S2 Ch15 (TS)

• Define diffusion: The net movement of substances from a region of higher concentration to a region of lower concentration
• Does diffusion require energy to take place?

  No
• Diffusion may occur across a membrane, as long as the diffusing particles are small enough to pass through
• Concentration of gradient is the difference in concentration of a substance between 2 regions. The steeper the concentration gradient, the higher the rate of diffusion
• The higher the temperature, the higher the rate of diffusion (heat: kinetic energy)
• The higher the mass of a particle, the slower it diffuses (eg: helium is lighter than co2, heavy objects move slower)
• Medium affects rate of diffusion: diffusion is faster through a gas than a liquid, very slow/impossible through solid (because particles closely packed)
• Surface area to volume ratio: the higher the surface area to volume ratio, the faster the rate of diffusion
• Define osmosis: the net movement of WATER molecules from a solution of higher water POTENTIAL to a solution of lower water POTENTIAL through a partially permeable membrane
• Does osmosis need energy to take place?

  No.
• A dilute solution has a smaller amount of dissolved solute, a concentrated solution has a higher amount of dissolved solute. Dilute solutions have higher water potential
• What is the function of plasma in blood?

  Transport dissolved substances around the body
• What is the function of red blood cells in blood?

  Transport oxygen from the lungs to the rest of the body
• Red blood cells contain: haemoglobin
• A feature of the red blood cell is its biconcave shape which increases surface area to volume ratio for faster diffusion of oxygen
• What is the function of white blood cells in blood?

  Protects the body against harmful organisms
• The 2 types of white blood cels are: Phagocytes (engulf and digest bacteria) Lymphocytes (antibody protection)
• What is the function of platelets in blood?

  Triggers a series of chemical reactions to form blood clot to prevent excessive bleeding
• What is the function of arteries?

  To carry oxygenated blood away from the heart to the rest of the body
• What is the function of capillaries ?

  The site of exchange of substances between blood and body cells
• What is the function of veins?

  Carries deoxygenated blood back into the heart
• arteries carry oxygenated blood away from the heart to the different parts of the body
• arteries branch into capillaries where nutrients and oxygen enter the organs and tissues while metabolic waste enter the blood in the capillaries
• capillaries join back to form veins where veins carry deoxygenated blood back to the heart
• deoxygenated blood is transported to the lungs where it is oxygenated and carbon dioxide leaves the blood
• what is the structural features of arteries?

  1. thick, muscular, elastic wall to withstand high pressure
  2. narrow lumen
• what is the structural features of capillaries?

  1. has one -cell thick wall to shorten diffusion distance of substances
• what is the structural features of veins?

  1. has thinner and less muscular wall (as compared to arteries)
  2. has wide lumen
  3. contains semilunar valves to prevent back -flow of blood
• Why are transport systems necessary?

  Multicellular organisms such as plants and animals are made of many cells, simple diffusion and osmosis are not sufficient to send substances around these organisms as some cells are deep inside the body
• what is division of labour in a multicellular organism?

  each type of cell, tissue, organ and system perform specialised functions
• a plant attains nutrients from its surrounding environment through photosynthesis in the leaves and absorption of mineral salts and water through the roots
• Why are transport systems needed in plants?

  Nutrients are required by all parts of the plant not just by the roots and leaves so a transport system is needed to distribute nutrients around the plant
• what do xylem vessels transport?

  water and mineral salts from the roots to the rest of the plant
• what do phloem tissues transport?

  sucrose and amino acids from the leaves to the rest of the plant
• What are structural features of xylem?

  • thick lignified walls to provide mechanical support
  • hollow and narrow lumen to allow water to pass through quickly without obstruction
• Xylem inside, phloem outside
• in plants, root hair cells absorb oxygen and mineral salts through?

  diffusion (higher concentration to lower concentration)
• in humans, oxygen gas diffuses from the lungs into the bloodstream by diffusion (higher concentration to lower concentration)
• in humans, carbon dioxide gas diffuses from the bloodstream into the lungs (higher concentration to lower concentration)
• in humans, digested food diffuses from the ileum into the bloodstream (higher concentration to lower concentration)