2.5 Membrane Permeability

• What does membrane permeability refer to?

  Extent molecules pass through
• Membrane permeability depends largely on the membrane's composition
• Membrane transport mechanisms can be categorized into passive and active transport.
• What is the key mechanism of passive transport?

  Movement down concentration gradient
• Active transport requires the direct use of energy
• Membrane proteins play a role in both passive and active transport.
• Order the steps of membrane permeability in terms of molecule type from highest to lowest permeability.

  1️⃣ Hydrophobic molecules

  2️⃣ Hydrophilic molecules

  3️⃣ Ions
• Match the molecule type with its permeability and transport mechanism:

  Hydrophobic ↔️ High permeability, Simple diffusion

  Hydrophilic ↔️ Low permeability, Protein channels/carriers

  Ions ↔️ Very low permeability, Specialized transport proteins
• What are the main factors affecting membrane permeability?

  Composition, temperature, solute size, charge
• Unsaturated lipids increase membrane permeability because they create more space within the bilayer.
• Higher temperatures increase kinetic energy, which in turn increases permeability
• Why do larger molecules have lower permeability?

  They struggle to pass through
• Match the transport type with its energy requirement and key mechanism:

  Simple Diffusion ↔️ No energy, Diffusion through lipid bilayer

  Facilitated Diffusion ↔️ No energy, Protein channels/carriers

  Active Pumps ↔️ Yes, ATP-dependent protein pumps
• Osmosis is a type of passive transport that involves water movement across a semipermeable membrane.
• What type of energy is used in active transport pumps?

  ATP
• Bulk transport includes endocytosis and exocytosis
• Hydrophobic molecules have high permeability and use simple diffusion for transport.
• Order the factors affecting membrane permeability from most significant to least significant based on their direct impact.

  1️⃣ Membrane Composition

  2️⃣ Temperature

  3️⃣ Solute Size

  4️⃣ Solute Charge
• What type of molecules move through simple diffusion?

  Small, nonpolar
• Osmosis does not require energy to move water across a membrane.
• What type of molecules move across the cell membrane in simple diffusion without energy expenditure?

  Small, nonpolar
• Facilitated diffusion relies on membrane proteins
• Oxygen moves across the cell membrane via osmosis.

  False
• What energy source is used by ATP-dependent protein pumps in active transport?

  ATP
• Match the active transport mechanism with its key feature:

  Pumps ↔️ Direct ATP use

  Cotransport ↔️ Electrochemical gradient

  Bulk Transport ↔️ Large material movement
• Bulk transport involves the processes of endocytosis and exocytosis
• Which type of passive transport involves water moving across a semipermeable membrane?

  Osmosis
• Active pumps move molecules down their concentration gradient.

  False
• Cotransport relies on an electrochemical gradient
• Steps in the process of passive transport:

  1️⃣ Simple diffusion: Molecules move through lipid bilayer

  2️⃣ Osmosis: Water moves across a membrane

  3️⃣ Facilitated diffusion: Proteins assist molecule movement
• In osmosis, what determines the direction of water movement across the membrane?

  Water concentration
• Passive transport requires energy from the cell in the form of ATP.

  False
• Which active transport mechanism uses ATP directly to move molecules against their concentration gradient?

  Pumps
• Cotransport can occur via symport or antiport
• The sodium-potassium pump maintains the electrochemical gradient in nerve cells.
• What type of transport involves the movement of large amounts of material via vesicles?

  Bulk transport
• Exocytosis releases substances from the cell.
• What is an example of a pump that uses direct ATP to move molecules against their gradient?

  Sodium-potassium pump
• Cotransport uses ATP indirectly by leveraging the electrochemical gradient
• What are the two main processes involved in bulk transport?

  Endocytosis and exocytosis