Diffusion

• Diffusion is the spreading out of particles resulting in a net movement from an area of higher concentration to an area of lower concentration.
• Cells need oxygen for respiration, which is carried out by mitochondria.
• Cells are surrounded by a high concentration of oxygen because oxygen is transported in the bloodstream from the lungs.
• The oxygen molecules move into the cell by diffusion.
• The oxygen molecules are moving from an area of higher concentration to an area of lower concentration.
• The oxygen is used to generate energy in respiration, producing the waste gas carbon dioxide.
• Cells have a higher concentration of carbon dioxide inside the cell than outside, so the carbon dioxide moves out of the cell by diffusion.
• Urea is a waste product produced inside cells that diffuses out of the cells into the blood plasma and is excreted by the kidneys.
• The rate of diffusion is affected by three main factors: the difference in concentrations, temperature, and the surface area of the membrane.
• The concentration gradient is the difference in concentrations between the outside and inside of a cell, and the greater the concentration gradient, the faster diffusion takes place.
• The surface area of the cell membrane affects the rate of diffusion, with a larger surface area leading to a greater rate of diffusion.
• The temperature affects the rate of diffusion, with a higher temperature leading to a greater rate of diffusion.