Organisation

• A cell makes up all living things. A tissue is a group of specialised cells with a similar function. Organs are made from different tissues working to perform a specific function. An organ system is a group of organs working together perform a specific function.
• Amylase is produced in the salivary glands and the pancreas. Amylase is a carbohydrase which breaks down starch into maltose.
• Protease is produced in the stomach and pancreas and breaks down proteins into amino acids.
• Lipase is produced in the pancreas and small intestine and breaks down lipids into fatty acids and glycerol.
• What are the products of digestion used for?

  Energy, growth, and repair. To build new enzymes, some glucose is used in respiration.
• Bile is made in the liver and stored in the gall bladder. It is alkaline to neutralise hydrochloric acid from the stomach. It also emulsifies fat to form small droplets which increases the surface area. The alkaline conditions and large surface area increase the rate of fat breakdown by lipase.
• What is the stomach's role in the digestive system?

  The stomach has acidic conditions and produces hydrochloric acid to kill bacteria and to provide optimum pH for protease to function.
• What is the pancreas' role in digestion?

  Pancreas produces digestive juices and enzymes (protease, lipase and amylase).
• What is the small intestines role in digestion?

  Partially permeable where soluble molecules are absorbed into the blood by diffusion/active transport.
• What does the liver do in digestion?

  The liver produces bile which emulsifies fats and has alkaline conditions to neutralise stomach acid.
• What are enzymes?

  Enzymes are biological catalysts made of proteins.
• Explain the lock-key hypothesis.

  Each enzyme has an active site. The shape of the substrate is complementary to the shape of the active site, forming an enzyme-substrate complex. When they are joined, the reaction takes place and the substrate is broken down into the products and the products are released from the surface of the enzyme.
• Proteins are a long chain of chemicals called amino acids. When proteins are digested, protease enzymes convert the protein back into amino acids which are absorbed into the blood stream.
• Protease: Stomach, pancreas and small intestine.

  Amylase: Salivary gland and pancreas.

  Lipase: Pancreas and small intestine.
• Explain the affect of temperature increase on enzymes.

  As the temperature increases, the rate of reaction increases as the substrate moves faster so there are more collisions per second. At optimum temperature, there is a maximum of successful collisions between the substrate and active site. When the temperature is too high, the bonds in the structure will break and the shape of the active site changes so the substrate can no longer fit. This means the enzyme has denatured and can no longer catalyse reactions.
• Explain the effect of pH on enzymes.

  If the pH is too high or too low, the active site denatures which changes the shape of the active site so the substrate can no longer fit in. The enzyme then denatures and can no longer catalyse reactions.
• Explain how you would measure the effect of pH on amylase.

  1. Place one drop of iodine solution into each well of a spotting tile.
  2. Take 3 test tubes. One with 2cm of starch solution, 2cm of amylase solution and 2cm of pH 5 solution.
  3. Place all test tubes in a water bath at 30 degrees for 5-10 mins so temp can equilibrate.
  4. Combine each solution into one test tube and place it into the waterbath again and start a stopwatch.
  5. After 30s, use the glass rod to place one drop of the solution into a well of the spotting tile. It should turn blue-black because starch is present.
• Explain how to test for starch.

  1. Place the food sample in a test tube.
  2. Add a few drops of iodine solution.
  3. If starch present, iodine goes from orange to blue/black.
• Explain how to test for sugars.

  1. Place a food sample in a test tube and add a few drops of Benedict's solution using a pipette.
  2. Place the test tube into a beaker with hot water.
  3. If lots of sugars are present, it will go from blue to red.
  4. Benedict's solution will only work on reducing sugars e.g glucose and not sucrose.
• Explain how to test for proteins.

  1. Place food sample in a test tube and add a few drops of biuret solution.
  2. If protein present, goes from blue to purple.
• Explain how to test for lipids.

  1. Place a food sample into a test tube and add a few drops of water and ethanol.
  2. Shake the tube lightly.
  3. If lipids are present, mixture goes from clear to cloudy.
• How is the small intestine adapted to perform its function?

  • Large surface area: absorption of products
  • Villi: Increase the surface area
  • Good blood supply: Increases concentration gradient.
  • Thin walls: Short diffusion pathway.
• The heart is an organ that pumps blood around the body in a double circulatory system. The right ventricle pumps blood to the lungs where gas exchange takes place. The left ventricle pumps blood around the rest of the body.
• The natural resting heart rate is controlled by a group of cells located in the right atrium that act as a pacemaker.
• What does the vena cava do?

  Bring in deoxygenated blood from the body to the right of the heart.
• The vena cava brings in deoxygenated blood from the body to the heart.

  The blood passes from the heart to the lungs in the pulmonary artery. In the lungs, the blood collects oxygen during gas exchange.

  Oxygenated blood passes from the lungs to the heart with the pulmonary vein.

  Oxygenated blood is pumped from the heart to the body with the aorta. The aorta carries blood with the highest pressure.
• Explain how oxygenated blood enters the heart.

  1. First oxygenated blood from the lungs goes through the pulmonary vein into the left atrium.
  2. The valves contract and blood goes into the left ventricle.
  3. The ventricle contracts and blood goes to the body through the aorta.
• Explain the blood flow of deoxygenated blood.

  1. First deoxygenated blood from the body enters the right atrium through the vena cava.
  2. The valves contract and blood flows to the right ventricles.
  3. The ventricles contract and blood flows to the lungs through the pulmonary artery.
• What do the valves do?

  The valves prevent the backflow of blood. Without the valves, blood would flow back into the heart, causing less oxygenated blood to flow around the body causing less aerobic respiration. The person would then lack energy.
• The left side of the heart is thicker because it pumps a greater volume of blood as it has to go all around the body and not just one place like the right.
• The coronary arteries branch out from the aorta and provide oxygen to the muscle cells of the heart.
• Capillaries allow blood to flow very close to cells for diffusion to take place. Capillaries have thin walls to create a short diffusion pathway and are narrow so that air bubbles can move faster. They also have permeable walls.
• Veins carry blood towards the heart. They have thinner walls and contain valves to prevent the backflow of blood and to make sure blood flows in the correct direction. They have a wide lumen to allow low pressure blood to flow through.
• Explain the process of ventilation/inhalation.

  1. The ribcage moves up and out and the diaphragm moves down, causing the volume of the chest to increase.
  2. Increased volume results in lower pressure.
  3. Air is drawn into the chest as air moves from areas of high pressure into low pressure (the lungs)
• What are the 4 parts of the blood?

  • Red blood cells
  • White blood cells
  • Plasma
  • Platelets
• What does blood plasma transport?

  Red/white blood cells, urea from the kidneys, soluble digestion products (glucose) carbon dioxide from organs to the lungs to be breathed out
• What do red blood cells do? What are their adaptations so they are suited to their functions?

  • Transport oxygen from lungs to body cells
  • Carries haemoglobin to carry oxygen
  • Have no nucleus to allow more room to carry oxygen
  • Biconcave disc shape to provide large surface area
• What are white blood cells? How are they adapted to their functions?

  • Part of the immune system and produce antibodies
  • Have a nucleus which contains DNA that instructs them to do their job
• What are platelets?

  • Help blood clots form at site of wounds
  • Without platelets cuts would excessively bleed and bruise
• What is coronary heart disease?

  In coronary heart disease layers of fatty material build up inside the coronary arteries, narrowing them. This reduces the flow of blood through the coronary arteries (which help supply oxygen to muscle heart) resulting in a lack of oxygen for the heart muscle. This could cause a heart attack.