Question

Which intracellular compartment in skeletal muscle is loaded with mitochondria?

a) Nucleus
b) Sarcoplasmic reticulum
c) T tubule
d) Myofibril

Answer 1

Mitochondria in skeletal muscle cells are abundantly found in the sarcoplasm, not in the nucleus, sarcoplasmic reticulum, T tubules, or myofibrils. The sarcoplasmic reticulum stores Ca²+ ions. Cardiac muscle cells also have a high concentration of mitochondria and this is unique to them among muscle cell types.

Step-by-step explanation:

The intracellular compartment in skeletal muscle that is loaded with mitochondria is none of the options provided (nucleus, sarcoplasmic reticulum, T tubule, or myofibril). However, mitochondria are abundant in the sarcoplasm, which is the cytoplasm of the muscle cell. When it comes to the question about where the Ca²+ ions are stored, the correct answer is d. sarcoplasmic reticulum. This specialized endoplasmic reticulum in muscle cells is responsible for storing calcium ions and releasing them during muscle contraction. Additionally, it is important to note that mitochondria and nuclei are not structures that are exclusive to either eukaryotic or prokaryotic cells, as prokaryotic cells do not have mitochondria. The unique feature of cardiac muscle cells is that they have a high concentration of mitochondria, as stated in answer option d. Lastly, fast muscle fibers, according to one of the statements provided, have many mitochondria as well.

Answer 2

Mitochondria in skeletal muscle are dispersed throughout the sarcoplasm, not specifically in the nucleus, sarcoplasmic reticulum, T tubule, or myofibril. The sarcoplasmic reticulum is mainly responsible for calcium ion storage, which is crucial for muscle contraction. Cardiac muscle cells are also noted for their high concentration of mitochondria.

Step-by-step explanation:

The intracellular compartment in skeletal muscle that is loaded with mitochondria is not the nucleus, sarcoplasmic reticulum, T tubule, or myofibril. Instead, mitochondria are dispersed throughout the muscle fiber, mostly concentrated near the sites where ATP is most needed, such as in the vicinity of the contractile elements of the muscle cells. Typically, mitochondria would be distributed throughout the sarcoplasm, which is the cytoplasm of muscle cells. However, the sarcoplasmic reticulum is specialized for storing calcium ions (Ca²⁺). This is important in muscle fiber contraction and relaxation as the release of calcium ions from the sarcoplasmic reticulum is a key step in the excitation-contraction coupling process.

Furthermore, it is worth noting that cardiac muscle cells have a high concentration of mitochondria to meet the high energy demands of the heart. While all muscle cells contain mitochondria, the utility of mitochondria in various muscle cell types relates directly to their function and energy needs.