A ring of actin filaments contract to form a ________ that pinches the two daughter cells apart.

A. skeletal MT:Skeletal muscle tissue is under voluntary control and is not found in the walls of the uterus. It is primarily responsible for movements of the skeleton rather than involuntary contractions needed for labor.

B. smooth MT:Smooth muscle tissue makes up the bulk of the uterine wall (myometrium) and is responsible for powerful, rhythmic contractions during labor. These contractions are involuntary and essential for expelling the fetus.

C. stratified squamous ET:Stratified squamous epithelium is a protective tissue commonly found in areas exposed to friction, such as the skin and vaginal canal. It does not contribute to the contractile activity of the uterus.

D. elastic cartilage CT:Elastic cartilage provides flexibility and support in structures like the ear and epiglottis. It has no role in uterine structure or the generation of contractions during labor.

A. Electron transport chain/oxidative phosphorylation:This stage of cellular respiration produces the majority of ATP, typically about 26–34 molecules per glucose. It relies on the transfer of electrons through protein complexes and the use of a proton gradient to drive ATP synthase activity.

B. oxidation reactions:Oxidation reactions remove electrons from molecules, often transferring them to NAD⁺ or FAD. While essential for energy extraction, these reactions alone do not directly generate large amounts of ATP.

C. substrate-level phosphorylation:This mechanism occurs during glycolysis and the Krebs cycle, producing ATP directly from enzyme-mediated reactions. However, it only accounts for a small fraction of ATP yield, about 2 ATP in glycolysis and 2 in the Krebs cycle.

D. lactic acid production:Lactic acid is formed in anaerobic respiration when pyruvate is reduced to lactate. This process regenerates NAD⁺ for glycolysis but yields no additional ATP beyond the small amount produced in glycolysis itself.