The Fundamental Unit of Life

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07 Chromatin, Chromosome and Cytoplasm


  • The chromatin material is a thin, thread-like intertwined mass of chromosome material present in the nucleus of the cell.
  • It is composed of the genetic substance DNA i.e. deoxyribonucleic acid and proteins i.e. histones.
  • Distinct segments of DNA are called genes.
  • Genes are arranged in a linear order along the chromosomes.
  • A gene is the functional unit of chromosome.
  • The chromatin is condensed into two or more thick ribbon like chromosomes during the division of cell.


  • The term chromosome is derived from the Greek words for the color called chroma and body which is soma.
  • This is because of the structure of chromosome or because they are cell structures or bodies that are heavily stained by some colorful dyes used in research.
  • Chromosomes are compact thread-like bodies woven together.
  • These are formed at the time of cell division from chromatin material.
  • DNA is responsible for storing and transmitting the hereditary information from one generation to another.
  • They are located inside the nucleus of animal and plant cells.
  • Each chromosome is made of proteinsand a single molecule of deoxyribonucleic acid or DNA that are passed from parents to offspring, over generations.
  • DNA contains the specific instructions that make each type of living creature different from the other.
  • It ensures uniqueness of an individual.

Properties of Chromosomes:

  • Bundles of tightly coiled DNA located within the nucleus of almost every cell in our body make up chromosomes.
  • There are 23 pairs of chromosomes in humans.
  • The unique structure of chromosome keeps DNA tightly wrapped around spool-like proteins, called histones. Otherwise, DNA molecules would be too long to simply fit inside cells because if all of the DNA molecules in a single human cell were unwound and placed tail-to-tail, they would stretch about 6 feet.
  • Cells must constantly divide to produce new cells to replace old, worn-out cells so that an organism is able to grow and function properly.
  • Chromosomes are an essential part of the process of cell division that ensures DNA is accurately copied and distributed. Yet, mistakes occur on rare occasions leading to disorders like cancer.
  • In humans, defective chromosomes made up of joined pieces of broken chromosomes cause one type of leukemia and some other cancers.


  • Cell organelles are structures present within the cell that are special and specific to their function.
  • Cytoplasm is one of the cell organelles that make the cells a self-sufficient element.
  • The three main constituents of cells are: plasma membrane, nucleus, and cytoplasm.
    • The cell membrane or plasma membrane: It is a bi-lipid membranous layer that separates the cell organelles from its external environment as well as from the other cells. It is the outer covering of a cell that encloses all other parts, including cytoplasm and nucleus.
    • The nucleus: It is the largest organelle and the remote control of a cell.
    • The cytoplasm: It is a jelly-like substance in which the cell organelles are embedded.
  • All the cell organelles like mitochondria, ribosomes, vacuoles, endoplasmic reticulum, etc., are embedded or suspended in the cytoplasm.
  • It is a semi-liquid jelly-like component that connects the cell membrane and the nucleus.
  • Cytoplasm can be easily observed under a microscope by staining technique.
  • Most of the chemical reactions and majority of cellular metabolism within a cell take place in the cytoplasm.
  • Protoplasm is the whole cellular content of a living cell.
  • It is made up of the nucleus, cytoplasm and all other living components of the cell.
  • Cytoplasm is a part of cell that between the plasma membrane and nuclear envelope


  • Cytosol (cytoplasm) acts as a store of vital chemicals such as, glucose, amino acids, vitamins, ions, etc.
  • It is the site of certain metabolic pathways, such as glycolysis. Synthesis of fatty acids, nucleotides, and some amino acids also take place in the cytosol.
  • Living cytoplasm is always in a state of movement.

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