Tag: cell as structural and functional unit

Ribosomes were first seen by Claude in 1941 but first studied by Robinsons and Brown in 1953 in bean root cells. Thus, the correct answer is option D.

Cell biology is a scientific study of the cells. It is concerned with the physiological properties, structure, the organelles it contains, interactions with the environment, life cycle, division and death of the cell. It is associated with the morphological and molecular level of the cell.

Robert Brown discovered the nucleus. He discovered the presence of nucleus in the cells of orchid root. Nucleus is a specialized double membrane bound protoplasmic body which contains all the genetic information for controlling cellular metabolism. 

Robert Hooke was mathematician and physicist. He discovered the cell. He took a piece of spanish oak and prepared thin slice by means of sharp pen knife. A deep planoconcave lens was used for throwing light on cork piece. The latter was observed under the microscope. The piece of cork was found to have a honey comb structure with a number of box like compartments, each having a pore and separated from others by diaphragms. Robert Hooke named the compartments as cellulae, now known as cells.
Nucleus was discovered by Robert Brown. He discovered the presence of nucleus in the cells of orchid root. Nucleus is a specialized double membrane bound protoplasmic body which contains all the genetic information for controlling cellular metabolism and transmission to the posterity.

The majority of cells are small. Normal animal cell size varies from 10 to 30 micrometer, while plant cell stretches from 10 to 100 micron. 

Cells are called the structural and functional unit of life because all the living organisms are made up of cells and also all the functions taking place inside the body of organisms are performed by cells. Cells provide specific conditions, for the occurrence of the metabolic reactions. These have specialized enzymes, which catalyze the biochemical reaction and regulates the functions of the body.

• Virus is an acellular microscopic infection-causing agent. It has only protein cover and a nucleic acid (either DNA or RNA). These are intracellular parasites that depend upon the host for nutrition.

The cell is the basic structural and functional unit of life. Whether it is a complex organism like humans, animals or plants or simple organisms like the bacteria, they are all made of cells. So, the cell forms the most basic level of organization of organisms.

There is a direct correlation between the shape of the cell and the function it performs. For example, the Red Blood Cells (RBCs) have a biconcave disc-shaped structure because they have to squeeze through blood capillaries to deliver oxygen to the various parts of the body. If the RBCs had any other shape, it would be difficult to perform the same function efficiently.

• The cell was discovered by Robert Hook in 1665. But the statement that cell is the structural and functional unit of life generalized as cell theory in 1839 by Schleiden and Schwann. Thus, the correct answer is option C.