Biological molecules

• Monomers


  Small, single units that act as the building blocks to create larger molecules
• Polymers


  Made up of many monomers, usually thousands, chemically bonded together
• Condensation reaction


  Monomers bond together, involves the removal of a water molecule
• Hydrolysis reaction


  The opposite of condensation, a water molecule is added between two bonded monomers to break the chemical bond
• Monosaccharides


  The monomers of carbohydrates, sugars that are soluble in water and can provide energy or be a building block

  
• Disaccharides


  Two monosaccharides bonded together by a glycosidic bond, formed by a condensation reaction

  
• Polysaccharides


  Polymers made up of many monosaccharides, created via condensation reactions
• Carbohydrates


  • Key biological molecules that store energy and can provide structural support to plant cells
  • Contain carbon, hydrogen and oxygen (CHO)
  • General formula for monosaccharides is CnH2nOn, where n = number of carbon atoms

  
• Glucose


  A very important monosaccharide that can provide energy or be polymerised to form structural support (cellulose) or energy storage (glycogen, starch)

  
• Isomers


  Compounds that have the same formula, but the atoms are arranged differently
• α glucose


  One structural isomer of glucose

  
• β glucose


  The second structural isomer of glucose, differs from α glucose in the position of the hydrogen (H) and hydroxyl group (OH) on carbon 1

  
• Condensation reaction creating a disaccharide


  A water molecule is removed, forming a glycosidic bond between two monosaccharides
• Glycosidic bond


  The bond formed between two monosaccharides in a disaccharide

  
• Maltose


  A disaccharide formed from two glucose molecules
• Lactose


  A disaccharide formed from glucose and galactose
• Sucrose


  A disaccharide formed from glucose and fructose

  
• Hydrolysis reaction breaking down a disaccharide

  A water molecule is added to break the glycosidic bond and separate the two monosaccharides

  
• Starch


  The major carbohydrate store in plants, made from excess glucose created during photosynthesis
• Starch


  • Insoluble due to its large size, so it can be stored without affecting water potential or causing osmosis
  • Made up of two polymers: amylose (glucose monomers joined by 1,4-glycosidic bonds in a spiral) and amylopectin (glucose monomers joined by 1,4 and 1,6-glycosidic bonds in a branched structure)
• Glycogen


  The major carbohydrate storage molecule in animal cells, found mainly in liver and muscle cells

  
• Glycogen


  • Insoluble due to its large size, so it can be stored without affecting water potential or causing osmosis
  • Highly branched structure with more 1,6-glycosidic bonds than starch, allowing faster hydrolysis back to glucose
• Cellulose


  A polysaccharide that provides structural strength in plant cell walls, made up of β-glucose monomers joined by 1,4-glycosidic bonds

  
• Cellulose


  • Insoluble and unbranched, the long straight chains are held together by hydrogen bonds to form strong fibrils and fibres
• Monomers join together by condensation reactions to make polymers, and polymers are hydrolysed back into monomers
• Key monosaccharides


  • Glucose
  • Galactose
  • Fructose

  
• Key disaccharides


  • Maltose
  • Lactose
  • Sucrose
• Key polysaccharides


  • Starch
  • Glycogen
  • Cellulose

  
• Glycogen is for glucose storage in animals, starch is for glucose storage in plants, and cellulose provides structural strength in plants

  
• Glucose


  Could link to titles on respiration, as a key respiratory substrate

  
• Glucose and glycogen


  Could link to homeostasis and the control of blood glucose levels

  
• Glycosidic bonds and hydrogen bonds (in cellulose)


  Could link to titles on bonding

  
• Monosaccharides and polysaccharides


  Could link to titles on monomers and polymers

  
• Amino acid


  The monomer in proteins, consisting of a central carbon, an amine group (NH2), a hydrogen atom, a carboxyl group (COOH), and a variable R group

  
• Polypeptide


  The polymer chain of amino acids in a protein, created via condensation reactions and held together by peptide bonds

  
• Primary structure


  The sequence of amino acids in a polypeptide chain, determined by DNA

  
• Secondary structure


  • Parts of the protein molecule bend into an α helix or fold into β pleated sheets, held in place by hydrogen bonds
• Quaternary structure


  A protein made up of more than one polypeptide chain, folded into a 3D shape and held by hydrogen, ionic and disulfide bonds

  
• Primary structure


  Sequence of amino acids

  
• α helix


  • Type of secondary structure