The Importance of Shapes fitting together in Cells and Organisms Enzymes are one of the major processes in biology which require complementary shapes. Enzymes are proteins that catalyse many different reactions in the body, e.g., in the mouth during chemical digestion. Enzymes have a specific tertiary structure, to ensure their active site is specifically complementary to the substrate. This ensures an enzyme-substrate complex can form. Active site and substrate are not identical, but active site Molds using the induced fit model, its highly important so the substrate’s bonds can be broken with help of the enzyme. For example, Maltase catalyses the hydrolysis of Maltose with the product of glucose. If the induced fit model cannot happen, I.e., shapes are no longer complementary due to active site change, vital chemical reactions cannot occur in the body. A change in the environment could cause this, I.e., temperature change which causes the enzyme to denature as its active site changes. This is bad because no more enzyme-substrate complexes can form, which slows down the chemical reactions within the body, which can lead to slowed metabolism, bad digestion of food. This can also be caused by mutations in the DNA sequence, coding for the wrong amino acids leading to defective enzymes. This highlights how important induced fit model is, as the effects of an active site change causes life threatening side effects on organisms.A further example is when molecules are attempting to cross the phospholipid membrane. If molecules are too large to diffuse across the membrane alone, they use facilitated diffusion via an intrinsic protein. As these proteins only allow certain molecules to use them, their cavities in their channels are substrate specific to prevent just any molecule passing. The specific molecules will enter the protein, once all cavities are full the entrance will close and the exit will open allowing the molecules to pass into the cell, aided by a phosphate molecule from the hydrolysis of ATP. If a molecule not suitable to that protein enters the channel, the protein won’t be able to close and transfer it across the membrane. This is essential as molecules like glucose enters the cell this way, and this is our energy to respire and survive.Another vital process which involves shapes fitting is the production of mRNA molecules. MRNA is used in making proteins, e.g., enzymes, by transporting certain required information from DNA in the nucleus, to the ribosomes in the cytoplasm using complimentary base pairing. Transcription is the formation of (pre)mRNA. For this to happen, the DNA stand must temporarily split to allow base pairing to happen, this is where RNA polymerase comes into play. This enzyme bonds to the DNA strand specifically and breaks the hydrogen bonds between the nucleotide0 bases to allow a template strand to be exposed. The RNA polymerase moves up the DNA strand, breaking the hydrogen bonds and connecting base paired nucleotides to form the pre-mRNA molecule, then reforming the hydrogen bonds to ensure DNA template strand isn’t exposed for longer than needed.This continues until RNA polymerase reaches a triplet called a ‘Stop Codon’ where it detaches, and the pre-mRNA is formed ready to be spliced to remove its introns, as introns would prevent the synthesis of a polypeptide. This is important to human life because without this precise formation of mRNA important proteins won’t be formed in the ribosomes as the wrong triplet codes and information would be transmitted, or worse, if the enzyme RNA polymerase didn’t fit so exactly it could leave the highly reactive nucleotides exposed with improper hydrogen bonding leaving them open to damage.Further examples of the importance of shapes fitting together is haemoglobin and red blood cells bonding to oxygen molecules. In the lungs, haemoglobin binds to oxygen in a process called ‘loading’ or ‘association’. The haemoglobin (in the red blood cells) carries oxygen through the body in the blood stream and ‘unloads’ at different tissues that require it. The shape of the red blood cells is
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