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
• Denaturation


  When bonds in enzyme structure break due to extreme temperature or pH, changing the shape of the active site so substrate can no longer fit
• Types of enzymes


  • Carbohydrases (convert carbohydrates into simple sugars)
  • Proteases (convert proteins into amino acids)
  • Lipases (convert lipids into fatty acids and glycerol)
• Bile


  • Produced in the liver, stored in the gallbladder, released into the small intestine
  • Alkaline to neutralise stomach acid
  • Emulsifies large fat droplets into smaller ones to increase surface area for lipase
• Investigating effect of pH on enzyme controlled reaction


  1. Use iodine test to detect presence of starch

  2. Vary pH of buffer solution

  3. Record time for complete breakdown of starch

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


  Calculated using change/time
• Heart


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


  1. Deoxygenated blood flows into right atrium, right ventricle, to lungs

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


  • Muscular walls
  • Thicker left ventricle wall
  • 4 chambers
  • Valves
  • Coronary arteries
• Heart pumping process


  Blood flows into atria, atria contract to force blood into ventricles, ventricles contract to pump blood out
• Pacemaker


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


  Electrical device that produces signal to make heart beat at normal speed
• Blood vessels


  • Arteries (carry blood away from heart, strong muscular and elastic walls)
  • Veins (carry blood towards heart, wide lumen, valves)
  • Capillaries (one cell thick walls, permeable)
• Lungs


  Found in thorax, supply oxygen to blood and remove carbon dioxide
• Ventilation


  Ribcage moves up and out, diaphragm moves down, increasing chest volume and drawing in air
• Gas exchange


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


  • Small, clustered, thin walls, large blood supply
• Blood


  Made up of plasma, red blood cells, white blood cells, platelets
• Blood components


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


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


  • Part of immune system, produce antibodies, phagocytes, lymphocytes
• Alveoli


  Very thin, meaning there is a short diffusion pathway
• Calculating breathing rate


  Divide the number of breaths by the number of minutes
• Components of blood


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


  Liquid that carries the components in the blood: red blood cells, white blood cells, platelets, glucose, amino acids, carbon dioxide, urea, hormones, proteins, antibodies and antitoxins
• Red blood cells


  • Carry oxygen molecules from the lungs to all the cells in the body
  • Biconcave disc shape provides a large surface area
  • No nucleus allowing more room to carry oxygen
  • Contain the red pigment haemoglobin, which binds to oxygen and forms oxyhaemoglobin
• White blood cells


  • Part of the immune system, which is the body's defence against pathogens (microorganisms that can produce disease)
  • Have a nucleus
  • Types: those that produce antibodies, those that engulf and digest pathogens, those that produce antitoxins to neutralise toxins
• Platelets


  • Help the blood clot form at the site of a wound
  • The clot dries and hardens to form a scab, which allows new skin to grow underneath while preventing microorganisms from entering
  • Small fragments of cells
  • No nucleus
  • Without them, cuts would result in excessive bleeding and bruising