Edexcel combined science bio p1

• 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 them 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
• Bacterial cells are slightly different from animal and plant cells
• Bacterial cell


  • Has a cell membrane, cytoplasm, ribosomes, and a cell wall like plant cells
  • Has DNA in two chunks - chromosomal DNA and plasmids
  • May have a flagellum tail to help them move
• Microscope


  • Produces magnified images
  • Magnification is how many times bigger an object appears than it really is
• Parts of a microscope

  • Objective lenses
  • Eyepiece lens
  • Coarse and fine adjustment dials
  • 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
• Using a microscope


  1. Place sample on slide

  2. Stain if needed

  3. Cover with coverslip

  4. Place slide on stage

  5. Select objective lens

  6. Use rough focus

  7. Use fine focus
• Enzyme


  Protein that speeds up chemical reactions
• Substrate


  Chemical that an enzyme works on
• Active site


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


  How enzymes work - substrate enters active site and is changed
• Types of digestive enzymes


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


  When an enzyme's active site changes shape and it stops working, can be caused by high temperature or extreme pH
• Investigating effect of pH on enzyme rate

  1. Set up with starch solution, amylase, and pH buffer

  2. Mix and take samples every 30 seconds

  3. Put in iodine to test for starch

  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 concentration to low concentration, down a concentration gradient
• Osmosis


  Diffusion of water across a partially permeable membrane, from high water concentration to low water concentration
• Active transport


  Movement of substances from low concentration to high concentration, up a concentration gradient, requires energy
• Investigating osmosis in potato chips


  1. Cut potato chips of similar size

  2. Weigh them

  3. Place in sucrose solution
• Active transport


  1. Moves substances from low concentration to high concentration

  2. Requires energy
• Active transport


  • Minerals from soil move into root hair cell
  • Sucrose moves into sieve cell in plant stem
• Active transport


  • Proteins in cell membranes grab substances from low concentration side and spit them out on high concentration side
• Cells that do a lot of active transport


  Have a lot of mitochondria to provide the energy
• Osmosis in potato chips

  1. Cut potato chips of similar sizes

  2. Brush them dry and record mass

  3. Place in sucrose solutions of different concentrations

  4. Leave for 15 minutes

  5. Blot dry and reweigh

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


  Swell up due to water moving from solution into potato by osmosis
• Potato chips in strong sugar solution


  Get smaller and lose mass as water leaves potato and enters solution by osmosis