Diffusion

• What is diffusion?

  Diffusion is the spreading out of particles resulting in net movement from higher to lower concentration.
• Why is diffusion considered a passive process?

  Because no energy is required for diffusion to occur.
• What types of molecules can move across cell membranes via diffusion?

  Small molecules like oxygen, glucose, amino acids, and water can move across.
• Where does oxygen move in the body during diffusion?

  Oxygen moves from the alveoli which is in lungs into red blood cells and is carried to cells across the body for respiration
• What is gas exchange?

  Gas exchange is the movement of gases like oxygen and carbon dioxide across membranes.
• What waste product moves from liver cells into blood plasma?

  Urea moves from liver cells into blood plasma.
• What factors affect the rate of diffusion?

  • Concentration gradient
  • Temperature
  • Surface area of the membrane
• How does the concentration gradient affect diffusion?

  The greater the difference in concentration, the faster the rate of diffusion.
• How does temperature affect the rate of diffusion?

  The greater the temperature, the greater the movement of particles, resulting in faster diffusion.
• How does surface area affect diffusion?

  The greater the surface area, the more space for particles to move through, resulting in faster diffusion.
• How is the surface area to volume ratio calculated?

  It is calculated by finding the volume and surface area, then writing the ratio in the smallest whole numbers.
• Why is a large surface area to volume ratio beneficial for organisms?

  A large ratio means diffusion is sufficient for supplying and removing necessary gases.
• Why can't multicellular organisms rely solely on diffusion?

  They have a small surface area to volume ratio, requiring adaptations for transport.
• What adaptations do lungs have for gas exchange?

  • Alveoli create a large surface area
  • Thin walls for short diffusion pathway
  • Constant oxygen supply maintains steep concentration gradient
• How do the small intestine and fish gills adapt for efficient diffusion?

  • Small intestine: Villi increase surface area for nutrient absorption
  • Fish gills: Lamellae increase surface area for gas exchange
• How do plant roots and leaves adapt for diffusion?

  • Roots: Root hair cells increase surface area for water and mineral uptake
  • Leaves: Stomata allow gas exchange for photosynthesis
• How do guard cells regulate stomata size?

  Guard cells swell with water to make stomata larger or shrink to make them smaller.
• What is the role of stomata in plants?

  Stomata allow carbon dioxide to enter and oxygen and water vapor to exit.
• How does the flattened shape of leaves aid in gas exchange?

  The flattened shape increases surface area, allowing more carbon dioxide to enter cells.
• What is the significance of air spaces inside leaves?

  Air spaces increase surface area, allowing more carbon dioxide to enter cells.
• How do adaptations in the lungs, small intestine, fish gills, and leaves contribute to diffusion?

  They all increase surface area, provide thin membranes, and maintain concentration gradients for efficient diffusion.
• Where does carbon dioxide move from and to?


  Red blood cells to the lungs to be exhaled- it’s the waste product of respiration
• Why is there a faster rate of diffusion when there is a greater difference in concentration?


  More particles are randomly moving down the gradient than are moving against it
• What molecules can not perform diffusion?


  Large molecules such as starch and proteins
• Name two examples of where diffusion takes place in the body: 


  Gas exchange

  Excretion
• Why is diffusion easy to occur in single-celled organisms?


  They have a large surface to area volume ratio, due to their low metabolic demands, diffusion across the surface of the organism is sufficient enough to meet its needs
• What happens with oxygen and carbon dioxide in the lungs?


  Oxygen is transferred to the blood

  Carbon dioxide is transferred to the lungs
• What is the surface of millions of air sacs in the lungs called?

  Alveoli
• What is alveoli covered in?


  Tiny capillaries which supply the blood
• What are cells that have projections called in the small intestine?

  Villi
• What is absorbed over the membrane of villi?


  Digested food which then go into the bloodstream
• Where does gas exchange take place in fish?


  Gills
• Where does water which contains oxygen passes through and over?


  It passes through the mouth and over the gills
• What are the plates that gills have called?

  Gill filaments
• What are upon gilI filaments?

  Gill lamellae
• Where does diffusion of oxygen into the blood and diffusion of carbon dioxide into the water take place in fish?


  Gills- gill filaments- gill lamellae
• What are the roots of planted adapted for?


  to take up water and mineral ions
• What cells do roots contain?

  Root hair cells with large surface areas
• Where does carbon dioxide diffuse through in the leaves of a plant?


  Stomata For photosynthesis
• Where does oxygen and water vapour move through in the leaves of the plant during gas exchange?


  Stomata, they move out through them