Cell membrane and transport test revision

• What is the fluid-mosaic model of cell membranes?

  A model that describes the structure of cell membranes as a mosaic of various components.
• What are the main components of the fluid-mosaic model?

  Phospholipids and proteins.
• What does it mean for a membrane to be selectively permeable?

  It allows some substances to pass through more easily than others.
• What is diffusion and how does it occur?

  • Net movement of particles from higher to lower concentration.
  • Continues until particles are evenly distributed.
  • Passive process; does not require energy.
• What factors affect the rate of diffusion?

  The concentration difference, temperature, surface area, and distance.
• What is facilitated diffusion?

  Diffusion across a membrane involving carrier or channel proteins.
• What is the role of channel proteins in facilitated diffusion?

  They help transport specific molecules across the membrane.
• What is active transport?

  The movement of molecules against their concentration gradient, requiring energy.
• How is the rate of active transport related to respiration?

  The rate of active transport is directly related to the rate of respiration.
• What are the key features of active transport?

  • Molecules move against the concentration gradient.
  • Requires energy (ATP).
  • Involves specific carrier proteins.
  • Rate affected by temperature and ATP availability.
  • Can be saturated; maximum transport rate.
• What is ATP and its role in active transport?

  ATP is adenosine triphosphate, the main energy currency of cells.
• What happens during the process of active transport?

  The carrier protein changes shape to move the molecule across the membrane.
• What is osmosis?

  The movement of water across a selectively permeable membrane.
• What is the water potential gradient?

  The difference in water potential across a distance that drives osmosis.
• How does osmosis affect plant cells?

  It helps maintain turgor pressure, keeping the plant upright.
• How does osmosis affect animal cells?

  It can cause animal cells to swell or shrink depending on the surrounding solution.
• What are the key terms related to transport across membranes?

  • Concentration gradient
  • Diffusion
  • Facilitated diffusion
  • Passive transport
  • Selectively permeable
  • Active transport
  • ATP
  • Carrier protein
• What are the two main processes for bulk transport in cells?

  Endocytosis and exocytosis
• How does endocytosis occur?

  Material is engulfed by extensions of the cell membrane, forming a vesicle
• What happens during phagocytosis?

  Granulocytes engulf bacteria, forming a phagosome that is digested by enzymes
• What are the two larger forms of endocytosis?

  • Phagocytosis: uptake of solid material
  • Pinocytosis: uptake of liquid
• What is formed when granulocytes engulf bacteria?

  A phagosome
• What occurs to the products of digestion in phagocytosis?

  They pass into the cytoplasm
• What is pinocytosis?

  The uptake of liquid by the cell membrane
• How do substances leave the cell during pinocytosis?

  They pass through the cytoplasm in a vesicle that fuses with the cell membrane
• What is exocytosis?

  The process by which substances leave the cell, packaged in vesicles
• What type of substances are often secreted by exocytosis?

  Digestive enzymes
• What is the energy requirement for endocytosis and exocytosis?

  • Both processes are active
  • They use ATP generated by respiration
  • The cell membrane changes shape during these processes
• What is required for the processes of endocytosis and exocytosis to occur?

  Energy in the form of ATP
• Why are endocytosis and exocytosis considered active processes?

  They require energy to change the shape of the cell membrane
• How does the cell membrane play a role in endocytosis and exocytosis?

  The cell membrane is essential for both processes to occur
• Hypertonic?


  A solution with low water potential (high solute concentration)
• Hypotonic?


  Solution with a high water potential (low solute concentration)
• Isotonic?


  Equal solute and water potential = no net movement of water
• Hydrophobic?


  Non-polar
• Hydrophillic?


  Polar
• How to determine the rate of diffusion?


  Rate of diffusion = surface area x difference in concentration/length of diffusion path
• What is co-transport in biology?

  Co-transport is a mechanism used by cells to move substances across their membrane.
• How does co-transport typically function?

  It involves the simultaneous transport of two different molecules across the membrane.
• In what directions can co-transport occur?

  Co-transport can occur in the same or opposite directions.