So how do we know that we are purifying our protein mixture following some type of technique? So in biochemistry, we actually developed five different types of quantities and these five different types of quantities can be measured following that purification procedure. And we can compare those quantities to before and basically they can tell us whether or not our procedure is actually working in purifying that protein mixture. So let's discuss what these five quantities are. We have the total protein. We have the enzyme activity, also known as the total activity.