Plasma membranes are said to be
(a) Impermeable
(b) Freely permeable
(c) Selectively permeable
(d) Actively permeable
(e) Slightly permeable

The transport of a certain molecule exhibits the following characteristics:

(1) The molecule moves down its concentration gradient;

(2) at concentrations above a given level, the rate of transport does not increase; and

(3) cellular energy is not required for transport to occur.

Which transport process is at work?

Solutions A and B are separated by a selectively permeable barrier. Over time, the level of fluid on side A increases. Which solution initially had the higher concentration of solute?

In the following diagram, identify the type of solution (hypertonic, hypotonic, or isotonic) in which the red blood cells are immersed.

The process that transports solid objects such as bacteria into the cell is called

(a) Pinocytosis

(b) Phagocytosis

(c) Exocytosis

(d) Receptor-mediated endocytosis

(e) Channel-mediated transport

____ ion concentration is high in extracellular fluids, and____ion concentration is high in the cytoplasm.

(a) Calcium; magnesium

(b) Chloride; sodium

(c) Potassium; sodium

(d) Sodium; potassium

The movement of water across a membrane from an area of low solute concentration to an area of higher solute concentration is known as

(a) Osmosis

(b) Active transport

(c) Diffusion

(d) Facilitated transport

(e) Filtration

A molecule that blocks the ion channels lining integral proteins in the plasma membrane would interfere with

(a) Cell recognition

(b) The movement of lipid-soluble molecules

(c) Producing changes in the electrical charges across a plasma membrane

(d) The ability of protein hormones to stimulate the cell

(e) The cell's ability to divide

Which molecule most easily diffuses across a biological membrane's lipid bilayer, without help of a protein?