Summary

• What is the fluid-mosaic model of membrane structure?

  Molecules move laterally in phospholipid bilayer
• What components are found in the fluid-mosaic model?

  Phospholipids, proteins, glycoproteins, glycolipids
• What is the basic structure of all cell membranes?

  Same for cell-surface and eukaryotic organelle membranes
• How do phospholipids arrange themselves in a cell membrane?

  Bilayer with fatty acid tails inward
• What are intrinsic proteins in a cell membrane?

  Proteins that span the bilayer
• What are extrinsic proteins in a cell membrane?

  Proteins located on the surface of the membrane
• Where are glycolipids found in a cell membrane?

  On the exterior surface of the membrane
• Where are glycoproteins found in a cell membrane?

  On the exterior surface of the membrane
• What role does cholesterol play in cell membranes?

  Increases rigidity and decreases fluidity
• How does the phospholipid bilayer adapt for vesicle formation?

  It is fluid, allowing bending and movement
• What is simple diffusion?

  Movement from high to low concentration
• What types of substances move by simple diffusion?

  Lipid-soluble or very small substances
• What is the nature of movement in simple diffusion?

  Passive, does not require energy
• What limitations does the phospholipid bilayer impose?

  Restricts movement of polar and larger substances
• What is facilitated diffusion?

  Movement through specific channel or carrier proteins
• What types of substances move by facilitated diffusion?

  Water-soluble, polar, or charged substances
• How do channel proteins function in facilitated diffusion?

  Facilitate diffusion of water-soluble substances
• What is the role of carrier proteins in facilitated diffusion?

  Change shape to transport substances
• How does osmosis occur?

  Water moves from high to low water potential
• What is the definition of water potential?

  Measure of likelihood of water movement
• What is active transport?

  Movement against a concentration gradient using ATP
• What is the role of ATP in active transport?

  Provides energy for carrier protein shape change
• What is co-transport?

  Simultaneous movement of two substances via a co-transporter
• How does sodium ion absorption occur in the ileum?

  Na⁺ actively transported to establish a gradient
• What happens to glucose during co-transport?

  Moves against its gradient with Na⁺ assistance
• How does the rate of movement across membranes increase?

  By increasing surface area and protein numbers
• What adaptations do specialized cells have for transport?

  More protein channels and larger surface area
• Why is it important to control variables in experiments?

  To ensure results are valid and comparable
• Why is % change in mass calculated?

  To enable comparison of different samples
• Why are potato samples blotted dry before weighing?

  To remove excess water affecting mass
• What happens to plant tissue in a higher water potential solution?

  Gains mass as water enters by osmosis
• What happens to plant tissue in a lower water potential solution?

  Loses mass as water exits by osmosis
• What happens to plant tissue in an isotonic solution?

  No net gain or loss of water occurs
• How does temperature affect membrane permeability?

  Higher temperatures increase permeability
• How does pH affect membrane permeability?

  Extreme pH levels denature transport proteins
• How do lipid-soluble solvents affect membrane permeability?

  Increase permeability by dissolving the bilayer
• What is the formula for calculating dilution?

  C₁ x V₁ = C₂ x V₂
• How do you calculate the dilution factor?

  Desired concentration divided by stock concentration
• How do you calculate the volume of stock solution?

  Dilution factor times final desired volume
• How do you calculate the volume of distilled water?

  Final volume minus volume of stock solution