Topic 2 : Organisation

• The five levels of organisation are, cells, tissues, organs, organ systems, and organisms
• Differentiation is the specialisation of cells
• A tissue is a group of similar cells that work together to carry out a particular function. eg. muscle tissue, glandular tissue, epithelial tissue
• An organ is a group of tissues that work together to perform a specific function. The stomach is an organ made of muscular, glandular and epithelial tissue.
• Organs are organised into organ systems. These are groups of organs that work together to carry out a particular function. The digestive system is made up of the pancreas and salivary glands, the stomach and small intestine, the liver and the large intestine
• Enzymes are catalysts, this is a substance that increases the speed of a reaction without being changed or used up in the reaction
• Every enzyme has an active site with a unique shape that fits onto a specific substrate. If the substrate does not match the enzymes active site, the reaction cannot be catalysed.

  
• Changing the temperature changes the rate of an enzyme - catalysed reaction

  
• pH affects enzymes, if its too high or too low, the pH interferes with the bonds holding together the enzymes, this changes the shape of an active sight and denatures the enzymes

  
• Carbohydrases convert carbohydrates into simple sugars
• Proteases convert proteins to Amino acids
• Amylase is a carbohydrase, it is produced in the salivary glands, the pancreas and the small intestine
• Proteases are produced in the stomach (called pepsin), the pancreas, and the small intestine
• Lipases convert convert lipids into glycerol and fatty acids
• Lipases are made in the pancreas, and the small intestine
• Bile neutralises the stomach acid and emulsifies fats
• The benedicts test tests for sugars, using a food sample, then adding 10 drops of benedicts solution, then placed in a water bath heated to 75 degrees celcius, if the solution turns, green, yellow or brick-red, then reducing sugars are present
• Iodine solution tests for starch, using a food sample, then adding a few drops of iodine solution and gently shaking the tube, if starch is present, the solution will change to blue/black, if not present, the colour will remain browny-orange
• The biuret test tests for proteins, this is done by taking a food sample, and adding biuret solution, if the food sample contains protein, the solution will change from blue to purple, if none is present, it will stay blue
• The Sudan III test is used to test for lipids, this is done by taking a sample of the specimen and adding the Sudan III solution to the sample. If lipids are present, the solution will seperate, the top layer being bright red, if lipids are not present, no seperate layer will form
• The lungs are in the thorax, the top part of the body seperated from the bottom by the diaphragm, the lungs act like large sponges and are protected by the ribcage, the air breathed in goes through the trachea, this splits into two tubes called the brinchi, which split further into the bronchioles, which end in the alveoli, where gas exchange takes place
• The alveoli are millions of little air sacs contained in the lungs, surrounded by a network of capillaries, this is where gas exchange occurs, the blood passing next to the alveoli just returned from the lungsso contains lots of carbon dioxide and very little oxygen, oxygen diffuses out of the alveolus (high concentration) into the blood (low concentration). Carbon dioxide diffuses out of the blood (high concentration) and into the alveolus (low concentration) to be breathed out
• When the blood reaches the body cells oxygen is released from the red blood cells (high concentration) and diffuses into the body cells (low concentration)
• Breaths per minute = number of breaths/number of minutes
• Humans have a double circulatory system, the first, the right ventricle, pumps deoxygenated blood to the lungs to take oxygen, the blood then returns to the heart, in the second, the left ventricle, oxygented blood is pumped around to all other organs of the body, the blood gives up its oxygen at the body cells and deoxygenated blood returns to the left ventricle
• The heart has valves to prevent backflow. Blood flows into the two atria from the vena cava and the pulmonary vein, the atria contract, pushing the blood to the ventricles, the ventricles contract, forcing blood to the pulmonary artery and the aorta, and then out of the heart, the blood flows to the organs the the arteries and returns through the vein, the atria will fill again and the process starts over

  
• Resting heart rate is controlled by a group of cells in the right atrium that act as a pacemaker, these create a small electric pulse which spread to the muscles causing them to contract, this group of nodes is called the sinus node
• The three types of blood vessels are the arteries, the capillaries and the veins
• The arteries carry blood away from the heart
• The capillaries are involved in the exchange of materials at the tissues
• Veins carry blood to the heart
• Veins take blood back to the heart. Capillaries eventually join back up to form veins, the blood being at a lower pressure so the walls don't need to be as thick as artery wall, they have bigger lumen than arteries to help blood flow despite the lower pressure, they also have valves to keep blood flowing in the correct direction
• Arteries carry blood under pressure, the heart pumps blood out at high pressure so the the artery walls are strong and elastic, the walls being thick compared to the lumen, they contain thick layers of muscle to make them strong and elastic fibres to allow them to stretch and spring back

  
• Veins take blood back to the heart. Capillaries eventually join back up to form veins, the blood being at a lower pressure so the walls don't need to be as thick as artery wall, they have bigger lumen than arteries to help blood flow despite the lower pressure, they also have valves to keep blood flowing in the correct direction

  
• Capillaries are the smallest blood vessel, they are one cell thick to increase the rate of diffusion and have a very thin wall, arteries branch out into capilleries, capillaries are too small to see and carry blood very close to every cell in the body to exchange substances, they have permeable wall, so substances can diffuse in and out, they supple food and oxygen, and take away wastes like carbon dioxide

  
• Rate of blood flow = volume of blood/number of minutes
• Red blood cells carry oxygen from the lungs all around the body, they have a biconcave shape so it has a large surface area, they don't have a nucleus to allow for more room to carry more oxygen.they contain a red pigment called haemoglobin which binds to oxygen to form oxyhaemoglobin, in body tissues, the revers happens, to release oxygen to the cells
• White blood cells are split into to two types, phagocytes and lymphocytes
• Phagocytes change shape to engulf pathogens to destroy them in phagocytosis
• lymphocytes produce antibodies that bind to antigens on pathogens to neutralise any toxins and allow for the phagocytes to engulf them