Organisation

• Organ Systems

  Similar Cells > Tissues > Organs > Organ Systems
• Catalyst


  A catalyst is a substance which increases the speed of a reaction, without being change or used up in the reaction.
• What are biological catalysts?


  Enzymes.
• Raising the Temp in Reactions


  Can speed up reactions but there is a limit to how much you can raise temp in a living creature before its cells start to get damaged.
• What are Enzymes made of?

  Large proteins and all proteins are made up of chains of amino acids. These chains are folded into unique shape which help enzymes fo their jobs
• Shapes of Enzymes

  Chemicak reactions usually invole things being split or joined together. Every enzyme has an active site with a unique shape that fits onto the substance in a reaction. Enzymes usually only catalyse one specific reaction.

  This is b/c for the enzyme to work the substrate has to fit into its active site. If the substrate doesnt match the enzyme's active site, then the reaction wont be catalysed. The active site changes shape a little as the substrate binds it to get a tighter fit.
• Enzyme Temperature 


  Enzymes need the right temp. Changing the temp changes the rate of an enzyme-catalysed reaction. At first, a higher temp increases the rate but if it gets too hot, some of the bonds holding the enzyme together break. This changes the shape of the enzyme's active site, so the substrate wont fit anymore. The enzyme is said to be denatured. All enzymes have an optimum temp that they work best at.
• Enzymes pH


  If the pH is too high or low, the pH interferes with the bonds holding the enzyme together. This changes the shape of the active site and denatures the enzyme. All enzymes have an optimum pH that they work best at. Its often neutral pH 7, but not always.
• Digestive Enzymes


  Break down big molecules (such as starch, proteins and fats that are too big too pass through the walls of the digestive systems) into smaller molecules like sugar, amino acids, glycerol and fatty acids that can easily pass through the walls of a digestive system.
• Carbohydrases


  Carbohydrases concert carbohydrates into simple sugars. Amalyse is an example of a carbohydrase and it breaks down starch into maltose and other sugars. Amalyse is in 3 places: salixary glands, pancreas and small intestine.
• Proteases


  Proteases convert proteins into amino acids. Proteins are broken down in amino acids. Proteases are made in 3 places: stomach, pancreas and small intestine.
• Lipases


  Lipases convert lipids into glycerol and fatty acids. Lipases are in 2 places: pancreas and small intestine.
• Bile


  Bile is produced by the liver and its stored in the gall bladder before it is released into the small intestine. The hydrochloric acid in the stomach makes the pH too acidic for enzymes in the small intestine to work properly. Bile is alkaline - it neutralises the acid and makes conditions alkaline. The enzymes in the small intestine work best in these alkaline conditions. It emulsifies fats (breaks it into tiny droplets). This gives a much larger surface area of fat for the enzyme lipase on - which makes its digestion faster.
• Enzymes and the Digestive System


  Enzymes used in the digestive system are produced by specialized cells in glands and in the gut lining. Diff enzymes catalyse the breakdown of diff food molecules.

  
• How to prepare a Food Sample for Food Tests

  1. Get a piece of food and break it up using a pestle and mortar.
  2. Transfer the ground up food to a beaker and add some distilled water.
  3. Give the mixture a good stir with a glass rod to dissolve some of the food.
  4. Filter the solution using a funnel lined with filter paper to get rid of the solid bits of food.
• Benedict's Solution (Tests for Reducing Sugars)

  1. Prepare a food sample and transfer 5cm3 to a test tube.
  2. Prepare a water bath so that its set to 75°C.
  3. Add some Benedict's solution to the test tube (about 10 drops) using a pipette.
  4. Place the test tube in the water bath using a test tube holder and leave it in there for 5 mins. Make sure the tube is pointing away from you.
  5. If the food sample contains a reducing sugar, the solution in the test tube will change from the normal blue colour to green, yellow or brick-red - it depends on the amount of sugar in the food.
• Iodine Solution (Tests for Proteins)

  1. Make a food sample and transfer 5 cm3 of your sample to a test tube.
  2. Then add a few drops of iodine solution and gently shake the tube to mix the contents. If the sample contains starch, the colour of the solution will change for browny-orange to black or blue-black.
• Biuret Test (Tests for Proteins)

  1. Prepare a sample of your food and transfer 2cm3 of your sample to a test tube.
  2. Add 2cm3 of biuret solution to the sample and mix the contents of the tube by gently shaking it.
  3. If the food sample contains protein, the solution will change from blue to pink or purple. If bo protein is present it will stay blue.
• Sudan III Test (Tests for Lipids)

  1. Prepare a sample of food you're testing and transfer about 5cm3 into a test tube.
  2. Use a pipette to add 3 drops of Sudan III stain solution to the test tube and gently shake the tube.
  3. Sudan III stain solutions stains lipids. If the sample contains lipids, the mixture will separate out into two layers. The top layer will be bright red. If no lipids are present, no separate red layer will form at the top of the liquid.
• Thorax


  The thorax is the top part of your body. It's separated from the lower part of the body by the diaphragm. The lungs are like nig sponges and are protected by the ribcage. They're surrounded by the pleural membranes. The air that you breath in goes through the trachea. This splits into two tubes called bronchi (each one is a bronchus), one goes into each lung. The bronchi split into progressively smaller tubes called bronchioles. The bronchioles finally end at small bags called alveoli where the gas exchange takes place.

