Biology: Cell Transport

Water moves from an area of higher water concentration (90%) to an area of lower water concentration (80%) via osmosis. Therefore, water will move into the cell.

Endocytosis is a form of active transport because it requires energy (ATP) to move large particles into the cell by engulfing them in a vesicle. Diffusion, facilitated diffusion, and osmosis are all passive processes.

Binding of a signal molecule to a receptor can trigger various cellular responses, including activation of second messengers, changes in membrane permeability, and alteration of enzyme activity.

The sodium-potassium pump is an active transport mechanism that moves sodium ions out of the cell and potassium ions into the cell. It uses ATP to maintain the electrochemical gradient across the plasma membrane.

Facilitated diffusion is a form of passive transport where molecules move down their concentration gradient using specific membrane proteins. It does not require ATP.

Exocytosis is the process by which cells move materials from within the cell into the extracellular fluid. It is commonly used to export waste products or secrete proteins.

When a cell is placed in a hypotonic solution, water moves into the cell due to osmosis. This influx of water causes the cell to swell and potentially burst.

The sodium-potassium pump requires energy (ATP) to move ions against their concentration gradients. The other options describe passive processes that move molecules with the gradient.

In an isotonic solution, the solute concentration is equal inside and outside the cell. Therefore, there is no net movement of water.

In a hypotonic solution, the solute concentration outside the cell is lower than inside. Water moves into the cell to balance the concentration.

Osmosis is specifically defined as the diffusion of water across a semipermeable membrane. Diffusion is a more general term for the movement of any particles.

In a hypertonic solution, the solute concentration outside the cell is higher than inside. Water leaves the cell, causing it to shrivel.

Sugar molecules (like glucose) are large and polar, requiring transport proteins to cross the membrane via facilitated diffusion. Water uses aquaporins (often considered separate from facilitated diffusion in some contexts), and ions typically use channels.

Active transport is the movement of substances against their concentration gradient, which requires the expenditure of energy in the form of ATP.