b2 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, substances that increase the rate of reaction without being used up
• How enzymes work (Lock and Key Hypothesis)

  1. Substrate binds to active site of enzyme

  2. Reaction takes place

  3. Products released
• 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
• Optimum pH and temperature for enzymes

  • Optimum temperature is around 37 degrees Celsius (body temperature)
  • Optimum pH for most enzymes is 7, some have a low optimum pH
• As temperature increases


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


  When bonds in 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 to be carried to all the cells around the body
• Tests for different 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 hydrochloric acid
  • Emulsifies large fat droplets to increase surface area for lipase
• Investigating effect of pH on enzyme controlled reaction

  1. Warm amylase, starch and buffer solution

  2. Take samples at regular intervals and test with iodine

  3. Time until starch is completely broken down

  4. Calculate rate using 1000/time
• Rate of enzymatic reactions


  Rate = change/time
• Heart


  An organ in the circulatory system, 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 to lungs, oxygenated blood around body
• Parts of the heart

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

  1. Blood flows into right atrium and left atrium

  2. Atria contract, forcing blood into ventricles

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

  4. Valves close to prevent backflow
• Pacemaker


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


  Electrical device that produces a signal to make the heart 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 between blood and cells
• Rate of blood flow


  Volume of blood/number of minutes
• Lungs


  Supply oxygen to blood and remove carbon dioxide
• Parts of the gas exchange system

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


  1. Ribcage moves up and out, diaphragm moves down, increasing volume and decreasing pressure

  2. Air drawn in from high to low pressure
• Gas exchange


  1. Oxygen diffuses from alveoli into blood

  2. Carbon dioxide diffuses from 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
• Breathing rate


  Number of breaths/number of minutes