What prevents backflow of blood inside the heart during contraction?

Which of the following is most appropriate for aerobic respiration?

After a vigorous exercise,you may experience cramps in your leg muscles. Why does this happen?

Represent the equation of photosynthesis. Explain the steps involved in photosynthesis. In which way are the steps of photosynthesis different in desert plants?

Assume that you are a veterinary surgeon and you have removed a significant length of the small intestine of a bear suffering from an intestinal tumour. After its recovery,would you suggest a plant-based or a meat-based diet for the bear? Provide a reason for your answer.

Explain the three pathways of breakdown of glucose in living organisms.