TeXes Science Practice Test 2026 - Free Science Exam Practice Questions and Study Guide

The type of respiration that is significantly less efficient than aerobic respiration is anaerobic respiration. This process occurs in environments where oxygen is absent or in low supply. Unlike aerobic respiration, which uses oxygen to break down glucose efficiently and produces a high yield of ATP (energy molecules), anaerobic respiration relies on alternative electron acceptors instead of oxygen.

This results in the incomplete breakdown of glucose and produces far fewer ATP molecules. For instance, while anaerobic respiration can lead to energy production, such as through fermentation, it typically produces only a fraction of the energy that aerobic respiration does. For example, fermentation processes yield only 2 ATP molecules per glucose molecule compared to the up to 38 ATP molecules generated via aerobic respiration under optimal conditions. Hence, anaerobic respiration is characterized by its lower efficiency in energy production.