Biology-Organisation

• Enzymes are present in many reactions so that they can be controlled
• Enzymes


  Can both break up large molecules and join small ones
• Enzymes


  Protein molecules, shape of enzyme is vital to its function
• Active site


  Uniquely shaped part of enzyme where substrate binds
• Lock and Key Hypothesis

  Simplified explanation of how enzymes work - shape of substrate is complementary to active site, forming enzyme-substrate complex
• Food Tests (Required Practical)

  1. Add 2cm3 of starch solution into the test tube

  2. Extract some of the amylase/starch solution after 10 seconds and place one drop into the first well of the spotting tile

  3. Continue to place one drop into the next well of the spotting tile, every 10 seconds, until the iodine remains orange

  4. Record the time taken for the starch to be completely digested by the amylase by counting the wells that were tested positive for starch

  5. Repeat steps 1 to 8 for pH values 7 and 10
• Effect of pH on the Rate of Reaction of Amylase (Required Practical)

  1. Use the marker pen to label a test tube with the first value of pH buffer solution (pH 4) and stand it in the test tube rack

  2. Into each well of the spotting tiles, place a drop of iodine

  3. Measure 2cm3 of amylase and pour into the test tube

  4. Measure 1cm3 of the buffer solution and pour into the test tube

  5. Leave this to stand for five minutes and then use the thermometer to measure the temperature
• Independent variable


  pH of the buffer solution
• Dependent variable


  Time taken for the reaction to complete (how long it takes for all the starch to be digested by the amylase)
• Iodine is used to test for the presence of starch
• If starch is present, the colour will change to blue-black
• Digestive system


  To break down large molecules into smaller, soluble molecules, which are then absorbed into the bloodstream
• The rate of these reactions is increased by enzymes
• Enzymes


  • They are biological catalysts that speed up chemical reactions without being changed or used up
  • They lower the activation energy required for the reaction to occur
  • They are made up of chains of amino acids folded into a globular shape
  • They have an active site which the substrate (reactants) fits into
  • They are very specific and will only catalyse one specific reaction
  • They work optimally at specific conditions of pH and temperature
  • In extremes of pH or temperature, the enzyme will denature and the active shape will deform
• Enzymes and their substrates

  • amylase - starch
  • protease - protein
  • lipase - lipid
• Heart


  A large muscular organ which pumps blood carrying oxygen or waste products around the body
• Lungs


  The site of gas exchange where oxygen from the air is exchanged for waste carbon dioxide in the blood
• Oxygen is used in the respiration reaction


  To release energy for the cells and carbon dioxide is made as a waste product during the reaction
• Types of blood vessels

  • Arteries
  • Veins
  • Capillaries
• Capillaries


  • They are narrow vessels which form networks to closely supply cells and organs between the veins and arteries
  • The walls of the capillaries are only one cell thick, which provides a short diffusion pathway to increase the rate at which substances are transferred
• Comparison of arteries and veins

  • Direction of blood flow - Arteries: away from the heart, Veins: towards the heart
  • Oxygenated or deoxygenated blood - Arteries: oxygenated (except pulmonary artery), Veins: deoxygenated (except pulmonary vein)
  • Pressure - Arteries: high, Veins: low (negative)
  • Wall structure - Arteries: thick, elastic, muscular, connective tissue for strength, Veins: thin, less muscular, less connective tissue
  • Lumen (channel inside the vessel) - Arteries: narrow, Veins: wide (with valves)
• Heart as a double pump

  The heart works as a double pump for two circulatory systems; the pulmonary circulation and the systemic circulation
• Pulmonary circulation


  Serves the lungs and brings deoxygenated blood to exchange waste carbon dioxide gas for oxygen at the alveoli
• Systemic circulation


  Serves the rest of the body and transports oxygen and nutrients from digestion to the cells of the body, whilst carrying carbon dioxide and other waste away from the cells
• The systemic circulation flows through the whole body, so the blood is flowing at a much higher pressure than in the pulmonary circuit
• Heart as pacemaker


  Small groups of cells in the muscular walls of the heart act as pacemakers, producing electrical impulses which stimulate the surrounding muscle to contract, squeezing the chambers of the heart and pumping the blood
• Artificial pacemakers can be surgically implanted into a person if their heart nodes are not functioning correctly
• Coronary heart disease


  A condition resulting from blockages in the coronary arteries, the main arteries which supply blood to the heart itself
• Coronary heart disease is a major cause of many deaths in the UK and around the world
• Symptoms of coronary heart disease

  • Chest pain
  • Heart attack
  • Heart failure
• Lifestyle factors that increase the risk of coronary heart disease

  • Diet - high-fat diet containing lots of saturated fat
  • Smoking - chemicals in cigarette smoke, including nicotine and carbon monoxide
  • Stress - prolonged exposure to stressful situations
• Blood


  Composed of red blood cells, white blood cells and platelets, all suspended within a plasma

  
• Plasma


  Transports the different blood cells around the body as well as carbon dioxide, nutrients, urea and hormones, and distributes the heat throughout the body
• Red blood cells


  Transport oxygen attached to the haem group in their structure, and have a biconcave shape to increase surface area and do not contain a nucleus so they can bind with more oxygen molecules
• White blood cells


  Form part of the immune system and ingest pathogens and produce antibodies
• Platelets


  Important blood clotting factors
• At the lungs


  Haemoglobin + oxygen -> oxyhaemoglobin
• At the cells


  Oxyhaemoglobin releases oxygen
• The blood only flows in one direction due to valves in the heart which close under pressure and prevent the backward flow of blood
• Leaves


  Plant organs whose main function is to absorb sunlight energy for use in photosynthesis