[Campbell Biology P.13] The 'MAKE CONNECTIONS' prompt at the end of the text asks to explai... | Practice Question

The 'MAKE CONNECTIONS' prompt at the end of the text asks to explain why ion movement across the plasma membrane is described as an electrochemical gradient. Which of the following best defines an electrochemical gradient in this context?

  • A: It refers to the combined effect of a concentration (chemical) gradient and an electrical potential difference across the membrane.
  • B: It describes the movement of electrons and ions simultaneously across the membrane.
  • C: It represents the potential energy stored solely due to the difference in ion concentration.
  • D: It indicates that ions move across the membrane only when a chemical reaction occurs.

Explanation

An electrochemical gradient is defined as the combination of a chemical force due to the concentration difference of an ion across a membrane and an electrical force due to the membrane potential, which is the charge difference across the membrane . Both forces influence the net movement of ions.