2.4 Transport Across Membranes

• Cholesterol in the cell membrane maintains fluidity and structural stability
• What is one function of the cell membrane other than acting as a selective barrier?

  Cell communication
• Passive transport does not require ATP
• What drives the movement of molecules in passive transport?

  Concentration gradient
• What is the primary difference between passive and active transport in terms of energy requirements?

  Active transport requires ATP
• Diffusion requires energy to occur.

  False
• Osmosis is the movement of water from an area of high water concentration to an area of low water concentration
• Give an example of gas exchange facilitated by diffusion in the human body.

  Oxygen to bloodstream
• Osmosis occurs from an area of high water concentration to low water concentration
• What happens to a cell when placed in a hypotonic solution?

  It becomes turgid
• Match the cell membrane component with its function:

  Phospholipids ↔️ Form bilayer, selective barrier

  Proteins ↔️ Facilitate transport, receptors

  Cholesterol ↔️ Maintains membrane fluidity
• What is one way the cell membrane supports the structure of the cell?

  Maintains cell shape
• What is an example of active transport in the cell?

  Sodium-potassium pump
• Diffusion occurs from an area of high concentration to low concentration
• Osmosis involves the movement of water molecules across a selectively permeable membrane
• What is diffusion and how does it occur?

  Movement from high to low concentration without energy
• Osmosis is the movement of water molecules across a selectively permeable membrane from an area of low water concentration to an area of high water concentration.

  False
• When a cell is placed in a hypertonic solution, it undergoes plasmolysis due to water moving out
• Ordering the effects of osmosis on a plant cell

  1️⃣ Hypertonic solution causes plasmolysis

  2️⃣ Water moves out of the cell

  3️⃣ Cell membrane shrinks away from the cell wall
• Facilitated diffusion is more efficient than simple diffusion because carrier proteins provide a dedicated pathway
• What is the primary function of ion channels?

  Enable rapid ion movement
• Exocytosis involves vesicles fusing with the cell membrane to release their contents outside the cell.


  True
• Ordering the steps of exocytosis

  1️⃣ Vesicles containing substances are formed

  2️⃣ Vesicles move toward the cell membrane

  3️⃣ Vesicles fuse with the cell membrane

  4️⃣ Substances are released outside the cell
• What is the primary component of the cell membrane?

  Phospholipid bilayer
• Match the component of the cell membrane with its function:

  Phospholipids ↔️ Form the bilayer; selectively permeable

  Proteins ↔️ Transport, receptors, recognition

  Cholesterol ↔️ Maintains fluidity and stability
• The cell membrane is composed solely of phospholipids.

  False
• Match the type of transport with its characteristics:

  Passive transport ↔️ Down concentration gradient, no ATP

  Active transport ↔️ Against concentration gradient, requires ATP
• Order the key functions of the cell membrane:

  1️⃣ Selective barrier

  2️⃣ Cell communication

  3️⃣ Shape maintenance
• Diffusion is the movement of molecules from an area of high concentration to an area of low concentration
• What is the definition of osmosis?

  Water movement across a membrane
• Diffusion allows for the exchange of gases and the movement of nutrients across the cell membrane
• Osmosis is the active movement of water molecules across a membrane.

  False
• Match the effect of osmosis with its description:

  Plasmolysis ↔️ Water moves out of cell

  Turgidity ↔️ Water moves into cell
• The cell membrane is composed primarily of a phospholipid bilayer
• The cell membrane allows cells to interact with their environment through cell communication
• Match the feature with the correct type of transport:

  Passive Transport ↔️ Moves down concentration gradient

  Active Transport ↔️ Requires ATP energy
• Passive transport requires energy to move molecules across the cell membrane.

  False
• Why is diffusion important for gas exchange in cells?

  Moves oxygen and carbon dioxide
• The effects of osmosis depend on the relative concentrations of solutes inside and outside the cell.


  True
• Diffusion allows cells to exchange gases like oxygen and carbon dioxide across the cell membrane