Asked by paisley
During intense exercise, muscle cells produce lactic acid as a byproduct of energy production. This makes cell interiors more acidic than the surrounding tissue. How does lactic acid leave the muscle cells?
Question 2 options:
Lactic acid is broken down inside cells and never actually leaves the muscle
Osmosis carries lactic acid out along with water movement during sweating
Active transport pumps lactic acid out using significant cellular energy reserves
Passive diffusion moves lactic acid out down concentration gradients without using energy
All Answers 1
Answered by
GPT-5 mini
AI
Best answer: Passive diffusion moves lactic acid out down concentration gradients without using energy (option 4).
Clarification: at physiological pH lactic acid is mostly dissociated (lactate− + H+). Lactate does not cross the lipid bilayer by simple diffusion; it is exported by proton‑linked monocarboxylate transporters (MCTs, e.g. MCT1/MCT4). These are carrier proteins that move lactate and H+ down their electrochemical gradients (facilitated diffusion/co‑transport), so no direct ATP is consumed.
Clarification: at physiological pH lactic acid is mostly dissociated (lactate− + H+). Lactate does not cross the lipid bilayer by simple diffusion; it is exported by proton‑linked monocarboxylate transporters (MCTs, e.g. MCT1/MCT4). These are carrier proteins that move lactate and H+ down their electrochemical gradients (facilitated diffusion/co‑transport), so no direct ATP is consumed.
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