biology paper 2🩷

• Eukaryotic cells


  Have a cell membrane, cytoplasm and genetic material (DNA) enclosed in a nucleus
• Prokaryotic cells


  Smaller than eukaryotic cells, the genetic material is not enclosed in a nucleus, the DNA is a single loop and there may be one or more rings of DNA called plasmids
• Bacterial cells are prokaryotic cells
• Prefixes

  • centi (cm) 1 cm = 0.01 m
  • milli (mm) 1 mm = 0.001 m
  • micro (μm) 1 μm = 0.000 001 m
  • nano (nm) 1 nm = 0.000 000 001 m
• Prefixes are used in science to make very small numbers more manageable. You need to learn the ones in the table and be able to convert to and from standard form.
• You will need to know the differences between animal, plant cells and bacterial cells
• Eukaryotes


  Cells that have a cell membrane, cytoplasm and genetic material (DNA) enclosed in a nucleus
• Prokaryotes


  Cells that are smaller than eukaryotic cells, with genetic material not enclosed in a nucleus. The DNA is a single loop and there may be one or more rings of DNA called plasmids
• Cell components


  • Cell membrane
  • Cytoplasm
  • Genetic material (DNA)
• Animal and plant cells are eukaryotic cells
• Prefix


  Used in science to make very small numbers more manageable
• Prefixes


  • centi (cm) - 1 cm = 0.01 m, x 10^-2
  • milli (mm) - 1 mm = 0.001 m, x 10^-3
  • micro (μm) - 1 μm = 0.000 001 m, x 10^-6
  • nano (nm) - 1 nm = 0.000 000 001 m, x 10^-9
• Animal cell


  • Contains a nucleus
  • Has cytoplasm
  • Has a cell membrane
• Plant cell


  • Contains a nucleus
  • Has cytoplasm
  • Has a cell membrane
  • Has a cell wall
• Bacterial cell


  • Genetic material not enclosed in a nucleus
  • Has a cell membrane
  • May have plasmids
• Cell specialisation


  The structure of different cells helps them to carry out a particular function within the organism
• Cell differentiation


  The process where a cell changes to become specialised
• Most types of animal cells differentiate in the early stage of development
• Most types of plant cells can differentiate throughout their life cycle
• Light microscope


  First used in 1590s, uses light rays, max magnification ~1500x, resolution 200nm
• Resolution


  The shortest distance between two objects that can be seen clearly
• Making a wet mount slide

  1. Place a thin section of the specimen onto slide

  2. Place a drop of water in the middle or stain the specimen

  3. Gently lower cover slip onto the specimen without trapping air bubbles

  4. Soak up any excess liquid
• Animal cell structure


  Has a diameter of 6 mm
• Actual diameter of the structure

  0.15 mm
• Calculating magnification


  1. OBJECT (A) = 0.15 mm

  2. IMAGE (I) = 6 mm

  3. MAGNIFICATION (M) = I/A
• The structure has been magnified 40 times
• Making a wet mount slide e.g. onion cells
• Bacteria multiply by binary fission
• Bacteria can be grown in the lab
• Testing effectiveness of antibiotics and disinfectants on bacteria
• Crop plants with special features such as disease resistance can be cloned to produce large numbers of identical plants for farmers, e.g. potatoes, strawberries and dates
• Chromosomes


  Coiled strands of DNA molecules
• Gene


  A section of DNA that codes for a protein
• DNA


  A genetic material found in the nucleus that codes for proteins
• Chromosomes are found in the nucleus of cells
• A human body cell has 23 pairs of chromosomes
• Stages of the cell cycle

  • Growth
  • DNA synthesis
  • Mitosis
• Mitosis


  Growth, repair and asexual reproduction
• Stem cell


  An undifferentiated cell
• Embryo stem cells


  Can differentiate into any human cell