**Core Concept:** A protein-to-lipid ratio is a measure of the proportion of proteins to lipids in a biological membrane. Membrane proteins facilitate various cellular functions, and understanding the ratio helps in identifying the organelle's role and structure.

**Why the Correct Answer is Right:** The correct answer is **D:** Mitochondria because the protein-to-lipid ratio on a weight basis is 1:1 in the mitochondrial membrane. This ratio is essential for the proper functioning of the membrane proteins involved in oxidative phosphorylation, the process that generates adenosine triphosphate (ATP) for cellular energy production.

**Why Each Wrong Option is Incorrect:**

**Option A:** Plasma membrane has a higher protein-to-lipid ratio (approximately 1:5). This is due to the presence of various membrane proteins involved in cell signaling, transport, and immune response.

**Option B:** Lysosomes have a lower protein-to-lipid ratio (approximately 1:20). This is because lysosomes primarily contain hydrolases and other enzymes for cellular digestion and waste disposal.

**Option C:** Ribosomes have a lower protein-to-lipid ratio (approximately 1:20). Ribosomes are sites for protein synthesis, so they have fewer membrane proteins for this process.

**Option D:** Mitochondria have a 1:1 protein-to-lipid ratio. This is essential for the proper functioning of membrane proteins involved in oxidative phosphorylation, which generates ATP for cellular energy production.

**Clinical Pearl:** The protein-to-lipid ratio in cellular membranes can provide valuable information about the organelle's function and the types of membrane proteins it contains. This information is useful for understanding cellular processes and knowing when to expect specific proteins in a cellular membrane.

**Correct Answer:** **D:** Mitochondria