2 - organisation

• Enzymes


  • Living things have thousands of different chemical reactions going on inside them all the time
  • Enzymes reduce the need for high temperatures to speed up reactions
• Active site


  The unique shape of an enzyme that fits the substrate involved in the reaction
• Optimum temperature


  The temperature at which an enzyme works best
• Optimum pH


  The pH at which an enzyme works best
• Rate of reaction


  A measure of how much something changes over time, calculated as the amount of change divided by the time taken
• Preparing a food sample

  1. Get a piece of food and break it up using a pestle and mortar

  2. Transfer the ground up food to beaker and add some distilled water

  3. 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 Test


  Test for reducing sugars in foods
• Benedict's Test

  1. Prepare a food sample and transfer 5cm to a test tube

  2. Prepare water bath so that it's set to 25 C

  3. Add some Benedict's solution to the test tube (about 10 drops) using a pipette

  4. Place the fost tube in the water bath using a test tube holder and leave it in there for 5 minutes

  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 how much sugar is in the food
• Reducing sugars


  Sugars that can be oxidised
• Non-reducing sugars


  Sugars that cannot be oxidised
• Iodine Solution Test


  1. Make a food sample and transfer 5 cm of your sample to a test tube

  2. Add a few drops of iodine solution and gently shake the tube to mix the contents

  3. If the sample contains starch, the colour of the solution will change from browny-orange to black or blue-black
• Biuret Test


  1. Prepare a sample of your food and transfer 2 cm of your sample to a test tube

  2. Add 2 cm³ 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 purple

  4. If no protein is present, the solution will stay blue
• Lipids


  Fats and oils found in foods
• Sudan III Test


  1. Prepare a sample of the food you're testing (but you don't need to filter it) and transfer about 5 cm into a test tube

  2. Use a pipette to add 3 drops of Sudan Ill stain solution to the test tube and gently shake the tube

  3. If the sample contains lipids, the mixture will separate out into two layers with the top layer being bright red

  4. If no lipids are present, no separate red layer will form
• The lungs are in the thorax, which is the top part of the body and is separated from the lower part by the diaphragm
• The lungs


  • They are like big pink sponges and are protected by the ribcage
  • They are surrounded by the pleural membranes
• Air flow through the lungs

  1. The air that you breathe in goes through the trachea

  2. The trachea splits into two tubes called bronchi, one going to each lung

  3. The bronchi split into progressively smaller tubes called bronchioles

  4. The bronchioles finally end at small bags called alveoli where the gas exchange takes place
• Alveoli


  Small air sacs in the lungs where gas exchange occurs
• Gas exchange in the alveoli


  1. The blood passing next to the alveoli has just returned to the lungs from the rest of the body, so it contains lots of carbon dioxide and very little oxygen

  2. Oxygen diffuses out of the alveolus (high concentration) into the blood (low concentration)

  3. Carbon dioxide diffuses out of the blood (high concentration) into the alveolus (low concentration) to be breathed out

  4. Oxygen is released from the red blood cells (where there's a high concentration) and diffuses into the body cells (where the concentration is low)

  5. Carbon dioxide diffuses out of the body cells (where there's a high concentration) into the blood (where there's a low concentration) to be carried back to the lungs
• Calculating breathing rate


  1. Count the number of breaths taken in a certain time period

  2. Divide the number of breaths by the time period to get the breathing rate in breaths per minute
• Double circulatory system


  The circulatory system has two circuits - one where deoxygenated blood is pumped from the right ventricle to the lungs, and one where oxygenated blood is pumped from the left ventricle to the rest of the body
• The heart


  • It is a pumping organ made mostly of muscle tissue
  • It has valves to ensure blood flows in the right direction
• How the heart pumps blood

  1. Blood flows into the two atria from the veins

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

  3. The ventricles contract, forcing the blood into the pulmonary artery and 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
• Pacemaker


  Group of cells in the right atrium wall that produce an electrical impulse to control the resting heart rate
• Arteries


  • They carry blood away from the heart at high pressure, so have strong and elastic walls
  • They have thick walls compared to the size of the lumen (opening) to withstand the pressure
• Capillaries


  • They are very small, with walls only one cell thick to facilitate diffusion
  • They carry blood close to every cell in the body to exchange substances
• Veins


  • They carry blood back to the heart at lower pressure, so don't need as thick walls as arteries
  • They have a larger lumen than arteries to help the blood flow despite the lower pressure
  • They have valves to prevent backflow of blood
• Calculating blood flow rate


  Divide the volume of blood that passed through an artery by the time it took to pass through
• Red blood cells


  They carry oxygen from the lungs to the body cells
• Red blood cells


  • They have a biconcave disc shape to maximise surface area for oxygen absorption
  • They lack a nucleus to allow more space for haemoglobin
• Haemoglobin


  Red pigment in red blood cells that binds to oxygen
• White blood cells


  They defend the body against infection
• White blood cells


  • Some can change shape to engulf microorganisms (phagocytosis)
  • Others produce antibodies and antitoxins to fight infections
• Platelets


  Small cell fragments that help blood to clot
• Plasma


  The liquid part of blood that carries nutrients, waste, hormones, and other substances
• Coronary heart disease


  Disease of the heart or blood vessels, e.g. when the coronary arteries supplying the heart muscle become blocked
• Using stents to treat coronary heart disease

  1. Stents are tubes inserted into blocked arteries to keep them open and allow blood flow to the heart muscle

  2. This prevents heart attacks by ensuring the heart muscle gets enough oxygen-rich blood
• Cardiovascular Disease


  Diseases of the heart or blood vessels, for example coronary heart disease
• Stents keep arteries open

  1. Coronary heart disease blocks arteries

  2. Stents are inserted to keep arteries open

  3. Allows blood flow to heart muscle
• Stents


  • They lower the risk of heart attack in people with coronary heart disease
  • They are effective for a long time
  • Recovery time from surgery is relatively quick