B1 Cell Transport

• What is diffusion?


  movement of particles from an area of high concentration to an area of low concentration along a concentration gradient. this is a passive process (does not require energy)
• What are three factors that affect the rate of diffusion?

  1. concentration gradient 2. temperature 3. membrane surface area
• How are villi adapted for exchanging substances?

  1. long and thin - increases surface area 2. one-cell thick membrane - short distance for gases to diffuse 3. good blood supply - maintains a steep concentration gradient
• How are the lungs adapted for efficient gas exchange?

  1. contain alveoli - large surface area 2. moist membrane - increases rate of diffusion 3. one cell thick - short distance for gases to diffuse 4. good blood supply - maintains steep concentration gradient
• How are fish gills adapted for efficient gas exchange?

  1. large surface area for gases to diffuse across 2. thin layer of cells - short distance for gases to diffuse 3. good blood supply - maintains steep concentration gradient
• What is osmosis?

  diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane
• Give one example of osmosis in a plant

  water moves from the soil into the plant root hair cell
• What is active transport?

  movement of particles against a concentration gradient (opposite of diffusion). move from an area of low concentration to an area of high concentration. Uses energy from respiration
• Why is active transport needed in plant roots?

  concentration of mineral ions in the soil is lower than in plant root hair cells. Mineral ions must move from a lower concentration to a higher concentration against the concentration gradient
• What is the purpose of active transport in the small intestine?

  sugars can be absorbed when the concentration of sugar in the small intestine is lower than the concentration of sugar in the blood