Cell organisation

• Large Multicellular Organisms are Made Up of Organ Systems
• Organ Systems


  • Group of organs working together to perform a particular function
• Similar Cells are Organised into Tissues


  Similar cells work together to carry out a particular function
• Tissues are Organised into Organs


  Group of different tissues work together to perform a certain function
• Organs are Organised into Organ Systems


  Group of organs working together to perform a particular function
• Enzymes are catalysts produced by living things
• Catalyst


  A substance that increases the speed of a reaction, without being changed up in the reaction
• Enzymes


  • They are made up of chains of amino acids folded into specific shapes
  • They have an active site with a unique shape that fits the substance involved in a reaction
• Changing the temperature


  Changes the rate of an enzyme-catalysed reaction
• Optimum temperature


  The temperature that enzymes work best at
• Optimum pH


  The pH that enzymes work best at, often neutral pH 7
• Investigating the effect of pH on enzyme activity

  1. Put iodine solution into wells of spotty tile

  2. Heat water bath to 35°C

  3. Add amylase and buffer solution to boiling tube, wait 5 mins

  4. Add starch solution

  5. Immediately mix and start stopwatch

  6. Take samples every 30s and test with iodine to see when starch is broken down

  7. Repeat with different pH buffers

  8. Control variables
• Rate of reaction


  Measure of how much something changes over time, calculated as amount of change divided by time taken
• Digestive enzymes are produced by organs and released into the gut to work on food
• Carbohydrases convert carbohydrates into simple sugars


  Amylase breaks down starch into maltose in the mouth, pancreas and small intestine
• Proteases convert proteins into amino acids

  Proteases are made in the stomach, pancreas and small intestine
• Lipases convert lipids into glycerol and fatty acids


  Lipases are made in the pancreas and small intestine
• Bile


  • Produced in the liver, stored in the gall bladder, released into the small intestine
  • Neutralises stomach acid and emulsifies fats
• The breakdown of food is catalysed by enzymes produced by specialised cells in glands and the gut lining
• There are tests to identify different food components: Benedict's test for sugars, iodine test for starch, biuret test for proteins, Sudan III test for lipids
• Testing for protein in food

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

  2. Add 2 cm 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

  4. If no protein is present, the solution will stay blue
• Testing for lipids in food using Sudan III


  1. Prepare a sample of the food you're testing and transfer about 5 cm³ 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 stain solution stains lipids. If the sample contains lipids, the mixture will separate out into two layers. The top layer will be bright red

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


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

  1. The air you breathe in goes through the trachea

  2. The trachea splits into two tubes called bronchi (each one is a bronchus), 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


  Little air sacs in the lungs where gas exchange happens
• 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. When the blood reaches body cells, 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. At the same time, carbon dioxide diffuses out of the body cells (where there's a high concentration) into the blood (where there's a low concentration). It's then carried back to the lungs
• Calculating breathing rate


  Divide the number of breaths by the number of minutes
• The circulatory system carries food and oxygen to every cell in the body, and also carries waste products to where they can be removed
• The double circulatory system

  • The right ventricle pumps deoxygenated blood to the lungs to take in oxygen
  • The left ventricle pumps oxygenated blood to the rest of the organs in the body
• How the heart pumps blood

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

  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
• The heart


  • It has valves to make sure blood flows in the right direction
  • It has its own supply of oxygenated blood through coronary arteries
• Pacemaker


  A group of cells in the right atrium wall that produce an electric impulse to control the resting heart rate
• Arteries


  • They carry blood under high pressure from the heart
  • They have thick walls and contain muscle to allow them to stretch and recoil
  • They branch into capillaries
• Capillaries


  • They are very small, only one cell thick
  • They carry blood slowly to every cell in the body to exchange substances
  • They have permeable walls to allow diffusion in and out
• Veins


  • They carry blood back to the heart at lower pressure
  • They have bigger lumens than arteries
  • They have valves to help keep blood flowing in the right direction
• Calculating blood flow rate


  Divide the volume of blood by the time taken
• 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 don't have a nucleus, allowing more space for haemoglobin
• White blood cells


  • Some can change shape to engulf pathogens (phagocytosis)
  • Others produce antibodies and toxins to fight microorganisms
  • They have a nucleus unlike red blood cells