Chemistry Mock Tests

The following passage is an excerpt from an article about biochemistry. Enzymes are biological catalysts—typically proteins—that accelerate chemical reactions in living organisms by lowering the activation energy required for the reaction to proceed. Each enzyme is highly specific for its substrate, the molecule upon which it acts. The active site of an enzyme, a specialized region with a unique three-dimensional shape and chemical environment, binds the substrate through multiple weak interactions, including hydrogen bonds, ionic interactions, and hydrophobic effects. The induced-fit model of enzyme action proposes that the active site is not a rigid structure but rather changes its conformation slightly upon substrate binding, "clamping down" on the substrate in a way that stresses the bonds to be broken and brings catalytic groups into optimal position. Enzyme activity is influenced by several factors. Temperature affects enzyme activity in two ways: increasing temperature increases the kinetic energy of molecules and thus the frequency of enzyme-substrate collisions, but excessive heat causes the enzyme to denature, losing its three-dimensional structure and its catalytic ability. Similarly, pH affects the ionization state of amino acid side chains in the active site, and each enzyme has an optimal pH at which it functions best—pepsin, for example, works optimally at pH 2 in the stomach, while trypsin, which functions in the small intestine, has an optimal pH of about 8. Enzyme activity can also be regulated by inhibitors: competitive inhibitors bind to the active site and compete with the substrate, while non-competitive inhibitors bind to a different site on the enzyme, causing a conformational change that reduces activity. According to the passage, how do competitive inhibitors differ from non-competitive inhibitors?

Which of the following is the chemical name of "Vinegar"?

Which of the following is the chemical name of "Baking Soda"?

The acid present in lemon and orange is:

The chemical formula of washing soda is:

Which metal is liquid at room temperature?

Which of the following is the chemical formula of common salt?

Which of the following is the chemical formula of common salt?