Definition

Noun: - The movement of molecules or ions across a cell membrane from a region of lower concentration to a region of higher concentration: This process requires the cell to expend energy, typically in the form of ATP (adenosine triphosphate), to work against the natural concentration gradient.

Usage

• General Scientific Context: The term is used primarily in biology, biochemistry, and cellular physiology to describe a fundamental cellular process.
• Key Feature: It is defined by its requirement for energy input and its movement against a concentration gradient, distinguishing it from passive transport.

Examples

• Noun:
  • Sodium-potassium pumps are a classic example of active transport in animal cells.
  • Root hair cells use active transport to absorb mineral ions from the soil.
  • The process of active transport is essential for maintaining cellular homeostasis.

Advanced Usage

• "Primary active transport": Directly uses metabolic energy (e.g., ATP hydrolysis) to pump molecules against their gradient.
  • The proton pump in plant cells is a form of primary active transport.
• "Secondary active transport": Uses the energy stored in an electrochemical gradient (created by primary active transport) to move another substance against its gradient.
  • The absorption of glucose in the intestines often occurs via secondary active transport coupled with sodium ions.

Variants and Related Words

• Active transporter (n): A protein that facilitates active transport.
  • The protein acting as an active transporter undergoes a conformational change.
• Actively transport (v): The verb form describing the action.
  • This cell must actively transport calcium ions out of its cytoplasm.

Synonyms

• Energy-dependent transport: Emphasizes the requirement for cellular energy.
• Uphill transport: A descriptive synonym highlighting movement against a concentration gradient.

Related Phrases

• "Against the concentration gradient": A key descriptive phrase integral to the definition of active transport.
  • Moving ions against the concentration gradient is a hallmark of active transport.
• "Requires ATP": A common explanatory phrase noting the energy source.
  • This form of active transport requires ATP to function.

Noun

1. transport of a substance (as a protein or drug) across a cell membrane against the concentration gradient; requires an expenditure of energy