In which of the following are lipids commonly found?

• A. Mitochondrial matrix
• B. Cell membranes
• C. DNA double helix
• D. Ribosomes

Answer: (B)

Verified step by step guidance

1. Step 1: Begin by understanding the structure and function of lipids. Lipids are a diverse group of hydrophobic molecules, including fats, oils, phospholipids, and steroids. They play key roles in energy storage, signaling, and forming structural components of cells.
2. Step 2: Review the composition of cell membranes. Cell membranes are primarily composed of a phospholipid bilayer, which provides structural integrity and regulates the movement of substances in and out of the cell. Lipids are essential for this bilayer structure.
3. Step 3: Examine the mitochondrial matrix. The mitochondrial matrix is the innermost compartment of mitochondria, containing enzymes for the citric acid cycle and mitochondrial DNA. Lipids are not commonly found here as structural components.
4. Step 4: Consider the DNA double helix. DNA is composed of nucleotides, which include a sugar, phosphate group, and nitrogenous base. Lipids are not part of the DNA structure.
5. Step 5: Analyze ribosomes. Ribosomes are composed of ribosomal RNA (rRNA) and proteins, and they function in protein synthesis. Lipids are not a structural component of ribosomes. Therefore, lipids are most commonly found in cell membranes.