1.3.1 Diffusion

• Diffusion is the net movement of molecules from an area of high concentration to an area of low concentration.
• The cell membrane is a selective barrier that surrounds cells and is composed of a phospholipid bilayer.
• Oxygen diffuses from the air in the lungs into the blood because the oxygen concentration is higher in the air than in the blood.
• A larger surface area decreases the rate of diffusion.

  False
• Match the type of transport with its description:

  Diffusion ↔️ Net movement of molecules from high to low concentration

  Osmosis ↔️ Diffusion of water across a semi-permeable membrane

  Active transport ↔️ Movement of molecules against the concentration gradient
• The greater the difference in concentration, the faster the net movement of molecules
• How does surface area affect diffusion?

  Provides more pathways
• Match the transport mechanism with its description:

  Diffusion ↔️ Movement from high to low concentration

  Osmosis ↔️ Diffusion of water across a membrane

  Active Transport ↔️ Movement against a concentration gradient
• What is required for active transport to occur?

  Energy input
• Active transport moves molecules from an area of low concentration to high concentration.

  True
• In diffusion, oxygen moves from the lungs into the blood because the oxygen concentration is higher in the air
• What is the primary structure of the cell membrane?

  Phospholipid bilayer
• Channel proteins allow ions and small polar molecules to cross the cell membrane.


  True
• Smaller molecules diffuse more quickly
• Diffusion requires energy input.

  False
• Small polar molecules can pass directly through the phospholipid bilayer of the cell membrane.

  False
• A higher temperature increases the rate of diffusion by affecting the kinetic energy of molecules.
• Arrange the following types of transport in order from least energy required to most energy required:

  1️⃣ Diffusion

  2️⃣ Osmosis

  3️⃣ Active transport
• What is the primary driver of diffusion?

  Concentration gradient
• Temperature increases the kinetic energy of molecules, thereby increasing the rate of diffusion.


  True
• Smaller molecules move through membranes more easily
• Osmosis involves the movement of water from an area of high solute concentration to low solute concentration.

  False
• Osmosis is the diffusion of water across a semi-permeable membrane
• Does diffusion require energy input?

  No
• Diffusion requires energy input to move molecules across a membrane.

  False
• Small, nonpolar molecules can diffuse directly through the cell membrane
• How does temperature affect the rate of diffusion?

  Increases kinetic energy
• Match the transport mechanism with its characteristics:

  Diffusion ↔️ Moves from high to low concentration without energy

  Osmosis ↔️ Water moves across a semi-permeable membrane

  Active Transport ↔️ Requires ATP to move against concentration