cell structure and functions

• Cells are the building blocks of life. They are called so because large number of cells assemble to make the body of a multicellular organisim
• Cytoplasm is the basic component of the cell, a jelly-like substance present between the cell membrane and nucleus
• Various organelles of the cell are present in the cytoplasm
• Protoplasm is made up of cytoplasm and the nucleus, it is the living substance present in a cell
• A tissue is a group of similar cells that combine together to perform a specific function
• Organelles are small structures scattered in the cytoplasm, each with a specific function inside the cell
• Examples of organelles include ribosomes, mitochondria, and vacuoles
• : Cell division is the process of formation of new cells from parent cells. Cell division is necessary for the growth and development of a multicellular organism because new cells are needed to replace the old and dead cells
• All living things are made up of cells. They are complex living structure; hence a Cell is the smallest living unit of life. (b) All cells are similar in their basic structure and function but are not identical. They differ in size and structure and also have different functions. (c) New cells are formed due to division in old cell. (d) The organisation of cell in a body of living organism determines its structure. (e) The way an organism function depends on the way cell works.
• Cell membrane:

  • Separates the cells from their external environment
  • Protects the cell from injury and provides shape
• Cytoplasm:

  • Jelly-like substance where cell expansion, growth, and replication occur
• Nucleus:

  • Stores genetic information in chromosomes
  • Controls overall cell metabolism and activities
  • Known as the control unit of the cell
• Chromosomes:

  • Contain genes
  • Hereditary information is located in the genes
  • Help in transferring characteristics from parent to child
• Mitochondria:

  • Known as the powerhouses of the cell
  • Food is oxidized inside them, releasing energy
• Vacuoles:

  • Store food, waste, and water
• Some cells, like nerve cells, are long and have extensive branching
• Amoeba has no fixed shape and keeps changing its shape
• White blood cells in humans can also change their shape
• There is a wide variation in the size of cells
• Most cells cannot be seen with the naked eye
• The smallest cell (a bacterium) is 0.001–0.005 mm in size
• The largest cell, measuring 170 mm x 130 mm, is the egg of an ostrich
• The longest cells in the human body are nerve cells, which may reach a length of 90 cm to 1m
• The smallest cell in the human body is the Red Blood Cell (RBC), which is around 0.007 mm