Enzymes: Key Concepts (A-level Biology)
Enzymes: Key Concepts
Enzymes are involved in structural and metabolic reactions
Enzymes are not just involved in metabolic reactions. They are also involved in formation of structural components
- Enzymes can facilitate formation of structural substances. Enzymes can help catalyse reactions that produce structural components of the organisms, such as cellulose in plants’ cell walls and collagen in animals.
- Enzymes participate in metabolic reactions. Enzymes are key in almost all metabolic reactions. Examples include cellular respiration, and digestion.
The structure of an enzyme is crucial to its function
Remember, the functionality of a protein is directly determined by its biochemical structure.
- All enzymes have an active site with a specific shape. The active site of an enzyme binds to a substrate (the target). The structure of an enzyme’s active site determines which substrates it is capable of binding to.
- Enzymes are substrate specific. Because of the unique structure of each enzyme’s active site, most enzymes can only readily bind to two substrates which “fit” into its active site.
Enzyme-Substrate Complexes
- Enzymes optimise the position of reactants. In order for chemical reactions to happen, reactants need to be in the right place at the right time, and they need to be very close to each other.
- Enzyme-substrate complexes are formed. When enzymes bind to their substrates, they form an “enzyme-substrate complex”. These complexes reduce activation energy in two ways:
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- Bringing substrates close together. By bringing two substrates together, the enzyme puts them in very close proximity to each other thereby allowing them to readily bond with each other.
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- Putting chemical strain. In catalysis (breakdown) reactions, the active site of an enzyme can put chemical strains on the bonds of a molecule causing them to break easily.
Enzyme-product Complexes
- Enzyme product complexes are formed towards the end of the reaction. Just before the reaction is complete, the substrate is changed into a product, which remains bound to the enzyme before it is released. We call this the “enzyme-product complex”.
- Most enzyme reactions are reversible. The importance of the enzyme-product complex is that in most cases, the enzyme could induce the product to change back into the substrate, i.e. reverse the reaction. This is why most reactions catalysed by an enzyme are reversible.
Changes in Tertiary Structure
- Enzymes are similar to most proteins. Enzymes are proteins and therefore their chemical properties are more or less similar to most proteins. The majority of the properties that will be discussed in this section can be readily applied to proteins as well.
- Like proteins, enzymes derive their properties from their tertiary structure. Changes to their tertiary structure will lead to changes in their functionality. The tertiary structure of an enzyme determines the structure of its active site, and therefore its substrate binding ability.
- Mutations can disrupt enzymes. Mutations in the DNA of an organism can lead to the development of proteins and enzymes with mutations. These mutations can cause a protein or enzyme to lose its intended function.
Natural Degradation
- Unlike most proteins, enzymes are reusable. Once they bind to a substrate and catalyse a reaction, enzymes will release the substrate and the active site will regain its shape, ready to bind to another set of substrates. However, over time, enzymes can degrade and be replaced by new enzymes.
FAQs
Enzymes are biological catalysts that are responsible for speeding up chemical reactions within cells. They are made up of proteins and are essential for many cellular processes, such as metabolism and energy production.
The function of enzymes is to lower the activation energy required for a chemical reaction to occur, making the reaction faster and more efficient. By reducing the amount of energy required for a reaction, enzymes help to keep cellular processes running smoothly and allow cells to carry out their functions.
Enzymes work by binding to specific substrate molecules and bringing them into close proximity with each other. This allows the substrate molecules to react more readily and increases the likelihood of a successful reaction. The enzyme itself remains unchanged and is able to continue catalyzing other reactions.
Enzyme activity can be influenced by several factors, including temperature, pH, and substrate concentration. Increasing the temperature can speed up enzyme activity, but if the temperature is too high, the enzyme will denature and lose its ability to function. Changes in pH can also affect enzyme activity, with each enzyme having a specific optimal pH range. The substrate concentration can also affect enzyme activity, with increasing substrate concentration leading to an increase in reaction rate.
The rate of reaction is directly proportional to the concentration of enzymes present. Increasing the number of enzymes will increase the rate of reaction, while decreasing the number of enzymes will decrease the rate of reaction. This relationship is important because it allows cells to control the speed of their reactions and to regulate their metabolic processes.
Enzymes help to lower the activation energy required for a chemical reaction to occur. By binding to substrate molecules and bringing them into close proximity, enzymes create the conditions necessary for a reaction to occur with less energy. This helps to make the reaction faster and more efficient.
Cofactors are non-protein compounds that are required for enzymes to function. Cofactors can be inorganic ions, such as iron or magnesium, or organic molecules, such as vitamins. Coenzymes are organic molecules that transfer functional groups between enzymes, and are often derived from vitamins.
The study of enzymes is important in A-Level Biology because it provides a fundamental understanding of the mechanisms behind many cellular processes. This knowledge is essential for understanding topics such as metabolism, energy production, and the regulation of cellular processes. Additionally, a deep understanding of enzymes is necessary for the development of treatments for diseases and conditions related to enzyme activity, such as genetic disorders.
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