Edexcel IGCSE Biology

Revision Notes

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

Cell Structures Table 1, downloadable AS & A Level Biology revision notes Cell Structures Table 2, downloadable AS & A Level Biology revision notes

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

Structures in an animal cell visible under a light microscope & an electron microscope, IGCSE & GCSE Biology revision notes

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:
    • A cell wall made of cellulose: gives the cell shape and protection
    • A 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

Structures in a plant cell visible under a light microscope & an electron microscope, IGCSE & GCSE Biology revision notes

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

Plant Cell Structure & Functions Table

Plant cell structure & function table, IGCSE & GCSE Biology revision notes

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.

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Ruth graduated from Sheffield University with a degree in Biology and went on to teach Science in London whilst also completing an MA in innovation in Education. With 10 years of teaching experience across the 3 key science disciplines, Ruth decided to set up a tutoring business to support students in her local area. Ruth has worked with several exam boards and loves to use her experience to produce educational materials which make the mark schemes accessible to all students.
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