Proteins are made of amino acids. what elements make up amino acids? look up the structures of the 20 amino acids in your textbook and list the 5 elements present.

What are some possible short and long term medical concerns for crew members on longer space exploration trips

Which of the following is not a symptom of desertification? a) decrease in salt content of the soil b) lowering of the water table c) reduced surface water d) increased soil erosion e) loss of native vegetation

All but one describes an effect of aging on the digestive system. a) decreased acid secretion b) decreased elasticity of stomach c) capacity to resist damage decreases d) food remains in stomach for less time