Chapter 1 - Biological Molecules

• What is a monomer?


  Smaller/ repeating molecules from which larger molecules or polymers are made.
• What is a polymer?


  Molecule made up of many identical/ similar molecules or monomers.
• What is a condensation reaction?

  2 molecules joint together

  Forming a chemical bond

  Releasing a molecule of water
• What is a hydrolysis reaction?

  2 molecules separated

  Breaking a chemical bond

  Using a molecule of water
• Name some examples of polymers and there constituent monomers.

  Polynucleotides (DNA / RNA) - Nucleotides

  Polysaccharides (e.g starch) - Monosaccharides (e.g glucose)

  Polypeptide (proteins) - Amino acids
• What are monosaccharides?


  Monomers from which larger carbohydrates are made.
• Give three examples of monosaccharides.

  Glucose, Fructose, Galactose
• Give the structure of alpha glucose.

  
• What is the difference between the structure of alpha and beta glucose?

  OH below carbon one on alpha glucose

  OH above carbon one on beta glucose
• How do alpha and beta glucose show isomerism?

  Same molecular formula, differently arranged atoms.
• What is a dissacharide?

  Two monosaccharides joined by a glycosidic bond.
• How are disaccharides formed?

  Condensation reaction releasing a molecule of water.
• List 3 common disaccharides and their constituent monomers.

  Maltose - Glucose + Glucose

  Sucrose - Glucose + Fructose

  Lactose - Glucose + Galactose
• How are two monosaccharides joined together ?

  
• What is a polysaccharide?

  Many monosaccharides joined by glycosidic bonds
• How are polysaccharides formed?

  Many condensation reactions releasing water molecules.
• What is the function of starch?

  Energy store in plants
• Describe the structure of starch.

  Polysaccharide of alpha glucose

  Amylose - 1,4 - glycosidic bonds - Unbranched

  Amylopectin - 1,4 and 1,6 glycosidic bonds - branched
• How does starches structure relate to its function?

  Helical - Compact for storage in cells

  Large - Cant leave cell / cross the membrane

  Insoluble - Water potential of cell not affected (no osmosis)
• What is the function of glycogen?

  Energy store in animals cells
• What is the structure of glycogen?

  Polysaccharide of alpha glucose

  1,4 and 1,6 glycosidic bonds - Branched
• How does glycogen structure link to its function?

  Compact - More molecules in a small area

  Branched - More ends for fast hydrolysis (release glucose for respiration to release ATP and energy)

  Large - Can't leave cell / cross cell membrane

  Insoluble - water potential of cell not affected. ( no osmotic effect)
• What is the function of cellulose?

  Provides strength and structural support for plant/ algal cell walls.
• What is the structure of cellulose?

  Polysaccharide of beta glucose

  1,4 glycosidic bonds - Straight and Unbranched chains

  Chains linked by hydrogen bonds forming microfibrils.
• How does the structure of cellulose link to its function?


  Every other beta glucose molecule is inverted in long straight chain.

  Many hydrogen bonds link parallel strands to form microfibrils.

  Hydrogen bonds in high numbers

  Provides collective strength to cell wall.
• Describe the test for a reducing sugar.

  1. Add Benedict's solution to sample

  2. Heat in a boiling water bath

  3. Positive result = Green - Brick red precipitate
• Describe the test for a non reducing sugar.

  1. Complete Benedict's test and if stays blue...

  2. Heat in boiling water bath with acid (hydrolyse reducing sugars)

  3. Neutralise with alkali (e.g sodium bicarbonate)

  4. Heat in boiling water bath with Benedict's solution

  5 Positive result = Green - Brick red Precipitate.
• Suggest a method to measure the quantity of sugar in a solution.

  Carry out Benedict's test

  Filter and dry precipitate

  Find mass / weigh
• How could a dilution series be used to measure quantity of sugar in a solution?

  1. Make sugar solutions of known concentrations.

  2. Heat with set volume of each sample with set volume of Benedictus for same time.

  3. Use colorimeter to measure absorbance (of light) for each known concentration.

  4. Plot calibration curve (conc. X - axis and absorb Y - axis) and draw line of best fit.

  5. Repeat Benedict's with unknown sample and measure absorbance.

  6. Read off calibration curve to find concentration associated with unknown sample.
• Describe the biochemical test for starch.

  1. Add iodine dissolved in potassium iodide (orange/brown) and shake / stir.

  2. Positive result = blue - black
• What are the two groups of lipids?

  Triglycerides

  Phospholipids
• Describe the structure of a fatty acid.

  Variable R group - hydrocarbon chain

  -COOH = carboxyl group
• What is a saturated fatty acid?

  No C=C double bonds in hydrocarbon chain (all single saturated bonds)
• What is an unsaturated fatty acid?


  One or more C=C bonds in hydrocarbon chain.
• Explain how the propeties of triglycerides are related to their function?

  High ratio C-H bonds to carbon atoms in hydrocarbon chain

  - used in respiration to release more energy than same carbohydrate mass.

  
  

  Hydrophobic / non polar fatty acids so insoluble in water

  - no effect on water potential of cell.
• How are triglycerides formed?

  1 glycerol molecule

  Condensation reaction

  Removing 3 water molecules

  Forming 3 ester bonds
• Describe the difference between the structure of triglycerides and phospholipids.

  One fatty acid on triglyceride is replaced with phosphate containing group on phospholipid.

  
• What is the function of a phospholipid?

  Form a bilayer in cell membrane allowing for diffusion of lipid soluble (non polar) or very small substances and restricting movement of water soluble (polar) or larger substances.
• How do the properties of phospholipids relate to their structure?

  Phosphate heads are hydrophilic

  - attracted to water so point to water (aqueous environment) on either side of the membrane.

  
  

  Fatty acid tails are hydrophobic

  - repelled by water so point away from water into membrane.
• Describe the test for lipids.

  1. Add ethanol and shake (to dissolve lipids) then add water.

  2. Positive = milky white emulsion