Ribosomes Essay

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Register to read the introduction… They are made within the nucleolus from 60% RNA and 40% protein, and consist of two subunits, one large and one small. When produced, the subunits stay separate to exit through the nuclear pores: it is only because of their miniscule size that they can fit through. Many ribosomes then bind themselves to the RER, although some stay free in the cytoplasm. Free and bound ribosomes both create polypeptide chains, which are used to make proteins. To create a polypeptide chain the large and small subunits must join together. Between the two, runs a strand of messenger RNA which holds the gene code for the ribosome to read. As the ribosome reads the mRNA, it collects amino acids from transfer RNA that match each codon. By having two separate units it keeps the mRNA secure which allows for accurate reading. New amino acids are brought into site A, and then joined via a peptide bond to the growing polypeptide chain held in site P. After the amino acid has joined, the tRNA leaves via the exit site (E). Once the mRNA strand has been read, the subunits separate again. The chain that is created is then released either into the cytoplasm or directly into the cisternal space of the RER, depending on where the ribosome …show more content…
The structure of the mitochondria is extremely important to the functioning of the organelle. It has two membranes, a smooth outer membrane, and a convoluted inner membrane which allows cristae to be formed. Between the two membranes is a narrow intermembrane space and within the inner membrane is a larger internal matrix. Both contain a complex mix of specialised proteins. The outer membrane acts like a filter by having channels that prevent large particles from passing through. The inner membrane, like the outer one, allows particles to pass through, although it is much more selective. To guarantee that only the correct molecules get to the matrix, the inner membrane uses transport proteins. Mitochondria’s role within the cell is to perform aerobic respiration (respiration in the presence of oxygen) to create ATP (adenosine 5′‐triphosphate) which is then transported around the cell to be used as chemical energy. The enzyme used to make the ATP is housed within the inner membrane which is why the convoluted shape is necessary. This shape maximises the surface area, and therefore maximises the amount of ATP that is generated. Within cells that are highly active such as muscle cells, the concentration of mitochondria is much greater as more energy is

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