1.1: cells

• Eukaryotes


  Often multicellular (in groups/ cells need to share tasks), 100-1000 times larger than a prokaryote
• Prokaryotes


  Unicellular (can function on its own), less complex
• Eukaryotic cells


  • Animal cells
  • Plant cells
  • Algae cells
• Prokaryotic cells


  • Bacterial cells
• Animal cells


  • Nucleus: contains chromosomes made up of genes (DNA) + controls the cell
  • Cell membrane: controls passage of substances in/ out of the cell
  • Mitochondria: releases energy in respiration
  • Cytoplasm: where metabolic reactions controlled by enzymes take place
  • Ribosome: where protein synthesis takes place
• Plant cells


  • Have all the organelles animal cells have + a few extra
  • Chloroplast: absorbs light energy to make food (glucose)
  • Cell wall: strengthens cell
  • Vacuole: filled with cell sap containing sugar
• Sperm cells


  • Carry male dna to egg cell (ovum) for successful reproduction
  • Enzymes in acrosome break down cell membrane of egg cell
  • Long tail to assist swimming
  • Mitochondria to provide energy for sperm for movement
• Nerve cells


  • Carries nerve impulses throughout the body
• Egg cells


  • Fertilised by sperm cell
• Muscle cells


  • To help the body to move
• Red blood cells


  • Transport oxygen around the body
• White blood cells


  • Fight pathogens that cause disease
• Ciliated epithelial cells


  • Sweeps dust and microorganisms away from the lungs
• Palisade cells


  • Carry out photosynthesis to make glucose
• Cell differentiation


  When a cell changes to become specialised at its job
• Cell differentiation process (animal cells)

  1. Starts off as a ball of unspecialised cells

  2. More cell division -> divided stem cells take up different tasks
• Plant cells never lose the ability to differentiate
• Cells that are soon to be differentiated in mature animals= repair/ replace cells
• Resolving power/ resolution


  The ability to distinguish between two separate points that are very close to each other
• Magnification


  Ability to make small objects seems larger
• Light microscopes


  Lower magnification/ resolution, cheaper
• Electron microscopes


  Higher magnifications/ resolution (can observe mitochondria/ ribosome), expensive
• Bacterial reproduction: Binary fission


  1. Circular dna + plasmids replicate

  2. Cell gets bigger + circular dna strands move to opposite ends of the nucleus

  3. Cytoplasm begins to divide + new cell walls form

  4. Cytoplasm divides -> 2 new identical daughter cells formed
• Optimal conditions for bacteria reproduction

  Warm temperatures + lots of nutrients
• Binary fission completes a cycle every 20 minutes