Plasma Membrane Structure - Function, and Fluid Mosaic Model

Plasma Membrane Structure: The plasma membrane, also known as the cell membrane, comprises a phospholipid bilayer interspersed with proteins. This bilayer consists of two layers of phospholipids with polar heads facing outward and non-polar tails facing inward, creating a barrier impermeable to water. The outer layer is rich in phosphatidylcholine, sphingomyelin, and glycolipids, while the inner layer contains phosphatidylethanolamine, phosphatidylserine, and phosphatidylinositol.

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What is Plasma Membrane?

Plasma Membrane Components

Mammary Glands

Plasma Membrane Structure

1. Lipids

Okazaki Fragments

2. Proteins

3. Carbohydrates

lymphocytes

4. Cholesterol

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Proportions in a Typical Human Cell

Free Study Material for NEET Preparation

Fluid Mosaic Model of Plasma Membrane

Fluid Mosaic Model

Gametes Types

Composition of the Plasma Membrane

Phospholipids

Plankton

Proteins

Carbohydrates

Role of Carbohydrates

Hypotonic Solution

Plasma Membrane Functions

• Passive transport: Passive transport doesn't require energy from the cell. Small, nonpolar molecules (like oxygen and carbon dioxide) and water can easily pass through the phospholipid bilayer. Ions and larger molecules require protein channels to move across the membrane. These channels act like specific doorways, allowing only certain molecules to pass.
• Active transport: Active transport utilizes cellular energy (ATP) to move molecules across the membrane against their concentration gradient (from low concentration to high concentration). Carrier proteins are responsible for active transport, binding to specific molecules and shuttling them across the membrane.

1. Enclosure and Insulation: Membranes protect cells and organelles mechanically and chemically, maintaining concentration differences between intracellular and extracellular compartments.
2. Regulated Transport: Membranes enable homeostasis by regulating the internal environment and selectively transporting substances through pores, channels, and transporters.
3. Signal Transduction: Membranes receive and transmit extracellular signals, producing cellular responses.
4. Enzymatic Catalysis: Membranes house important enzymes, facilitating reactions with apolar substrates like lipid biosynthesis and the metabolism of apolar xenobiotics.
5. Energy Conversion: Key energy conversion reactions like oxidative phosphorylation and photosynthesis occur in membranes.
6. Interactions with Other Cells: Membranes play roles in cell fusion, tissue formation, and communication with the extracellular matrix.
7. Anchoring of the Cytoskeleton: Membranes help maintain cell and organelle shape and provide a basis for movement processes.