Cell Structure

Basic Cell Structure

  • All living organisms are composed of cells. The cell is the smallest functional and structural unit of life.
  • Cells can be categorised as prokaryotic and eukaryotic.
  • Prokaryotic cells are simpler and smaller, with no nucleus or membrane-bound organelles. For instance, bacteria and archaea.
  • Eukaryotic cells are complex and larger, with a nucleus and organelles that are enclosed within membranes. Examples include cells of animals, plants, fungi, and protozoa.

Structure of Prokaryotic Cells

  • Prokaryotic cells have a cell wall which maintains shape and provides protection.
  • They have a plasma membrane that controls the entry and exit of substances.
  • The cytoplasm is where most of the cell’s metabolic reactions occur.
  • Ribosomes are the sites of protein synthesis.
  • Genetic material in prokaryotic cells is in the form of a single DNA loop and possibly extra small rings of DNA called plasmids.

Structure of Eukaryotic Cells

  • Eukaryotic cells also consist of a plasma membrane, cytoplasm, and ribosomes.
  • They have a true nucleus containing genetic material in the form of chromosomes. The nucleus controls cell function.
  • Mitochondria are the sites of aerobic respiration, providing energy for the cell.
  • The Endoplasmic Reticulum (ER) processes and transports proteins within the cell. The ER can be of two types: Rough ER (has ribosomes for protein synthesis) and Smooth ER (lipid synthesis).
  • Golgi apparatus is involved in packaging and modifying substances for transport out of the cell.
  • In plant cells, chloroplasts are present which are used for photosynthesis.
  • Plant cells also have a rigid cell wall made of cellulose which provides support.

Specialised Cells

  • Some eukaryotic cells are specialised to carry out particular functions, for example, neurones in animals are specialised for rapid signal transmission.
  • In plants, root hair cells are specialised for nutrient uptake.

Brief on Organelles

  • Organelles are specialised structures within the cell that have specific functions.
  • They each have a distinct structure and role in the functioning of the cell.
  • Eukaryotic cells contain a variety of organelles, including the nucleus, mitochondria, ER, Golgi apparatus, lysosomes, and in plant cells, chloroplasts.