PAPER 1

• 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 several features that animal cells don't share, e.g. 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 electron microscopes controlled by computer
• Magnification calculation


  Magnification = image height / object height
• Measurement units


  • Meter (m)
  • Centimeter (cm) - 1 x 10^-2 m
  • Millimeter (mm) - 1 x 10^-3 m
  • Micrometer (μm) - 1 x 10^-6 m
  • Nanometer (nm) - 1 x 10^-9 m
  • Picometer (pm) - 1 x 10^-12 m
• Enzymes


  Work with the lock and key mechanism - have a specifically shaped active site that only certain substrates can fit into
• Temperature affects enzyme activity

  Lopsided curve - low temp not enough energy, optimal temp, then denaturation after peak
• pH affects enzyme activity

  Symmetrical curve - optimal pH, denaturation at too high or too low pH
• 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 the final equilibrium point
• Digestive enzymes


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


  Movement of particles from high to low concentration down a concentration gradient
• Osmosis


  Specific 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 the concentration gradient
• Cancer


  Uncontrolled cell division leading to lumps, can be benign or malignant
• Cancer risk factors


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


  Have the potential to turn into any other type of cell, used for treating diseases and injuries
• Nervous system


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

  • Genetically diverse population
  • Better protection from diseases
• Advantages of asexual reproduction

  • Only one parent required
  • Energy conserved by parent
• Mitosis


  1. DNA condenses into chromosomes

  2. Chromosomes line up in middle

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


  1. Chromosomes line up and undergo crossing over

  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. 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°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)
• Chromosome


  Bundled up DNA
• Alleles


  Different versions of genes
• Dominant


  Need one gene to express characteristic