Lessons 21–22 · 2 lessons · A. Zikiryayev, A. To‘xtayev, I. Azimov, N. Sonin. Biology. Basics of Cytology and Genetics, Grade 9, revised and expanded 5th edition. “Yangiyul Poligraph Service”, Tashkent, 2019
21
Biomolecules
Textbook: p. 58
GoalKnow biomolecules, the ideas of monomer and polymer (biopolymer) and their main groups.
Organic compounds, the biomolecules, make up about 20–30 % of cell mass. Simple small-molecule compounds are called monomers; many monomers join to form a macromolecule or polymer. Four main groups occur in living organisms: carbohydrates, lipids, proteins and nucleic acids. Proteins (monomer: amino acid), nucleic acids (nucleotide) and polysaccharides (monosaccharide) are biopolymers; lipids are not chains of such monomers, so they are not counted among biopolymers. Biopolymers do three jobs: building structures (cellulose, some proteins), carrying out biological functions (catalysis, transport — mostly proteins) and storing information (nucleic acids). Each species makes its own specific biopolymers, while carbohydrates and lipids serve as the main source of energy.
Worked examples
Starch is a polymer built of glucose monomers; DNA is a polymer built of four kinds of nucleotides.
Olive oil is a lipid but, unlike protein or starch, is not a chain of monomers, so it is not a biopolymer.
Class activity
“Monomer–polymer pairs”. Cards show amino acid, nucleotide, glucose, protein, DNA, starch, fat. Place them in the monomer, biopolymer and “neither” columns and say why.
Practice
1
State the difference between a monomer and a polymer.
A monomer is a small simple molecule; a polymer is a large molecule made of many monomers.