Biology paper 1

• Preparing a slide


  1. Add a drop of water to the middle of a clean slide

  2. Cut up an onion and separate it into layers, use tweezers to peel off some epidermal tissue from the bottom of one of the layers

  3. Place the epidermal tissue into the water on the slide

  4. Add a drop of iodine solution

  5. Place a cover slip on top
• Using a light microscope

  1. Clip the slide onto the stage

  2. Select the lowest powered objective lens

  3. Use the coarse adjustment knob to move the stage up to just below the objective lens

  4. Look down the eyepiece, use coarse adjustment to move the stage downwards until the image is roughly in focus

  5. Adjust the focus with the fine adjustment until you get a clear image

  6. Swap to a higher-powered objective lens and refocus if you need to see the slide with greater magnification
• Investigating the effect of pH on enzyme activity

  1. Put a drop of iodine solution into every well of a spotting tile

  2. Heat water in a beaker on a tripod and gauze to 55°C, try to keep the temperature constant

  3. Use a syringe to add 2cm³ of amylase solution and 1cm³ of buffer solution with a pH of 5 to a boiling tube, put the tube in the water bath for 5 minutes

  4. Use a different syringe to add 5cm³ of starch solution to the boiling tube, mix immediately and start a stopwatch

  5. Take a sample from the boiling tube every 30 seconds and put a drop into a well, when the iodine solution remains brown-orange, the starch is no longer present

  6. Repeat the whole experiment with different pH buffer solutions
• Enzymes


  • They are catalysts produced by living things
  • They increase the speed of a reaction without being used up
  • They are large proteins made up of chains of amino acids
• Digestion


  1. Digestive enzymes are produced by cells and secreted into the digestive system to break down large molecules like proteins and fats into smaller, soluble molecules that can be absorbed

  2. Carbohydrases convert carbohydrates into simple sugars, e.g. amylase breaks down starch

  3. Proteases convert proteins into amino acids, e.g. pepsin in the stomach

  4. Lipases convert lipids into glycerol and fatty acids

  5. Bile neutralises stomach acid and emulsifies fats to increase the surface area for enzymes to work on
• The circulatory system


  • It is a double circulatory system with two circuits - one to the lungs to oxygenate the blood, and one to the body organs to deliver oxygen
  • The heart has four chambers - right atrium, right ventricle, left atrium, left ventricle - that pump the blood around the circuits
• Types of blood vessels

  • Arteries - carry blood away from the heart
  • Capillaries - involved in the exchange of materials
  • Veins - carry blood back to the heart
• Arteries


  • They have strong, elastic walls to withstand the high pressure of blood pumped from the heart
  • They have thick walls compared to the size of the lumen
  • They contain thick layers of muscle and elastic fibres
• Capillaries


  • They branch off from arteries
  • They are very small to get close to every cell in the body
  • They have permeable walls to allow diffusion of substances in and out
  • They supply oxygen and nutrients, and remove waste
• Veins


  • They have lower pressure so don't need thick walls
  • They have a larger lumen than arteries to help blood flow
  • They have valves to prevent backflow of blood
• Components of blood

  • Red blood cells - carry oxygen
  • White blood cells - protect against infection
  • Platelets - help blood clot
  • Plasma - the liquid that carries everything in the blood
• Red blood cells


  • They have a biconcave disc shape to increase surface area for oxygen absorption
  • They lack a nucleus to have more room to carry haemoglobin
• White blood cells


  • Some can change shape to engulf microorganisms
  • Others produce antibodies and antitoxins to fight infection
• Platelets


  • They are small fragments of cells without a nucleus
  • They help blood to clot at a wound to stop bleeding and prevent infection
• Plasma


  • It carries nutrients, waste, CO2, hormones, and proteins including antibodies
• Photosynthesis


  The process that uses light energy to convert carbon dioxide and water into glucose and oxygen
• Limiting factors for photosynthesis

  • Light intensity
  • Carbon dioxide concentration
  • Temperature
  • Chlorophyll
• Respiration


  The process of transferring energy from glucose, which occurs in every cell
• Aerobic respiration


  Glucose + oxygen -> carbon dioxide + water
• Anaerobic respiration


  Glucose -> lactic acid
• the nature of god 


  “Nothing is impossible with god“