Final answer:
The percentage of body weight represented by water is greater in an infant than in adults and the elderly. Water content decreases from approximately 75% in infants to 50-60% in adults and around 45% in old age.
Step-by-step explanation:
The percentage of body weight represented by water is greater in an infant compared to adults and the elderly. Human body water content varies at different stages of life, starting at about 75% in infants and decreasing to 50-60% in adults, and can go even lower in old age, around 45%. The distribution of water throughout the body is essential as it is involved in numerous biological processes, including serving as a medium for cellular reactions and aiding in osmosis to maintain normal cellular functions.
Infants have a higher percentage of body water due to the distinct proportions of organs, muscles, fat, bone, and other tissues that change from infancy into adulthood. For example, a high proportion of water is found in the brain and kidneys, making up 80-85% of their mass. In contrast, teeth contain the lowest proportion of water at 8-10%.
As people grow older and develop more body fat, the percentage of body water typically decreases, reflecting the inverse relationship between water content and body fat. It is important for adequate body function that an appropriate balance of solutes and water is maintained, facilitated by the process of osmosis where water moves through semi-permeable membranes to areas with lower water concentration.