Bioenergetics - Free MCQ Practice Test with solutions, MCAT General Chemistry

Adenosine triphosphate (ATP) is the primary energy currency of cells. It stores and releases energy during cellular processes, such as metabolism, by undergoing hydrolysis to form adenosine diphosphate (ADP) and inorganic phosphate (Pi). This release of energy powers various cellular activities.

Oxygen serves as the final electron acceptor in the electron transport chain during cellular respiration. Electrons are transferred along the chain, and oxygen accepts these electrons, forming water as a byproduct. This process is essential for generating ATP through oxidative phosphorylation.

Aerobic cellular respiration is the process by which cells convert glucose (C₆H₁₂O₆) and oxygen (O₂) into carbon dioxide (CO₂), water (H₂O), and ATP. This reaction occurs in multiple steps, including glycolysis, the Krebs cycle, and oxidative phosphorylation.

Chlorophyll a is the primary pigment involved in capturing light energy during photosynthesis. It is responsible for absorbing light in the red and blue regions of the electromagnetic spectrum. Other pigments, such as chlorophyll b and various carotenoids, assist in capturing light energy and transferring it to chlorophyll a.

The thylakoid membrane is the site of the light-dependent reactions during photosynthesis. These reactions involve the capture of light energy by pigments, the splitting of water molecules, the generation of ATP and NADPH, and the release of oxygen as a byproduct. The light-independent reactions, or Calvin cycle, occur in the stroma of the chloroplast.

The primary function of the citric acid cycle, also known as the Krebs cycle, is the oxidation of acetyl-CoA. Acetyl-CoA enters the cycle and undergoes a series of reactions that result in the release of carbon dioxide, the generation of NADH and FADH2, and the production of ATP through substrate-level phosphorylation.

An endergonic reaction requires an input of energy to proceed. Photosynthesis is an example of an endergonic process because it requires light energy to convert carbon dioxide and water into glucose and oxygen. In contrast, cellular respiration and ATP hydrolysis are exergonic reactions that release energy.

Amylase is the enzyme responsible for breaking down carbohydrates in the digestive system. It catalyzes the hydrolysis of starch and glycogen into smaller sugar molecules, such as maltose and glucose. Lipase breaks down lipids, protease digests proteins, and nuclease cleaves nucleic acids.

Glycolysis is the initial stage of cellular respiration and occurs in the cytoplasm. It yields a net production of 2 ATP molecules per glucose molecule. Although four ATP molecules are formed during glycolysis, two ATP molecules are consumed in the process, resulting in a net gain of 2 ATP molecules.

Anabolic processes involve the synthesis of complex molecules from simpler precursors, requiring an input of energy. DNA replication is an example of an anabolic process as it involves the synthesis of a new DNA strand from existing DNA templates. Protein degradation, glycolysis, and cellular respiration are catabolic processes that involve the breakdown of molecules to release energy.