Cell Membrane Composition and Fluidity Quiz

Cell Membranes

• The plasma membrane is distinct from internal membranes in a cell due to its selective permeability and ability to regulate the exchange of materials with the external environment.

Transport Mechanisms

• Carrier proteins use ATP energy to move molecules against their concentration gradient, a process known as active transport.
• Ligand-gated channels respond to specific molecules (ligands) to facilitate transport across the membrane.

Membrane Composition

• All biological membranes have a common composition featuring a phospholipid bilayer with hydrophilic heads and hydrophobic tails.
• The fluidity of a membrane is directly impacted by temperature, with increased temperature leading to increased fluidity.

Osmosis and Solutes

• Osmosis refers specifically to the movement of water across a semi-permeable membrane.
• A hypertonic solution has a higher solute concentration, leading to water moving out of a cell.

Lipid Components and Rafts

• Cholesterol is enriched in rafts within a membrane, contributing to membrane fluidity and structure.
• Cholesterol helps maintain membrane fluidity by interacting with both hydrophilic and hydrophobic regions.

Protein Structure and Function

• A single amino acid change can alter protein shape due to changes in hydrophobic and hydrophilic interactions.
• Integral proteins (20-30% of encoded proteins) have both hydrophobic and hydrophilic regions, allowing them to span the membrane.

Lipid Types and Functions

• Phospholipids, characterized by a glycerol backbone and phosphate group, are essential for membrane structure.
• Glycolipids, prominent in the nervous system, function as cell surface receptors and in cell-cell interactions.
• Sphingolipids, less common in cell membranes, contain longer, highly saturated fatty acyl chains.