Final answer:
The elemental composition of the human body refers to the various elements present and their relative abundances, whereas the molecular composition pertains to how these elements combine to form molecules, which are the chemical building blocks of all body structures.
Step-by-step explanation:
The human body consists of various elements and molecules. The elemental composition refers to the relative abundance of elements in the body. For example, oxygen is the most abundant element in both the human body and on Earth. The body contains 31 elements divided into essential and non-essential. Essential elements are required for the organism to survive, grow, and reproduce. These include carbon (C), hydrogen (H), oxygen (O), and nitrogen (N), which comprise about 98% of our body mass and are considered macronutrients due to their high concentration. The molecular composition, on the other hand, deals with how these elements are combined to form molecules. Molecules are unions of two or more atoms that display specific chemical and physical properties. These molecular structures, and how they are aligned with each other, establish the living state. In the human body, millions of chemical compounds are formed from the different combinations of elements, such as water molecules, proteins, and sugars, which are fundamental for life's processes. Overall, while elemental composition lists out the basic elements and their quantities, molecular composition describes how these elements connect to form the intricate network of molecules that constitute living beings, including us.