bio topic 1

• Monomers


  Smaller units from which larger molecules are made
• Monomers


  • Monosaccharides
  • Nucleotides
  • Amino acids
• Polymers


  Made from a large number of monomers joined together
• Polymers


  • Starch
  • Proteins
  • DNA
• Condensation reaction


  Two molecules are joined together, with the elimination of water
• Hydrolysis reaction


  Two molecules are broken apart, with the addition of water
• Carbohydrates


  Molecules that consist exclusively of carbon, hydrogen and oxygen atoms
• Monosaccharides


  A single carbohydrate monomer, sweet and soluble
• Reducing sugars


  Can donate electrons, allowing them to give the atoms in benedict's reagent the extra atom needed for a full shell, turning the solution from blue to brick-red
• Non-reducing sugars


  Must first be hydrolysed before the Benedict's test can be carried out
• Glucose


  The chemical formula is C6H12O6, with two common isomers: Alpha glucose and Beta glucose

  
• Monosaccharide general formula


  (CH2O)n, where n is any number from 3 to 7
• Disaccharide formation


  Two monosaccharides join together via a condensation reaction, with the removal of a water molecule
• Polysaccharides


  Polymers made up of many monosaccharides
• Polysaccharides


  • Glycogen
  • Starch
  • Cellulose
• Starch


  A storage molecule in plants, made up of chains of alpha glucose monosaccharides joined by glycosidic bonds

  
• Starch


  • Insoluble
  • Doesn't affect water potential or osmotic activity
  • Large and insoluble, too large to diffuse through the cell membrane
  • Compact, ideal for storage
  • Can be hydrolysed to form beta glucose, which is easily transportable and readily used in respiration
  • Branched, helix, spiral structure allows all ends to be acted on by enzymes simultaneously for rapid glucose monomer release

  
• Glycogen


  A storage molecule found in animals, similar in structure to starch but with shorter chains and more branches
• Glycogen


  • Insoluble, doesn't tend to draw water into the cell by osmosis
  • Insoluble, doesn't diffuse out of cells
  • Compact, a lot can be stored in a small space
  • Highly branched, more ends for enzymes to work on, allowing rapid breakdown to glucose monomers for respiration

  
• Cellulose


  Made from beta glucose chains, forms long, straight and unbranched chains that run parallel to each other
• Cellulose


  • Hydrogen bonds between adjacent parallel chains create rigidity and strength
  • Cellulose molecules are grouped into microfibrils and then fibres to provide further strength
  • The cellulose cell wall prevents the cell from swelling and bursting as water enters by osmosis, exerting inwards pressure to keep plant cells turgid and semi-rigid
• Lipids


  A varied group of substances that contain carbon, hydrogen and oxygen, are insoluble in water, and soluble in organic solvents
• Lipids


  • Roles include: energy source, waterproof barriers, insulation, protection for delicate organs
• Triglycerides


  Lipids made from 3 fatty acids combined with 1 glycerol
• Triglycerides


  • High ratio of energy-storing carbon-hydrogen bonds to carbon atoms, making them a great energy source
  • Low mass to energy ratio, good for storage
  • Insoluble in water, so their storage doesn't affect water potential
  • Release water molecules when oxidised, providing an important source of water
• Phospholipids


  Lipids made up of two fatty acids, one glycerol and one phosphate molecule
• Phospholipids


  • Have a hydrophobic tail (fatty acids) and a hydrophilic head (glycerol and phosphate)
  • Form a bilayer in cell surface membranes
  • Can join with carbohydrates to form glycolipids important for cell recognition
  • Composition affects membrane fluidity
• Amino acids


  The monomers of proteins, which combine via condensation to form polypeptides
• Polypeptides


  Polymers formed by the condensation of amino acids
• Amino acid structure


  • Central carbon with 4 groups attached: R group, carboxyl group, amine group, hydrogen atom
• Peptide bond formation


  Amino acids combine via condensation, eliminating a water molecule from the carboxyl and amine groups
• Protein structure levels


  Primary, secondary, tertiary, quaternary
• Primary structure


  • Sequence of amino acids in a polypeptide chain, determines protein shape and function
• Secondary structure


  • Shape of the amino acid chain, either alpha helix or beta pleated sheet, formed by hydrogen bonds
• Tertiary structure


  • 3D shape of the polypeptide chain, formed by disulfide bonds, ionic bonds and hydrogen bonds
• Quaternary structure


  • When multiple polypeptide chains are linked together, may also include prosthetic groups
• Starch test


  Add iodine, positive = blue/black, negative = orange
• Reducing sugar test


  Add Benedict's reagent, heat, positive = red, negative = blue
• Hydrogen bonds


  Form between the slight positive charge of the hydrogen in the NH of the amino group and the slight negative charge of the oxygen in the CO of the carboxyl group
• Tertiary structure


  The 3d shape of a polypeptide chain, which is formed from further folding due to 3 bonds; disulfide bonds, ionic bonds and hydrogen bonds