Simple and Facilitated Diffusion

Why is the phospholipid bilayer considered selectively permeable?

Because it has a hydrophobic region which allows only specific molecules, typically small and non-polar, to enter and exit while blocking larger polar molecules.

What type of molecules are most permeable through the phospholipid bilayer?

Small, nonpolar molecules.

What are transmembrane integral proteins?

Proteins that span the width of the phospholipid bilayer and assist in the transport of materials across the membrane.

What property do integral proteins possess?

They are amphipathic, having both hydrophilic and hydrophobic properties.

What is a concentration gradient?

The difference in concentration of a substance that can be visualized by a hill, indicating the change over time.

What does 'down the concentration gradient' mean?

It refers to the movement from higher concentration to lower concentration levels.

Distinguish between active and passive transport.

Active transport requires energy to move substances against their concentration gradient, while passive transport does not require energy and substances move down their concentration gradient.

What are the types of passive transport?

Types of passive transport include simple diffusion, facilitated diffusion, and osmosis.

What is diffusion?

The movement of a substance down a concentration gradient (from high to low) that requires no energy input.

What factors affect the rate of diffusion?

Factors include concentration gradient, distance, temperature, and size of molecules.

Define dynamic equilibrium.

A state where opposite processes occur at equal rates, leading to a stable internal environment.

What types of molecules can perform simple diffusion?

Small, nonpolar molecules like Oxygen (O2) and Carbon Dioxide (CO2).

What defines facilitated diffusion?

The movement of molecules down a concentration gradient assisted by transport proteins.

What are the requirements for facilitated diffusion to occur?

Molecules require assistance from transmembrane integral proteins, specifically channel proteins and carrier proteins.

Name the types of transmembrane proteins used in facilitated diffusion.

Channel proteins and carrier proteins.

Why must it be a transmembrane integral protein?

Because only transmembrane integral proteins can function on both sides of the bilayer and transport molecules across it.

How is facilitated diffusion controlled?

It is controlled by the selective passage of specific molecules through the presence of transmembrane integral proteins.