Why blood in pulmonary artery is voilet but in pulmonary vein is scarlet?

The blood in the pulmonary artery is violet because it is not oxygenated, while the blood carried by the pulmonary veins is oxygenated and its color is scarlet.

Explanation:

Under normal conditions, the arteries carry oxygenated blood, giving it a dazzling red or scarlet color, while the veins carry non-oxygenated blood —called venous blood— of a purplish and dark red color.

The only exceptions are the pulmonary arteries and veins

Pulmonary arteries carry non-oxygenated blood from the right ventricle to the lungs. They are the only arteries that carry non-oxygenated blood.Pulmonary veins carry oxygenated blood from the lungs to the left atrium, being the only veins to carry blood with oxygen.

This is why in the pulmonary arteries the blood is violet, and in the pulmonary veins the blood is scarlet.

Atp is is our little "pocket" of energy. of course, if you have too little, then it means you have too little energy, and you'll pass out. the way to not have enough, is to have no energy sources (glucose, fats, proteins). you can't have too many atp molecules. cycles like the krebs cycle produce it, but if you have too much of any substrate (or too little for that matter), the cycle stops and atp is no longer made (it stops until substrate levels are such that the process can go on). in any case, this is unlikely since atp is constantly hydrolyzed and remade, even while you're asleep. you won't have too much. if you have zero, you are dead or dying.