Protein structure is conceptually divided into four levels, from most basic to higher order: primary structure describes the order of amino acids in the peptide chain. secondary structure describes the basic three-dimensional structures, α-helices and β-sheets. tertiary structure describes how the secondary structures come together to form an individual globular protein. quaternary structure results from individual proteins coming together to form multi-subunit protein complexes.

the answer is cell division : )

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.

answer/// to address the needs of adults with mental illness and increase their ability to function;