Skeletal muscle use the
**Core Concept**
The question is testing the student's knowledge of the energy sources used by skeletal muscle. Skeletal muscles are a type of striated muscle that are responsible for voluntary movements of the body. They require a continuous supply of energy to maintain their contraction and relaxation cycle.
**Why the Correct Answer is Right**
Skeletal muscles primarily use **creatine phosphate** as their immediate energy source, which is a high-energy compound that is rapidly depleted and replenished during muscle activity. Creatine phosphate donates a phosphate group to ADP to form ATP, which is then used to fuel muscle contraction. This process is facilitated by the enzyme **creatine kinase**. In addition to creatine phosphate, skeletal muscles also use **glycolysis** as a secondary energy source, where glucose is broken down to produce ATP.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because **lactic acid** is not a primary energy source used by skeletal muscles. While lactic acid can be produced as a byproduct of anaerobic glycolysis, it is not a direct energy source.
**Option B:** This option is incorrect because **fatty acids** are not a primary energy source used by skeletal muscles. While fatty acids can be used as an energy source by the liver and other tissues, they are not a preferred energy source for skeletal muscles.
**Option C:** This option is incorrect because **ketone bodies** are not a primary energy source used by skeletal muscles. While ketone bodies can be used as an energy source by the brain and other tissues, they are not a preferred energy source for skeletal muscles.
**Clinical Pearl / High-Yield Fact**
It's worth noting that during intense, short-duration activities, skeletal muscles can deplete their creatine phosphate stores, leading to a rapid increase in lactic acid production and a decrease in muscle performance.
**Correct Answer: C. Fatty acids are not the primary energy source, however, option C is not correct, it is actually D. Glycogen.**