Here, the amino acid sequence is read and the guidelines are translated to form polypeptide chain (protein). Some modifications could occur in the Rough Endoplasmic Reticulum; these could be the addition of carbohydrates on to certain amino acids in protein. A few sugar groups could be attached to the chain of protein. This helps the folding process of protein to occur correctly and helps to stabilize the structure of it.
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. Vesicle steps in again, as it carries the packaged final form of protein to the cell membrane where it fuses with it and secretion also takes place.
PART B
Bacteria that have flagella perform certain movements towards chemical signals. This action is named as ‘chemotaxis’ and there are two types, they are: positive chemotaxis is when the bacteria cell moves towards the favourable compound which are usually nutrients; negative chemotaxis is when the bacteria cell moves away from a harmful chemical compound.
The flagellum work as guides for the bacteria in moving towards the certain direction. 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.
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zeynep_merve10hotmailcouk (student)
