The biological membranes are composed of:

Question

The biological membranes are composed of:

1. A. Lipids and proteins in varying combinations which are specific to each species, cell type and organelle (Correct answer)
2. B. Lipids only
3. C. Proteins only
4. D. None of the above

Correct Answer

Option A — Lipids and proteins in varying combinations which are specific to each species, cell type and organelle

Detailed Solution & Explanation

The correct answer is Lipids and proteins in varying combinations which are specific to each species, cell type and organelle.

Key Points

• Biological membranes are composed of lipids and proteins in varying proportions, and these proportions differ between species, between cell types, and even between the different organelles of a single cell.
• The accepted model of membrane structure is the Fluid Mosaic Model, proposed by Singer and Nicolson in 1972.
• In this model, a phospholipid bilayer forms the basic fluid framework, with the hydrophilic phosphate heads facing outward towards the aqueous environment and the hydrophobic fatty acid tails facing inward. Proteins are embedded within this bilayer as integral (intrinsic) proteins that span the membrane, or attached at the surface as peripheral (extrinsic) proteins, forming a mosaic that can move laterally.
• Membranes also contain cholesterol, which regulates fluidity, and carbohydrates bound as glycolipids and glycoproteins that function in cell recognition.

Exam Tip

• the inner mitochondrial membrane is notably protein-rich because it carries the electron transport chain.

प्रश्न (हिन्दी में)

जैविक झिल्ली (Biological membranes) किससे बनी होती है?

1. A. लिपिड और प्रोटीन के विभिन्न संयोजन जो प्रत्येक प्रजाति, कोशिका प्रकार और अंग के लिए विशिष्ट होते हैं
2. B. केवल लिपिड
3. C. केवल प्रोटीन
4. D. उपरोक्त में से कोई नहीं