KA2

• The structure off a cell membrane is composed of proteins and phospholipids molecules
• The membrane is selectively permeable
• The membrane allows small, soluble molecules to pass across but stops the passage of large, insoluble molecules
• One of the functions proteins have is they form channels to allow small molecules to pass through the membrane
• one of the functions protein have is it acts as a carrier for substances in and out of the cell (active transport)
• passive transport occurs down a concentration gradient and doesn’t require energy
• 2 examples of passive transport is diffusion and osmosis
• Diffusion is the movement of molecules down a concentration gradient from a high concentration to a of low concentration
• diffusion occurs whenever there is a difference in concentration
• diffusion is passive transport
• osmosis is the diffusion of water down a concentration gradient from higher water concentration to a lower water concentration through the selectively permeable membrane
• Active transport requires energy for the membrane proteins to move molecules and ions against a concentration gradient
• Active transport requires energy
• passive transport is the movement of molecules or ions from a lower concentration to a higher concentration
• osmosis moves proteins and ions against the concentration gradient
• Plant cell in pure water will cause the plant cell to swell and become turgid
• plant cell in a stronger salt/sugar solution will cause the cell membrane to shrink and become plasmolysed
• animal cell in a strong salt/sugar solution will cause the cell to shrink
• animal cell in pure water solution will cause the cell to burst