Paper 1 Biology GCSE edexcel

• Cells


  The basic structure unit of all living organisms
• Parts of animal and plant cells


  • Cytoplasm
  • Nucleus
  • Ribosome
  • Mitochondria
  • Cell membrane
  • Chloroplasts
  • Vacuole
  • Cell wall
• Organelle


  Each part of a cell
• Nucleus


  Contains DNA and controls the cell
• Cell membrane


  Controls what enters and leaves the cell
• Cytoplasm


  Where chemical reactions inside the cell happen
• Ribosome


  Makes proteins
• Mitochondria


  Where aerobic respiration takes place and releases energy
• Chloroplasts

  Contain chlorophyll and where photosynthesis happens
• Specialized cells


  • Cells adapted for a specific role with features called adaptations
• Specialized cells


  • Sperm cell
  • Egg cell
• Sperm cell


  • Great big long tail to help swim
  • Section packed with mitochondria for energy
  • Haploid nucleus with 23 single chromosomes
  • Acrosome to help digest into egg
• Egg cell


  • Haploid nucleus with 23 single chromosomes
  • Thick jelly coat that hardens when first sperm penetrates
  • Lots of mitochondria and nutrients
• Other specialized cells


  • Ciliated cells
  • Red blood cells
  • Nerve cells
  • Xylem cells
  • Root hair cells
• Bacterial cells


  • Have cell membrane, cytoplasm, ribosomes, cell wall
  • May have flagellum for movement
  • Have chromosomal DNA and plasmids instead of nucleus
• Microscope


  Produces magnified images
• Magnification


  How many times bigger an object appears than it really is
• Parts of a microscope


  • Objective lenses
  • Eyepiece lens
  • Coarse adjustment dial
  • Fine adjustment dial
  • Stage
• Micrograph

  Picture produced by a microscope
• Using a micrograph to find actual size


  1. Measure size on micrograph

  2. Divide by magnification
• Standard form


  Way of presenting very large or very small numbers in terms of powers of 10
• Core practical: Using a microscope


  1. Place sample on slide

  2. Stain with iodine

  3. Cover with coverslip

  4. Place slide on stage

  5. Select objective lens

  6. Use coarse then fine focus
• Enzymes


  Proteins that speed up chemical reactions
• Substrate


  Chemicals that enzymes work on
• Active site


  Part of enzyme that has same shape as substrate
• Lock and key mechanism


  Substrate enters enzyme active site and is changed
• Digestive enzymes


  • Lipase
  • Protease
  • Amylase
• Denaturation


  When enzyme active site changes shape and stops working
• Core practical: Investigating effect of pH on enzyme activity


  1. Set up starch and amylase in test tubes

  2. Mix and start timer

  3. Take samples every 30 seconds and test with iodine

  4. Repeat with different pH buffers

  5. Compare times to find optimum pH
• Concentration


  Number of particles in a given volume
• Diffusion


  Movement of substances from high to low concentration
• Osmosis


  Diffusion of water across a partially permeable membrane
• Active transport


  Movement of substances from low to high concentration, requiring energy
• Core practical: Investigating osmosis in potato chips


  1. Cut potato chips of similar size

  2. Weigh and record mass

  3. Place in sucrose solutions of different concentrations

  4. Leave for 15 minutes

  5. Weigh again and record change in mass
• Concentration gradient


  Low concentration to high concentration
• Minerals from soil move into root hair cell


  Sucrose moves into phloem cell in plant stem
• Active transport


  Proteins in cell membranes grab substances from low concentration side and spit them out on high concentration side, requires energy
• Cells that do a lot of active transport will have a lot of mitochondria to provide energy
• Osmosis in potato chips experiment


  1. Cut potato chips of similar sizes

  2. Blot dry and record mass

  3. Place in sucrose solutions of different concentrations

  4. Leave for 15 minutes

  5. Blot dry and re-weigh

  6. Calculate percentage change in mass
• Potato chips in weak sugar solution


  Swell up due to water moving into potato by osmosis