Biological molecules

• What are the three main types of biological molecules.


  • Carbohydrates, proteins, and lipids.
• Why are carbohydrates, proteins, and lipids described as organic molecules?


  They all contain carbon
• What elements are found in carbohydrates?


  Carbon, hydrogen, and oxygen.
• What is a monosaccharide? Give an example.


  A simple sugar, e.g., glucose (C₆H₁₂O₆) or fructose.
• How is a disaccharide formed? Give an example.


  By joining two monosaccharides; e.g., maltose is formed from two glucose molecules.
• what is a polysaccharide, and name three examples.


  Large, complex carbohydrates formed by many monosaccharides; examples include starch, glycogen, and cellulose.
• What are most lipids in the body made of?


  Triglycerides.
• Describe the basic structure of a triglyceride.


  One glycerol molecule chemically bonded to three fatty acid chains.
• What is the difference between fats and oils?


  Fats are solid at room temperature, while oils are liquid.
• What are proteins made from?


  Long chains of amino acids.
• How do different proteins have different functions?


  Different amino acid sequences give proteins unique shapes, determining their function.
• Give examples of proteins.


  Enzymes, haemoglobin, ligaments, and keratin.
• What are the steps to prepare a food sample for testing?

  Break up the food, add distilled water, stir, filter the mixture, and collect the solution.
• Which solution is used to test for glucose, and what is the color change for a positive result?


  Benedict’s solution; color changes from blue to orange/brick red.
• What solution is used to test for starch, and what is the color change for a positive result?

  Iodine solution; changes from orange-brown to blue-black.
• What solution is used to test for protein, and what is the color change for a positive result?

  Biuret solution; changes from blue to violet/purple.
• Describe the emulsion test for lipids and its positive result.


  Mix food sample with ethanol, add to cold water; a cloudy emulsion indicates lipids.
• List important safety measures for handling chemicals in food tests.

  Wear goggles for Biuret solution (copper sulfate) and iodine (irritant); keep ethanol (flammable) away from flames.
• What are enzymes, and why are they important?


  Proteins that act as catalysts to speed up reactions without being changed; essential for life-sustaining metabolic reactions.
• Why are enzymes specific to substrates?


  Enzymes have an active site with a shape complementary to the substrate
• What forms when a substrate binds to an enzyme?


  An enzyme-substrate complex, allowing the reaction to proceed.
• What is the optimum temperature for most enzymes in the human body?


  37°C
• What happens to enzymes at temperatures above their optimum?


  They denature and lose their shape, stopping their activity.
• Why do low temperatures slow down enzyme activity?

  Molecules have less kinetic energy, resulting in fewer collisions between enzymes and substrates.
• How can the effect of temperature on amylase activity be investigated?


  Mix starch and amylase, add to iodine solution, time color change, repeat at different temperatures.
• What is the optimum pH for most enzymes, and how does pH affect enzymes?


  Optimum pH is 7; extremes in pH can disrupt enzyme shape and function.