Tag: cell as structural and functional unit

A micrometre is also known as a micron. It is an SI derived unit of length. Its value is 1×10$^{−6}$ metres or one millionth of a metre. Thus the correct answer is option B.

Living organisations have capacity to reproduce for ex animals give both to young ones of their kind, either directly or through egg.

• Endoplasmic reticulum (ER) is a system of membrane-lined channels found in all eukaryotic cells except mature erythrocytes. 
• Endoplasmic reticulum was discovered by Porter and Thompson (1945). 
• The name endoplasmic reticulum was given by Porter in 1953.
  Hence, option A is correct.

Lysosomes are small vesicles containing hydrolyzing enzymes and surrounded by a single membrane of lipids. They were discovered by Christian de Duve in 1955 but were named and observed under an electron microscope by Novikoff in 1956. 

Pasteur work on fermentation and germ theory of biology. Schleiden and Schwann are the co-founders of cell theory. Robert Brown was a Botanist and he discovered the nucleus. Rudolf Virchow was a German Physician, Biologist, Pathologist as well as a writer. The phrase 'Omnis cellula e cellula' is coined by Virchow which means all cells come from a cell, all cells born from a previous cell. So the answer is 'Virchow'.

Cell principle states that the cell is a fundamental unit of life and has all structural and functional properties of an organism. Also according to this principle cells are made from pre-existing cells and all organisms are made up of cells. Bacteria, algae and fungi obey the cell principle rules whereas viruses are under debate of being living or dead. They have many features of life but according to cell theory, they are not alive. Viruses lack cellular structure (cell wall, cytoplasm, ribosomes etc.) but do have genetic material in the form of RNA and they can only multiply when inside a host cell. Outside a host, they are unable to survive. Since a virus is not a cell, cell principle is not applicable to them. 

• A cell is a unit mass of protoplasm which is surrounded by protective and semi-permeable plasma membrane which separates the cell contents from the environment. 
• It is the basic unit of life and carries out the different functions of life. The body of all organisms is made up of cells so it is the structural unit of life. 
• Also, all the physiological, biochemical and genetic functions of the body are carried out by cells so it is called a functional unit of life. So, the correct answer is option D.

Micrographia is a book written by Robert Hooke when he discovered the cells in 1665. His all observation about the discovery of cells is detailed in this book. Hans and Zacharias designed the first compound microscope and by using this microscope Robert Hooke studied insects, sand, bird feathers, snowflakes and plants. He also observed a piece of cork which made him discover a framework of cells with empty spaces within it. its visual similarity with honeycomb cells made him name those units as the cell. He recorded all such observation through different lenses in the book Micrographia which is the first scientific bestseller.