Discovery of Cells and the Development of Cell Theory - Essay Example

Each protein is formed in accordance with a set of instructions contained within the nucleic acid, which accounts for the cell's genetic material. These set of instructions regulate which of the twenty amino acids are to be incorporated into the protein, and in what sequence. The final shape of the protein and its chemical properties is decided by the R groups of the amino acid subunits.There are four levels of protein structural organization: primary (1°), secondary (2°), tertiary (3°), and quaternary (4°).

The primary structure is defined as the linear sequence of amino acids in a polypeptide chain. The secondary structure refers to certain spatial arrangements of the main peptide chain, examples of which are the alpha helix and the beta-pleated sheet. Tertiary structure results from long-range contacts within the chain. The quaternary structure is the organization of protein subunits, or two or more independent polypeptide chains, as found in hemoglobin and certain enzymes.Proteins are broken down in the stomach into amino acids by enzymes known as proteases.

These amino acids help build protein for the body organs, muscles, bones, blood, besides also acting as an important nutritional source of nitrogen. They also act as a storehouse of energy, containing around 4 kilocalories per gram. In addition to their function in growth and cell maintenance, proteins are also responsible for muscle contraction. Insulin, hormones and most digestive enzymes are all proteins. The antibodies in the immune system are well-known proteins, and they are also the chief constituents of hemoglobin, which does the work of carrying oxygen to all parts of the body.

The cell theory states that all organisms are made up of similar units of the organization, called cells. This idea was conceived by Schleiden and Schwann in the year 1839 and has been one of the major milestones in the history of biology. The road to the cell theory was set up by the discoveries of the Italian Physiologist, Marcello Malpighi. He was the first to bring to light, the red blood corpuscles, and also described the network of pulmonary capillaries connecting the small veins to the small arteries, thus wrapping up the chain of circulation proposed by the English physician, William Harvey.

He also made many invaluable examinations on the structure of plants and animals and is renowned for his studies of the structure of glands and of the brain, spleen, liver, and kidneys; of the anatomy of the silkworm and the embryo of the chick.The cell theory was built upon ideas from various scientists such as Hooke, Leeuwenhoek, Oken, Brown, etc. Each of them contributed to the cell theory in a unique but significant way. In 1663 an English scientist, Robert Hooke, discovered cells in a piece of cork, which he examined using his primitive microscope.

He drew the cells he saw and also coined the word CELL, though he didn’t realize the importance of what he had seen then. The word cell is derived from the Latin word cellula, which means a small compartment, as those resembled cells in a monastery. Hooke revealed his findings in his acclaimed book, Micrographia. Ten years later, Anton van Leeuwenhoek, a Dutch businessman, with the help of his own monocular microscopes, was the first person to observe bacteria and protozoa. He is credited with having made over 500 microscopes, of which some are in use even today.

The most powerful of these instruments can magnify objects to an impressive 275 times. He discovered blood cells and was the first to see the living sperm cells of animals. He brought to view, microscopic animals such as nematodes and rotifers. As more of his letters were published and translated, he began to achieve fame and prominence.The theory put forward by Schleiden and Schwann failed to explain how new cells were formed. The explication for this was given by Rudolf Virchow, a German physiologist, who stated that cells divided and new cells are formed from pre-existing ones.

The modern cell theory, as understood today, is:1. All living organisms are made up of cells. 2. The cell is the basic structural and functional unit of all living things.3. All cells come from pre-existing cells by division. 4. Cells contain hereditary information which is passed during cell division. 5. All cells are basically the same in chemical composition. 6. All energy flow (metabolism & biochemistry) of life occurs within cells.The cell theory is one of the central foundations of biology.

All those early discoveries which led to the formulation of the cell theory have paved the way for breakneck advances in the disciplines of science and medicine, and even today, cell research is being carried on vigorously, which will lead to many more new astounding discoveries that could change our lives forever.