Unit3

• diffusion is the net movement of particles from a higher concentration region to a lower concentration region, as a result from their random movement
• the rate of diffusion depends on temperature, surface area, concentration gradient, and distance travelled
• Energy for diffusion comes from the kinetic energy of random movement of molecules and ions
• Some substances move in and out of the cell by diffusion through the cell membrane
• The diffusion of gases and solutes is important as without it, molecules which are needed for life, for example, glucose and oxygen for respiration, would not be able to get to the places they are needed. Water is needed as a solvent
• the role of water as a solvent in digestion is to help break down food into smaller molecules
• the role of water as a solvent in excretion is to transport substances out of the body
• the role of water as a solvent in transport is to allow the movement of molecules
• water diffuses through partially membranes by osmosis
• water moves in and out os the cells by osmosis through the cell membrane
• Osmosis is the net movement of water molecules from a region of higher water potential to a region of lower water potential through a partially permeable membrane
• hypertonic solution has a higher concentration of solute than another solution, meaning water will flow into it.
• hypotonic solution has a lower concentration of solute than another solution, meaning water will flow out of it.
• An isotonic solution is any external solution that has the same solute concentration and water concentration compared to body fluids.
• In an isotonic solution, no net movement of water will take place.
• in a hypotonic solution as compared to inside the cell, water from the solution moves into the cell, creating ​turgor pressure ​on the wall​. This makes the cell ​turgid​, therefore supporting the plant, and giving it its shape. The cell wall is inelastic, so doesn't burst

  
• In ​isotonic solutions there is no concentration gradient, so the cell doesn’t change shape

  
• In a ​hypertonic solution ​as compared to inside the cell, water leaves the cell as the solution inside the cell has higher water potential. The cell shrivels and becomes ​flaccid

  
• When too much water is lost from the cell by osmosis, the cell membrane is pulled away from the cell wall and the cell undergoes ​plasmolysis​.

  
• Water potential and osmosis govern the uptake and loss of water by organisms, with water moving from areas of higher to lower potential, ensuring proper hydration and osmotic balance within cells and tissues.
• active transport is the movement of particles through a cell membrane from a region of lower concentration to a region of higher concentration using energy from respiration
• protein carriers move molecules or ions across a membrane during active transport
• Active transport is needed when an organism wants to optimize the number of nutrients it can take up - ion uptake by root hairs and uptake of glucose by epithelial cells of villi.
• turgid- swollen and distended or congested.
• turgor pressure- the force within the cell that pushes the plasma membrane against the cell wall.
• Plasmolysis- the process in which cells lose water when they are placed in a hypertonic solution.
• flaccid- when water is lost from the cells by osmosis and becomes soft
• explain how active transport takes place in villi?

  during digestion, the villi absorb the soluble nutrients over time, the concentration of nutrients in the villi reach an equilibrium with the concentration in the gut
• minerals in the soil are absorbed by active transport using energy from respiration
• explain the importance of diffusion of gases and solutes in living organisms

  • obtain many of their requirements
  • get rid of many of their waste products
  • carry out gas exchange for respiration