Diffusion and Membrane Transport Concepts

The video tutorial explains facilitated diffusion, a process where hydrophilic substances cross cell membranes via protein molecules without interacting with the hydrophobic center. It covers diffusion basics, the role of cell membranes, and the mechanisms of facilitated diffusion, including carrier proteins and protein channels. The tutorial emphasizes that facilitated diffusion is passive and does not require metabolic energy.

What is the primary characteristic of diffusion?

• It requires energy from respiration.

• It is a passive process.

• It only occurs in liquids.

• It moves particles from low to high concentration.

Why do hydrophobic substances diffuse easily across the cell membrane?

• They are repelled by the hydrophobic center.

• They are attracted to water.

• They are larger than hydrophilic substances.

• They can interact with the hydrophobic center.

What is the significance of the hydrophobic center of the cell membrane?

• It allows all substances to pass freely.

• It prevents hydrophilic substances from diffusing easily.

• It is only present in plant cells.

• It requires energy for substances to pass.

What is the main problem for cells regarding hydrophilic substances?

• They require energy to pass through the membrane.

• They are too large to pass through the membrane.

• They are not needed by the cell.

• They cannot enter the cell due to the hydrophobic membrane center.

How do carrier proteins assist in facilitated diffusion?

• They repel hydrophilic substances.

• They create a pore for substances to pass through.

• They change shape to transport specific chemicals across the membrane.

• They provide energy for the process.

What is a key feature of protein channels in facilitated diffusion?

• They are always open.

• They only transport hydrophobic substances.

• They are selective for specific chemicals.

• They require ATP to function.

What triggers some protein channels to open?

• The presence of water.

• A chemical binding or a change in voltage.

• The size of the molecule.

• A change in temperature.

What is the role of hydrophilic amino acids in protein channels?

• They line the channel to allow hydrophilic substances to pass.

• They repel water.

• They block the channel.

• They provide energy for diffusion.

Which of the following is true about facilitated diffusion?

• It moves substances against the concentration gradient.

• It requires metabolic energy.

• It is a type of active transport.

• It does not require metabolic energy.

What is the main difference between carrier proteins and protein channels?

• Carrier proteins transport hydrophobic substances, while channels do not.

• Carrier proteins require energy, while channels do not.

• Carrier proteins change shape, while channels provide a pore.

• Carrier proteins are always open, while channels are not.