Tag: cell and cellular organization

Prokaryotic cells are primitive cells. They do not possess many membrane bound organelles as endoplasmic reticulum, mitochondria, lysosomes etc. Therefore, option B is correct. 

On the basis of the structure of cells, organisms are classified as eukaryote and prokaryote. The main differentiating factor between a eukaryote and prokaryote is that the cell organelles of eukaryotic cells are membrane-bound, while that of others are not.
Hence, the correct answer is D.

Prokaryotic cells do not possess membrane bound organelles. It possesses ribosomes which are not bounded by membrane. Ribosomes are necessary for protein synthesis. Hence, option A is correct.

• Both animal and plant cells are eukaryotic cells. 
• A plant cell differs from an animal cell in being surrounded by a well-developed cell wall. 

Phase contrast microscopy is particularly important in biology. It reveals many cellular structures that are not visible with a simpler bright field microscope. These structures were made visible to earlier microscopists by staining, but this required additional preparation and killed the cells. The phase contrast microscope made it possible for biologists to study living cells and how they proliferate through cell division. So, phase contrast microscope is best to study cell division in functional state compared to EM, SEM and simple microscope.

• Robert Hooke discovered cell in the year 1665. He observed cork cell in the bark of Spanish oak tree under a simple microscope and was able to see the empty structures surrounded by walls and named it a cell. 
• He elucidated his observation in a book called "Micrographia.

• Robert Hooke discovered cell in the year 1665. He observed cork cell in the bark of Spanish oak tree under a simple microscope and was able to see the empty structures surrounded by walls and named it a cell. 
• He elucidated his observation in a book called "Micrographia". He was unable to see the organelles inside the cell as cork cell which he observed was dead.

The invention of the microscope allowed the first view of cells. English physicist and microscopist Robert Hooke (1635–1702) first described cells in 1665. He made thin slices of cork and likened the boxy partitions he observed to the cells (small rooms) in a monastery. The open spaces Hooke observed were empty, but he and others suggested these spaces might be used for fluid transport in living plants. He did not propose, and gave no indication that he believed, that these structures represented the basic unit of living organisms.