Biochemistry
Introduction
Cell is the fundamental unit of life and it forms the basis of all living things. They are the smallest single unit of life, in the smallest bacteria to larger blue whales and giant trees. Cells are often called the "building blocks of life". The study of cells is called cell biology. An understanding of cells is vital in any understanding of life itself. Cell biology is the study of cells and how they function, from the subcellular processes which keep them functioning, to the way that cells interact with other cells. Cell biology concerns itself with how the biomolecules are used by the cell to survive, reproduce and carry out normal cell functions.
Cell
Cells were discovered by Robert Hooke in 1665. Cells consist of cytoplasm enclosed within a membrane, which contains many biomolecules such as proteins and nucleic acids. Organisms can be classified as unicellular (consisting of a single cell; including bacteria) or multicellular (including plants and animals). The number of cells in plants and animals varies from species to species, it has been estimated that humans contain somewhere around 40 trillion (4×1013) cells. Most plant and animal cells are visible only under a microscope, with dimensions between 1 and 100 micrometers.
Cell theory
Cell theory, first developed in 1839 by Matthias Jakob Schleiden and Theodor Schwann, states that all organisms are composed of one or more cells, that cells are the fundamental unit of structure and function in all living organisms, and that all cells come from pre-existing cells. Cells emerged on Earth at least 3.5 billion years ago.
Structure of cell
A cell consists of three parts: the cell membrane, the nucleus, and, between the two, the cytoplasm. Within the cytoplasm lie intricate arrangements of fine fibers and hundreds or even thousands of miniscule but distinct structures called organelles.
Function of cell