Basis of Cell Structure and Development, Biology tutorial


The study of cell structure was revolutionized by the discovery of the electron microscope. The best optical (that is, light) microscopes can magnify specimens around 1,500 times under most favorable conditions. By means of the electron microscope, magnifications of 100,000 times or more are possible that facilitates detailed inspection of sub-cellular components. This structural information, in combination with the biochemical studies, has given prosperity of information regarding how cells are made and how they work.

All living things are comprised of cells. Cells are the fundamental units of life and all tissues and organs are comprised of cells. They are so small that they should be observed by means of a microscope. There are different kinds of cells. Cells can either be prokaryotic or eukaryotic. Eukaryotic cells encompass a nucleus and membrane bound organelles. Plant and animal cells are examples of eukaryotes. Plant cells are usually a square shape whereas animal cells are generally circular. Plant cells and animal cells have developed various organelles to carry out particular functions. Plant cells contain chloroplasts, a cell wall and a central vacuole. Animal cells are deficient in such three organelles. Plant cells contain chloroplasts as they prepare their own food. Plant cells include a cell wall in such a way that they don't burst if the central vacuole fills up with water. Prokaryotes don't encompass a nucleus, and be deficient in membrane bound organelles. They are the oldest cells on earth. Bacteria are prokaryotes. Prokaryotes frequently move by employing special structures like cilia or flagella.

Cells contain many structures within them termed as organelles. Such organelles are similar to the organs in a human and they assist the cell to stay alive. Each and every organelle has its own particular function to assist the cell survive. The nucleus of a eukaryotic cell directs the cell's actions and stores DNA. Eukaryotes as well encompass a Golgi apparatus which packages and distributes the proteins. Mitochondria are the power-house of the cell and give the cell with energy. Both animal and plant cells encompass mitochondria. Lysosomes are similar to the stomach of the cell. They encompass enzymes which digest the cell's utilized parts. All of the cell's organelles should work altogether to keep the cell strong.

The cell membrane is the protecting barrier which borders the cell and prevents unnecessary material from getting into it. The cell membrane consists of numerous functions; however one main function which it consists is to transport the materials (such as salts, glucose, electrolytes and other essential molecules) into the cell to support obligatory life functions.

Fundamental cell structures:

All cells at their essence encompass at least three things in common:

a) Cell membrane: All cells encompass a phospholipid based cell membrane. The cell membrane is selectively permeable in that it lets some materials to pass into or out of the cell however not others.

b) Cytoplasm: Cells are filled by a complex collection of substances in a water based solution. This substance is termed as cytoplasm. Across all the cells there are a number of common characteristics to all the cell cytoplasm.

c) DNA: All cells include DNA. In the simplest cells, the DNA is in one loop more loop similar structures free in the cytoplasm. In several cells like those building up our body the DNA is isolated from the cytoplasm in a special structure termed as a nucleus.

Omnis Cellula e Cellula:

Factually all the cells are from preexisting cells. This statement summarizes what has become termed as the cell theory. Nowadays when we talk about this theory we comprehend the theory as having least three portions:

a) All living things are building up of cells.

b) All cells come from the pre-existing cells.

c) There is no spontaneous generation beneath current conditions.

Nowadays such seem self obvious; however this theory in reality only dates from the mid 19th century. For instance, before the mid 19th century most of the people believed in spontaneous generation. This is the idea that living things can grow from non-living things. People, for example, used to suppose that flies in reality developed from rotten meat or that bacteria grow from stagnant water and so on. Gradually, however scientists cleared up these thinking until now we believe the concept that under current conditions, life doesn't occur from non life.

Cell theory is in reality significant as it provided, and still gives one of the great unifying theories in biology: one that states despite all the enormous diversity of organisms, they are united at a very basic level that is the presence of cells.

Types of Cells:

In the living world there are two fundamental kinds of cells: prokaryote and eukaryote cells. 

Prokaryotic cells comprise what we generally refer to as bacteria. Prokaryotic cells encompass DNA however it is not isolated from the rest of the cell within of a nucleus. Rather the DNA is a single loop free in the cytoplasm. Moreover, prokaryotes frequently have small loops of DNA termed as plasmids that can be transferred to other cells.

Eukaryotic cells in general are bigger and more complicated than the prokaryotic cells. Eukaryotic cells encompass a true nucleus having the DNA and also different other membrane bound organelles. A few of these organelles are pretty much common in eukaryotes. These comprise mitochondria, rough and smooth ER, the nucleus. Other organelles are limited to one or more kingdoms. For instance chloroplasts are limited to the Kingdoms Protista and Plantae. 

Prokaryotes usually don't encompass membrane bound organelles however the cell membrane might, as in photosynthetic bacteria, encompass intricate enfolding to raise surface area for different chemical procedures. Moreover, a lot of bacteria move by employing a structure termed as a bacterial flagellum. This is quite dissimilar than the flagella found in eukaryotes in that it consists of a rotating base similar to a wheel which supplies torque to the rest of the flagellum.


Organelles are well stated large scale structures which encompass a specific set of functions in the cell. A few organelles like cilia, Centrioles, and ribosome and the membrane enfolding of some prokaryotes are not isolated from the cytoplasm of the cell. However in eukaryotes, most of the organelles are what are termed as 'membrane bound' organelles, that is, organelles fully surrounded by the plasma membrane, or even a double membrane.

In fact, the concept of membrane bound organelles is so significant that most of the texts restrict the definition of organelles to mean membrane bound structures in a cell. Though, this leaves out significant structures in prokaryotes like the bacterial flagella and membrane enfolding found in the bacteria. As well, people who study bacteria generally consider such non membrane bound structures as the ribosome to be organelles.

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