Question

Which of the following would you not expect to find both in a skeletal muscle cell and a cardiac muscle cell?
A. Actin filaments
B. Myosin filaments
C. Potassium channels that close slowly after an action potential
D. Large number of mitochondria

Answer 1

Hint:
Skeletal muscles are those muscles that are present in the skeletal organs and are responsible for locomotory movement. They have striations and hence are called striated muscles. The activity is under the control of the voluntary part of the nervous system and is hence called voluntary muscles. Cardiac muscles are those muscles that are present in the heart. They are branched and based on their appearance they are striated. They are involuntary muscles.

Complete answer:
The cytoplasm of the muscle fiber is called the sarcoplasm which contains many parallelly arranged filaments called myofilaments or myofibrils. Each myofibril has a striated appearance due to the distribution of two important proteins:- actin and myosin. All three types of muscles:- skeletal, visceral, and cardiac possess actin and myosin. These proteins are important for muscle contraction. These proteins bind together to form cross-bridges and thus enable muscle contraction. The function of the potassium channel is to lower the excitability of the cell and stabilize it. Same cell may have different types of potassium channels and different cells may have the same type of potassium channels. These potassium channels are found in both skeletal as well as cardiac muscles. Cardiac muscles require more energy as they are more dependent on aerobic respiration than skeletal muscles. As we know that mitochondria are the powerhouse of a cell that provides energy in the form of ATP molecules, cardiac muscles have more mitochondria than skeletal muscle.
Thus, the correct answer is large number of mitochondria.

Option ‘D’ is correct

Note:
Cardiac muscles contract for a longer period so as to maintain a visible heartbeat. Along with a greater period of muscular contraction, cardiac muscles do not become fatigued, unlike skeletal muscles.