Unit 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 example


  • Stomach
• 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 equation: rate = change/time
• Heart


  An organ in the circulatory system, pumps blood around the body in a double circulatory system
• Double circulatory system


  Deoxygenated blood flows into right atrium, right ventricle, then to lungs

  2. Oxygenated blood flows into left atrium, left ventricle, then around body
• Heart structure


  • Muscular walls, 4 chambers, valves, coronary arteries
• Heart pumping process


  Blood flows into atria

  2. Atria contract, forcing blood into ventricles

  3. Ventricles contract, pushing blood to lungs and around body

  4. Valves close to prevent backflow
• Pacemaker

  Group of cells in right atrium that provide electrical stimulation to control heart rate
• Artificial pacemaker


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

  • Arteries (carry blood away from heart, strong walls), Veins (carry blood towards heart, wide lumen, valves), Capillaries (allow close blood flow to cells)
• Lungs


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

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


  Ribcage moves up and out, diaphragm moves down, increasing chest volume

  2. Increased volume results in lower pressure, drawing air into lungs

  3. Opposite happens when exhaling
• Gas exchange


  Alveoli fill with oxygen on inhalation

  2. Oxygen diffuses into deoxygenated blood in surrounding capillaries

  3. Carbon dioxide diffuses from blood into alveoli
• Alveoli adaptations


  • Small size, arranged in clusters, large blood supply, thin walls
• Blood


  Made up of plasma, red blood cells, white blood cells, platelets
• Components of blood


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


  • Biconcave disc shape, no nucleus, contain haemoglobin
• White blood cells


  Part of the immune system, produce antibodies