Biological molecules

• Monomer


  - The smaller units form which larger molecules are made

  
• Polymer


  - Molecules made from a large number of monomers joined together
• Monosaccharide


  - The monomers from which larger carbohydrates are made

  - Glucose, fructose, galactose
• Disaccharide


  - Formed by the condensation of two monosaccharides held together by a glycosidic bond

  - e.g. maltose, sucrose, lactose
• Polysaccharide


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

  - e.g starch, glycogen and cellulose
• Cellulose


  - Polysaccharide in plant cell walls

  - Formed by the condensation of β-glucose
• Glycogen


  - Polysaccharide in animals

  -formed by the condensation of α-glucose
• Starch


  - Polysaccharide in plants

  - formed by the condensation of α-glucose contains two polymers - amylose and amylopectin
• 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

  - involcvesthe elimination of a molecule of water
• Hydrolysis reaction


  - 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
• glucose


  - Monosaccharide that exists as two isomers

  - β glucose and α glucose

  
• Galactose


  - monosaccharide

  - forms lactose

  
• Fructose


  - monosaccharide

  - 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
• Explain how the structure of cellulose means that it provides rigidity and strength to cell walls.


  - Cellulose is made up of many long, straight, unbranched chains of beta glucose.

  - The chains are joined with many weak hydrogen bonds.

  - These grouped chains form micro- and macro-fibrils.
• Triglyceride


  - Formed by the condensation of one molecule of glycerol and three molecules of fatty acids

  - forming 3 ester bonds

  - removal of three water molecules

  
• Phosphlipids


  - 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

  
• primary structure


  - The sequence of amino acids on a polypeptide chain

  
• 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 bond

  
• Quaternary structure


  - More than one polypeptide chain in a protein

  
• Peptide bond


  - Covalent bond joining amino acids together in proteins

  - C-N link between two amino acid molecules

  - formed by a condensation reaction
• What is the effect of temperature on enzyme controlled reaction?


  - At low temperatures, there is not enough kinetic energy for successful collisions between the enzyme and substrate.

  - At too high a temperature, enzymes denature, the active site changes shape and enzyme substrate complexes cannot form.
• 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

  - Different enzymes have a different optimal pH
• What is the effect of substrate concentration on enzyme-controlled reaction?


  - At low substrate concentrations, there will be fewer collisions between the enzyme and substrate.

  - At high substrate concentrations, the rate plateaus

  - because all the enzyme active sites are saturated
• 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.
• Ester bonds


  -COO- chemical bond

  - formed between glycerol and fatty acids

  
• Hydrophilic


  - The ability to mix, interact or attract water
• Hydrophobic


  - The tendency to repel and not mix with water
• Polypeptide


  - Polymer chain of a protein

  - made up of amino acids

  - bonded together by peptide bonds - following condensation reactions