BIO

• All living things are made of cells, which can either be prokaryotic or eukaryotic.
• Eukaryotic cells


  • Animal cells
  • Plant cells
• Prokaryotic cells


  • Bacterial cells
• Eukaryotic cells


  • Cell membrane
  • Cytoplasm
  • Nucleus containing DNA
• Prokaryotic cells


  • Cell wall
  • Cell membrane
  • Cytoplasm
  • Single circular strand of DNA and plasmids
• Organelles


  Structures in a cell that have different functions
• Nucleus


  • Contains DNA coding for a particular protein needed to build new cells
  • Enclosed in a nuclear membrane
• Cytoplasm


  • Liquid substance in which chemical reactions occur
  • Contains enzymes
  • Organelles are found in it
• Cell membrane


  • Controls what enters and leaves the cell
• Mitochondria


  • Where aerobic respiration reactions occur, providing energy for the cell
• Ribosomes


  • Where protein synthesis occurs
  • Found on rough endoplasmic reticulum
• Chloroplasts


  • Where photosynthesis takes place
  • Contains chlorophyll pigment
• Permanent vacuole


  • Contains cell sap
  • Improves cell’s rigidity
• Cell wall (in plants)

  • Made from cellulose
  • Provides strength to the cell
• Flagella


  • Long, thin ‘whip-like’ tails attached to bacteria that allow them to move
• Plasmids


  • Small rings of DNA that code for extra genes
• Specialised cells in animals

  • Sperm cells
  • Egg cells
  • Ciliated epithelial cells
• Sperm cells


  • Streamlined head and long tail
  • Many mitochondria
  • Acrosome with digestive enzymes
  • Haploid nucleus
• Egg cells


  • Special cell membrane for fertilisation
  • Lots of mitochondria
  • Large size and cytoplasm
• Ciliated epithelial cells


  • Long, hair-like processes called cilia
• Specialised cells in plants

  • Root hair cells
  • Xylem cells
  • Phloem cells
• Root hair cells


  • Large surface area
  • Large permanent vacuole
  • Mitochondria for energy
• Xylem cells


  • Hollow and joined end-to-end
  • Lignin deposited in spirals
• Phloem cells


  • Cell walls form sieve plates
  • Energy supplied by companion cells
• Extremely small structures such as cells cannot be seen without microscopes.
• The first cells of a cork were observed by Robert Hooke in 1665 using a light microscope.
• Light microscope


  • Two lenses
  • Illuminated from underneath
  • Maximum magnification of 2000x
  • Resolving power of 200nm
• Electron microscope


  • Developed in the 1930s
  • Uses electrons to form an image
  • Magnification of up to 2,000,000x
  • Resolving power of 10nm (SEM) and 0.2nm (TEM)
• The discovery of the electron microscope has allowed us to view many organelles more clearly.

  
• Enzymes are biological catalysts.
• Active site


  The uniquely shaped part of an enzyme where the substrate binds
• Lock and Key Hypothesis

  1. Shape of substrate matches active site

  2. Forms enzyme-substrate complex

  3. Reaction takes place

  4. Products are released
• Enzyme specificity


  Enzymes can only catalyse reactions with complementary shaped substrates
• Optimum conditions for enzymes

  • Optimum pH
  • Optimum temperature
  • Optimum substrate concentration
• The optimum temperature in humans is around 37 degrees Celsius.
• Enzymes are vital to their function
• Active site


  Where the substrate binds on an enzyme
• Lock and Key Hypothesis

  A simplified explanation of how enzymes work
• Lock and Key Hypothesis steps

  1. Shape of substrate is complementary to active site

  2. Enzyme-substrate complex forms

  3. Reaction takes place

  4. Products are released
• Enzyme specificity


  Enzymes can only catalyse reactions with a complementary shaped substrate