Membrane Transport Mechanisms

The video explains the concept of concentration gradients across plasma membranes and how certain molecules, due to their charge or size, cannot diffuse through the membrane by simple diffusion. It introduces facilitated diffusion, which involves ion channels for charged molecules and carrier proteins for larger molecules. Channel mediated diffusion allows ions like sodium to pass through selective and gated ion channels, while carrier mediated diffusion involves carrier proteins that undergo conformational changes to transport large molecules like glucose. Both processes do not require ATP and continue until equilibrium is reached.

What is the term for the difference in solute concentration across a membrane?

• Diffusion rate

• Membrane potential

• Concentration gradient

• Osmotic pressure

Why might highly charged solute molecules struggle to cross a plasma membrane?

• They require energy

• They dissolve in the membrane

• Their size is too large

• Their charges prevent simple diffusion

What process allows highly charged molecules to cross the membrane?

• Endocytosis

• Active transport

• Channel-mediated diffusion

• Simple diffusion

Which type of protein assists large molecules in crossing the membrane?

• Enzymes

• Carrier proteins

• Receptor proteins

• Ion channels

What is a characteristic of ion channels in channel-mediated diffusion?

• They are non-selective

• They require ATP

• They are often selective

• They transport large molecules

What feature might ion channels have that controls diffusion?

• They are pH-sensitive

• They are temperature-sensitive

• They are gated

• They are always open

In carrier-mediated diffusion, what happens after a solute binds to a carrier protein?

• The solute is expelled from the cell

• The carrier protein changes shape

• The carrier protein releases energy

• The solute is broken down

What is a common feature of both channel-mediated and carrier-mediated diffusion?

• They require ATP

• They involve endocytosis

• They move solutes against the gradient

• They do not require ATP

When do facilitated diffusion processes stop?

• When the temperature drops

• When the membrane is damaged

• When solute concentration is equal on both sides

• When ATP is depleted