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Multiple Choice
Which of the following statements is true regarding active transport and facilitated diffusion?
A
Both processes involve the movement of water molecules across the cell membrane.
B
Active transport requires energy, while facilitated diffusion does not.
C
Facilitated diffusion requires ATP, whereas active transport does not.
D
Both active transport and facilitated diffusion move substances against their concentration gradient.
Verified step by step guidance
1
Understand the definitions: Active transport is the movement of molecules across a cell membrane from a region of lower concentration to a region of higher concentration, using energy in the form of ATP. Facilitated diffusion is the passive movement of molecules across the cell membrane via specific transmembrane integral proteins, without the use of energy.
Identify the role of energy: Active transport requires energy because it moves substances against their concentration gradient. Facilitated diffusion does not require energy as it moves substances down their concentration gradient.
Analyze the movement direction: In active transport, substances move against their concentration gradient (from low to high concentration), whereas in facilitated diffusion, substances move along their concentration gradient (from high to low concentration).
Consider the involvement of proteins: Both processes involve proteins. Active transport uses carrier proteins that change shape to move molecules, while facilitated diffusion uses channel or carrier proteins to assist the passive movement of molecules.
Evaluate the statements: Based on the definitions and characteristics, the true statement is that active transport requires energy, while facilitated diffusion does not.