The \'lock-and-key\' hypothesis PDF

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Lock-and-key...

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The 'lock-and-key' educated guess This educated guess hints that there is a high (when two things work together equally well) between the enzyme and its (supporting structure/chemical being changed) - almost the same as a lock and key. The level of detail is figured out by/decided by the amino acid residues in the active site that are not involved in binding or catalysis of the (supporting structure/chemical being changed). These interactions may be the result of (completing/matching) shape, the presence of chemically (completing/matching) charges, or a combination of both. The caused fit educated guess The caused fit educated guess hints that interactions between an enzyme and its (supporting structure/chemical being changed) result in an arrangement/shapeal change, 'steric strain' that (helps increase/shows in a good way) the catalysis of the reaction. In multisubunit proteins, the binding of a ligand to one (unit that's a smaller part of a bigger unit) may cause an arrangement/shapeal change in the other (units that are smaller parts of bigger units) to (help increase/show in a good way) binding further, e.g. in haemoglobin. Multienzymes Enzymes are often found in large multimeric complexes. These multienzymes consist of (more than two, but not a lot of) copies of each (unit that's a smaller part of a bigger unit) and co-factors that are needed/demanded. Pyruvate dehydrogenase is an example of a multienzyme. Multienzymes may also express different (units that are smaller parts of bigger units)in a tissue-specificmanner. These isoenzymes may have different (movement-related) properties or (a) little different (movement-related) functions. Lactate dehydrogenase is a tetramer made up of two different types of (unit that's a smaller part of a bigger unit):'H' form (units that are smaller parts of bigger units) are found mostly in the heart, whereas 'M' form (units that are smaller parts of bigger units) are found in the muscles. The different (units that are smaller parts of bigger units) have different properties - 'H' (units that are smaller parts of bigger units) catalyse the (changing from one form, state, or state of mind to another) of lactate to pyruvate, whereas the 'M' forms are needed/demanded for (not needing oxygen) glycolysis and catalyse the (changing from one form, state, or state of mind to another) of pyruvate to lactate. As a result of these two (unit that's a smaller part of a bigger unit) types, five different proteins may be produced: H4, H3M, H2M2, HM3, M4. Co-factors Co-factors are nonprotein molecules that aid the function of an enzyme: . Metal ions are often used as electron (people who give money or other things)/acceptors because they can exist in a variety of oxidation states. . Organic molecules are referred to as coenzymes and bind a (supporting structure/chemical being changed) needed/demanded for the reaction, or may be reduced or oxidised during the enzymatic reaction. NADþ and NADP þ are examples of cofactors that become reduced, and can be used in other reactions. Protein (moving things illegally from one place to another) Proteins must be targeted to the correct places/locations in the cell to (do/complete) a function. This information is contained in the amino acid sequence of the protein. The following are two broad methods by which this information is (translated/put into secret code): 1 The signal peptide results from a chain of around 15-60 amino acids usually located at one end of the polypeptide. This signal sequence (translates/puts into secret code) the destination of the protein and is recognised by different proteins to trigger the transport of the protein. After targeting of the protein, the signal peptide is be (cut in half/clinged/clung) from the polypeptides by enzymes known as signal peptidases. 2 Signal patches are a less well-understood method of targeting. The fully folded protein (translates/puts into secret code) an area in its structure that is recognised and targets the

protein to a particular location. Signal patches are very hard to identify, because they depend on the folded nature of the protein, and are not (able to be seen or picked out) only from the amino acid sequence. Targeting of protein to the endoplasmic reticulum All protein (creation/combination) is started on free-floating ribosomes, yet the protein (creation/combination) must be targeted to the correct location as a result of a signal peptide (translated/put into secret code) at the start of the amino acid chain. This ER-targeting sequence produces a series of changes :. The signal peptide quickly folds around the ribosome such that it pauses in translation. . The signal peptide allows the binding of the ribosome to clearly stated/particular pores in the ER. . Cleavage of the signal peptide permits the continuation of translation, with the protein product being (released fluid) into the ER lumen....