the cascade by which epinephrine stimulates the activation of the enzyme glycogen phosphorylase? A.Adenosine B.Caffeine C.Citric acid D.Cyclic AMP E.Adenylyl cyclase

Cyclic AMP

The hydrophilic regions of a membrane protein are most likely A.present only in muscle cells. B.associated with the fatty acid region of the lipids. C.in the interior of the membrane. D.exposed on the surface of the membrane. E.either on the surface or inserted into the interior of the membrane.

D.exposed on the surface of the membrane

Signal ligands can be divided into two general classes according to their receptors. Which of the following are the two kinds of receptors? A.Plasma membrane and ion channel B.Plasma membrane and protein kinase C.Ion channel and cytoplasmic D.G protein-linked and protein kinase E.Plasma membrane and cytoplasmic

E.Plasma membrane and cytoplasmic

Which of the following statements about diffusion is false? A.Diffusion does not require ATP. B.Diffusion continues until the molecular concentrations are in equilibrium. C.In diffusion, molecules move from areas of greater concentration to areas of lesser concentration. D.Diffusion is a random process. E.Simple diffusion depends upon specific carrier proteins.

E.Simple diffusion depends upon specific carrier proteins.

Which of the following statements about peripheral membrane proteins is true? A.They have hydrophobic regions within the lipid portion of the bilayer. B.They have hydrophilic regions that protrude in aqueous environments on both sides of the membrane. C.They frequently flip from one side of the bilayer to the other. D.They control the rate of diffusion. E.Their polar regions interact with similar regions of integral membrane proteins.

E.Their polar regions interact with similar regions of integral membrane proteins.

Which of the following processes does not involve the uptake of materials into the cell? A.Exocytosis B.Pinocytosis C.Endocytosis D.Receptor-mediated endocytosis E.Phagocytosis

Exocytosis

Which type of membrane protein would likely be most easily removed in a laboratory experiment? A.Integral proteins B.Channel proteins C.Peripheral proteins D.Transmembrane proteins E.Gated channels

Peripheral proteins

Which of the following molecules has a protein kinase receptor? A.Insulin B.Estrogen C.Acetylcholine D.Sodium E.G protein

a.Insulin

Plant cells transport sucrose across the vacuole membrane against its concentration gradient by a process known as A.simple diffusion. B.active transport. C.passive transport. D.facilitated diffusion. E.cellular respiration.

active transport.

The rate at which a substance diffuses is not affected by the A.diameter of the molecules or ions. B.temperature of the solution. C.color of the substance. D.concentration gradient in the system. E.Both a and b

color of the substance.

Adenosine is the normal _______ for its membrane receptor. A.antagonist B.enzyme C.ligand D.fatty acid E.carbohydrate moiety

ligand

To respond to a signal, a cell must have a(n) _______ molecule that can detect the signal. A.paracrine B.receptor C.autocrine D.responder E.All of the above

receptor

Amino acids enter cells against their concentration gradients by means of A.simple diffusion. B.facilitated diffusion. C.primary active transport. D.secondary active transport. E.osmosis.

secondary active transport.

When placed in a hypertonic solution, animal cells A.shrink. B.swell. C.burst. D.transport water out using ATP. E.become concentrated

shrink.

For each molecule of ATP consumed during active transport of sodium and potassium, there is an import of _______ ion(s) and an export of _______ ion(s). A.two Na+; three K+ B.two Na+; one K+ C.one K+; three Na+ D.two K+; three Na+ E.three K+; two Na+

two K+; three Na+