Active transport enables cells to move substances across the plasma membrane using energy, often from ATP. This lesson introduces the gradients that influence ion movement, explains why cells sometimes need to move substances against those gradients, and distinguishes the main types of transport proteins.
A concentration gradient is a difference in the concentration of a substance between two regions. Substances tend to move down their concentration gradient, from higher concentration to lower concentration, when a pathway across the membrane is available.
All flashcards
What is an electrochemical gradient?
It is the combined influence of a concentration difference and an electrical charge difference on the movement of an ion across a membrane.
How do primary and secondary active transport differ?
Primary active transport uses ATP directly. Secondary active transport uses energy stored in an electrochemical gradient, usually created by primary active transport, rather than directly using ATP at its transport step.
What does a uniporter carry?
A uniporter carries one specific type of ion or molecule across a membrane.
How does a symporter differ from an antiporter?
A symporter carries two different substances in the same direction; an antiporter carries two different substances in opposite directions.
Why can active transport be affected by metabolic poisons?
Many active transport mechanisms depend on ATP, so poisons that interfere with metabolism or ATP production can reduce the energy available for transport.
Quiz questions
What two factors combine to form an ion's electrochemical gradient?Answer: The ion's concentration gradient and the electrical gradient across the membrane.
Why do sodium ions tend to move into many living cells?Answer: They are more concentrated outside, and the negatively charged cell interior attracts them.
What defines primary active transport?Answer: It uses ATP directly to move substances across a membrane.
A transporter moves two different substances in the same direction. What type is it?Answer: A symporter.
In many cells, how do the concentration and electrical gradients affect potassium ions?Answer: The concentration gradient tends to drive them out, while the electrical gradient tends to draw them in.
Based on Biology 2e by Mary Ann Clark, Matthew Douglas, Jung Choi (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.