Although amino acids have "acid" in their name, some are acidic in water solutions, some are basic, and others are neutral. propose an explanation for this observation based on the structures and descriptions of the amino acids below.

Amino acids are organic compounds containing amine (-NH2) and carboxyl (-COOH) functional units. They have a side chain and this side chain determines if an amino acid is basic or neutral. The acidic ones have acidic side chain and the basic ones have a basic side chain at neutral pH.

Arginine, lysine, and histidine are the basic ones. Aspartate and glutamate are the acidic ones. Glutamic acid is the one shown in the figure. Acidic amino acid have more Carboxyl group than amino group . Basic amino acids like lysine (shown in the figure in your question) have side chains that resemble ammonia which is basic.

allowed for the prediction of the properties of missing elements.

estuaries are the partially enclosed coastal bodies of brackish water formed at the mouth of sea where river meets an ocean. it is a transition zone between river and sea water so estuaries are influenced to both marine environment such as tides, waves and to riverine such as flow of fresh water and sediments. the mixing of sea and fresh water provide high level of nutrients, making estuaries a high product habitats.

many estuaries suffers degradation from a variety of human activities like erosion from deforestation, overgrazing, overfishing, drainage and eutrophication.

so from the above statement answers will be

1. false as estuaries are formed due to both brackish and freshwater.

2.true, due to high productivity estuaries are breeding ground for many marine species.

3. direct and indirect activities of man that contribute to pollution and deposition of sediments.