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Protein Synthesis and Chemotaxis in Bacteria

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´╗┐PART A The guidelines to assemble a polypeptide chain, also known as Protein are coded in a particular sequence in the DNA, which is called a ?gene?. Before the certain type of protein is synthesised, the copy of the particular gene is made onto mRNA (messenger RNA). This is because DNA cannot leave the nucleus due to safety reasons and mRNA can exit the nucleus because its size is suitable to go through the nuclear pore. The process that occurs to copy the gene sequence from DNA onto the mRNA is called ?Transcription?. Once it is done, mRNA leaves through the nuclear pore and travels either directly to the ribosomes or to the ones that are found on the Rough Endoplasmic Reticulum. ...read more.


The next stage is when the produced protein is pinched off from the Rough Endoplasmic Reticulum and taken to the Golgi apparatus with the help of Vesicles. The polypeptide chain goes through a certain modification for the final protein to be formed. The Golgi apparatus consists of numerous sacs and each one of them is called cisterna. Each of the cisternae has different enzymes that do protein modification. These enzymes control the removal and addition of sugars in protein. They also control the addition of phosphate groups and sulphate groups. Some of the modifications mediated by the Golgi act as signals to allow the proteins to find their way to their final stop inside the cell before exiting and being secreted through the plasma membrane. ...read more.


This is because the receptors (molecules found on the cell surface which bind with other chosen molecules) in the cell membrane transmit signals to the flagellum, once a sufficient amount of the molecules, found in the environment attach to them (receptors). This process enables the flagellum to move in a rotary motion. When a flagellum rotates anti-clockwise, the bacteria cell swims towards the stimulus compound in a smooth and linear motion. This action itself is named as a ?run?. Runs could be interrupted by ?tumbles? which are caused by the flagellum operating clockwise in the case of a negative stimulus. These tumbles allow the cell to change its course and even stop. Runs are increased and tumbles are inhibited once an attractant molecule (i.e. nutrient) is detected; and vice versa during the detection of any repellent molecule. ...read more.

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