Biology Passive Transport Quiz

Passive Transport

• Passive transport occurs without energy expenditure from the cell.
• Includes simple diffusion and facilitated transport.
• Active transport requires energy and features primary and secondary active transport.

Simple Diffusion

• Involves the movement of molecules driven by random thermal motion.
• The direction of net flux is determined by concentration gradients.
• Achieves diffusion equilibrium with equal movement in both directions.
• No carrier proteins are needed; molecules must be permeable to the lipid bilayer (examples: fatty acids, gases, steroids).

Facilitated Diffusion

• Requires membrane proteins for transport.
• Involves ion channels that allow ions to cross the lipid bilayer, often gated by factors like ligands or voltage.
• Carrier-mediated facilitated diffusion transports molecules from high to low concentrations, requiring specific binding and conformational changes of the carrier protein.

GLUT Transporters

• Classic example of carrier-mediated transport, specifically for glucose.
• The operation of transporters can change depending on intracellular glucose concentration.

Osmosis

• Described as the passive diffusion of water across a selectively permeable membrane.
• Aquaporin channels enhance water movement as they facilitate the transport of polar molecules.
• Movement of water is influenced by the number of osmotically active particles present, following the concentration gradient.

Osmolarity

• Refers to the concentration of osmotically active particles in a solution, calculated as Osm/L.
• Formula: Posm = n * C * RT, where 'n' is the number of particles, and 'C' is concentration.
• Example: 150 mM NaCl represents 2 Osm due to ion dissociation.

Osmotic Pressure

• Net water movement is dictated solely by the concentration of impermeable solutes.
• Impermeable solutes contribute to osmotic pressure, whereas permeable solutes do not.
• Osmotic pressure formula: π = φ n * C * RT, where φ is the permeability factor (0 for permeable, closer to 1 for impermeable solutes).

Test your understanding of passive transport mechanisms in cells, including simple and facilitated diffusion. Explore how molecules move across the membrane without energy expenditure and the roles of various transport proteins. Suitable for biology students wanting to deepen their knowledge of cell transport processes.