2.3.1 Movement across membranes

• What surrounds all living cells?

  Water
• What is the function of the cellulose cell wall in plant cells?

  It provides structure and support
• What is tissue fluid in mammals?

  Fluid that bathes living cells
• Why do reactions happen faster in solution?

  Water is a solvent
• What is diffusion?

  Movement of particles from high to low concentration
• What is a concentration gradient?

  The difference in concentration between two areas
• What is dynamic equilibrium in diffusion?

  Even dispersion of particles throughout a space
• Is diffusion a passive process?

  Yes, it requires no energy
• Which molecules can pass through the lipid bilayer?

  Fat-soluble molecules like alcohol and steroids
• What type of molecules must pass through protein pores?

  Larger water-soluble molecules like glucose
• What happens to very large molecules in terms of diffusion?

  They cannot diffuse into cells
• How does surface area affect the rate of diffusion?

  Greater surface area increases the rate of diffusion
• What role do microvilli play in cells?

  They increase the surface area for absorption
• How does distance affect the rate of diffusion?

  Greater distance slows the rate of diffusion
• How does the concentration gradient affect diffusion?

  A greater concentration gradient increases the rate of diffusion
• What is Fick's Law related to diffusion?

  Rate of diffusion is proportional to surface area x concentration difference / distance
• How does temperature affect the rate of diffusion?

  Increasing temperature increases the rate of diffusion
• What is facilitated diffusion?

  Diffusion aided by proteins in the membrane
• What are carrier proteins?

  Proteins that change shape to transport molecules
• What are channel proteins?

  Proteins that form channels for molecule passage
• How do solute molecules affect water movement?

  They reduce the opportunities for water to cross
• What is water potential?

  A measure of the free kinetic energy of water
• What is the unit for measuring water potential?

  kPa (Kilopascals)
• What does a higher water potential indicate?

  Greater tendency of water to leave a solution
• What happens to water potential when solute is added?

  It lowers the water potential value
• What is osmosis in animal cells when placed in dilute solutions?

  Water enters and cells swell up
• What happens to animal cells in concentrated solutions?

  Water leaves and cells shrink
• What is cell lysis?

  When animal cells swell and burst
• What is an isotonic solution?

  A solution with the same solute concentration as cytoplasm
• What is osmoregulation?

  Regulating water and mineral salts in blood
• What happens to plant cells when they take up water by osmosis?

  They swell but do not burst due to cell wall
• What does turgid mean in plant cells?

  Swollen and hard due to water uptake
• What happens to plant cells in concentrated sugar solutions?

  They lose water and become flaccid
• What is plasmolysis in plant cells?

  Contents shrink and pull away from cell wall
• What characterizes cells carrying out active transport?

  Presence of numerous mitochondria
• What is active transport?

  Movement against concentration gradient requiring energy
• What is endocytosis?

  Process of engulfing material to form a sac
• What is exocytosis?

  Process of removing materials out of the cell
• What is co-transport?

  Transport of two substances simultaneously across a membrane
• How does sodium-glucose co-transport work?

  Sodium ions help glucose enter the cell