Biological molecules

• 2.8 Describe the structure of carbohydrates, proteins and lipids as large molecules made up from smaller basic units

  Starch and glycogen from simple sugars, protein from amino acids, and lipid from fatty acids and glycerol

  
• Living things are made of organic matter
• Elements in organic matter

  • Carbon
  • Hydrogen
  • Oxygen
  • Nitrogen
• The Chemicals of Life

  • Water
  • Carbohydrates
  • Proteins
  • Fats (Lipids)
  • Nucleic Acids

  
• Water


  80% of most organisms, Important solvent needed for metabolic reactions
• Where can we find water in living organisms?

  • Cell cytoplasm
  • Spaces between cells
  • Blood plasma
• Carbohydrates


  Elements: Carbon (C), Hydrogen (H), Oxygen (O)
• Types of Carbohydrates


  • Sugar
  • Starch
• Simple Sugar (Monosaccharide)


  Very small, Soluble in water, Taste sweet, Glucose
• Complex Sugar (Disaccharide)


  Formed by two simple sugars joining, Soluble in water, Taste sweet, Examples: sucrose, maltose
• Polysaccharide


  Many simple sugars join to form large molecules, Very large, Insoluble, Does not taste sweet
• Examples of Polysaccharides


  • Starch
  • Cellulose
  • Glycogen
• Starch


  • Stored inside plant cells
• Cellulose


  • Makes the plant cell wall
• Glycogen


  • Stored inside animal cells
• Functions of Carbohydrates


  • Energy (respiration uses glucose)
  • Storing energy
  • Sucrose is transported around plants
  • Cellulose forms the structural part of the plant cell wall

  
• Lab Tests for Carbohydrates

  1. Iodine test for starch

  2. Benedict's test for reducing sugars (simple sugars)
• Iodine Test for Starch

  Put a small piece of the test solution or food onto a white tile or in a test tube, Add a few drops of iodine solution, If there is starch present, the iodine solution will turn blue-black, If there is no starch present, the iodine will stay brown
• Benedict's Test for Reducing Sugar (Simple Sugar)


  Cut/grind the food sample into small pieces and put into a test tube with some water, Add some Benedict's solution (it is blue because it contains copper (II) sulphate), Heat the test tube in a water bath at 80oC for 5 minutes, If there are simple sugars present, the Benedict's will change colour to brick-red, If there is no simple sugar present, the Benedict's will stay blue
• Colour changes in Benedict's test

  • no sugar - blue
  • a little sugar - green
  • some sugar - orange
  • a lot of sugar - brick red
• Carbohydrates


  Large molecules made up from smaller basic units of simple sugars
• Proteins


  Large molecules made up from smaller basic units of amino acids
• Lipids


  Large molecules made up from smaller basic units of fatty acids and glycerol
• Practical: Investigate food samples for the presence of glucose, starch, protein and fat


  1. Cut/grind the food sample into small pieces and put into a test tube with some water

  2. Add Biuret reagent

  3. If protein is present, the colour will change to purple
• Enzymes


  Biological catalysts in metabolic reactions
• Temperature changes


  Can affect enzyme function, including changes to the shape of active site
• Changes in pH


  Can affect enzyme function by altering the active site
• Elements that make up proteins

  • Carbon (C)
  • Hydrogen (H)
  • Oxygen (O)
  • Nitrogen (N)
  • Sulphur (S)
• Proteins


  • Made up of many amino acids joined together to form long chains
  • Different sequences of amino acids give different shapes of protein molecules, which determines their function
• Functions of proteins


  • Enzymes
  • Antibodies
  • Make up parts of the cell membrane
  • Carrying oxygen in the blood (haemoglobin)
  • Making up part of the skin, hair and nails (keratin, collagen)
• Biuret test


  Test for the presence of proteins in a food sample
• Biomolecules


  Biomoleküle
• Milk from cows contains a higher concentration of proteins than milk from goats
• Exercise 4.3 Testing a Hypothesis


  1. Variable to change:

  2. Variables to keep the same:

  3. What to measure: