Question

Which stage of cellular respiration produces the most ATP? Explain.

Explain why skeletal muscle is voluntary and cardiac muscle and smooth muscle are involuntary

Answer 1

Cellular respiration is the process in which cells break down glucose, release the stored energy, and use it to make ATP. The process begins in the cytoplasm and is completed in a mitochondrion. Cellular respiration occurs in three stages: glycolysis, the Krebs cycle, and electron transport.

The electron transport chain of the cellular respiration process produces maximum ATP.

Here is the breakdown of net ATP production:

• Glycolysis: 2 ATP.
• Krebs Cycle: 2 ATP.
• Oxidative Phosphorylation (Electron Transport Chain/Chemiosmosis): 28 ATP.

Skeletal Muscles

The skeletal muscle is attached to the bones and its contraction makes locomotion, facial expressions, posture and other voluntary movements of the body possible. Forty percent of our body mass is made up of skeletal muscles. Skeletal muscles generate heat as a by-product of their contraction and thus participate in thermal homeostasis. The chill is an involuntary contraction of the skeletal muscles in response to a perceived lower than normal body temperature. Skeletal muscle tissue is organized into bundles surrounded by connective tissue. Under the light microscope, the muscle cells appear to be striated with numerous nuclei tight along the membranes. The striation is due to the regular alternation of the contractile proteins actin and myosin, as well as structural proteins which couple the contractile proteins to the connective tissues. The cells are multinucleated as a result of the fusion of the numerous myoblasts which merge to form each long muscle fiber.

Smooth Muscle:- The contraction of smooth muscle tissue is responsible for involuntary movements in the internal organs. It constitutes the contractile component of the digestive, urinary and reproductive systems as well as the respiratory tract and arteries. Each cell is spindle shaped with a single nucleus and no visible striations.

Cardiac muscle is also an involuntary muscle, found only in the heart.The heart muscle forms the contractile walls of the heart. The cells of the heart muscle, called cardiomyocytes, also appear striated under the microscope. Unlike skeletal muscle fibers, cardiomyocytes are single cells with usually a single nucleus located in the center. A main characteristic of cardiomyocytes is that they contract on their own intrinsic rhythms without any external stimulation. Cardiomyocytes attach to each other with specialized cell junctions called interleaved discs. Interleaved discs have both anchor junctions and spacing junctions. The attached cells form long branched cardiac muscle fibers which are essentially a mechanical and electrochemical syncytium allowing the cells to synchronize their actions. The heart muscle pumps blood through the body and is under involuntary control. Attachment junctions hold adjacent cells together through changes in dynamic pressures in the heart cycle.