12) Which of the following terms is used to define the structure that separates the contents of a human cell from its surrounding medium?

A) cell wall

B) cell layer

C) plasma membrane

D) cell boundary

E) nuclear envelope

13) The plasma membrane

A) is a watery gel in which structures are suspended.

B) contains the powerhouse of the cell.

C) is the central government of the cell.

D) regulates the exchange of substances with the environment.

E) carries the cell’s hereditary information.

14) Membrane-bound proteins that allow identification of a cell as “self” or “nonself” are called ________ proteins.

A) integral

B) recognition

C) carrier

D) peripheral

E) channel

15) The classes of membrane proteins that are sensitive to extracellular materials are called

A) receptor proteins.

B) channel proteins.

C) carrier proteins.

D) anchor proteins.

E) identifier proteins.

16) The phosphate “head” of a phospholipid is

A) hydrophobic.

B) hydrophilic.

C) polar.

D) nonpolar.

E) both hydrophilic and polar.

17) Structurally, the plasma membrane

A) contains no imbedded proteins.

B) separates the chromatin from the cytoplasm in eukaryotes.

C) contains carbohydrate molecules only.

D) is nonporous.

E) is composed of a bilayer of lipids.

18) Which of the following is a function of the plasma membrane?

A) continuation of the cytoplasm with the extracellular fluid

B) a free passageway for materials to the environment

C) sensitivity to changes in the extracellular fluid

D) enzyme production

E) controlling movement into the nucleus

19) Which of the following is a function of the membrane proteins called channel proteins?

A) They bind to specific extracellular molecules to trigger a cellular change.

B) They regulate the passage of ions, bypassing the lipid portion of the cell membrane.

C) They are enzymes.

D) They serve as anchors or stabilizers for the cell membrane.

E) They are used as a source of energy.

20) Plasma membranes allow certain molecules to pass, while blocking others. Membranes with this property are called

A) impermeable.

B) freely permeable.

C) selectively permeable.

D) actively permeable.

E) nonpermeable.

21) The movement of water across a membrane from an area of higher water (lower solute) concentration to an area of lower water (higher solute) concentration is known as

A) filtration.

B) active transport.

C) diffusion.

D) facilitated diffusion.

E) osmosis.