Proteins and Cell Membrane Transport

Protein Classification

• Peripheral proteins make up 10% of membrane proteins, while integral proteins make up 90%
• Integral proteins are transmembrane or in-wall, meaning they span across the membrane or are embedded in it

Transport Mechanisms

Passive Transport

• Occurs along the concentration gradient, requiring no energy
• Examples include passive diffusion, where molecules move from an area of higher concentration to an area of lower concentration

Facilitated Diffusion

• Involves the use of channel proteins or carrier proteins to facilitate transport
• Channel proteins form a pore or channel in the membrane, allowing specific molecules to pass through
• Examples include porin proteins

Active Transport

• Transport occurs against the concentration gradient, requiring energy consumption
• Examples include the Na+ pump, which transports sodium ions into the cell against their concentration gradient

Osmosis

• Movement of water molecules from an area of higher concentration to an area of lower concentration
• Occurs through a selectively permeable membrane, allowing polar molecules like water to pass through

Plasma Membrane

• Discovered by Singer and Nicolson in 1972
• Labeling proteins on the membrane surface confirms the fluid mosaic model, where proteins are able to move laterally but do not flip-flop across the membrane

Glycoproteins and Cell Recognition

• Glycoproteins, or sugar-proteins, are important for cell-to-cell recognition
• They provide mobility and flexibility to the cell surface, allowing for interactions with other cells

This quiz covers the types of proteins and their roles in cell membrane transport, including peripheral and integral proteins, passive and active transport, facilitated diffusion, and osmosis.