2.2

• Covalent bonding


  Sharing of electrons in the outer shell, the strongest known bond and the most common one in biology
• Condensation reaction


  Usually for polymerization reactions, creates water as a by-product
• Hydrolysis reaction


  Breaking of covalent bonds by addition of water
• Monomers


  Small molecules that bind to identical molecules, subunits of polymers
• Monomers


  • Monosaccharides (carbohydrates)
  • Amino acids (proteins)
  • Nucleotides (DNA/RNA)
• Hydrogen bonds


  Weak interactions between slightly positively charged hydrogen atoms and slightly negatively charged atoms
• Hydrogen bonds are not actual bonds, they are just interactions, much weaker than covalent bonds
• Water molecule


  • Polar molecule
  • Rigid lattice structure
• Cohesion


  Water molecules sticking together
• Surface tension


  Uppermost water molecules are closely attracted to each other, creating an area of surface tension
• Specific heat capacity


  A lot of energy is required to break the hydrogen bonds between water molecules, keeping bodies of water at a stable temperature
• Solvent properties


  Water is an excellent solvent due to the tiny charges on its molecules attracting other molecules or ions
• Latent heat


  Water can hold a lot of heat energy before becoming a gas, good for thermoregulation
• Density and viscosity


  Water is relatively dense and viscous, most living organisms have a density close to water's, aquatic organisms need to be streamlined
• Carbohydrates


  Insoluble in water, do not affect the water potential of a cell
• Forming polysaccharides


  1. Monosaccharides join together through glycosidic bonds (condensation reaction)

  2. Water is produced
• Monosaccharides


  • Alpha glucose
  • Fructose
  • Beta glucose
  • Beta galactose
• Disaccharides

  • Maltose
  • Sucrose
  • Lactose
  • Cellobiose
• Reducing sugars


  Monosaccharides, lactose
• Non-reducing sugars


  Sucrose, cellobiose
• Hydrolysis of glycosidic bonds


  Breaks down disaccharides and polysaccharides into monosaccharides
• Alpha glucose


  • Symmetrical molecule
  • Carbon 1 hydrogen, carbon 1 hydroxide groups
• Beta glucose


  • Carbon 1 hydrogen, carbon 1 hydroxide groups flipped upside down compared to alpha glucose
• Ribose


  Pentose sugar (5 carbon)
• Deoxyribose


  Pentose sugar (5 carbon), one hydroxyl group replaced with hydrogen compared to ribose
• Cellulose


  • Found in plant cell walls
  • Formed of beta glucose molecules
  • Chains rotated 180 degrees alternately
  • Hydrogen bonds between chains for strength
  • Microfibrils and macrofibrils
• Glycogen


  • Stored in liver
  • Made of alpha glucose
  • Alpha 1-4 and alpha 1-6 glycosidic bonds
  • Branched structure
  • Compact, easy to hydrolyze for glucose
• Amylose


  • Alpha glucose with alpha 1-4 glycosidic bonds
  • Coils into a helix
• Amylopectin


  • Alpha glucose with alpha 1-4 and alpha 1-6 glycosidic bonds
  • Branched structure
  • Longer bonds than glycogen, more tendency to coil
• Cellulose provides tensile strength to plant cell walls
• Lignin makes plant cell walls waterproof and impermeable
• Polysaccharides and disaccharides are less soluble in water, do not affect water potential of cells
• Lipids


  Formed of carbon, hydrogen and oxygen, insoluble, nonpolar, dissolve in alcohol
• Types of lipids


  • Triglycerides
  • Phospholipids
  • Steroids
• Glycerol


  An alcohol with three hydroxide groups
• Fatty acids


  Have a carboxyl group on one end and a hydrocarbon tail
• Formation of triglycerides


  1. Glycerol and fatty acids bind together in a condensation reaction, releasing water

  2. Three fatty acids bind to one glycerol molecule
• Saturated fatty acids


  No double carbon bonds
• Unsaturated fatty acids


  Contain double carbon-carbon bonds, making them more fluid
• Phospholipids


  Have a hydrophilic head and hydrophobic tails, making them amphipathic