Most Repeated MDCAT Biology: Enzymes MCQs

Explanation

An enzyme binds to its specific substrate at its active site and facilitates the conversion of substrates into products. By lowering the activation energy, enzymes make it easier for reactions to occur.

Explanation

Coenzymes are small organic molecules that assist enzymes in catalyzing biochemical reactions. They are often derived from vitamins, which are essential organic compounds that the body requires in small amounts for various metabolic processes.

Explanation

Option B should be non competitive inhibition instead of incompetitive inhibition.Option A: Competitive inhibition: Many antibiotic are inhibitors of specific enzyme in bacteria e.g. penicillin blocks the active site of an enzyme that many bacteria use tomade cell-walls. These antibiotics are example of competitive inhibition. Hence, this option is correct.

Explanation

Non-competitive inhibitors obstruct enzymatic reactions by binding to a part of the enzyme away from the active site. This interaction causes the enzyme molecule to change its shape, rendering the active site unreceptive to substrate or leaving the enzyme less effective at catalyzing. Hence this option is correct.

Explanation

Inhibitors are substances that react with enzyme in place of substrate but are not converted into product.

Explanation

Pepsin is an enzyme found in the stomach that breaks down proteins. It works optimally in an acidic environment, with a pH around 2.0. This acidic environment is created by hydrochloric acid secreted by the stomach lining.

Explanation

This is the correct answer. The lock-and-key model proposed by Emil Fischer suggests that enzymes are highly specific and can only catalyze one type of reaction. This is because the active site of an enzyme has a specific shape that complements the shape of its substrate, much like a lock and key. Only the correct substrate can fit into the active site and undergo the catalyzed reaction.

Explanation

Activation Energy is the minimum amount of energy that the reacting species must possess in order to undergo a specified reaction. Enzymes speed up reactions by lowering this energy and hence the reaction occurs faster by the virtue of more reactants being capable of initiating and taking part in the reaction due to the lowered energy threshold. Kinetic energy (KE) of an object is the energy that it possesses due to its motion. Heat energy is the result of the movement of tiny particles called atoms, molecules or ions in solids, liquids and gases. Potential energy is energy that is stored – or conserved - in an object or substance.

Explanation

Most enzymes have an optimum temperature at which they function most efficiently. For many enzymes in the human body, this optimum temperature is around 37 degrees Celsius (98.6 degrees Fahrenheit), which is the normal body temperature. However, the specific optimum temperature can vary for different enzymes. Hence here we will select 40 degrees Celsius.