2.5.1 Cell Surface Membrane

• What are membranes considered in all cells?

  Vital structures
• What does the cell surface membrane create?

  An enclosed space separating the internal cell environment from the external environment
• What do intracellular membranes form within the cell?

  Compartments such as organelles and vacuoles
• What is the permeability characteristic of membranes?

  They are partially permeable
• What roles do membranes play in material exchange?

  They control the exchange of materials passing through them
• What types of transport can substances use to cross membranes?

  Diffusion, facilitated diffusion, osmosis, and active transport
• How do membranes contribute to cell signaling?

  By acting as an interface for communication between cells
• What is an example of a membrane-bound organelle?

  Lysosome
• What do lysosomes contain that is crucial for their function?

  Hydrolytic enzymes
• Why is compartmentalization important for lysosomes?

  To prevent hydrolytic enzymes from breaking down cellular components
• When was the fluid mosaic model of membranes first outlined?

  1972
• What does the fluid mosaic model explain?

  How biological molecules are arranged to form cell membranes
• Why are cell membranes described as 'fluid'?

  Because phospholipids and proteins can move around via diffusion
• How do phospholipids mainly move within the membrane?

  Sideways, within their own layers
• What analogy is used to describe the movement of proteins in the fluid mosaic model?

  Like icebergs in the sea
• What does the term 'mosaic' refer to in the fluid mosaic model?

  The scattered pattern produced by proteins within the phospholipid bilayer
• What are the four main components of the fluid mosaic model?

  Phospholipids, cholesterol, glycoproteins, and glycolipids
• What forms the basic structure of the membrane?

  Phospholipids
• What do the tails of phospholipids form in the membrane?

  A hydrophobic core
• How do phospholipid bilayers act as barriers?

  They prevent most water-soluble substances from passing
• What happens to water-soluble molecules due to phospholipid bilayers?

  They cannot leak out of the cell and unwanted molecules cannot enter
• How can phospholipids act as signaling molecules?

  By moving within the bilayer to activate other molecules
• What is the effect of cholesterol on membrane fluidity at low temperatures?

  It increases fluidity, preventing rigidity
• How does cholesterol stabilize the cell membrane at higher temperatures?

  By stopping the membrane from becoming too fluid
• What is the role of cholesterol in relation to phospholipid tails?

  It binds to the hydrophobic tails, stabilizing them
• What is the effect of cholesterol on the impermeability of the membrane to ions?

  It affects the impermeability
• What do glycolipids and glycoproteins contain that allows them to act as receptors?

  Carbohydrate chains on their surface
• What are the three main receptor types associated with glycolipids and glycoproteins?

  Signaling receptors, endocytosis receptors, and adhesion receptors
• What role do some glycolipids and glycoproteins play in cell recognition?

  They act as cell markers or antigens
• What do transport proteins create to facilitate movement across the membrane?

  Hydrophilic channels
• What are the two types of transport proteins?

  Channel proteins and carrier proteins
• How do carrier proteins function in transporting substances?

  They change shape to transport a substance across the membrane
• What is the specificity of transport proteins?

  Each transport protein is specific to a particular ion or molecule
• How do transport proteins contribute to cellular control?

  They allow the cell to control which substances enter or leave
• What are the main components of cell membranes and their functions?

  • Phospholipids: Form the bilayer and act as a barrier
  • Cholesterol: Increases fluidity and stability
  • Glycoproteins: Act as receptors and cell markers
  • Glycolipids: Involved in cell recognition and signaling
  • Transport proteins: Facilitate movement of substances
• What is the fluid mosaic model and its significance?

  • Describes the arrangement of molecules in cell membranes
  • Explains fluidity and mosaic appearance due to proteins
  • Important for understanding membrane functions like transport and signaling
• How do the components of the fluid mosaic model interact to maintain membrane integrity?

  • Phospholipids create a barrier
  • Cholesterol modulates fluidity and stability
  • Proteins facilitate transport and signaling
  • Glycolipids and glycoproteins assist in recognition and communication