Ch. 5

• Hydrophobic: water-fearing


  Hydrophilic: water-loving
• Hydrophilic: water-loving
• Turgor:

  plant cells fill central vacuoles with water which press against the cell wall to keep cells rigid
• Isosmotic regulation:

  adjust internal concentration of solutes to match the external water (common in sea life)
• Osmosis: movement of water in the direction of more particles
• Extrusion: actively pumping out through contractile vacuoles
• Plasma membranes have 4 components:

  • Phospholipid bilayer
  • Transmembrane proteins
  • Interior protein network
  • Cell surface markers
• Phospholipid structure has 3 main parts:

  1. Glycerol: a 3-carbon polyalcohol that acts as a backbone for the phospholipid

  2. Fatty acids (2): attached to the glycerol, nonpolar chains of carbon and hydrogen, (Nonpolar nature makes them hydrophobic)

  3. Phosphate group: attached to the glycerol (Polar nature makes it hydrophilic)
• What are the 3 parts of a Phospholipid structure?

  • Glycerol
  • Fatty Acids
  • Phosphate group
• • Bilayers are formed by partial hydrophilic and hydrophobic areas
  • Fatty acids are on the inside
  • Phosphate groups are on the outside
• • Plasma membrane protects the inside of the cell
  • Membrane proteins allow water-soluble substances to pass through
  • Membrane is stable due to Hydrogen bonds with water and phosphate groups
  • Membrane is fluid; Fluid mosaic model of phospholipids and unanchored proteins can move through the membrane

  
  

  • Some amino acids are polar, and others are non-polar, non-polar segments stay toward the middle of the bilayer
• Fluid mosaic model: mosaic of proteins float in the fluid lipid bilayer, other proteins are anchored at specific locations
• Functions of membrane proteins

  1. Transport

  2. Act as enzymes

  3. Cell surface receptors

  4. Cell surface identity markers

  5. Cell-to-cell adhesion proteins

  6. Attachments to the cytoskeleton
• Transmembrane proteins: extend the full depth of the membrane

  • Integral membrane proteins provide passageways for substances and information to cross
  • Proteins can be floating or anchored
  • Non-polar regions remain in the interior of the bilayer, polar regions protrude from both sides
• (1/7 Types of membrane proteins)

  • Transporters: transport water-soluble molecules or ions across membrane
• (2/7 Types of membrane proteins)

  Carriers and channels or pores
• (3/7 Types of membrane proteins)

  Receptors: surface proteins that respond to chemical messages

  Must have a receptor on a cell in order for a chemical to affect that cell
• (4/7 Types of membrane proteins)

  Enzymes: Attached to the interior membrane, chemical reactions can occur here
• (5/7 Types of membrane proteins)

  Attachment to cytoskeleton: Reinforces membrane’s shape and anchors some proteins to specific sites on the membrane
• (6/7 Types of membrane proteins)

  Cell surface markers: Attached to exterior membrane, different varieties of glycoproteins and glycolipids, work as cell identity markers
• (7/7 Types of membrane proteins)

  Cell adhesion proteins: Attached to exterior membrane, “glue” to hold cells to one another
• The Types of membrane proteins

  • Transporters
  • Carriers and channels or pores
  • Receptors
  • Enzymes
  • Attachment to cytoskeleton
  • Cell surface markers
  • Cell adhesion proteins
• Selective permeability: Not everything can pass through
• Diffusion: random motion with net movement of substances from regions of high concentration to low concentration

  • Passive, no energy needed to moves down the gradient
  • Non-polar molecules can diffuse through lipid bilayer
  • O2, CO2, fatty acids, steroids, and fat-soluble vitamins
• Osmosis: process of water diffusing through the membrane, mediated by membrane proteins
• Channels: specific channels for specific molecules, passive, Ca2+, Na+, K+, Cl-, water (aquaporins)
• Carriers: sugars and amino acids need transport carrier proteins to move through the membrane, bind to molecules on one side of the membrane and releases them on the other, specific and passive
• Osmosis

  • Water moves from areas of low solute concentration to areas of high solute concentration
  • Osmotic Concentration: concentration of all solutes in a solution
  • Hyperosmotic: higher solute concentration outside of the cell, water leaves the cell
  • Hypoosmotic: lower solute concentration outside of the cell, water moves into cell
  • Isosmotic: solute concentrations are equal, water flows in and out of the cell
• Active transport requires energy