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An Anatomy and Physiology of the organelles of the cell In this paper I will examine an anatomy and physiology of the organelles of the cell. The branch of science which research deeply cells is called cytology. I will not deepen in the cytology because it is a really huge branch of science. What I want to do is make a brief introduction and acquaint you with main cytology thesis.
After this I will concentrate all my attention in organelles. The cell is the structural and functional unit of all living organisms, and are sometimes called the "building blocks of life. " Some organisms, such as bacteria, are unicellular, consisting of a single cell. Other organisms, such as humans, are multicellular, (humans have an estimated 100, 000 billion = 1014 cells). (1, 1) The famous cell theory can be formulate in three main thesises: all living beings are made of cells, cells are the basic units of life, cells come only fron other cells. There are two known the of cells: prokaryotic and eukaryote. Prokaryotic cells are the most simple because they do not contain nuclear and organelles with membranes. Organelles in cell can be compared to the organs in human body.
As well as organs, organelles have their own little function, which ensure vital activity of cell. Why organelles and nothing else? There are several reasons why cells evolved organelles. First, organelles can perform specialized functions. Second, membrane bound organelles can act as containers, separating parts of the cell from other parts of the cell. Third, the membranes of organelles can act as sites for chemical reactions.
An example of the first type of organelle is cilia, these short filaments act as "paddles" to help some cells move (1, 2). We will start to examine organelles from the nucleus because it is cells brain and have very important functions. The DNA is kept in nucleus and RNA is transcribed. Through the nuclear pores the RNA is transported out of the nucleus. And proteins are transported in through the nuclear pores. Such nuclear pores are called Nuclear Pore Complex (NPC).
The nucleolus is sub organelle" of the nucleus. The nucleolus consists of three distinct regions: the fibrilla r centres, the dense fibrilla r component and the granular component. It is a consequence of ribosomal RNA (rRNA) synthesis: nucleolar organizers. Thus it can be said the nucleolus consists basically of nucleolar organizers and the transcribed rRNA (plus associated proteins) (2, 1). The next important organelles are Ribosomes. They are tightly connected with the nucleus because they are the sites of protein synthesis where RNA is translated into protein.
Throughout the cells can be found a great number of ribosomes because protein synthesis is vitally important to cells. Ribosomes consist of two subunits that fit together and work as one to translate the mRNA into a polypeptide chain during protein synthesis. Each subunit consists of one or two very large RNA molecules (known as ribosomal RNA or rRNA) and multiple smaller protein molecules (3, 1). Mitochondria are the main energy center of cell. Its main purpose is to convert organic materials into energy in the form of ATP via the process of Oxidative phosphorylation. Mitochondria consist of two membranes, inner and outer, which main material is phospholipid bilayers studded with proteins.
The outer mitochondrial membrane contains numerous integral proteins called print. The inner membrane also has folding's called the crystal which allow the inner membrane to have a greater surface area for the electron transport chains (4, 1). Vacuoles are another type of organelles. Their structure I very simple: vacuoles contains of a single membrane the liquid or solid elements. They acts as container. In plants vacuoles can contain water, sugar, amino acids, etc.
The largest vacuoles, I think, can be found in watermelon. In some plants vacuoles can occupy from 50 % to 90 % of the cell space. The main function of Golgi apparatus is collecting materials for export from the cell. Golgi apparatus (sometimes called the Golgi body) is similar to endoplasmic reticulum (ER). Golgi apparatus consists of sacs (with a single membrane), which are stacked like pancakes. Closely associated with the edges of the flattened sacs you will see vesicles, which have pinched off from the Golgi (2, 2).
Golgi apparatus modifica tes lipids and proteins and collect and storage materials for export from the cell. Lysosomes also take part lipid modifications but make this on more complicated level. They are a liquid filled sac surrounded by a single membrane and are situated within Golgi apparatus. When viewed through a microscope they closely resemble vacuoles, peroxisome's and vesicles (3, 2) Lysosomes digest macromolecules and use acid hydrolases (enzymes) for this.
At pH 4. 8, the interior of the lysosomes is more acidic than the cytosol (pH 7). The lysosomes single membrane stabilizes the low pH by pumping in protons (H+) from the cytosol, and also protects the cytosol, and therefore the rest of the cell, from the degradative enzymes within the lysosomes (5, 1). Endoplasmic Reticulum is a membrane system of folded sacs and tunnels in the cytoplasm. It acts like r transport network dedicated to certain modifications and specific final destinations. There are two types ER: rough and smooth. Rough "ER" is covered with ribosomes.
It is common in cells that export proteins and directs the proteins flow. Smooth "ER" as few or no ribosomes. It functions as a pathway for molecules to follow (1, 3). For a plant cells chloroplasts are important because they are the sites of photosynthesis in eukaryote cells. Chloroplast consists of single membrane surrounding it.
Membrane is surrounded with a fluid called stroma. In stroma float stacks of disk grand. Stacks are made from individual hollow disks called thylakoids. The light reactions take place on the membranes of the grand. The dark reactions (also called light-independent reactions and / or Calvin-Benson Cycle) take place in the stroma (4, 2).
For animal cells centrioles are important because they take part in cell division process. Centrioles organize mitotic spindle upon which the chromosomes are divided. Centrioles consist of barrel shaped microtubule, which is prevalent for animal cells. Bibliography Cell (biology), Wikipedia [online]. 2005 [cited 2005 Nov 10 ]. Available from: URL: web Structure and Function of Organelles, [online]. [cited 2005 Nov 10 ]. Available from: URL: web Jim Askew, Biology 101 Sample Curriculum [online]. [cited 2005 Nov 10 ].
Available from: URL: web Campbell, Neil A. and Reece, Jane B. ; 2002. Biology 6 th ed. Benjamin Cummings. San Fransisco. ISBN 0805366245 Renshaw A.
A. , Aspiration Cytology; 2005.
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Research essay sample on An Anatomy And Physiology Of The Organelles Cell
