Creatine kinase is found predominantly in which tissues?

Creatine kinase is found predominantly in which tissues?

• A. Skeletal and cardiac muscles and brain
• B. Liver and kidneys
• C. Skin and muscle
• D. Lungs

Answer: (A)

Creatine kinase is central to the phosphocreatine energy shuttle, rapidly regenerating ATP in cells that have high and fluctuating energy demands. Because of this, the enzyme is most abundant in tissues with persistent, intense energy use: skeletal muscle, cardiac muscle, and the brain. In clinical contexts, different CK isoforms reflect this distribution (CK-MM in muscle, CK-MB in heart, CK-BB in brain), which is why the tissues listed—skeletal muscle, heart, and brain—best fit the question. Other organs like liver and kidneys, skin, or lungs have much lower CK activity and are not the primary sources of the enzyme.

Creatine kinase is central to the phosphocreatine energy shuttle, rapidly regenerating ATP in cells that have high and fluctuating energy demands. Because of this, the enzyme is most abundant in tissues with persistent, intense energy use: skeletal muscle, cardiac muscle, and the brain. In clinical contexts, different CK isoforms reflect this distribution (CK-MM in muscle, CK-MB in heart, CK-BB in brain), which is why the tissues listed—skeletal muscle, heart, and brain—best fit the question. Other organs like liver and kidneys, skin, or lungs have much lower CK activity and are not the primary sources of the enzyme.