Question

Sterols are classified as a. sugars. b. amino acids. c. nucleotides. d. lipids.

Short answer

d. lipids.

Step-by-step solution

- Understanding the Definitions

First, review the definitions of sugars, amino acids, nucleotides, and lipids. Sugars are carbohydrates, amino acids are the building blocks of proteins, nucleotides are the building blocks of nucleic acids (DNA and RNA), and lipids are a diverse group of hydrophobic molecules.

- Define Sterols

Sterols are a subgroup of steroids and are important components of cell membranes in plants and animals. A well-known example is cholesterol.

- Classify Sterols

Identify which of the groups sterols best fit into. Since sterols are hydrophobic and part of cell membranes (similar to other lipids like fats), they do not fit into the categories of sugars, amino acids, or nucleotides.

- Choose the Correct Option

Given that sterols are hydrophobic molecules that are crucial components of cell membranes, the correct classification for sterols is lipids.

Key concepts

lipids

Lipids are a broad group of naturally occurring molecules that include fats, oils, waxes, and sterols. They are characterized by their hydrophobic nature. This means they do not mix well with water. Lipids play several crucial roles in organisms.
They are important for energy storage, as they store more energy compared to carbohydrates.
They are also vital components of cell membranes, which protect and organize cells.
Additionally, lipids act as signaling molecules in various biological processes.

cell membranes

Cell membranes are the outer layer that surrounds cells in all living organisms. They act as a barrier that protects the cell's interior from the outside environment.
The primary structure of the cell membrane is a lipid bilayer, consisting of two layers of lipid molecules.
This bilayer is semi-permeable, allowing certain molecules to pass through while blocking others.
Apart from lipids, cell membranes also contain proteins that assist in various processes such as transport, signaling, and structural support.

steroids

Steroids are a type of organic compound that includes many important substances like hormones and vitamins. They have a core structure of four fused carbon rings. Sterols, such as cholesterol, are a subgroup of steroids.
Steroids play diverse roles in the body including:
- Acting as signaling molecules (hormones) like estrogen and testosterone.
- Contributing to the structure of cell membranes, where sterols like cholesterol are essential.
- Influencing metabolism, immune function, and the development of sexual characteristics.

cholesterol

Cholesterol is one of the most well-known sterols and an important molecule in the body. It is a type of lipid found in animal cell membranes. Cholesterol helps maintain the fluidity and integrity of cell membranes.
It serves as a precursor for the synthesis of other important steroids, including hormones like cortisol and sex hormones.
While cholesterol is vital for health, high levels of cholesterol in the blood can lead to cardiovascular diseases.
Thus, maintaining a balance is crucial for overall health.