Diffusion

• What is the primary composition of the cell membrane?

  Phospholipid bilayer with embedded proteins
• Why is the cell membrane described as a "fluid mosaic"?

  Phospholipids and proteins can move laterally
• What is the function of cholesterol in the cell membrane?

  Stabilizes the membrane's fluidity
• How do small non-polar molecules pass through the cell membrane?

  By simple diffusion
• What is the role of glycoproteins and glycolipids in the cell membrane?

  Involved in cell recognition and signaling
• What is required for active transport?

  Energy (metabolic)
• What is passive transport?

  No energy required for substance movement
• Why is diffusion considered a passive process?

  It relies on natural motion of particles
• What causes particles to be in motion during diffusion?

  Kinetic energy they possess
• How do small non-polar molecules like oxygen diffuse across membranes?

  They can easily diffuse across plasma membranes
• What is the definition of diffusion?

  The net movement of particles from an area of high concentration to an area of low concentration
• What is facilitated diffusion?

  Movement through transmembrane channels and carriers
• What types of proteins facilitate facilitated diffusion?

  Protein channels and carrier proteins
• What do protein channels do?

  Form open passageways for specific molecules
• How do gated channels function?

  Open for specific ions when bound
• What happens when ions bind to gated channels?

  The protein changes shape to regulate flow
• How do carrier proteins facilitate diffusion?

  By binding specific molecules and changing shape
• What is the energy requirement for carrier proteins during diffusion?

  No ATP is required
• What drives the movement of molecules through carrier proteins?

  Kinetic energy of the molecules
• What does it mean that the plasma membrane is selectively permeable?

  It allows certain substances to pass through
• What is the significance of moving substances down their concentration gradient?

  It allows for passive transport without energy
• Why can't charged ions and polar molecules easily diffuse across membranes?

  Due to hydrophobic fatty-acid tails
• What do transmembrane channels and carriers facilitate?

  Movement for charged ions and polar molecules
• How do gated channels differ from regular channels?

  They open only for specific ions
• What happens during the binding of a molecule to a carrier protein?

  The protein changes shape to transport the molecule