topic 2: organisation

• Cells


  Make up all living things
• Tissue


  A group of specialised cells with a similar structure and function, can be made of more than one type of cell
• Tissue examples


  • Muscular tissue
  • Epithelial tissue
• Organs


  Formed from a number of different tissues, working together to produce a specific function
• Organ systems


  Organs organised to work together to perform a certain function
• Organ system example


  • Digestive system
• Organs in the digestive system

  • Glands (salivary glands, pancreas)
  • Stomach
  • Small intestine
  • Liver
  • Gall bladder
  • Large intestine
  • Rectum
  • Anus
• Enzymes


  Biological catalysts that increase the rate of reaction without being used up
• Enzymes

  • They can both break up large molecules and join small ones
  • They are protein molecules and the shape of the enzyme is vital to its function
  • Each enzyme has its own uniquely shaped active site where the substrate binds
• Lock and Key Hypothesis


  1. Substrate shape is complementary to active site shape, forming enzyme-substrate complex

  2. Reaction takes place and products are released
• Optimum pH


  Most enzymes have an optimum pH of 7, some produced in acidic conditions have a low optimum pH
• Optimum temperature


  Around 37 degrees Celsius (body temperature), rate increases up to this then rapidly decreases
• When temperature becomes too hot, the bonds in the structure will break, changing the shape of the active site so the substrate can no longer fit in. The enzyme is denatured and can no longer work.
• If the pH is too high or too low, the forces that hold the amino acid chains that make up the protein will be affected, changing the shape of the active site so the substrate can no longer fit in. The enzyme is denatured and can no longer work.
• Types of enzymes


  • Carbohydrases (convert carbohydrates into simple sugars)
  • Proteases (convert proteins into amino acids)
  • Lipases (convert lipids into fatty acids and glycerol)
• Benedict's test

  Test for sugars (turns brick red)
• Iodine test


  Test for starch (turns blue-black)
• Biuret test

  Test for protein (turns purple)
• Emulsion test


  Test for lipids (add ethanol which results in a cloudy layer if a lipid is present)
• Sudan III test


  Test for lipids (red layer forms on top)
• Bile


  Produced in the liver, stored in the gallbladder, released into the small intestine. Alkaline to neutralise hydrochloric acid, and emulsifies large fat droplets.
• Investigating effect of pH on enzyme controlled reaction

  Use iodine which turns blue-black in presence of starch, take drops of solution at regular intervals and record time for starch to be completely broken down
• Rate of enzymatic reactions

  Calculated using the equation: rate = change/time
• Heart


  An organ in the circulatory system that pumps blood around the body
• Circulatory system


  Carries oxygen and nutrients to every cell in the body and removes waste products
• Double circulatory system


  Two circuits - deoxygenated blood flows to the lungs, oxygenated blood flows around the body
• Parts of the heart


  • Right atrium
  • Right ventricle
  • Left atrium
  • Left ventricle
  • Muscular walls
  • Valves
  • Coronary arteries
• Blood flow through the heart

  Blood flows into right atrium and left atrium, atria contract forcing blood into ventricles, ventricles contract pumping blood to lungs and around body, valves close to prevent backflow
• Pacemaker

  Group of cells in the right atrium that provide electrical stimulation to make the heart contract
• Artificial pacemaker

  Electrical device that produces a signal causing the heart to beat at a normal speed
• Types of blood vessels

  • Arteries (carry blood away from heart)
  • Veins (carry blood towards heart)
  • Capillaries (allow blood to flow close to cells)
• Lungs


  Found in the thorax, supply oxygen to blood and remove carbon dioxide
• Parts of the gas exchange system

  • Trachea
  • Intercostal muscles
  • Bronchi
  • Bronchioles
  • Alveoli
  • Diaphragm
• Ventilation


  Ribcage moves up and out, diaphragm moves down, increasing volume and decreasing pressure, drawing air into the lungs
• Gas exchange


  Oxygen diffuses from alveoli into capillary blood, carbon dioxide diffuses from blood into alveoli
• Alveoli


  • Very small and arranged in clusters, creating large surface area
  • Capillaries provide large blood supply
  • Walls are very thin, short diffusion pathway
• Components of blood

  • Plasma
  • Red blood cells
  • White blood cells
  • Platelets
• Red blood cells


  • Biconcave disc shape provides large surface area
  • No nucleus allows more room to carry oxygen
  • Contain haemoglobin which binds to oxygen
• White blood cells


  Part of the immune system, defend against pathogens
• Types of white blood cells


  • Those that produce antibodies
  • Those that engulf and digest pathogens
  • Those that coordinate the immune response