Organisation topic

• 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
• Organ


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


  • Stomach
• Organ system


  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


  The pH at which an enzyme works best, usually around 7 but some have a lower optimum pH
• Optimum temperature


  The temperature range around 37 degrees Celsius at which an enzyme works best
• Temperature increases


  Rate of reaction increases up to optimum, then rapidly decreases
• Denaturation


  When the bonds in the enzyme structure break, changing the shape of the active site so the substrate can no longer fit
• Types of enzymes


  • Carbohydrases
  • Proteases
  • Lipases
• Carbohydrase example


  • Amylase
• Protease example


  • Pepsin
• Soluble glucose, amino acids, fatty acids and glycerol pass into the bloodstream
• Tests for biological molecules

  • Benedict's test for sugars
  • Iodine test for starch
  • Biuret test for protein
  • Emulsion test for lipids
  • Sudan III test for lipids
• Bile


  Produced in the liver, stored in the gallbladder, released into the small intestine. Alkaline to neutralise stomach acid, emulsifies fats.
• Investigating effect of pH on enzyme activity

  Use iodine to detect presence of starch, take samples at regular intervals, record time for complete breakdown, calculate rate
• Circulatory system


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


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


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

  1. Blood flows into right atrium, then right ventricle, pumped to lungs

  2. Blood flows into left atrium, then left ventricle, pumped around body
• Pacemaker


  Group of cells in 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
  • Veins
  • Capillaries
• Arteries


  • Layers of muscle and elastic fibres to withstand high pressure
  • Carry blood away from the heart
• Veins


  • Wide lumen to allow low pressure blood flow
  • Have valves to ensure one-way flow
  • Carry blood towards the heart
• Capillaries


  • One cell thick walls for short diffusion pathway
  • Permeable walls to allow substances to move across
• Gas exchange system


  Trachea, intercostal muscles, bronchi, bronchioles, alveoli, diaphragm
• Ventilation


  1. Ribcage moves up and out, diaphragm moves down, increasing chest volume and decreasing pressure, drawing air in

  2. Opposite happens on exhalation
• Gas exchange


  1. Oxygen diffuses from alveoli into capillary blood

  2. Carbon dioxide diffuses from capillary blood into alveoli
• Alveoli


  • Small size and clustered arrangement for large surface area
  • Thin walls for short diffusion pathway
  • Large blood supply to maintain concentration gradient
• Blood


  Composed of plasma, red blood cells, white blood cells, platelets
• Red blood cells


  • Biconcave disc shape for large surface area
  • No nucleus for more space to carry oxygen
  • Contain haemoglobin to bind oxygen
• White blood cells


  Part of the immune system, produce antibodies to defend against pathogens
• Alveoli


  Very thin, meaning there is a short diffusion pathway