paper 1 bio

• 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 and focus to sophisticated lenses to 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


  Amylase, protease and lipase work with the lock and key mechanism - enzyme has a specifically shaped active site that only certain substrates can fit into
• Enzyme activity


  • Affected by temperature - optimal temperature, then denatured at higher temperatures
  • Affected by pH - optimal pH, then denatured at too high or too low pH
  • Limited by number of active sites
• Enzyme as catalyst


  Increases the rate of reaction but doesn't change the final equilibrium
• Digestive enzymes


  • Lipase - breaks down fats, made in pancreas and small intestine, works in small intestine
  • Protease - breaks down proteins, made in stomach, pancreas and small intestine, works in stomach and small intestine
  • Amylase - breaks down starch, made in salivary glands, pancreas and small intestine, works in mouth and small intestine
• Diffusion


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


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


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


  Cells divide uncontrollably, leading to lumps which can be benign (slow growing, harmless) or malignant (fast growing, aggressive, mobile)
• Cancer risk factors


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


  Have the potential to turn into any other type of cell, can be used to grow new cells/tissues/organs
• Stem cell creation


  Nucleus from patient cell inserted into empty egg cell, which then develops into an embryo that stem cells are extracted from
• Nervous system


  • Central nervous system (brain and spinal cord)
  • Neurons, receptors and effectors
  • Reflex actions vs conscious actions
  • 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
  • Energy conserved for own genes rather than offspring
• Mitosis


  1. DNA condenses into chromosomes

  2. Chromosomes line up in middle

  3. Chromosomes pulled apart to opposite ends

  4. New nuclei form

  5. Cell divides into two identical daughter cells
• Meiosis


  1. Chromosomes line up

  2. Crossing over occurs to increase genetic diversity

  3. Cell divides into two

  4. Cell divides again into four genetically distinct 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 the stigma, pollen on the stamen
• Extracting DNA


  1. Mash up

  2. Add salt water

  3. Add detergents

  4. Leave for 15 minutes at 60 degrees C

  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
• Recessive


  Need two identical recessive genes to express characteristic