Blood flows through blood vessels, which form the closed system called the circulatory system. Like a system of roads, the circulatory system has its highways, back roads, and alleyways, which we call arteries, veins, and capillaries
Capillaries are the alleyways that extend and branch into every tissue of your body, ensuring that every cell has a blood supply. It is here, in the capillary beds, that your cells pick up oxygen and nutrients and drop off carbon dioxide and wastes
Muscles are composed of two major protein filaments: a thick filament composed of the protein myosin and a thin filament composed of the protein actin. Muscle contraction occurs when these filaments slide over one another in a series of repetitive events
All muscles contract as a result of interaction between special proteins within the myocytes. Skeletal, cardiac, and smooth muscle cells synthesize the contractile proteins actin and myosin, which are needed for muscular contraction
When DNA ligase has compelted its job catalyzing the formation of a phosphodiester bond to bring together the backbone of two separate DNA strands and bind them together, the result is that two separate strands of DNA become one.
