• Cell is defined as the structure and functional unit of the living body
  • A cell consists of a cell membrane inside which a number of organelles suspended in a watery fluid called cytosol
  • The cell organelles include the nucleus, mitochondria, ribosomes, endoplasmic reticulum, Golgi apparatus, lysosomes, peroxisomes, and cytoskeleton.

Cell membrane/ Plasma membrane/ Plasmalemma:

  • The cell membrane is a protective sheath, enveloping the cell body
  • This membrane separates the fluid outside the cell called extracellular fluid (ECF) and the fluid inside the cell called intracellular fluid (ICF)
  • The cell membrane consists of two layers of phospholipids with protein and sugar molecules embedded in them


  • It protects the cytoplasm and the organelles present in the cytoplasm
  • It acts as a semipermeable membrane which allows only some substances to pass through it
  • The nutrients are absorbed and waste products are excreted out through the cell membrane
  • It is responsible for the maintenance of the shape and size of the cell.

Cell organelles:


  • It is the most prominent and the largest cellular organelle
  • The nucleus is covered by a membrane called nuclear membrane
  • The major components of the nucleus are nucleoplasm, chromatin, and nucleolus


  • It controls all the cellular activities and storage of hereditary material
  • Cellular activities include metabolism, protein synthesis, and cell division.


  • The mitochondria is a membrane bound cytoplasmic organelle concerned with the production of energy
  • The inner membrane is folded in the form of shelf like inward projections called cristae and it covers the inner matrix space

The cristae contain many enzymes and other protein molecules which are involved in respiration and synthesis of adenosine triphosphate (ATP).


  • The ribosomes are the organelles without limiting membrane
  • The organelles are granular and composed of RNA and protein


  • Ribosomes are involved in the synthesis of proteins
  • mRNA carries the genetic code for protein synthesis from the nucleus to the ribosomes.

Endoplasmic reticulum:

  • ER is a network of tubular and microsomal vesicular structures which are interconnected with one another
  • The lumen of endoplasmic reticulum contains a fluid medium called endoplasmic matrix
  • The ER is of two types namely, rough ER and smooth ER

Functions of rough ER:

  • Synthesis of proteins
  • Degradation of worn out organelles

Functions of smooth ER:

  • Synthesis of non-protein substances
  • Detoxification of toxic substances.

Golgi apparatus/ Golgi complex/ Golgi body:

  • GA is a membrane bound organelle involved in the processing of proteins
  • The GA is situated near the nucleus. It has two ends or faces namely, cis face and trans face

The major functions of GA are the processing, packing, labeling, and delivery of proteins and other molecules to different parts of the cell.


  • Lysosomes are the membrane bound vesicular organelles found throughout the cytoplasm
  • The enzymes synthesized in rough ER are processed and packed in the form of small vesicles in the GA. Then, these vesicles are pinched off from GA and become the lysosomes

The lysosomal enzymes are involved in breaking down fragments of organelles and large molecules inside the cell into smaller particles that are either recycled or extruded from the cell as waste material.

Peroxisomes/ Microbodies:
Peroxisomes are the membrane limited vesicles like the lysosomes. Unlike lysosomes, peroxisomes are pinched off from ER, not from the Golgi apparatus


  • The major function is breaking down the fatty acids by means of beta-oxidation
  • Degrade the toxic substances by means of detoxification.

The cytoskeleton is a cellular organelle that consists of three major protein components namely, microtubules, intermediate filaments, and microfilaments

The cytoskeleton determines the shape of the cell and gives support to the cell.

Book Recommendations:
Anatomy and Physiology

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