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
• 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
• Enzymesdefinition


  Biological catalysts, substances that increase the rate of reaction without being used up
• Lock and key hypothesis


  The shape of the substrate is complementary to the shape of the active site, so when they bond it forms an enzyme-substrate complex. Once bound, the reaction takes place and the products are released from the surface of the enzyme.
• 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


  The optimum pH for most enzymes is 7, but some that are produced in acidic conditions, such as the stomach, have a low optimum pH
• Optimum temperature


  The optimum temperature is a range around 37 degrees celsius (body temperature)
• As temperature increases


  The rate of reaction increases up to the optimum, but above this temperature it rapidly decreases and eventually the reaction stops
• Denaturation


  When the temperature becomes too hot or the pH is too high or too low, the bonds in the structure will break, changing the shape of the active site so the substrate can no longer fit in. The enzyme is said to be denatured and can no longer work.
• 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 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 and stored in the gallbladder, then released into the small intestine. It is alkaline to neutralise the hydrochloric acid from the stomach, and it emulsifies large drops of fat into smaller ones to increase the surface area for lipase to break them down.
• Investigating the effect of pH on an enzyme controlled reaction

  1. Warm a solution of amylase, starch and a buffer solution

  2. Take drops of the solution at regular points and place in wells with iodine

  3. The time for the starch to be completely broken down is recorded and the rate is calculated
• Rate of enzymatic reactions

  Rate = change/time
• Heart


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


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


  There are two circuits - deoxygenated blood flows to the lungs, then oxygenated blood flows around the 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 the right atrium and left atrium

  2. The atria contract forcing the blood into the ventricles

  3. The ventricles contract, pushing blood to the lungs and around the body

  4. Valves close to prevent backflow
• Pacemaker


  A group of cells in the right atrium that provide stimulation through small electrical impulses to control the natural resting heart rate
• Artificial pacemaker


  An 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 in the walls make them strong
  • Elastic fibres allow them to stretch to withstand the high pressure from the heart
• Veins


  • The lumen is wide to allow the low pressure blood to flow through
  • They have valves to ensure the blood flows in the right direction
• Capillaries


  • One cell thick walls create a short diffusion pathway
  • Permeable walls so substances can move across them
• Rate of blood flow


  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 volume and decreasing pressure to draw air in

  2. Opposite happens when exhaling
• Gas exchange


  1. Oxygen diffuses from the alveoli into the capillary bloodstream

  2. Carbon dioxide diffuses from the blood into the 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
• Breathing rate


  Number of breaths/number of minutes