This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: membrane structure and function, Subject name: Biochemistry
[{'content': '"Molecular logic of living state" states all except \nSelect and explain. \nA. Cells maintain a rigid state, B. A basic simplicity in biological macromolecular, C. Cells maintain maximum economy, D. All of the above', 'role': 'user'}, {'content': 'Answer: A \nExplanation: All macromolecules are constructed from a few simple compounds. * * Carbon atoms covalently joined with other carbon atoms and with the hydrogen, oxygen, and nitrogen. * Organic compounds with relative molecular mass less than about 500, such as amino acids, nucleotides, and monosaccharides, serve as monomeric subunits of macromolecules such as proteins, nucleic acids, and polysaccharides. * A single protein may have 1000 or more amino acids, and deoxyribonucleic acids has millions of nucleotides * eg. Escherichia coli have several proteins, nucleic acids molecules, carbohydrates and lipids. * DNA (Deoxyribonucleic acid) are constructed from only four different kinds of simple monomeric subunits the deoxyribonucleotides * RNA (Ribonucleic acid) are composed of just four types of ribonucleotides * Proteins are composed of 20 different kinds of amino acids * All proteins are built identically in all living organisms * All living organisms build molecules from same kind of monomeric subunits * The structure of a macromolecule determines its specific biological function * Each genus and species is defined by its distinctive set of macromolecules', 'role': 'assistant'}]