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How the protein insulin is made.

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´╗┐Unit 1 Unit 1 ? Human Biology The protein I have chosen, and will discuss in further detail, is insulin. Insulin is a hormone produced by the Beta cells, which are located in the pancreas, in clusters, known as the islets of Langerhans. It regulates blood sugar levels, however in diabetes there is a deficiency in production of this essential hormone. To start the process of protein synthesis, energy in the form of ATP (Adenosine Tri-Phosphate) is required. ATP is the main energy source for the majority of cellular functions; including protein synthesis and transportation of vital substances across the cell membrane. These vital substances include glucose and oxygen, which the cell needs for respiration, water for cells daily function, amino acids to make proteins and waste substances such as carbon dioxide and water. The cell membrane acts as a selective barrier between the inside of the cell and the external environment, only allowing certain molecules to leave and enter; this makes it semi-permeable. ...read more.


The molecule attaches itself to a channel protein in the membrane, the protein changes shape releasing the molecule on the opposite side of the membrane. Just like diffusion, it also follows the concentration gradient from an area of high to low concentration until equilibrium is achieved. Osmosis is the passive transportation of water which is a vital substance for the cell to function; the water diffuses through the cell membrane to follow the concentration gradient from a high water potential to a low water potential. Active transport works in a similar way of facilitated diffusion as it requires a channel protein that changes shape to release the molecule on the other side of the membrane. However, it needs energy in the form of ATP because it moves the molecule against the concentration gradient from an area of low to high concentration. Once these vital substances have been transported into the Beta cell; it can begin to make insulin. The Beta cell is a eukaryotic cell; the nucleus is the most obvious organelle and the starting point of protein synthesis (fig. ...read more.


This is the main transport system within a cell; its main function is to modify proteins. As the protein travels between the layers of the cisternae some sugar groups are added or taken away, the proteins are then labelled for delivery. Pro-insulin is exposed to specific enzymes which generate the mature form of insulin; it is then packed in membranous sacs called secretary vesicles which leave the GA and head to the cell membrane for secretion. Mitochondria are found in the cytoplasm of the cell, it is usually oval-shaped and has a double membrane; the inner one is folded to form cristae. This is the site of respiration and where energy is produced in the form of ATP required protein synthesis. In the Beta cell, once insulin is ready to be secreted, it is done by exocytosis; an active transport method which requires ATP. It migrates packaged substances to the inner surface of the membrane, which fuse and release their contents outside the cell. Insulin is released when a high level of glucose has been detected in the blood. It causes cells to store glucose which reduces the blood sugar levels. Human Biology ...read more.

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