Biological membranes

• What are cell membranes described as?

  Partially permeable barriers
• What is the function of cell membranes?

  They separate the cell from the environment
• What is compartmentalisation in cells?


  • Formation of separate membrane-bound areas
  • Allows distinct environments for different processes
• How do biological membranes regulate permeability?

  Through properties of component molecules
• What types of proteins determine cell membrane permeability?

  Carrier and channel proteins
• What are the roles of membranes at the cell surface?


  • Separate cell components from the environment
  • Regulate transport of materials
  • Contain enzymes for metabolic pathways
  • Have antigens for immune identification
  • Release chemicals to other cells
  • Contain receptors for signaling
• What are the roles of membranes within the cell?


  • Separate organelle contents from cytosol
  • Lysosomes keep enzymes separate
  • Mitochondria's inner membrane forms cristae for respiration
  • Chloroplast thylakoids house chlorophyll for photosynthesis
• What is the cell surface membrane also known as?

  Plasma membrane
• What is the structure of the phospholipid bilayer?


  • Hydrophilic phosphate heads form inner and outer layers
  • Hydrophobic fatty acid tails are sandwiched in between
  • Creates a hydrophobic core
• What model describes the structure of cell membranes?

  Fluid mosaic model
• What are the components of phospholipids?

  Phosphate group and fatty acids
• How do phospholipids behave in water?

  They form a bilayer due to amphipathic nature
• What are the types of membrane proteins?

  • Channel proteins: allow passive movement
  • Carrier proteins: facilitate diffusion and active transport
• What do channel proteins do?


  Form channels for passive movement of molecules
• What is the function of carrier proteins?


  Facilitate diffusion and active transport
• What are glycoproteins and their functions?

  • Proteins with attached carbohydrates
  • Used in cell adhesion and signaling
  • Act as receptors for neurotransmitters and hormones
• What are glycolipids and their roles?

  • Lipids attached to carbohydrates
  • Serve as antigens or cell markers
  • Signal to the immune system for self-identification
• What is the role of cholesterol in cell membranes?

  Regulates fluidity and stability of membranes
• How does temperature affect membrane fluidity?

  Higher temperatures increase fluidity and permeability
• What happens to saturated fatty acids when temperature drops?


  They become compressed
• How do unsaturated fatty acids respond to temperature changes?


  They maintain fluidity due to kinks
• What role does cholesterol play at low temperatures?


  Prevents phospholipids from packing closely
• How do organisms adapt their membranes in cold environments?

  • Change the ratio of saturated to unsaturated fatty acids
  • Some plants and microorganisms do this
• What happens to phospholipids when temperature rises?


  They move faster, increasing fluidity
• How does increased membrane fluidity affect membrane proteins?

  Proteins may drift, altering reaction rates
• What happens to proteins at high temperatures?

  They may denature and lose function
• What is the effect of temperature on beetroot cell membranes?

  Heating disrupts membranes, causing pigment leakage
• How is betalain leakage measured?

  Using a colorimeter to measure absorbance
• What effect do organic solvents have on cell membranes?

  • Dissolve lipids and disrupt membranes
  • Increase fluidity and permeability
• What happens to proteins in the cytoskeleton at high temperatures?

  • They may denature, increasing membrane permeability
  • Membrane-embedded enzymes cease to function
• What is the function of lysosomes in a cell?

  • Keep hydrolytic enzymes separate from the cell
  • Prevents damage to other cellular components
• What is the role of the inner mitochondrial membrane?

  Site of aerobic respiration
• What is the role of thylakoids in chloroplasts?

  House chlorophyll for photosynthesis
• What is the definition of the fluid mosaic model?

  Fluid- phospholipids are free to move within the layer

  Mosaic- proteins are embedded in the bila
• What is the function of glycoproteins in cell membranes?

  Cell adhesion and signaling
• What is the function of glycolipids in cell membranes?

  Act as antigens or cell markers
• How does cholesterol contribute to membrane stability?

  Regulates fluidity and prevents crystallization
• What happens to proteins at high temperatures?

  They may denature and lose function
• What is the effect of solvents on phospholipids?

  They dissolve lipids and disrupt membranes
• What is diffusion?

  The movement from high to low concentration