BIOLOGY 1

• Cells


  The building blocks of every organism on the planet
• Organisms


  • Can be Eukaryotes or Prokaryotes
• All living things are made of cells
• Eukaryotic cells


  Complex cells that include all animal and plant cells
• Prokaryotic cells


  Smaller and simpler cells, e.g. bacteria
• Eukaryotes


  Organisms made up of eukaryotic cells
• Prokaryote


  A prokaryotic cell (a single-celled organism)
• Subcellular structures in animal cells

  • Nucleus
  • Cytoplasm
  • Cell membrane
  • Mitochondria
  • Ribosomes
• Nucleus


  Contains genetic material that controls the activities of the cell
• Cytoplasm


  Gel-like substance where most chemical reactions happen, containing enzymes
• Cell membrane


  Holds the cell together and controls what goes in and out
• Mitochondria


  Where most of the reactions for respiration take place, transferring energy the cell needs
• Ribosomes


  Involved in translation of genetic material in the synthesis of proteins
• Additional structures in plant cells

  • Rigid cell wall
  • Large vacuole
  • Chloroplasts
• Cell wall


  Made of cellulose, supports and strengthens the cell
• Vacuole


  Contains cell sap, a weak solution of sugar and salts, maintains internal pressure to support the cell
• Chloroplasts


  Where photosynthesis occurs, containing chlorophyll
• Subcellular structures in bacterial cells

  • Chromosomal DNA
  • Ribosomes
  • Cell membrane
  • Plasmid DNA
  • Flagellum
• Chromosomal DNA


  One long circular chromosome that controls the cell's activities and replication
• Plasmid DNA


  Small loops of extra DNA that aren't part of the chromosome, containing genes for things like drug resistance
• Flagellum


  A long, hair-like structure that rotates to make the bacterium move
• Cells aren't all the same - they have different specialised structures
• Multicellular organisms contain lots of different types of cells with different structures
• Specialised cells


  Cells that have a structure which makes them adapted to their function
• Examples of specialised cells

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


  • Contains nutrients in the cytoplasm to feed the embryo
  • Has a haploid nucleus
  • Changes membrane structure after fertilisation to stop more sperm getting in
• Sperm cell


  • Has a long tail to swim to the egg
  • Has lots of mitochondria in the middle section for energy
  • Has an acrosome at the front to store enzymes needed to digest the egg cell membrane
  • Contains a haploid nucleus
• Ciliated epithelial cells


  • Have cilia (hair-like structures) that beat to move substances in one direction along the surface of the tissue
• Microscopes allow us to see cells and their internal structures
• Light microscopes


  Work by passing light through the specimen, allowing us to see things like nuclei and chloroplasts, and study living cells
• Electron microscopes


  Use electrons rather than light, have higher magnification and resolution, allowing us to see much smaller things in more detail like the internal structure of mitochondria and chloroplasts
• Using a light microscope

  1. Prepare a thin slice of the specimen

  2. Place it on a slide with a drop of water

  3. Add a stain if needed

  4. Place a cover slip

  5. Use the coarse adjustment to bring the specimen into focus

  6. Use the fine adjustment to get a clear image

  7. Measure the field of view
• Creating a scientific drawing of a specimen

  1. Draw outlines of the main features using clear, unbroken lines

  2. Make sure the drawing takes up at least half the space and keep the parts in proportion

  3. Label the important features with straight lines that don't cross over
• Magnification


  How many times bigger the image is compared to the real object
• Standard form


  A way to write very big or small numbers with a decimal point and a power of 10
• Units and their standard form equivalents

  • Millimetre (mm) = 10^-3 m
  • Micrometre (μm) = 10^-6 m
  • Nanometre (nm) = 10^-9 m
  • Picometre (pm) = 10^-12 m
• Catalyst


  A substance that increases the speed of a reaction without being changed or used up
• Enzyme


  A biological catalyst produced by living things to speed up useful chemical reactions
• Enzymes


  • Have an active site that the substrate fits into
  • Usually only work with one specific substrate (high specificity)
• Substrate


  The molecule changed in an enzyme-catalysed reaction