Natural polymer monomers: DNA, proteins, carbohydrates

Organic chemistry • Synthetic and natural polymers

Flashcards

Test your knowledge with interactive flashcards

Which glycosidic bond predominates in starch?

Click to reveal answer

α-1,4 glycosidic bonds predominate in starch, with α-1,6 branches in amylopectin.

Key concepts

What you'll likely be quizzed about

Nucleotides - monomers of DNA

Nucleotides form the repeating units of DNA. Each nucleotide contains a phosphate group, a five-carbon sugar (deoxyribose) and one nitrogenous base (adenine, thymine, cytosine or guanine). Nucleotides join by phosphodiester bonds between the phosphate of one nucleotide and the sugar of the next, producing a sugar–phosphate backbone. The sequence of bases along the backbone encodes genetic information and determines base-pairing between complementary strands.

Amino acids - monomers of proteins

Amino acids act as the building blocks of proteins. Each amino acid contains an amino group, a carboxyl group and a distinct side chain (R group). Amino acids link through peptide bonds formed by condensation between the carboxyl group of one amino acid and the amino group of another. The order and chemical properties of amino acids determine a protein's folding and function. Peptide-bonded chains fold into secondary and tertiary structures stabilized by hydrogen bonds and other interactions.

Glucose monomers - common sugar unit

Glucose functions as a common monosaccharide monomer in many polysaccharides. Two stereochemical forms exist: alpha (α) and beta (β) glucose. The orientation of the hydroxyl group on carbon 1 determines whether a glucose molecule is α or β. The type of glycosidic bond formed between glucose units dictates polysaccharide structure and properties, causing differences in digestibility and mechanical strength.

Starch - polymer of α-glucose for energy storage

Starch contains α-glucose monomers linked mainly by α-1,4 glycosidic bonds and occasional α-1,6 branches (amylopectin). The α-1,4 linkage causes the chain to coil into a helical structure, producing a compact molecule suited for energy storage. Branching through α-1,6 bonds increases solubility and provides many ends for enzymatic breakdown, enabling rapid release of glucose when needed.

Cellulose - polymer of β-glucose for structural support

Cellulose consists of β-glucose monomers joined by β-1,4 glycosidic bonds. Each glucose unit flips orientation relative to its neighbor, producing straight, unbranched chains. Straight chains align side by side and form hydrogen bonds between hydroxyl groups on adjacent chains, producing strong microfibrils. The hydrogen-bonded network gives cellulose high tensile strength and insolubility, enabling structural roles in plant cell walls.

Key notes

Important points to keep in mind

Nucleotides are the monomers of DNA and contain phosphate, deoxyribose and a base.

Amino acids are the monomers of proteins and contain an amino group, carboxyl group and R group.

Glucose is the monosaccharide monomer for both starch and cellulose.

α-Glucose forms α-1,4 and α-1,6 bonds in starch, producing helical and branched structures.

β-Glucose forms β-1,4 bonds in cellulose, producing straight chains and strong fibres.

Phosphodiester bonds join nucleotides into a sugar–phosphate backbone.

Peptide bonds join amino acids into polypeptide chains via condensation reactions.

Condensation reactions form bonds by removing water; hydrolysis breaks bonds by adding water.

Branching in starch increases accessibility for enzymes and speeds glucose release.

Hydrogen bonding between cellulose chains causes high tensile strength and insolubility.