Question

which process moves an ion across a cell membrane against the concentration gradient?
o active transport
o diffusion
o osmosis
o facilitated diffusion

Explanation:

• Active transport is the process that moves substances (including ions) across a cell membrane against their concentration gradient. This process requires energy (usually in the form of ATP).
• Diffusion is the movement of substances from an area of higher concentration to an area of lower concentration (down the concentration gradient) without the need for energy.
• Osmosis is the diffusion of water molecules across a semi - permeable membrane from an area of lower solute concentration (higher water concentration) to an area of higher solute concentration (lower water concentration) (down the concentration gradient of water).
• Facilitated diffusion is a type of passive transport (no energy required) where substances move across the membrane with the help of transport proteins, still moving down the concentration gradient.

Answer:

Active transport