Making and breaking Biological molecules

• Organisms can break big molecules down into smaller ones and build small molecules back up into bigger ones. 
• Organic molecules

  •  are molecules that contain carbon. 
  • Carbohydrates, lipids and proteins are all organic molecules and so are the smaller molecules they're made up from:
• Carbohydrates

  • Basic units: sugars
  • Provide energy and structural support. Fiber is a carbohydrate, rate that prevents constipation.
  • Foods: breads, cereals, vegetables, fruits, & seeds. Extra glucose is converted into glycogen in the liver.
• Three types of carbohydrates:

  • Monosaccharide: Glucose
  • Disaccharides: Lactose, Maltose
  • Polysaccharides: Starch, Cellulose
• Long-chain carbohydrates, e.g. starch are made from simple sugars.
• Proteins are made from amino acids.
• Lipids are made by joining fatty acids and glycerol.

  • fats and oils
• Producers


  Organisms that take in the elements they need to survive from their environment, e.g. plants take in carbon from the air and nitrogen compounds from the soil
• Photosynthesis


  Plants use carbon (along with oxygen and hydrogen) to make glucose
• Glucose


  Used to make other small organic molecules, e.g. other sugars, fatty acids and glycerol
• Amino acid synthesis


  Glucose and nitrate ions are combined to make amino acids
• Synthesis of larger molecules

  Small molecules are used by the producer to create long-chain carbohydrates, lipids and proteins
• Proteins


  Amino acids are joined together to make proteins
• Sugars


  Types of sugar molecules
• Larger molecules


  Used to build structures like cell membranes and organelles
• Reducing sugars


  Sugars (e.g. glucose) with certain chemical properties
• All these synthesis reactions are catalysed by enzymes
• Using Benedict's Reagent to test for sugars

  1. Add Benedict's reagent (which is blue) to a sample

  2. Heat it in a water bath set to 75 °C
• Consumers


  Unlike plants, can only get carbon and nitrogen compounds by eating and digesting the large organic molecules in producers or other consumers in the food chain
• Positive test result


  • Forms a coloured precipitate (solid particles suspended in the solution)
• Digestion


  Breaks large molecules down into smaller ones, which can be more easily absorbed by the consumer
• Higher concentration of reducing sugar


  Further the colour change goes
• Digestion of large molecules

  • Proteins are broken down into amino acids, starch is broken down into simple sugars, and lipids are broken down into fatty acids and glycerol
• This is a qualitative test as you don't have a numerical value for the concentration of sugar
• Digestion reactions are also catalysed by enzymes
• You can use this to compare the amount of reducing sugar in different solutions
• Absorption and synthesis in consumers

  The small molecules are then transported to the consumer's cells (usually in the blood supply) to be built up into larger molecules (proteins, etc.) again
• These larger molecules form the biomass of the consumer
• Sugars


  Types of sugar molecules
• Reducing sugars


  Sugars (e.g. glucose) with certain chemical properties
• Using Benedict's Reagent to test for sugars

  1. Add Benedict's reagent (which is blue) to a sample

  2. Heat it in a water bath set to 75°C

  3. If positive, forms a coloured precipitate

  4. The higher the concentration of reducing sugar, the further the colour change goes
• This is a qualitative test as you don't have a numerical value for the concentration of sugar
• You don't need to know exactly what reducing sugars are, but you do need to know how to test for them
• STARCH

  Starch is tested for with iodine

  lodine solution -  is iodine dissolved In potassium iodide solution.

  1. Just add iodine solution to the test sample.
  2. If starch is present, the sample changes from browny-orange to a dark, blue-black colour.
  3.  If there's no starch, it stays browny-orange.
• LIPIDS

  • Are compounds that are soluble in organic solvents and insoluble in polar solvents such as water
• Structure

  • Lipid are made out of monomers (basic units): fatty acids. 
  • Polymer (chain og units): Lipid
  • Triglycerides, Phospholipids

  Examples: 

  Fats, Oils, Waxes, Hormones

  • Steroids
  • Sex Hormones
  • Testosterone (Male) 
  • Estrogen (Female)
• Use the ethanol emulsion test for lipids to find out if there are any lipids in a sample:

  1. Shake the test substance with ethanol for about a minute until it dissolves, then pour the solution into water.
  2. If there are any lipids present, they will show up as a milky emulsion.
  3. The more lipid there is, the more noticeable the milky colour/cloudy will be.

  An emulsion is when one liquid doesn't dissolve in another - it just forms little droplets.
• PROTEINS

  • Are a diverse group of large and complex polymer molecules, made up of long chains of amino acids.

  They have a wide range of biological roles, including:

  Structural: proteins are the main component of body tissues, such as muscle, skin, ligaments and hair

  Catalytic: all enzymes are proteins, catalyzing many biochemical reactions.
• The Biuret Test is used for proteins

  If you needed to find out if a sample contains protein you'd use the biuret test:

  1. First, add a few drops of sodium hydroxide solution to make the solution alkaline.
  2.  Then add some copper(Il) sulphate solution (which is bright blue).

  •  If there's no protein, the solution will stay blue.
  • If protein is present, the solution will turn purple.