2. Transport across Cell Membranes

• The cell membrane is selectively permeable, meaning only certain substances can pass through it. The cell membrane is made up of proteins and phospholipids.
• High concentration to a Low concentration requires no energy. This is passive transport.
• Low concentration to High concentration requires energy. This is active transport.
• Diffusion is the movement of molecules from an area of of High concentration to a area of Low concentration. This is a passive process and does NOT require energy,
• Active transport is the movement of molecules or ions against a concentration gradient. This uses membrane proteins. This is an active process and requires energy.
• Proteins in the cell membrane are responsible for moving molecules through active transport.
• When you place an animal cell into a water concentration that is higher than outside the cell, water will enter the cell and the cell will swell up and burst due to Osmosis.
• If you place an animal cell into a water concentration that is lower than inside the cell, water will exit the cell and it will shrink.
• If you place a plant cell into a water concentration that is higher outside, water will move into the cell and the cell will become turgid.
• If you place a plant cell into a water concentration that is lower outside, water will exit the cell and the cell will become plasmoyed.
• Osmosis is the movement of molecules from a higher water concentration to a lower water concentration through a selectively permeable membrane.
• What a turgid plant cell looks like

  
• What a plasmoysed plant cell looks like

  
• When a red blood cell shrinks

  
• When a red blood cell will swell up and burst