germination

• Germination


  The start of growth in the seed
• Factors required for successful germination


  • Water
  • Oxygen
  • Warmth
• Water


  • Allows the seed to swell up, which causes the seed coat (testa) to burst, allowing the growing embryo plant to exit the seed
  • Allows the enzymes in the embryo to start working so that growth can occur (increases metabolic activity)
• Oxygen


  • Required for respiration, so that energy can be released for germination
• Warmth


  • Germination improves as temperature rises (up to a certain point) as the reactions which take place are controlled by enzymes, which cannot function effectively when temperatures are too low
• Carbon dioxide is not necessary for germination and does not inhibit it
• Apparatus


  • Test tubes
  • Test tube holder
  • Cress seeds
  • Cotton wool
  • Fridge
• • As germination cannot occur if the conditions are not right (i.e. if even one of the three factors required is absent), it would be expected that only the seeds in the control tube will germinate  
• carbohydrate: source of energy. this includes bread, cereals pasta, rice, potatoes
• protein - essential for growth and repair, this includes meat, fish, eggs, pulses, nuts
• lipid- insulation and energy storage. this includes butter, oil, nuts
• dietary fibre- provides bulk (roughage) for the intestine to push food through it. this includes vegtables, whole grains
• vitamins - needed in small quantities to maintain health. this includes fruits and vegetables
• minerals: needed in small quantities to maintain health - includes fruits and vegetables
• water: needed for chemical reactions to take place in cells - includes water, juice, milk, fruits, and vegetables
• calcium - needed for strong teeth and bones, and involved in the clotting of blood. deficiency can lead to osteoporosis later in life
• vitamin D helps the body to absorb calcium and so required for strong bones and teeth
• vitamin c forms an essential part of collagen proteins which makes up hair, skin and gums. deficiency can cause scurvy
• vitamin a - needed to make the pigment in the retina for vision.
• iron - needed to make hemoglobin, the pigment in red blood cells that transports oxygen.
• Digestion


  The process of breaking down large, insoluble molecules into smaller, soluble molecules that can be absorbed into the bloodstream
• Mechanical digestion


  1. Chewing

  2. Churning

  3. Emulsification
• Mechanical digestion breaks large pieces of food into smaller pieces, increasing the surface area for enzymes to work on
• Chemical digestion


  Bonds holding the large molecules together are broken to make smaller and smaller molecules
• Enzymes


  Biological catalysts that speed up chemical reactions without themselves being used up or changed in the reaction
• Main types of digestive enzymes


  • Carbohydrases
  • Proteases
  • Lipases
• Carbohydrases

  • Carbohydrases are enzymes that break down carbohydrates to simple sugars such as glucose
  • Amylase is a carbohydrase which is made in the salivary glands, the pancreas and the small intestine
  • Amylase breaks down starch into maltose
  • Maltase then breaks down maltose into glucose
• Starch is broken down into glucose using two enzymes: amylase and maltase.
• Proteases

  • Proteases are a group of enzymes that break down proteins into amino acids
  • Pepsin is an enzyme made in the stomach which breaks down proteins into smaller polypeptide chains
  • Proteases made in the pancreas and small intestine break the peptides into amino acids
• Proteins are broken down using pepsin and other proteases
• ipases

  • Lipases are enzymes that break down lipids (fats) to glycerol and fatty acids
  • Lipase enzymes are produced in the pancreas and secreted into the small intestine
• The pancreas is an accessory organ in the digestive system. Food does not pass directly through it, but it has a key role in producing digestive enzymes as well as the hormones that regulate blood sugar (insulin and glucagon).