Edexcel IGCSE Biology 复习笔记 2.2.1 Cell Structure

Edexcel IGCSE Biology 复习笔记 2.2.1 Cell Structure

Cell Structures


  • Eukaryotic cells have subcellular structures contained within their cytoplasm
  • Each cellular structure carries out a particular function
  • Organelles are subcellular ‘compartments’ where specific processes take place within the cell
  • Within the cytoplasm, the following organelles are visible in almost all cells (except prokaryotes) when looking at a higher magnification
    • Mitochondria (singular: mitochondrion) are organelles found throughout the cytoplasm and are the site of respiration
    • Ribosomes are tiny structures that can be free within the cytoplasm or attached to a system of membranes within the cell known as the Endoplasmic Reticulum
    • The endoplasmic reticulum studded with ribosomes looks rough under the microscope; this gives rise to its name of Rough Endoplasmic Reticulum (often shortened to R.E.R.)
    • Vesicles can also be seen using a higher magnification - these are small circular structures found moving throughout the cytoplasm



Cell Structures & Functions


Cellular Structures & Functions Table





Plant & Animal Cells


  • The main subcellular structures in animal cells are:
    • The nucleus: contains genetic material
    • Cell membranes: controls what enters and leaves the cell
    • Mitochondria: site of aerobic respiration
    • Ribosomes: site of protein synthesis
    • Cytoplasm: chemical reactions take place in this jelly-like substance






Some cellular structures can only be seen when viewed with an electron microscope




  • In addition to the subcellular parts found in animal cells, plant cells have:
    • cell wall made of cellulose: gives the cell shape and protection 
    • permanent vacuole filled with cell sap: pushes the cytoplasm against the cell wall, keeping the cell turgid
    • Plant cells found in the leaf and stem may also contain chloroplasts: the site of photosynthesis 






The plant cell shown above contains chloroplasts, so it would be found in the leaves of a plant




Plant Cell Structure & Functions Table



Exam Tip

You need to be able to recognise, draw and interpret images of cells, so practice drawing and labelling animal and plant cells as part of your revision.