THE CELL MEMBRANE: STRUCTURE AND FUNCTION

Define the following term: Intracellular fluid.

• Fluid contained within a cell

• Fluid found outside the cell

• Fluid in the bloodstream only

• Fluid in the digestive tract

Define the following term: Selectively permeable.

• A membrane that allows some substances to pass through it but not others.

• A membrane that allows all substances to pass through it freely.

• A membrane that blocks all substances from passing through it.

• A membrane that only allows water to pass through it.

The functions of the cell membrane include:

• Controlling the movement of substances in and out of the cell

• Producing energy for the cell

• Storing genetic information

• Synthesizing proteins

The structure of the cell membrane is best described as:

• A phospholipid bilayer with embedded proteins

• A single layer of carbohydrates

• A rigid wall made of cellulose

• A layer of nucleic acids and proteins

The fluid-mosaic model of the cell membrane describes the membrane as:

• A rigid structure with proteins fixed in place.

• A static layer of lipids only.

• A flexible layer with proteins embedded in or attached to a phospholipid bilayer.

• A solid wall impermeable to all substances.

Channel proteins and carrier proteins differ in their mechanism of transporting substances across the cell membrane.

• Channel proteins form pores for passive transport, while carrier proteins undergo shape change to move substances.

• Both channel and carrier proteins form pores for active transport.

• Carrier proteins allow only water molecules, while channel proteins transport ions.

• Channel proteins require energy, while carrier proteins do not.

The function of cholesterol in a cell membrane is to:

• Maintain membrane fluidity

• Provide energy for the cell

• Facilitate protein synthesis

• Store genetic information

The arrangement of phospholipids in the cell membrane can be described as:

• A bilayer with hydrophilic heads facing outward and hydrophobic tails facing inward.

• A single layer with hydrophobic heads facing outward and hydrophilic tails facing inward.

• A bilayer with hydrophobic heads facing outward and hydrophilic tails facing inward.

• A random arrangement of phospholipids with no specific orientation.

Passive and active transport can be distinguished by which of the following characteristics?

• Passive transport does not require energy, while active transport does.

• Passive transport moves substances against the concentration gradient, while active transport moves them along the gradient.

• Active transport does not involve carrier proteins, while passive transport does.

• Both passive and active transport require the same amount of energy.

Which types of substances can move across the lipid bilayer by simple diffusion?

• Large charged molecules

• Small uncharged molecules such as gases

• Proteins

• Polysaccharides