Biological Molecules

• What is the biological role of magnesium ions?

  Constituent of chlorophyll so essential for photosynthesis
• What is the biological role of iron ions?

  Constituent of haemoglobin so transports oxygen in red blood cells
• Why is nitrate important for organisms?

  Needed for making nucleotides/nucleic acids and amino acids
• What is the biological role of phosphate ions?

  Used for making nucleotides/nucleic acids and phospholipids
• What is the role of calcium ions in organisms?

  Strengthens tissues e.g. bones and teeth in animals and cell walls in plants
• What are inorganic ions often called?

  Minerals
• What are micronutrients?

  Minerals needed in trace concentrations
• What are macronutrients?

  Minerals needed in small concentrations
• What is the general formula for monosaccharides?

  • General formula: (CH2O)n
  • Building blocks of carbohydrates
• What is a dipole in the context of water?

  A polar molecule with positive and negative charges
• What forms when two water molecules are in close contact?

  Hydrogen bonds

  
• What is cohesion in water molecules?

  Attraction between water molecules from opposing charges
• What are the properties of water and their functions?

  1. Solvent: Attracts charged particles and allows polar molecules to dissolve within it
  2. Transport medium: Transports dissolved substances
  3. Chemical reactions: Occur in water
  4. High specific heat capacity: Stabilizes temperature
  5. High latent heat of vaporization: Cools body
  6. Cohesion: Allows water transport in plants through xylem
  7. Surface tension: Supports small organisms
  8. Density: Ice floats, insulating water below (water has max density at 4
• What is the function of triose sugars?

  Important in metabolism
• What are pentose sugars constituents of?

  Nucleotides like DNA and RNA
• What is the role of glucose in respiration?

  Source of energy through bond breaking
• What are isomers?

  • Same chemical formula
  • Atoms arranged differently
• What are the two isomers of glucose?

  α glucose and β glucose
• How do α glucose and β glucose differ?

  Arrangement of H and OH at carbon 1
• What is a disaccharide?

  • Composed of two monosaccharides
  • Formed by glycosidic bond and condensation reaction

  
• What is maltose composed of?

  Two α glucose molecules
• What is the process of hydrolysis in disaccharides?

  Chemical addition of water to break glycosidic bond

  
• What is the role of Benedict's reagent?

  • Tests for reducing sugars
  • Requires heat for reaction
• Why is sucrose considered a non-reducing sugar?

  It does not reduce copper II sulfate
• What must be done to sucrose before testing with Benedict's reagent?

  Hydrolyze it with dilute hydrochloric acid then neutralised with dilute sodium hydroxide and then tested with benedicts
• What are polysaccharides?

  • Large complex polymers
  • Formed from many monosaccharide units
• What is the function of starch in plants?

  1. Stores glucose
  2. Starch is compact and has no osmotic effect on the cell; it does not affect the water potential of the cell
• What are the two types of polysaccharides in starch?

  Amylose and amylopectin
• How does amylose differ from amylopectin?

  1. Amylose is unbranched and coiled and forms 1-4 glycosidic bonds;
  2. Amylopectin is branched and forms 1-4 + 1-6 glycosidic bonds
• What is glycogen's role in animals?

  Main storage product
• How does glycogen differ from amylopectin?

  Glycogen has shorter chains and more branches

  
• What is cellulose's function in plants?

  Structural component of cell walls
• How are β glucose units arranged in cellulose?

  1. Long parallel chains joined by C1 – C4 glycosidic bonds
  2. The β bond rotates adjacent glucose molecules by 180° ; this allows hydrogen bonds to form between OH groups of adjacent cellulose chains.
  3. Tightly cross-linked to form bundles called microfibrils.
  4. Microfibrils are bunched together in bundles to form fibres.
  5. Cellulose is unreactive and stable (due to being unbranched) and has a high tensile strength (due to the formation of microfibrils and fibres).

  
• What is chitin's role in organisms?

  Structural polysaccharide in exoskeletons and fungi cell walls
• How does chitin differ from cellulose?

  1. Long chains of β glucose molecules linked by C1 – C4 glycosidic bonds.
  2. Chitin has an acetylamine group in monomers
  3. Like cellulose alternate glucose molecules are rotated by 180° ; this allows hydrogen bonds to form between the OH groups of adjacent chitin chains.
  4. The cross-linked parallel chains form microfibrils.
  5. Chitin is strong, waterproof and lightweight.

  
• What are triglycerides?

  • Common types of lipids
  • Formed by glycerol and fatty acids

  
• Why are triglycerides insoluble in water?

  1. They are non-polar molecules
  2. Soluble in other solvents such as ethanol, chloroform and ether.
• What is the bond formed between glycerol and fatty acids?

  1. Ester bond
  2. The ester bond can be broken by hydrolysis.
  3. A triglyceride has three ester bonds

  
• What characterizes unsaturated fatty acids?

  Presence of carbon to carbon double bonds between carbon atoms
• What is the difference between monounsaturated and polyunsaturated fatty acids?

  Monounsaturated has one double bond; polyunsaturated has two or more