membranes

• What does the cell membrane appear as under an electron microscope?

  A double line
• What is the width of the cell membrane?

  7-8 nm
• What is the primary function of the cell membrane?

  Separates the living cell from surroundings
• How does the cell membrane control substance movement?

  It regulates which substances enter and exit
• What role does the cell membrane play in nutrient uptake?

  It controls the uptake of nutrients
• What does the cell membrane allow to pass out of the cell?

  Waste products
• What substances does the cell membrane secrete?

  Enzymes and glycoproteins
• What is one function of the cell membrane related to cell recognition?

  It facilitates cell recognition
• How do phospholipids arrange themselves in the membrane?

  They form bilayers
• What is the nature of the phosphate head of a phospholipid?

  It is polar and hydrophilic

  
• What is the nature of the fatty acid tails of a phospholipid?

  They are non-polar and hydrophobic

  
• What does the phospholipid bilayer allow to enter and leave the cell?

  Lipid-soluble (non-polar) molecules

  
• What does the phospholipid bilayer prevent from entering the cell?

  Water-soluble (polar) molecules
• What happens to the cell membrane at temperatures above 40°C?

  It becomes increasingly unstable
• How does increased heat energy affect phospholipids?

  They vibrate more and move apart
• What effect does high temperature have on membrane permeability?

  It increases membrane permeability
• How does ethanol affect cell membranes?

  It dissolves phospholipids
• What happens to membrane permeability with increasing sodium chloride concentration?

  It decreases membrane permeability
• How do detergents affect cell membranes?

  They increase membrane permeability
• What type of molecules can pass through the membrane by simple diffusion?

  Small uncharged molecules

  
• What impedes the transport of ions and polar molecules across the membrane?

  The hydrophobic core of the membrane
• What type of proteins allow charged particles to cross the membrane?

  Intrinsic proteins
• What is facilitated diffusion?

  Diffusion helped by an intrinsic protein

  
• What do pumps in the membrane do?

  Carry out active transport

  
• What is the role of betalains in beetroot cells?

  They are red pigments
• How is the permeability of cell membranes investigated?

  Using beetroot and measuring betalain diffusion
• What does the phospholipid bilayer allow to transport?

  Small non-polar molecules

  
• What do extrinsic proteins do in the membrane?

  Provide structural support and recognition sites
• What is the function of intrinsic proteins?

  Transport molecules across the membrane
• What is the Fluid Mosaic model?

  A model describing membrane structure
• What does the term 'fluid' refer to in the Fluid Mosaic model?

  Phospholipids can move relative to each other
• What does the term 'mosaic' refer to in the Fluid Mosaic model?

  Proteins are arranged in a mosaic pattern
• What increases the rigidity and stability of the membrane?

  Cholesterol
• What role do glycolipids play in the membrane?

  Involved in cell-to-cell recognition
• What do glycoproteins do in the membrane?

  Stick out of some membranes
• What are the functions of the cell membrane?

  • Separates living cell from surroundings
  • Controls substance passage in and out
  • Regulates nutrient uptake
  • Allows waste product removal
  • Secretes enzymes and glycoproteins
  • Facilitates cell recognition
• What are the factors affecting cell membrane permeability?

  • Temperature
  • Ethanol concentration
  • Sodium chloride concentration
  • Detergent concentration
• What are the components of the cell membrane structure?

  • Phospholipid bilayer
  • Extrinsic proteins
  • Intrinsic proteins
  • Cholesterol
  • Glycolipids
  • Glycoproteins

  
• What is the role of intrinsic and extrinsic proteins in the cell membrane?

  • Intrinsic proteins: span the membrane, facilitate transport
  • Extrinsic proteins: provide support, form recognition sites
• What is the significance of the Fluid Mosaic model?

  • Describes the arrangement of phospholipids and proteins
  • Phospholipids are fluid, proteins form a mosaic pattern