Cell Membrane Transport Questions

Which of the following substances is found in large amounts in the extracellular fluid but only in a small amount in the intracellular fluid?

• Potassium

• Phosphate

• Proteins

• Sodium

The cell membrane is almost entirely composed of a lipid bilayer with many protein molecules, many of which penetrate all the way through the membrane. This lipid bilayer serves as a barrier against the movement of:

• Lipid-soluble substances

• Water molecules and water-soluble substances

• Gases like oxygen and carbon dioxide

• Steroid hormones

Which type of membrane protein forms watery spaces all the way through the molecule, allowing free movement of water and selected ions or molecules?

• Channel proteins

• Carrier proteins

• Receptor proteins

• Enzyme proteins

Facilitated diffusion requires the interaction of a carrier protein that aids passage of molecules or ions by:

• Creating a membrane opening without interaction.

• Moving substances against an energy gradient.

• Binding chemically with them and shuttling them through the membrane.

• Using ATP to power movement.

What is the primary energy source that causes diffusion?

• ATP hydrolysis

• The normal kinetic motion of matter

• Electrical potential differences

• Concentration gradients maintained by pumps

Simple diffusion through the cell membrane can occur via two pathways: through the interstices of the lipid bilayer if the diffusing substance is lipid-soluble, and through:

• Carrier proteins.

• Watery channels that penetrate large transport proteins.

• Active transport pumps.

• Ligand-gated receptors.

Aquaporins are protein pores known to permit rapid passage of which substance through cell membranes, while excluding hydrated ions?

• Glucose

• Sodium

• Water

• Amino acids

The high selectivity of potassium channels for potassium ions over sodium ions is largely explained by:

• The larger molecular diameter of potassium ions.

• Carbonyl oxygens in the selectivity filter interacting with dehydrated potassium ions but not smaller sodium ions.

• Strong negative charges attracting only potassium ions.

• The presence of a specific carrier protein for potassium.

Gating of protein channels can be controlled in two principal ways: voltage gating and:

• Mechanical gating.

• Pressure gating.

• Chemical (ligand) gating.

• Osmotic gating.

The patch clamp method is a technique used to record:

• Ion current flow through single protein channels.

• The overall electrical potential of an entire cell.

• The rate of ATP synthesis in mitochondria.

• Muscle contraction forces.