Knowledge-7 TACM

Cards (25)

  • The cell membrane is made up of a phospholipid bilayer.
  • The fatty acids in a phospholipid bilayer form a hydrophobic layer sandwiched between hydrophilic phosphate heads.
  • Within the phospholipid bilayer you can find cholesterol between fatty acids, glycolipids and glycoproteins attached to the phospholipid surface.
  • the arrangements of phospholipids and proteins is called the fluid mosaic model:
    • fluid- phospholipids move relative to each other.
    • mosaic- the proteins dotted between the phospholipids are of various shapes and sized like a tile mosaic.
  • Phospholipids function:
    • form the basic structure of the bilayer membrane, which is partially permeable.
    • make the membrane flexible
    • prevent passage of water soluble molecules
    • allow movement of lipid soluble molecules
  • Extrinsic proteins function:
    • found on the surface or embedded in one layer of the membrane.
    • provide mechanical support.
    • act as cell receptors for hormones and other molecules
  • Glycoproteins function:
    • are receptors for chemical signals
    • act as receptors for toxins and drugs
    • have a roll in cell adhesion in some tissues
  • Glycolipids function:
    • have a role in cell recognition, acting as cell markers or antigens
  • cholesterol:
    • may be present: restricts movement of other membrane components , makes membranes less fluid , providing mechanical stability.
  • An adaptation to maximize membrane transport might be that a cell has a large surface area due to infoldings. Examples of this are cristae in mitochondria or the root hair cell in plants or microvilli on the villi.
  • An adaptation to maximize membrane transport might be that a cell has a large number of specific protein channels and carrier molecules embedded in the membrane. For example liver cells take up large amounts of glucose due to the high amount of glucose channels on their cell surface.
  • Simple diffusion:
    • movement from high to low concentration
    • no proteins required for transport
    • no energy from ATP required
    • examples are lipid based hormones or oxygen
  • Facilitated diffusion:
    • movement from high to low concentration
    • channel proteins or carrier proteins required
    • No energy from ATP required
    • examples are glucose ,insulin and ions
  • Osmosis:
    • movement from a higher water potential to lower water potential
    • No proteins required but aquaporins can increase osmosis
    • no energy from ATP required
    • water only
  • Active transport:
    • movement from higher to lower concentration
    • uses carrier proteins
    • energy from ATP required
    • example is magnesium ions into root hair cells from soil
  • Co-transport:
    • movement from higher to lower concentration
    • co-transported proteins required
    • no energy from ATP required
    • examples are the co-transport of sodium ions and glucose in the ileum.
  • Simple diffusion is a passive and random process that relies on kinetic energy of molecules.
  • Facilitated diffusion is where large water soluble molecules and charged ions cannot pass through the phospholipid bilayer through diffusion so they use facilitated diffusion.
  • Channel proteins form small pores in the membrane and are often specific to a ion or molecule.
  • carrier proteins change shape once an ion or molecule is attached to allow a molecule through the membrane.
  • Co-transport is a special type of facilitated diffusion, it is carried out by co-transporter proteins.
  • Water potential is a measure of the ability for water molecules to diffuse , pure water has the highest water potential.
  • Hypotonic is where a cell has too much water
  • hypertonic is where a cell has too little water
  • Active transport is the movement of substances against the concentration gradient using energy.