  
• Alveoli


  The lungs contain millions of alveoli (little air sacs) surrounded by a network of blood capillaries. The blood passing next to the alveoli has just returned to the lungs from the rest of the body, so it contains lots of CO2 and very few oxygen. Oxygen diffuses out of the alveolus to the blood. CO2 diffuses out of the blood into the alveolus to be breathed out. When the blood reaches body cells oxygen is released from the red blood cells and diffuses into the body cells. At the same time, CO2 diffuses out of the body cells into the blood. It's then carried back to the lungs.
• Calculate Breathing Rate


  breaths per minute = number of breaths ÷ number of minutes
• What is the Circulatory System made of?

  The heart, blood vessels, and blood.
• Circulatory System in Humans


  Humans have a double circulatory system - two circuits joined together. 1st one contains the right ventricle which pumps deoxygenated blood to the lungs to take in oxygen. The blood then returns to the heart. 2nd one contains the left ventricle which pumps oxygenated blood around all the other organs of the body. The blood gives up its oxygen at the body cells and the deoxygenated blood returns to the heart to be pumped out to the lungs again.
• Heart


  A pumping organ that keeps the blood flowing around the body
• Heart


  • Walls are mostly made of muscle tissue
  • Has valves to make sure blood flows in the right direction and prevent it flowing backwards
• How the heart pumps blood around


  1. Blood flows into the two atria from the vena cava and the pulmonary vein

  2. The atria contract, pushing the blood into the ventricles

  3. The ventricles contract, forcing the blood into the pulmonary artery and the aorta, and out of the heart

  4. The blood then flows to the organs through arteries, and returns through veins

  5. The atria fill again and the whole cycle starts over
• The heart also needs its own supply of oxygenated blood
• Coronary arteries


  Arteries that branch off the aorta and surround the heart, making sure it gets all the oxygenated blood it needs
• Arteries

  • Carry blood away from the heart.
  • The heart pumps the blood out at high pressure so the artery walls are strong and elastic.
  • Walls are thick compared to the size of the hole down (the 'lumen').
  • Contain thick layers of muscle to make them strong, and elastic fibres to allow them to stretch and spring back.

  
• Capillaries

  • Involved in the exchange of materials at the tissue.
  • Really small.
  • Arteries branch into capillaries.
  • Carry blood close to every cell in the body to exchange substamces with them.
  • Permeable walls so substances can diffuse in and out.
  • Supply food and oxygen, and take away waste such as CO2
  • Walls are usually one cell thick - increases the rate of diffusion by decreasing the distance over which it occurs.

  
• Veins

  • Take blood to the heart.
  • Capillaries join up to form veins.
  • Blood is at lower pressure so the walls dont need to be as thick.
  • Have a bigger lumen than arteries to help blood flow despite the lower pressure.
  • Have valves to help keep blood flowing in the right direction.

  
• Formula for Blood Flow

  rate of blood flow = volume of blood ÷ number of minutes
• Red Blood Cells

  • Carry oxygen from the lungs to all the cells in the body.
  • Shape is a biconcave disc - this gives a large surface area for absorbing oxygen.
  • Dont have a nucleus so they can carry more oxygen.
  • Contain haemoglobin (a red pigment).
  • Haemoglobin bind to oxygen in the lungs to produce oxyhaemoglobin.
  • The reverse happens in body tissues - oxyhaoglobin splits into haemoglobin and oxygen, to release oxygen to rhe cells.
• Whats in blood?

  • Red Blood Cells
  • White Blood Cells
  • Platelets
  • Plasma
• White Blood Cells

  • Some can change shape to destroy unwelcome organisms in a process called qhagocytosis.
  • Others produce antibodies (to fight microorganisms) and antitoxins (to neutralise toxins produced by the microorganisms).
  • Do have a nucleus.
• Platelets

  • Help blood clot at a wound to stop blood pouring out and stop microorganisms getting in.
  • Small fragments of cell.
  • No nucleus.
  • Lack of platelets can cause excessive bleeding and bruising.
• Plasma

  • Pale straw-coloured liquid which carries: red and white blood cells, platelets, nutrients (such as glucose and amino acids),carbon dioxide, urea, hormones, proteins, antibodies and antitoxins.