The basics

• What are cell membranes primarily known for?

  They are the boundaries of cells
• What surrounds all cells?

  All cells are surrounded by membranes
• What is another name for the cell-surface membrane?

  Plasma membrane
• What do cell-surface membranes control?

  Which substances enter and leave the cell
• How do substances move across the cell surface membrane?

  By diffusion or active transport
• What is the role of membranes around organelles?

  They divide the cell into different compartments
• What do membranes around organelles act as?

  A barrier between the organelle and cytoplasm
• What substances are kept together inside a mitochondrion?

  Substances needed for respiration
• What happens to RNA in relation to the nuclear membrane?

  RNA leaves the nucleus via the nuclear membrane
• Why does DNA remain in the nucleus?

  It is too large to pass through the membrane
• What are the main components of all cell membranes?

  Lipids, proteins, and carbohydrates
• What model describes the arrangement of molecules in the membrane?

  The fluid mosaic model
• What forms the bilayer in cell membranes?

  Phospholipid molecules
• Why is the phospholipid bilayer described as fluid?

  Phospholipids are constantly moving
• How are proteins arranged in the membrane?

  Scattered through the bilayer like tiles
• What types of proteins are found in the membrane?

  Channel proteins and carrier proteins
• What do receptor proteins on the cell-surface membrane do?

  Allow the cell to detect chemicals
• What is an example of a chemical that binds to receptor proteins?

  Insulin
• What is the basic structure of all cell membranes?

  • Composed of lipids (mainly phospholipids)
  • Proteins
  • Carbohydrates attached to proteins or lipids
• What is the role of cholesterol in cell membranes?

  Restricts the movement of other molecules
• What is required for Practical 4 regarding cell membranes?

  Investigate the effect of a named variable on permeability