cell structure and organisation

• Cell structure and organisation


  There are many diverse life-forms, but all have the same basic building block called cells
• Structures visible under the light microscope

  • Epidermal cells from Onion leaf
  • Mesophyll cells from Hydrilla leaf
• Viewing cells under the light microscope

  1. Mounting and staining technique

  2. Using the light microscope
• Why are there no chloroplasts in epidermal cells of onion leaf?
• Iodine solution is used as a stain to enhance the visibility of the nucleus
• Parts of a plant cell as seen under the light microscope, and their functions

  • Cellulose cell wall
  • Cell membrane
  • Cytoplasm
  • Chloroplast - Site of photosynthesis, Produces glucose from carbon dioxide and water
  • Cytoplasm - Site of chemical reactions
• Where is the nucleus and vacuole?

  Mesophyll cells of Hydrilla leaf
• Parts of an animal cell as seen under the light microscope, and their functions

  Nucleus - Controls cell activity and essential for cell division
• Quick check - The diagram shows the outline of a root hair cell and some of the soil particles which surround it. On the diagram, draw and label the following - cell wall, cytoplasm, vacuole and nucleus.
• Structures visible under the electron microscope

  • Mitochondrion - Site of aerobic respiration, breaks down glucose to release energy
  • Ribosome - Involved in protein synthesis
• Animal and plant cells seen under electron microscope. Which organelles are now visible?


  • Rough endoplasmic reticulum - Transports protein made by the ribosomes to the Golgi body
  • Golgi body - Stores and packages substances in vesicles for transport out of the cell
• Do animal cells have vacuoles?
• Quick check - Chlamydomonas is a single-celled organism (alga) with plant and animal like features. State the function of the labelled parts.
• Video - https://www.youtube.com/watch?v=cFfiCzKV9-k
• Specialised cells


  • Bone cells
  • Muscle cells
  • Sperm cells
  • Nerve cells
• How is the structure of the red blood cell adapted to its function?

  • Contains haemoglobin - Binds to oxygen and transports it around the body
  • Circular biconcave shape - Increases surface area-to-volume ratio for increased rate of oxygen uptake
  • Absence of nucleus - Allows packing of more haemoglobin for transport of oxygen
  • Flexible - Easily squeezes through capillaries
• How is the structure of the muscle cell adapted to its function?

  • Contain many mitochondria - Provide energy for contraction of muscle cell
  • Has contractile protein fibres - Contract and relax to bring about movement
  • Has many nuclei - Allow for cell division
• How is the structure of the root hair cell adapted to its function?

  • Long and narrow extension - Increase surface area-to-volume ratio for increased rate of absorption of water and mineral salts
  • Maintains a lower water potential in vacuole - Allow water to enter the root hair cell via osmosis
• Self-directed lesson review (video) - https://www.youtube.com/watch?v=wNe6RuK0FfA
• Stem cells can develop into other specialised cells
• Scientists can grow cells of different organs in the laboratory and transplant them into humans
• Potential to treat diseases that were once considered untreatable
• Extension videos on donor stem cells - How bones make blood and bone marrow transplant (stop 2:35) - https://www.youtube.com/watch?v=1Qfmkd6C8u8
• What is a bone marrow transplant? - https://www.youtube.com/watch?v=xUtdWWd6yyE
• What happens during a bone marrow transplant? - https://youtu.be/BUs4ykI0KNU
• Our knowledge of cell biology has enabled humans to enjoy consuming meat without having to destroy any animals!
• Based on the concept of lab-grown meat, do you think a functioning organ can be created using cells from that particular organ?
• What are the benefits of using models to study processes in the human body?