Chapter 34, Problem 21A

Summary Introduction

Introduction:

Every cell in our body requires oxygen to function. The air we inhale is composed of 20 percent oxygen. The remaining of the air is mostly nitrogen (79%). Our body cells use the oxygen we breathe and we eat to get energy from the food. This method is known ascellular respiration. During cellular respiration, the cell utilizes oxygen to break down sugar. Breaking down sugar forms the energy our body requires.

Answer to Problem 21A

Correct answer:

The correct answer is option (D) oxygen.

Explanation of Solution

Explanation/justification for the correct answer:

Option (D) oxygen. During cellular respiration, the cell utilizes oxygen to break down sugar. Breaking down sugar forms the energy which our body requires. So, the correct answer is option (B).

Explanation for incorrect answer:

Option (A) sulfur. In anaerobic respiration still incorporates the respiratory electron transport chain, however without using oxygen as the terminal electron acceptor. Instead, molecules such as sulfate (SO₄^2-), nitrate (NO₃⁻), or sulfur (S) are utilized as electron acceptors. So, this is an incorrect answer.

Option (B) hydrogen. In cellular respiration, Oxygen is the last electron acceptor of theelectron transportchain in the last step of respiration in cells. Oxygen combines with electrons and hydrogen ions to formwater.So, this is an incorrect answer.

Option (C) carbon dioxide. When the cell uses oxygen to break down sugar, oxygen is utilized, carbon dioxide is formed, and energy is released out. So, this is an incorrect answer.