Plasma Membrane Composition and Function

The ability of the phospholipid bilayer to move and change shape, allowing flexibility and transportation.

The degree of unsaturation in fatty acid chains directly affects membrane fluidity. Saturated fatty acids pack tightly, making the membrane less fluid, while unsaturated fatty acids with kinks create gaps, increasing fluidity.

Temperature plays a crucial role in membrane fluidity. Colder temperatures decrease fluidity, making the membrane more rigid. Conversely, warmer temperatures increase fluidity, making the membrane more flexible.

Sterols like cholesterol help maintain membrane fluidity by acting as stabilizers. They prevent excessive fluidity at high temperatures and prevent solidification at low temperatures.

A membrane protein that is fully embedded within the lipid bilayer, with both hydrophilic and hydrophobic regions.

A membrane protein that is loosely attached to the surface of the membrane, either on the inner or outer side.

A type of integral membrane protein that spans the entire lipid bilayer, with hydrophobic regions embedded within the membrane and hydrophilic regions exposed to the environment.

Membrane proteins that facilitate the movement of substances across the membrane, either through channels or by changing shape to carry specific molecules.

Phospholipids are a type of lipid that forms the structural basis of cell membranes. They have both a hydrophilic (water-loving) head and a hydrophobic (water-fearing) tail. This dual nature allows them to spontaneously self-assemble into a bilayer, with the hydrophilic heads facing the aqueous environment inside and outside the cell, while the hydrophobic tails are shielded from water, forming a barrier that regulates what enters and exits the cell.

The fluid mosaic model describes the structure of cell membranes as a fluid phospholipid bilayer with embedded proteins. The phospholipids are constantly moving, making the membrane fluid-like. The 'mosaic' part refers to the embedded proteins, which are diverse in function and can move laterally within the membrane.

The phospholipid bilayer is a thin, double-layered sheet that forms the structural basis of cell membranes. It consists of two layers of phospholipids, with their hydrophilic heads facing the aqueous environment inside and outside the cell, and their hydrophobic tails sandwiched in the middle.

In the fluid mosaic model, the term 'fluid' refers to the constant movement of phospholipids within the cell membrane. These movements include vibration, flexing, spinning, lateral movement, and flip-flopping between the bilayer's leaflets. Unlike phospholipids, proteins are larger and typically move much slower.

In the fluid mosaic model, 'Mosaic' refers to the diverse collection of proteins embedded within the phospholipid bilayer. These proteins have various functions, including transportation, enzymatic activity, and anchoring to cytoskeletal structures. Hence, the membrane resembles a mosaic tile design with different elements.

The cell membrane is asymmetrical, meaning that the two leaflets of the phospholipid bilayer differ in composition and function. Carbohydrates and glycolipids are associated primarily with the outer leaflet, while cytoskeleton components attach to proteins on the inner leaflet. This asymmetry is crucial for cellular signaling, transport, and recognition processes.

Glycoproteins are membrane components that have a carbohydrate attached to an amino acid. These sugar-protein complexes play crucial roles in cell-cell recognition, signaling, and immune responses.

Glycolipids are membrane lipids with a carbohydrate attached to them. These molecules primarily reside on the outer leaflet of the cell membrane and participate in cell-cell interactions, recognition, and signaling processes.