cell membranes

• Membranes are found in all cells and have the same basic structure.
• Membranes are partially permeable and can separate the inside from the outside of a cell.
• Membranes can control what enters and leaves the cell.
• Membranes are composed of a bilayer of phospholipids, also known as a phospholipid bilayer.
• Charged, polar and large particles cannot pass through membranes.
• Proteins transport molecules that cannot fit through the membrane, while water is small enough to move through the membrane without a transport protein.
• Cholesterol makes the membrane fluid.
• Types of proteins include channel proteins, carrier proteins, glycoproteins, glycolipids, integral proteins, and peripheral proteins.
• Channels proteins open and close pores.
• Carrier proteins are a type of protein where the substrate binds to the receptor and changes the shape of the protein, allowing the substrate to pass through.
• Glycoproteins are a type of protein where branching carbohydrates are attached, used for cell to cell recognition.
• Glycolipids are a type of protein where branching carbohydrates are attached to phospholipids, used for cell communication.
• Integral proteins are proteins that go all the way through the membrane.
• Peripheral proteins are proteins that float on the surface of the membrane.
• Cholesterol stabilises the fluid mosaic, makes the membrane less permeable to water soluble molecules, separates phospholipids and prevents the membrane crystalising, anchors peripheral proteins to the membrane, and is not found in plant cells because they have a cell wall.
• Very small, without charge, non-polar and lipid soluble particles can fit through the plasma membrane.
• Cholesterol stabilises the fluid mosaic, makes the membrane less permeable to water soluble molecules, separates phospholipids and prevents the membrane crystalising, anchors peripheral proteins to the membrane, and is not found in plant cells because they have a cell wall.