Biological Membranes - BIOL 150

These flashcards cover key concepts and definitions from the lecture notes on biological membranes.

What is the function of transport proteins in cell membranes?

provide a selective passage for substances across the membrane by forming hydrophilic channels or changing shape.

Describe enzymatic activity in relation to cell membranes.

involves membrane proteins that act as enzymes with active sites exposed to the environment, organizing into enzyme teams for metabolic pathways.

What is signal transduction in cell membranes?

involves membrane proteins that act as receptors, binding specific chemical messengers and relaying messages to the inside of the cell.

What is the difference between cell-cell recognition and intercellular joining?

Cell-cell recognition involves short-lived binding between glycoproteins of different cells, while intercellular joining is a more stable bonding of membrane proteins in junctions.

What are the two layers of the phospholipid bilayer composed of?

hydrophilic 'heads' and hydrophobic fatty acid 'tails'.

What role do integral membrane proteins play in a cell?

connect the cell to its extracellular environment and may have various shapes and structures.

What are the main transport mechanisms for molecules across cell membranes?

simple diffusion, facilitated diffusion, and active transport (primary or secondary).

Define simple diffusion.

movement of molecules from a region of high concentration to low concentration due to their kinetic energy.

What is osmosis?

movement of water across a selectively permeable membrane from a lower solute concentration to a higher solute concentration.

Explain the difference between primary and secondary active transport.

Primary active transport requires ATP directly to move substances against their concentration gradient, while secondary active transport relies on the concentration gradient established by primary transport.

What is the role of the sodium-potassium pump?

actively transports sodium out of and potassium into the cell against their electrochemical gradients, requiring ATP.

Define cotransporter in the context of active transport.

a protein that moves two substances simultaneously; a symporter moves them in the same direction, and an antiporter moves them in opposite directions.

What happens to Na+ and Cl- ions in relation to a semipermeable membrane?

cannot cross the semipermeable membrane, causing a net movement of water instead.

When does membrane transport require energy?

requires energy when a solute is moved against its electrochemical gradient.

What is facilitated diffusion?

 the movement of molecules across a membrane via a channel or carrier protein, moving from high to low concentration.

What conditions influence the direction of water movement in osmosis?

influenced by the solute concentrations on either side of the semipermeable membrane.