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
• Organ


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


  Organs organised to work together to perform a certain function
• The digestive system is an organ system, as it is made up of organs working together to perform a certain function
• Organs of the digestive system

  • Glands (salivary glands and pancreas)
  • Stomach
  • Small intestine
  • Liver
  • Gall bladder
  • Large intestine
  • Rectum
  • Anus
• Enzymes


  Biological catalysts, a substance that increases the rate of reaction without being used up
• How enzymes work (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
• 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
• Types of enzymes


  • Carbohydrases (convert carbohydrates into simple sugars)
  • Proteases (convert proteins into amino acids)
  • Lipases (convert lipids into fatty acids and glycerol)
• Soluble glucose, amino acids, fatty acids and glycerol pass into the bloodstream to be carried to all the cells around the body
• Tests to determine composition of a solution

  • 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 and stored in the gallbladder, alkaline to neutralise hydrochloric acid and emulsifies large fat droplets
• Investigating the effect of pH on an enzyme controlled reaction

  1. Use iodine to detect presence of starch, take samples at regular intervals and record time for starch to be completely broken down

  2. Repeat at different pH values while controlling other factors
• The heart is an organ in the circulatory system
• Double circulatory system


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

  • Muscular walls
  • 4 chambers
  • Valves
  • Coronary arteries
• Blood flow through the heart

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

  2. Blood flows into the left atrium and left ventricle, then around the body
• Natural resting heart rate

  Controlled by pacemaker cells in the right atrium providing electrical stimulation
• Artificial pacemaker


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

  • Arteries (carry blood away from the heart)
  • Veins (carry blood towards the heart)
  • Capillaries (allow blood to flow close to cells)
• The lungs are found in the thorax and supply oxygen to the blood and remove carbon dioxide
• Components of the gas exchange system

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


  Ribcage moves up and out, diaphragm moves down, increasing volume and decreasing pressure, drawing air into the lungs
• Gas exchange


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


  • Very small and arranged in clusters, creating a large surface area
  • Capillaries provide a large blood supply
  • Walls are very thin, short diffusion pathway
• Blood is made up of plasma, red blood cells, white blood cells and platelets
• Plasma


  Liquid that carries the components in the blood
• Red blood cells


  Carry oxygen molecules from the lungs to all the cells in the body, contain haemoglobin
• White blood cells


  Part of the immune system, defend the body against pathogens
• Alveoli are 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


  • They carry oxygen molecules from the lungs to all the cells in the body
  • Their bioconcave disc shape provides a large surface area
  • They have no nucleus allowing more room to carry oxygen
  • They contain the red pigment haemoglobin, which binds to oxygen and forms oxyhaemoglobin
• White blood cells


  • They are a part of the immune system, which is the body's defence against pathogens (microorganisms that can produce disease)
  • They have a nucleus
  • There are a number of types: those that produce antibodies against microorganisms, those that engulf and digest pathogens, and those that produce antitoxins to neutralise toxins produced by microorganisms
• Platelets


  • They 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
• Coronary heart disease


  When the coronary arteries that provide blood to the heart become blocked with the build up of fatty material, resulting in less blood flowing to the heart and reducing its oxygen supply, which may lead to a heart attack
• Stents


  • Metal mesh tubes inserted in arteries to keep them open and allow blood to flow through
  • They are effective in lowering the risk of a heart attack
  • The recovery time from surgery is quick