Another of the universal features of cells as described by Alberts et al. is that:
By stringing together monomeric building blocks drawn from a standard inventory that is the same for all living cells, protein molecules are formed, similar to DNA and RNA molecules. Protein molecules are long, unbranched polymer chains, and similar to DNA and RNA, they carry information in the form of a sequence of linear symbols. Proteins are so numerous within cells that excluding water, they form the majority of the cell’s mass (Alberts et al. 2014).
Though DNA and RNA and proteins are similar in that they both use a sort of “alphabetical” language to encode information, proteins are different from DNA and RNA in that there are 20 different types of monomers for them, known as amino acids. Amino acids all have the same core structure and can be connected to each other in any order. They also have individually different side groups attached to the core that they all share. Joining the amino acids of a protein in a particular sequence creates what is known as a polypeptide. Specific sequences have, over time, transformed to give the protein a specific and useful function. Amino-acid polymers bind in a highly specific manner to other molecules. Amino-acid polymers also serve as enzymes to catalyze reactions that form or destroy covalent bonds. Essentially, they direct most of the cell’s chemical processes (Alberts et al. 2014).
Proteins have a number of other functions in cell, all based on their amino acid sequence, as mentioned before. Among these amazing functions is maintaining structures, generating movements, sensing signals, and more. Proteins put into action the genetic information of the cell (Alberts et al. 2014).
Within cells, a feedback loop exists connecting proteins and polynucleotides. The cycle begins when polynucleotides specify the amino acid sequences of proteins. Proteins then go on to catalyze chemical reactions that drive the cell, including those reactions that involve the synthesis of new DNA. Fundamentally, the feedback loops is as follows: a cell’s catalysts take in food, the food is processed, and building blocks and energy to create more catalysts is extracted from the food, waste materials are discarded, and the process repeats (Alberts et al. 2014).
A prospective medical student, looking to help others succeed.