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Cell

Soham Paul | 7 September 2024

Introduction:

The cell is the basic structural7 and functional8 unit of all life forms.

Cells can be broadly categorized into prokaryotic and eukaryotic types, typically differentiated by the presence and absence of a well defined, membrane-bound nucleus9. Whereas prokaryotes are unicellular10, eukaryotes can be unicellular as well as multicellular11. Prokaryotes represent some of the first forms of life to appear on the planet.

Cellular Components:

  1. Cytoplasm: Gelatinous fluid filling up a cell, containing several membrane-bound organelles.
  2. Cell Membrane: Selectively permeable1 membrane surrounding the cell(cytoplasm). Responsible for protection as well as interaction with the help of protein2 molecules. Essentially, a phospholipid3 bilayer.
  3. Genetic Material: RNA and DNA comprising chromosomes, which show different arrangements in prokaryotic and eukaryotic forms.
  4. Cell Nucleus: Houses chromosomes, and is the site for DNA replication and transcription. Contains the genetic information and controls other cell organelles.
  5. Mitochondria: Energy-house of the cell, responsible for producing ATP4.
  6. Chloroplast: Found only in plants and algae. Can produce carbohydrates5 by photosynthesis6.
  7. Endoplasmic Reticulum: Plays a key role in intracellular transport. Found in two forms, differentiated by the presence or absence of ribosomes.
  8. Golgi Apparatus: Responsible for packaging and processing of cellular products.
  9. Vacuoles: Primarily store water and waste products, and may participate in controlling hydrostatic pressure[^12].

  10. Ribosome: Large complex of protein and RNA molecules. Consist of two subunits and help in the translation process (protein synthesis). Read more about ribosomes here.

    (NOTE: cellular components 4-9 are present only in eukaryotes. Prokaryotes lack membrane-bound organelles)

Cell Wall: Extracellular protective cover present in certain cells. Composition differs from one cell type to the other.

Sources:

  1. Ahmed S, Shah P, Ahmed O. Biochemistry, Lipids. [Updated 2023 May 1]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK525952/
  2. Dunn J, Grider MH. Physiology, Adenosine Triphosphate. [Updated 2023 Feb 13]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK553175/
  3. https://www.nature.com/scitable/topicpage/photosynthetic-cells-14025371/

References:

  1. a cell is the smallest unit, which in aggregates/alone can make up an organism. Cell gives rise to tissues, which can specialise to form organs and subsequently, organ systems and the entire organism ↩

  2. a cell is the smallest unit capable of performing all the basic functions of life ↩

  3. refer 4th cellular component ↩

  4. organisms made of only one cell ↩

  5. organisms made of more than one cells ↩

  6. allowing only selected substances to pass through itself ↩

  7. amino acid polymers ↩

  8. compounds made of saturated/unsaturated fatty acids, with phosphate groups attached ↩

  9. Adenosine Triphosphate, a compound storing energy in chemical bonds, known as energy currency of body ↩

  10. polymers/monomers of sugar molecules ↩

  11. biochemical process carried out by certain organisms to produce food with the help of sunlight ↩