Cell structure and size of specimens

• Head to www.savemyexams.com for more awesome resources
• Page 1 of 32
• © 2015−2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers
• CIE IGCSE Biology
• Contents


  • 2.1.1 Cell Structure
  • 2.1.2 Organisation of Cells
  • 2.1.3 Magnification Formula
  • 2.1.4 Converting Between Units: Extended
• Animal cells


  • Multicellular
  • Nucleus with distinct membrane
  • No cellulose cell walls
  • No chloroplasts
  • Feed on organic substances
  • Store carbohydrates as glycogen
  • Have nervous coordination
  • Able to move from place to place
• Plant cells


  • Multicellular
  • Nucleus with distinct membrane
  • Cell walls made of cellulose
  • Contain chloroplasts
  • Feed by photosynthesis
  • Store carbohydrates as starch or sucrose
  • No nervous coordination
• Cell structures found in both animal and plant cells

  • Nucleus
  • Cell membrane
  • Cytoplasm
  • Mitochondria
  • Ribosomes
  • Endoplasmic reticulum
  • Golgi apparatus
  • Lysosomes
  • Vacuoles
• Cell structures found only in plant cells


  • Cell wall
  • Chloroplasts
  • Central vacuole
• Bacteria


  • Microscopic single-celled organisms
  • Possess cell wall, cell membrane, cytoplasm and ribosomes
  • Lack a nucleus but contain circular chromosome of DNA
  • May have plasmids
  • Lack membrane-bound organelles
  • Some have flagella
• Examples of bacteria include Lactobacillus and Pneumococcus
• Mitochondria


  Organelles found throughout the cytoplasm
• Ribosomes


  Tiny structures that can be free in cytoplasm or attached to endoplasmic reticulum
• Rough endoplasmic reticulum (RER)

  Endoplasmic reticulum studded with ribosomes
• Vesicles


  Small circular structures found moving throughout the cytoplasm
• Cells need to divide to help the body grow and repair itself
• Specialised cells in animals

  • Ciliated cells
  • Nerve cells
  • Red blood cells
  • Sperm cells
  • Egg cells
• Specialised cells in plants

  • Root hair cells
  • Xylem cells
  • Palisade mesophyll cells
• Levels of organisation in an organism

  • Cells
  • Tissues
  • Organs
  • Organ systems
  • Organism
• Magnification formula

  Magnification = Image size / Actual size
• 1 mm = 1000 μm
• 1 cm = 10,000 μm
• When converting between units, ensure both are in the same unit before proceeding with calculations