Biology STAAR (State of Texas Assessments of Academic Readiness) Practice Test

What is the main characteristic of smooth endoplasmic reticulum (ER)?

1. It has ribosomes attached

2. It synthesizes DNA

3. It makes lipids and detoxifies

4. It assists in cell division

The correct answer is: It makes lipids and detoxifies

The main characteristic of smooth endoplasmic reticulum (ER) is that it makes lipids and detoxifies. Smooth ER is a type of endoplasmic reticulum that lacks ribosomes on its surface, which distinguishes it from rough ER that has ribosomes and is primarily involved in protein synthesis. In addition to lipid synthesis, smooth ER plays a crucial role in detoxifying certain chemicals and metabolizing carbohydrates. This makes it essential for processes such as the synthesis of phospholipids, cholesterol, and steroid hormones, as well as detoxifying drugs and poisons in liver cells. The other characteristics mentioned in the options do not apply to smooth ER. For instance, the presence of ribosomes indicates rough ER, and synthesizing DNA is a function associated with the nucleus rather than the ER. Similarly, while the endoplasmic reticulum has roles in various cellular functions, it is not directly involved in assisting with cell division. Therefore, the ability of smooth ER to produce lipids and effectively detoxify substances is the defining feature that accurately characterizes it.