Advanced Placement (AP) Biology Practice Exam

Disable ads (and more) with a membership for a one time $2.99 payment

Prepare for the AP Biology Exam with engaging quizzes. Test your knowledge with multiple-choice questions, complete with detailed explanations. Elevate your exam readiness!

Practice this question and more.

What is the purpose of energy coupling in biological systems?

To create more heat
To save energy by coupling exergonic and endergonic reactions
To produce energy from light
To eliminate waste products

The correct answer is: To save energy by coupling exergonic and endergonic reactions

Energy coupling in biological systems refers to the process where the energy released from an exergonic reaction (which occurs spontaneously and releases energy) is used to drive an endergonic reaction (which requires energy input to occur). This mechanism is crucial because it allows cells to perform necessary functions and maintain order without violating the laws of thermodynamics. The synergy between these types of reactions enables organisms to transform energy from one form to another efficiently. For example, in cellular respiration, the breakdown of glucose releases energy that can be used to phosphorylate ADP to ATP. The ATP produced can then be utilized in various cellular processes that require energy, such as muscle contraction, active transport, and biosynthesis. By coupling these reactions, biological systems conserve energy by making it available in a usable form rather than letting it dissipate as heat or waste. This highlights the efficiency and sophistication of metabolic pathways, allowing living organisms to thrive in various environments while maximizing their energy resources.