Actin: example of contractile protein Introduction (classification criteria) Proteins can be classified according to the functions they perform in the body. Carrier proteins These are the proteins that carry molecules in and out of cells. They are plasma membrane proteins.
Demographic TransitionRecall from the Populations chapter that the population growth rate (r) equals the birth rate minus the death rate. Slowly declining birth rates following an earlier sharp decline in death rates are today characteristic of most of the less-developed regions of the world. The shift from high birth and death rates to low birth as well as death rates is called the demographic transition.