Cell Biology 1. Levels of Organization Living things are highly organized and structured, following a hierarchy that can be examined on a scale from small to large. The atom ( such as oxygen, hydrogen, carbon, nitrogen,..) is the smalles t and most fundamental unit of matter. Atoms form molecules ( such as monosaccharide, amino acid, glycerol, ...) which is a chemical structure consisting of at least two atoms held together by one or more chemical bonds. Many molecules that are biologically important are macromolecules . There are 4 important kinds of macromolecules in living organism: carbohydrate, protein, nucleic acid and lipid. The aggregates of macromolecules lead to the formation of organelles . When organelles surrounded by membranes and carry out indispensable functions, these are called cell . All living things are made of cells; the cell itself is the smallest fundamental unit of structure and function in living organisms. This requirement is why viruses a
Biology is the natural science that studies life and living organisms , including their physical structure, chemical processes, molecular interactions, physiological mechanisms, development and evolution. Biology recognizes: - the cell as the basic unit of life, - genes as the basic unit of heredity, - evolution as the engine that propels the creation and extinction of species The living organism is considered an open system because they absorb energy and release heat and metabolic waste.