Examlex
The appearance of which of the following structures has been widely accepted as the key event in the evolution of vertebrates?
Beta-pleated Sheet
A beta-pleated sheet is a common protein secondary structure formed by parallel or antiparallel beta-strands linked together by hydrogen bonding.
Carbohydrate
Organic compounds, such as sugars, starches, and cellulose, consisting of carbon, hydrogen, and oxygen, that are an essential source of energy for living organisms.
Lipid
A class of organic compounds that are fatty acids or their derivatives, insoluble in water but soluble in organic solvents, used for energy storage, as structural components of cell membranes, and in signaling.
Nucleic Acid
Macromolecules essential for life, including DNA and RNA, which carry genetic information in cells.
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