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• In this video, we're gonna be covering all the knowledge that you need for your first Edexcel biology exam
• You can get the free revision guide over on my website which has loads and loads of knowledge checklist, keywords, crosswords, pictures, questions and student friendly specification statements with links to videos
• Plant cell


  • Cell membrane - responsible for determining which bits go to in or out of the cell
  • Cell wall - important for structure
  • Vacuole - important for structure
  • Cytoplasm - where most reactions take place
  • Ribosomes - responsible for protein synthesis
  • Chloroplasts
  • Mitochondria - where energy is produced
  • Nucleus
• Animal cell


  • Cell membrane - controlling what goes in and out
  • Mitochondria - where energy is produced
  • Ribosomes - protein synthesis
  • Cytoplasm - where most reactions take place
  • Nucleus - where DNA is held and control center of the cell
• Plant cells have features that animal cells don't share, like cell wall, vacuole, chloroplasts
• There isn't really a typical type of cell because there are a wide range of differentiated specialized cells
• Differentiation


  When various different genes will be turned on and turned off, and that's when cells will start to specialize
• Microscope techniques


  From basic lenses to sophisticated lenses to electron microscopes controlled by computer
• Calculating magnification from microscope image


  Magnification = image height / object height
• Metric prefixes


  • Meter (m)
  • Centimeter (cm) - 10^-2 m
  • Millimeter (mm) - 10^-3 m
  • Micrometer (μm) - 10^-6 m
  • Nanometer (nm) - 10^-9 m
  • Picometer (pm) - 10^-12 m
• Enzymes


  • Amylase, protease, lipase
  • Work with lock and key mechanism
  • Have specific active sites that only certain substrates can fit into
  • Form enzyme-substrate complex, then catalyse reaction and release products
• Temperature affects enzyme activity


  Optimal temperature, then denaturation at higher temperatures
• pH affects enzyme activity


  Optimal pH, then denaturation at too high or too low pH
• Enzyme saturation


  Enzyme activity increases with substrate concentration until active sites are full, then no further increase
• Enzymes as catalysts


  Increase rate of reaction but don't change equilibrium
• Digestive enzymes


  • Lipase - breaks down fats
  • Protease - breaks down proteins
  • Amylase - breaks down starch
• Diffusion


  Movement of particles from high to low concentration
• Osmosis


  Movement of water through a partially permeable membrane from high to low water concentration
• Active transport


  Movement of substances from low to high concentration, against concentration gradient
• Cancer


  • Uncontrolled cell division leading to lumps (tumors)
  • Benign tumors are slow-growing and harmless
  • Malignant tumors are fast-growing, aggressive and can spread to other parts of the body
• Cancer risk factors


  • Smoking
  • Diet
  • Sun exposure
  • Unprotected sex
• Stem cells


  • Have potential to develop into any cell type
  • Can be used to grow new cells/tissues/organs to treat injuries and diseases
• Stem cell production


  Take nucleus from patient cell and insert into empty egg cell, which then develops into an embryo from which stem cells are extracted
• Nervous system


  • Central nervous system (brain and spinal cord)
  • Neurons, receptors and effectors
  • Reflex actions vs conscious responses
  • Electrical signals in neurons, chemical signals at synapses
• Advantages of sexual reproduction

  • Genetically diverse population, better protection from diseases
• Disadvantages of asexual reproduction


  • Genetically identical population, susceptible to diseases
  • Requires finding a mate
  • Conserves energy of parent
• Mitosis


  1. DNA condenses into chromosomes

  2. Chromosomes line up in middle of cell

  3. Chromosomes pulled apart to form two identical daughter cells
• Meiosis


  1. Chromosomes line up, some crossing over occurs

  2. Two cell divisions to form four genetically distinct daughter cells
• Selfish gene


  The parent is putting all of its energy into conserving its own genes
• Mitosis


  1. DNA condenses into chromosomes

  2. Chromosomes line up down the middle

  3. Chromosomes pulled apart to either end of the cell

  4. New nuclei form

  5. Two identical daughter cells
• Meiosis


  1. Chromosomes line up

  2. Crossing over occurs

  3. Divide into two

  4. Line up and divide into two again

  5. Four different daughter cells
• Mitosis


  Leads to two identical daughter cells
• Meiosis


  Leads to four different daughter cells
• Gametes


  Eggs in women, sperm in men
• Plant gametes


  Eggs in stigma, pollen on stamen
• Extracting DNA


  1. Mash up

  2. Add salt water

  3. Add detergents

  4. Leave at 60 degrees C for 15 minutes

  5. Filter

  6. Add iced ethanol
• DNA structure


  • Made of A, T, C, G bases
  • Sugar phosphate backbone
  • Double helix
• Gene


  Stretch of DNA that codes for a characteristic
• Genome


  All the genes in a body
• Gamete


  Sex cell (sperm or egg)