Topic 1

• Monomer: The smaller units from which larger molecules are made

  
• Polymer: Molecules made from a large number of monomers joined together
• Disaccharide: Formed by the condensation of two monosaccharides held together by a glycosidic bond

  
• Polysaccharide:

  • Formed by the condensation of many glucose units
  • held by glycosidic bonds

  
• Glycogen:

  • Polysaccharide in animals
  • formed by the condensation of α-glucose

  
• Glycosidic bond:

  • C–O–C link
  • between two sugar molecules
  • formed by a condensation reaction
  • it is a covalent bond
• Amylose:

  • Polysaccharide in starch
  • made of α-glucose
  • joined by 1,4 - glycosidic bonds
  • coils to form a helix

  
• Amylopectin:

  • Polysaccharide in starch
  • made of α-glucose joined by 1,4 and 1,6 -glycosidic bonds
  • branched structure

  
• Condensation reaction:

  • A reaction that joins two molecules together
  • with the formation of a chemical bond
  • involves the elimination of a molecule of water
• Hydrolysis reaction:

  • A reaction that breaks a chemical bond
  • between two molecules
  • involves the use of a water molecule
• Fibrils:

  • Long, straight chains of β-glucose glucose
  • held together by many hydrogen bonds

  
• Triglyceride:

  • Formed by the condensation of one molecule of glycerol and three molecules of fatty acids
  • forming 3 ester bonds
• Phospholipid:

  • Formed by the condensation of one molecule of glycerol and two molecules of fatty acid
  • held by two ester bonds
  • a phosphate group is attached to the glycerol
• Induced-fit model:

  • The enzyme active site is not initially complementary to the substrate
  • the active site moulds around the substrate
  • this puts tension on bonds
  • lowers the activation energy
• Competitive inhibitor:

  • A molecule that is the same/similar shape as the substrate
  • binds to the active site
  • prevents enzyme-substrate complexes from forming

  
• Non-competitive inhibitor:

  • A molecule that binds to an enzyme at the allosteric site
  • causing the active site to change shape
  • preventing enzyme-substrate complexes from forming
• Secondary structure:

  • The folding or coiling
  • to create a β pleated sheet or an α helix
  • held in place by hydrogen bonds

  
• Tertiary structure:

  • The further folding
  • to create a unique 3D shape
  • held in place by hydrogen, ionic and sometimes disulfide bonds

  
• Quaternary structure: More than one polypeptide chain in a protein

  
• What is the effect of pH on enzyme-controlled reaction?

  • Too high or too low a pH will interfere with the charges in the amino acids in the active site.
  • This breaks the ionic and hydrogen bonds holding the tertiary structure in place
  • therefore the active site changes shape and the enzyme denatures
• What is the effect of enzyme concentration on enzyme-controlled reaction?

  • At low enzyme concentrations, there will be fewer collisions between the enzyme and substrate.
  • At high enzyme concentrations, the rate plateaus because there are more enzymes than the substrate, so many empty active sites.
• Hydrophobic: The tendency to repel and not mix with water
• Galactose: An example of a monosaccharide that forms lactose
• Fructose: An example of a monosaccharide that forms sucrose
• Isomer: Molecules with the same molecular formula but the atoms are arranged differently
• Maltose:

  • Disaccharide
  • formed by the condensation
  • of two glucose molecules
• Lactose:

  • Disaccharide
  • formed by the condensation
  • of a glucose molecule and a galactose molecule
• Sucrose:

  • Disaccharide
  • formed by the condensation
  • of a glucose molecule and a fructose molecule
• Polypeptide:

  • Polymer chain of a protein
  • made up of amino acids
  • bonded together by peptide bonds
  • following condensation reactions
• Amino acid:

  • The monomer of a protein
  • formed from C,H,O,N
  • contains a carboxyl group, amine group and an R group
• Carboxyl group:

  • COOH group
  • made up of a C with hydroxyl (OH) and carbonyl (double-bonded O) group bonded to it
  • found in amino acids and fatty acids

  
• Amine group: NH2 group found on amino acids

  
• R group on amino acids:

  • The variable group
  • the part of each of the 20 amino acids that is different
• α helix: A secondary structure in proteins a coiled shape held in place by hydrogen bonds

  
• β pleated sheet:

  • A secondary structure in proteins
  • a folded, pleated shape
  • held in place by hydrogen bonds
• Hydrogen bonds:

  • Weak bond
  • forms between H and O
  • in many biological molecules e.g. proteins, water, DNA, tRNA
• Ionic bonds:

  • A bond that forms between the R groups of different amino acids
  • in the tertiary structure of proteins
• Disulfide bonds:

  • A strong covalent bond
  • between two sulfur atoms in the R groups of different amino acids
  • in the tertiary structure of proteins
• Active site:

  • Unique-shaped part of an enzyme
  • that the substrate binds to

  
• Activation energy: The minimum amount of energy required for a reaction to occur