BIO

• CHAPTER 1: MOLECULES OF LIFE
• Molecules of Life


  • Water
  • Carbohydrates
  • Lipids
  • Proteins
  • Nucleic Acids
• Water


  Structure and properties of water molecules
• Properties of water


  1. Universal solvent

  2. High specific heat capacity

  3. High latent heat of vaporization

  4. Cohesion of water molecules

  5. Maximum density at 4°C
• Water molecule


  • Consists of 2 hydrogen atoms & 1 oxygen atom
  • Atoms share electrons in covalent bonds
  • Chemical formula: H2O
  • Form triangle shape, hydrogen atoms are 104.5° from each other

  
• Polar molecule


  Due to unequal distribution of electron within the molecule<|>Oxygen atom is more electronegative than hydrogen atom<|>Shared electron of the covalent bond are closer at oxygen atom then hydrogen atom
• Hydrogen bond


  Attraction between δ+ H atom of one water molecule and δ- O atom of nearby water molecules<|>Weaker than covalent bonds but strong enough to hold water molecules
• One water molecule can form maximum of 4 hydrogen bonds with 4 water molecules
• In liquid state, water molecules continuously form, break and reform hydrogen bonds with each other
• Universal solvent


  Water's ability to dissolve many substances such as ionic compounds, other polar molecules and organic molecules
• Specific heat capacity


  Quantity of heat that must be absorbed or lost for 1g of substance to increase temperature by 1°C
• Water has high specific heat capacity because a lot of energy is needed to increase the temperature of water to 1°C
• Latent heat of vaporization

  Quantity of heat must be absorbed for 1g of liquid to be converted to gaseous state
• Water has high latent heat of vaporization because a lot of energy is absorbed to break the hydrogen bonds between water molecules to change from liquid to vapor
• Cohesion of water molecules

  Attractive forces between molecules of the same type (water)
• Cohesive forces enable water molecules to stick together by hydrogen bond, producing high surface tension
• Water has maximum density at 4°C
• Above 4°C, water expands as it warms and contracts as it cools
• At 0°C, water molecules form a crystalline lattice with each molecule hydrogen bonded to 4 other molecules

  
• Ice is less dense than water because the hydrogen bonds in ice space the water molecules relatively far apart
• The floating layer of ice insulates the water below, preventing them from losing heat and freezing
• Classes of carbohydrates


  • Monosaccharide
  • Disaccharide
  • Polysaccharides
• Formation and breakdown of maltose

  1. Condensation reaction to form maltose

  2. Hydrolysis reaction to break down maltose
• α-glucose


  Monomer of amylose, amylopectin and glycogen
• Amylose


  • Monomers: α-glucose molecules
  • Joined together by α-1,4 glycosidic bond
  • Helical, unbranched chain (variable length of monomers)
• Amylopectin


  • Monomers: α-glucose molecules
  • Joined together by α-1,4 glycosidic bond and α-1,6 glycosidic bond
  • Helical, branched chain (variable length of monomers)
  • Branches occur within 30 units
  • Folded & branched ~ very compact (ideal for storage)
• Glycogen


  • Monomers: α-glucose molecules
  • Joined together by α-1,4 glycosidic bond and α-1,6 glycosidic bond
  • Helical, highly branched chain (variable length of monomers)
  • Structure is similar to amylopectin, but more branched
• Cellulose


  Monomers: β-glucose<|>Bonded by β-1,4 glycosidic bond<|>Unbranched, long straight chain
• Cellulose


  • Major component of plant cell wall
  • Straight chains are arranged parallel to one another
  • Linked together by hydrogen bonds (form microfibril)
  • Very stable & tough structure ~ provide support to plant cell
• Types of lipid


  • Triglycerides (fat & oil)
  • Phospholipids
  • Steroids
• Lipids


  Water insoluble organic molecules that contain C, H & O atoms<|>Soluble in organic solvent (alcohol, ether & chloroform)<|>Not true polymer- Not big enough to be considered macromolecules<|>Group of hydrophobic molecules ~ insoluble in water
• Triglycerides


  Consist of three fatty acids linked to one glycerol by ester linkage<|>Can be classified as saturated fat or unsaturated fat
• Phospholipids


  Major component of cell membrane<|>Amphipathic molecule, have both polar hydrophilic head and non-polar hydrophobic tails<|>Made up of glycerol, fatty acids and phosphate group
• Steroids


  Carbon skeleton consisting of 4 fused rings<|>No fatty acids
• Glycerol


  3C alcohol with 3 hydroxyl groups (-OH) attached
• Fatty acids


  Have a carboxyl group (-COOH) at one end and a hydrocarbon chain (R) at the other end<|>Can be classified as saturated or unsaturated
• Formation of triglycerides


  1. 3 condensation/esterification reactions between 3 fatty acids and 1 glycerol

  2. Removal of 3 water molecules
• Breakdown of triglycerides


  1. 3 hydrolysis reactions to break the 3 ester linkages

  2. Addition of 3 water molecules
• Amino acids


  Building blocks/monomers of proteins<|>Have a central carbon atom, amino group (-NH2), carboxyl group (-COOH) and a side chain (R group)
• Groups of amino acids

  • Non-polar
  • Polar
  • Basic
  • Acidic