biology

• Specialisation


  Stem cells can specialise to perform specific functions
• Stem cells


  • Found in animal embryos and plant meristems
  • Some still made in bone marrow, but can only specialise into blood cells
• Embryo clones


  Can be made of a person to harvest stem cells that can be used to treat conditions without being rejected by the patient's body
• Cloning


  Can be used to preserve species or produce crops with desired traits
• Bacterial reproduction


  Binary fission: they divide every 10 minutes
• Aseptic technique for making bacterial cultures

  1. Lift lid of petri dish towards name

  2. Put drops of culture on agar/spread evenly

  3. Put drops of antibiotics on culture if needed

  4. Secure lid with tape to allow aerobic respiration, incubate at 25°C

  5. Measure size of cultures with no bacteria with πTr
• Mitosis


  Process by which new (diploid) cells are made for growth and repair
• Mitosis


  1. Nucleus dissolves, genetic material is duplicated

  2. Two sets of chromosomes move to different sides

  3. Mitochondria, ribosomes and other organelles are duplicated

  4. Cell divides, producing two genetically identical diploid cells
• Eukaryotic cells


  Have membrane-bound organelles including chloroplasts and mitochondria
• Prokaryotic cells


  Have no membrane-bound organelles, only a circular chromosome and ribosomes
• Light microscopes


  Cheap to make, allow you to see the outlines of cells
• Electron microscopes


  Allow you to visualise finer details including organelles due to their greater resolving power and higher resolution
• Magnification


  Image size / object size
• Prokaryotic cells


  Cells that have no membrane-bound organelles, only a circular chromosome and ribosomes. Examples include bacteria and archaea.
• Diffusion


  The movement of particles from an area of high concentration to low concentration, this is passive as it requires no energy
• Osmosis


  The diffusion of water across a semi-permeable membrane to balance the concentrations of solution inside and outside cell
• Practical: Osmosis

  1. Weigh and place identical cylinders from same vegetable in sugar solutions of varying concentrations

  2. After set time, remove excess water and reweigh

  3. Calculate % change in mass = (final - initial mass) / initial mass * 100
• Digestive system

  • Teeth break down food mechanically, saliva contains amylase (an enzyme)
  • Stomach contains hydrochloric acid and enzymes that chemically break down food
  • Liver produces bile which is stored in the gall bladder before going to the small intestine, bile emulsifies lipids to form droplets, increasing their surface area
  • Pancreas secretes amylase which breaks down starch into glucose in the small intestine
  • Water is absorbed into the bloodstream in the large intestine
  • Nutrients like glucose are absorbed into the bloodstream by the villi in the small intestine using active transport
• Enzymes


  • Proteins that act as biological catalysts, often breaking down molecules into shorter ones
  • They are specific so only break down substrates that fit their active site (lock and key)
  • Activity increases with temperature until the enzyme denatures (active site changes shape)
• Enzyme practical


  1. Mix amylase with starch and start timer

  2. Remove a few drops every 10 secs and add iodine

  3. Record time taken for no starch detected (remains orange)

  4. Repeat at different temperatures

  5. Optimum pH/temp is between two lowest times
• Active transport


  Movement of particles through a membrane via carrier proteins, this requires energy and can move them against the concentration gradient
• Starch


  Turns iodine from orange to black
• Sugars


  Turn Benedict's solution from blue to orange
• Protein


  Turns biuret's reagent from blue to purple
• Lipids (fats)


  Turn cold ethanol cloudy
• Air goes down from

  1. Trachea

  2. Bronchi

  3. Bronchioles

  4. Alveoli
• Alveoli (air sacs)


  • Have a large surface area to allow gas exchange to occur at a fast rate
• Double circulatory system


  Blood enters the heart twice every time it is pumped round the body
• Blood flow


  1. Pulmonary artery (to lungs)

  2. Pulmonary vein (from lungs)

  3. Vena cava

  4. Aorta
• Left side of the heart

  • Has thicker walls due to the higher pressure needed to pump blood to the body
• Electrical pulse


  Created by cells near the right atrium that causes the heart to contract
• Artery


  Carries blood away from the heart
• Capillary


  One cell thick to allow fast diffusion
• Coronary heart disease


  When an artery is blocked and can't supply blood
• Treating coronary heart disease

  1. Fat can build up to restrict blood flow

  2. A stent can be inserted to open up the vessel

  3. Statins are drugs that reduce fatty deposits
• Blood


  Carries RBC, WBC, platelets and everything except oxygen in the plasma
• Benedict's test

  Test to detect the presence of sugars
• Foods containing sugars

  • Biscuits
  • Cereal
  • Bread
• Types of sugars

  • Reducing
  • Non-reducing
• Benedict's test for reducing sugars

  1. Prepare food sample

  2. Add Benedict's solution

  3. Heat in water bath for 5 minutes

  4. Solution changes from blue to orange if sugars are present