organization

• 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
• 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, and emulsifies fats.
• Investigating effect of pH on enzyme activity

  1. Use iodine to detect presence of starch

  2. Warm amylase, starch and buffer solution

  3. Take samples at regular intervals and test with iodine

  4. Time until starch is completely broken down

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


  Calculated as change/time
• Heart


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


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


  Two circuits - deoxygenated blood to lungs, oxygenated blood to 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 body

  4. Valves close to prevent backflow
• Pacemaker


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


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


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


  • Allow blood to flow very close to cells
  • Have one cell thick walls for short diffusion pathway
  • Have permeable walls to allow substances to move across
• Blood flow rate


  Calculated as volume of blood/number of minutes
• Parts of the 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

  2. Air is drawn into the lungs
• Gas exchange


  1. Oxygen diffuses from alveoli into blood

  2. Carbon dioxide diffuses from blood into alveoli
• Alveoli


  • Very small and arranged in clusters for large surface area
  • Capillaries provide large blood supply
  • Walls are very thin for short diffusion pathway
• Breathing rate


  Calculated as number of breaths/number of minutes
• Components of blood


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