A) What type of macromolecule are enzymes (lipids, proteins, carbohydrates, or nucleic acids)? Explain why this makes enzymes so sensitive to changes in temperature. B) Enzymes can speed up chemical reactions, but how do they do it? Describe three ways that enzymes can speed up chemical reactions through lowering the activation energy.
The Correct Answer and Explanation is :
A) Enzymes are proteins, which are macromolecules made up of long chains of amino acids. The structure of a protein is essential for its function, and this structure is highly sensitive to temperature changes. At a molecular level, proteins have a specific 3D shape, or tertiary structure, that enables them to interact with other molecules in a specific way. Temperature can affect the bonds and forces (such as hydrogen bonds, ionic interactions, and hydrophobic interactions) that hold this shape together. When the temperature rises too much, these bonds can break, causing the protein to denature. Denaturation results in the loss of the enzyme’s specific shape, and consequently, it can no longer bind to its substrate or perform its catalytic function effectively. Conversely, extremely low temperatures can slow down the movement of molecules and reduce the enzyme’s activity, as the molecules involved in the reaction move slower, leading to fewer successful collisions between the enzyme and substrate.
B) Enzymes speed up chemical reactions by lowering the activation energy (the energy required to start a reaction). Here are three ways enzymes achieve this:
- Proximity and Orientation: Enzymes bring reactant molecules (substrates) together in the correct orientation, which increases the likelihood that a reaction will occur. By binding to the substrates in the active site, enzymes help bring them close together in a precise orientation, increasing the chances of a successful collision.
- Straining Bonds: Enzymes can stress or distort the bonds in the substrate, making them easier to break. By binding to the substrate, the enzyme can change its shape slightly (known as induced fit), which can weaken certain chemical bonds in the substrate and make them more susceptible to being broken during the reaction.
- Providing a Favorable Microenvironment: The active site of an enzyme can provide a microenvironment that is more conducive to the reaction, such as a specific pH or ionic conditions. Enzymes can also use cofactors (non-protein molecules) to assist in catalysis, offering additional chemical groups that participate in the reaction, further lowering the activation energy.
By lowering the activation energy, enzymes significantly speed up reactions, allowing biochemical processes to occur efficiently and rapidly in living organisms.