Biological Molecules

• What chemical elements are carbohydrates made of?

  Carbon, hydrogen and oxygen.
• What chemical elements are proteins made of?

  Carbon, hydrogen, oxygen and nitrogen. Sometimes sulfur.
• What chemical elements are lipids made of?

  Carbon, hydrogen and oxygen.
• What is the structure of carbohydrates?

  Large molecules made up of simple basic units, in this case simple sugars.
• What is the structure of proteins?

  Large molecules made up of simple basic units, in this case amino acids.
• What is the structure of lipids?

  Large molecules made up of simple basic unit, in this case glycerol and fatty acids.
• What are biological molecules?

  Molecules that are inside living organisms and are produced by them. They are organic, and all contain at least carbon and hydrogen.
• Examples of biological molecules:

  Carbohydrates, lipids and proteins.
• What is the function of a carbohydrate?

  To provide energy from glucose for respiration and to store energy in the form of glycogen.
• What is the function of a protein?

  • Provide structure
  • Repair and build body tissues
  • Keeps the immune system strong
  • Transports and stores nutrients
  • (Drives metabolic reactions)
  • (Maintains pH and fluid balance)
  • (Can act as an energy source)
• What is the function of a lipid?

  • Energy storage: When food is scarce, plants and animals can use the stored chemical energy.
  • Insulation: Adipose tissues help conserve body heat. They can also protect the body by acting as a 'shock absorber'.
  • Cell membrane: Control the materials entering or leaving cells.
• What is the role of enzymes as biological catalysts in metabolic reactions?

  They are molecules that speed up a chemical reaction without being changed by the reaction.
• PRACTICAL: Presence of starch

  • Name -> Iodine test.
  • Method -> Put a few drops of the iodine solution onto the sample.
  • Positive result -> If starch is present, the sample will turn from orange to blue-black.
• PRACTICAL: Presence of glucose (sugar)

  • Name -> Benedict's test.
  • Method -> Put double the volume of Benedict's solution compared to the volume of the sample into the test tube. Then heat to more than 80*C for 5 minutes.
  • Positive result -> If glucose is present, the sample will turn from blue to green to orange to brick-red (depending on the sugar concentration)
• PRACTICAL: Presence of proteins

  • Name -> Biuret test.
  • Method -> Add a drop at a time of the biuret solution to the sample.
  • Positive result -> If protein is present, the sample will turn from blue to lilac.
• PRACTICAL: Presence of lipids

  • Name -> Emulsion test
  • Method -> Mix an equal volume of the sample with ethanol and shake. Add an equal amount of distilled water and shake.
  • Positive result -> If lipids are present, the sample will turn milky white and cloudy, usually in a layer at the top of the mixture.
• How do temperature changes affect enzyme function?


  • As temperature increases to the optimum, the kinetic energy of the enzyme and substrate increases, causing more collisions between the enzyme and substrate. This leads to an increase in enzyme activity.
  • However, an increase in temperature beyond the optimum causes the enzyme’s active site to become denatured (a permanent change). This means the active site loses its shape, leading to a decrease in enzyme activity.
• How do pH changes affect enzyme function?

  Deviating from the optimum pH (too high or too low) causes the enzyme’s active site to become denatured. This means the active site loses its shape, leading to a decrease in enzyme activity.
• How to plan an experiment with CORMMSS:

  Change: What is the independent variable?

  Organism: What is the organism that is staying the same (if applicable)?

  Reliability: How close are the results to the truth?

  Measure: What is the dependent variable?

  Measure: What rules apply to the dependent variable?

  Stays the same: What is the first control variable?

  Stays the same: What is the second control variable?