Transport Across Membranes

Flashcards covering key concepts about transport across membranes, osmosis, and the functioning of cells.

What is the function of a plasma membrane?

To separate and protect the chemical components of a cell from its surroundings.

What is osmosis?

The diffusion of free water across a selectively permeable membrane.

What molecules need to be transported across the membrane?

Ions, sugars, amino acids, nucleotides, and metabolites.

Why are lipid bilayers impermeable to ions and most large polar molecules?

Because the hydrophobic bilayer creates a barrier to most hydrophilic molecules.

What are the two types of transport across a membrane?

Passive transport (no energy required) and Active transport (requires energy).

What is facilitated diffusion?

The process that requires transport proteins to move substances across the membrane.

What happens in a hypertonic solution?

The cell loses water as the solute concentration outside is greater than inside the cell.

What happens in an isotonic solution?

There is no net water movement across the plasma membrane as solute concentrations are the same inside and outside the cell.

What role do aquaporins play in cells?

They facilitate the movement of water across cell membranes.

What is the primary function of the Na+-K+ pump?

To maintain a balance of sodium and potassium ions across the cell membrane.

What type of gradient does a cell maintain for sodium ions?

A chemical gradient, where sodium concentration is higher outside the cell.

What is the significance of active transport?

It helps maintain the appropriate composition of ions inside the cell, moving substances against their gradient.

What drives the Na+-K+ pump?

The hydrolysis of ATP to drive uphill transport.

How does the Na+-K+ pump cycle work?

It binds Na+ ions, is phosphorylated by ATP, releases Na+ outside, binds K+, and releases K+ inside.

What is tonicity?

The relative concentration of solutes dissolved in solution that determines the direction and extent of water movement.