Molecules CCEA

• This polarity of H2O molecules causes them to be attracted to each other by their opposite charges
• Hydrogen bonds

  Attractive forces that form between one water molecule and the next water molecule
• Water as a solvent


  Water readily dissolves a wide range of inorganic and organic substances
• How water is used as a solvent

  • Transport
  • Removal of wastes
  • Secretions
• Importance of water


  • Hydrolysis
  • Medium for chemical reactions
  • Diffusion and Osmosis
  • Photosynthetic substrate
  • Lubricant
  • Supporting role
• Properties of water


  • Cohesion and Surface Tension
  • Adhesion and capillarity
  • Thermal Stability
  • Density
  • Buoyancy
• Hydrophilic


  Molecules that are soluble in water because they will bond with hydrophilic water molecules
• Hydrophobic


  Molecules that are not soluble in water
• Hydrophobic molecules are not soluble in water because they do not bond with hydrophilic water molecules
• Inorganic ions


  • Potassium
  • Calcium
  • Magnesium
  • Iron
  • Hydrogen Carbonate
  • Nitrate
  • Phosphate
• Buffer


  A solution that resists changes in pH by neutralizing added acids or bases
• Amino acids as buffers

  Amino acids have both acidic and basic properties and can mop up hydrogen ions to function as important buffers
• Elements in carbohydrates: Carbon, Hydrogen, Oxygen in a 1:2:1 ratio
• Monosaccharides


  Single unit sugars (monomers)
• Isomers


  Molecules with the same molecular formula but different structural arrangements
• Glucose can exist in two isomeric forms: alpha glucose and beta glucose

  
• Condensation


  The process where two molecules join together and release a water molecule
• The bond formed between two monosaccharides is called a glycosidic bond
• Physical properties of monosaccharides and disaccharides

  • Soluble in water
  • Sweet taste
  • Can be crystallised

  
• Three main polysaccharides


  • Starch
  • Glycogen
  • Cellulose

  
• Polysaccharides are insoluble in water, non-sweet, and cannot be crystallised
• Components of starch


  • Amylose
  • Amylopectin

  
• Amylose

  A polysaccharide formed from unbranched curved chains of several hundred α glucose molecules, 1,4-linked

  
• Amylopectin


  A polysaccharide formed from branched chains of over 1000 α glucose molecules, 1,4-linked and 1,6-linked

  
• Starch is stored in plants as starch grains, which are abundant in chloroplasts and in storage organs such as potato tubers and also in some seeds
• Glycogen


  A polysaccharide formed from long, highly branched chains of glucose monomers, found in animal cells

  
• Starch


  Polysaccharide formed from long, 1,4-linked and 1,6-linked chains of α glucose molecules

  
• There are approximately twice as many glucose molecules in amylose as in amylase

  
• Starch


  • Chains are multihelical
  • Amylopectin forms about 70-80% of starch
  • Amylopectin has many terminal end glucose molecules so it is more readily hydrolysed

  
• Properties of starch


  • Insoluble
  • Compact
  • Unreactive
• Function of starch


  Stored in plants as starch grains, abundant in chloroplasts and storage organs
• Glycogen


  Polysaccharide formed from long, highly branched, curved chains of α glucose molecules, held together by 1,4-linked and 1,6-linked glycosidic bonds

  
• Glycogen is slightly more soluble than starch, however we still say it is insoluble
• Function of glycogen


  Main storage carbohydrate molecule in animals, found as glycogen granules in liver and muscle cells

  
• Cellulose


  Polysaccharide formed from straight, unbranched chains of up to 10,000 β glucose molecules, 1,4-linked by glycosidic bonds

  
• Alternate glucose molecules in cellulose are rotated 180 degrees to allow glycosidic bonding

  
• Parallel cellulose chains are held together by hydrogen bonds
• Properties of cellulose


  • Insoluble
  • Strong
  • Hard to digest

  
• Function of cellulose


  Structural molecule in plants providing support/strength and rigidity to the cell walls
• Cellulose is described as strong and offering high tensile strength due to the layers of cellulose β glucose chains held together by hydrogen bonds and arranged at varying angles