Edexcel IGCSE Biology 复习笔记 2.2.1 Cell Structure

• 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

   

Cellular Structures & Functions Table

• 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:
  • 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 

   

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

Plant Cell Structure & Functions Table