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The Cell
In order to understand the importance of the cell to humanity, one must first consider the cell theories. Accordingly, the three cell theories explain that the cell is the basic unit of function in organisms, all living things contain one or more cells and that cells are arise from the replication of other cells (Pollard 1). By understanding this, one can comprehend the importance of the cell for life. Relevantly, understanding the importance of the cell also requires a comprehension of the structure and functioning of cells in organisms that help give life for these organisms.
This paper presents a brief introduction to the cell. The paper examines the external and internal cell structure with relation to cell shape, cell size, and internal makeup of the cell.
Cell Shape
Depending on the function cells play in the body of an organism, different cells vary in their shapes (Pollard 3). Researchers explain that the shape of the cell is highly reliant on the role the cell plays in the body. For example, blood cells come in the form of rounded or oval disks, so as to increase the surface area for the flow of air in and out of the blood. In addition to this, these cells are also circular in shape so as to allow ease of transportation throughout the body.
Cell Size
In relation to the shape of the cell, cell size are not constant and they differ from one cell to another. Most cells in organisms are too small to be observed with the common eye, and for that reason need the use of the microscope for identification. As researchers explain, most cells, irrespective of whether they are animal or plant cells are small because of the ability of the nucleus to balance the volume of the cytoplasm, as well as, the surface area to volume ration of the cell (Pollard 6). However, very few cells are large enough to be seen by the human eye with the human egg identified as the largest cell in the human body.
External and Internal Makeup
The external and internal makeup of the cell is said to be made up of three main parts including the cell surface, cytoplasm, and nucleus, which is the center of the cell. These parts consist of various organelles, which are defined as the cell components that perform certain functions within the cell itself.
Nucleus
The nucleus is identified as the inner most part of the cell and it consists of the nucleolus, chromosomes, and the nuclear membrane. The nucleolus is a cell organelle that is made up of nucleic acids and proteins in the nucleus. The nucleolus is only visible during the division of cells and for that reason, cannot be identified in the cell during inactivity. This organelle is spherical in shape and is composed of RNA, which function as protein manufacturers in the cell (Pollard 11). The second organelles found in the nucleus are the chromosomes, which are composed of DNA and carry genetic information in the cell. Chromosomes are made up of chromatin and their function is to give the cell its genetic structure. The nuclear membrane is the third and final organelle found in the cell and it consists of two layers surrounding the nucleus.
Cytoplasm
The cytoplasm is the second section of the cell and it consists of nine main organelles including vacuoles, ribosomes, mitochondria, lysosomes, Golgi apparatus, cytoskeleton, chloroplasts, centrioles, and the endoplasmic reticulum (Pollard 14). Vacuoles are water solutions that are used for storage digestion and excretion of waste in the cell. Ribosomes, on the other hand, refer to miniature cell organelles and structure that function as protein factories for the cell. Considered one of the largest organelles in the cell, the mitochondria are double layered organelles that function as energy production centers for the cell. Lysosomes are used for the transport of undigested materials to the cell membrane for removal and is therefore dubbed the digestive plant for the cell (Pollard 18). Also known as the protein packaging organelle in the cell, the Golgi apparatus, is a protein membrane found near the nucleus. The endoplasmic reticulum is considered as the cell’s transport system as it stores, separates materials and substances in the cell. The cytoskeleton provides the shape and support for the cell, the chloroplasts are sights for photosynthesis whereas the centrioles are the organelles involved in cellular division.
Surface
The cell surface is the third section of the cell and it makes up the external part of the cell structure. This section surrounds the cell and provides protection against internal damage of the cell (Pollard 21). The cell surface is made up of two main organelles including the cell wall and the plasma membrane. The plasma membrane is the outermost organelle in the cell that controls the passage of materials and substances in and out the cell. The plasma membrane is made up of proteins that are surrounded by two phospholipid layers. The cell wall, on the other hand refers to the extracellular structure surrounding the plasma membrane. The cell wall is only found in plants and cannot be observed in animal cells.
Work Cited
Pollard, Thomas dean et al. Cell Biology. New York: Saunders/Elsevier, 2008. Print.
