Question

Macromolecules. How do cells exploit properties of the four major macromolecules? Describe properties of the four macromolecular classes and provide examples of how each are employed in cells.

Answer 1

Macromolecules are formed by polymerization of smaller subunits (monomers and composed of thousands or more atoms. Most common macromolecules are biopolymers (nucleic acids, proteins, carbohydrates and polyphenols) and large non-polymeric molecules (such as lipids ).

Physical properties of macromolecules that do not occur for smaller molecules:

For example, DNA in a solution can be broken by sucking the solution through an ordinary straw because the physical forces on the molecule can overcome the strength of its covalent bonds. DNA, RNA and proteins all consist of a repeating structure of related building blocks (nucleotides in the case of DNA and RNA, amino acids in the case of proteins). They can be viewed as a string of beads, with each bead representing a single nucleotide or amino acid monomer linked together through covalent chemical bonds into a very long chain.

1.      DNA is an information storage macromolecule that encodes the complete set of instructions (egenome) that are required to assemble, maintain, and reproduce every living organism.

2.      Proteins are functional macromolecules responsible for catalysing the biochemical reactions that sustain life and perform functions of an organism, for example photosynthesis, neural function, vision, and movement.

3.      RNA encodes genetic information that can be translated into the amino acid sequence of proteins, as evidenced by the messenger RNA molecules present within every cell, and the RNA genomes of a large number of viruses.

4.      Carbohydrate (polysaccharides) are formed from polymers of monosaccharides. Because monosaccharides have multiple functional groups, polysaccharides can form linear polymers (e.g. cellulose) or complex branched structures (e.g.glycogen). Polysaccharides perform numerous roles in living organisms, acting as energy stores (e.g. Starch) and as structural components (e.g.chitin in arthropods and fungi).

5.      Lipids include fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E, and K), monoglycerides, diglycerides, triglycerides, phospholipids, and others. Main functions of lipids include storing energy, signaling, and acting as structural components of cell membranes.