Cell Macromolecules


The distinctive properties of living organisms arise from very large molecules called macromolecules, which may contain anything from hundreds to many billions of atoms. Macromolecules are polymers made in the cell by linking small chemical subunits together in a specific sequence. Nucleic acids – deoxyribonucleic acid and ribonucleic acid – are polymers of nucleotide bases and their principle function is to store and transmit hereditary information encoded in the sequence of subunits. Proteins are chains of amino acids that fold up into distinctive shapes and thereby acquire distinctive chemical properties, they are the principal building blocks of the cell and also responsible for activities such as enzyme catalysis, the synthesis of molecules and movements. Nucleic acids, proteins and other macromolecules such as polysaccharides interact with each other and with small molecules through weak chemical bonds. These allow specific molecular recognition to occur and form the basis of information transfer, cell movements, differentiation and the formation of distinctive cells and tissues.

Key Concepts:

  • Macromolecules are polymers built from subunits in a specific sequence.

  • Covalent bonds hold a macromolecule together; noncovalent bonds enable it to recognise other molecules.

  • RNA and DNA carry information in their nucleotide sequence.

  • Proteins fold into specific shapes and provide the building blocks of the cell.

  • The function of a protein depends on its ability to interact with and modify other molecules.

Keywords: macromolecules; nucleic acid; proteins; polysaccharides

Figure 1.

A single point mutation in the gene for the β chain of human haemoglobin changes the amino acid encoded by codon 6 from glutamine to valine. This single subunit dramatically alters the properties of the protein product, which aggregates within red blood cells, causing them to be fragile and liable to clog fine capillaries and producing a form of anaemia: sickle cell disease.

Figure 2.

The catalytic activity of the enzyme (PKC) is regulated by (DAG). In the absence of DAG, the active site of PKC is occupied by another part of the macromolecule (the pseudosubstrate), rendering the enzyme inactive. PKC is activated when DAG binds, causing a conformational change such that the active site is no longer occupied by the pseudosubstrate and can interact with its substrate.


Further Reading

Alberts B, Bray D, Hopkin K et al. (2010) Essential Cell Biology, 3rd edn. New York: Garland.

Berg JM, Tymoczko JL and Stryer L (2006) Biochemistry, 6th edn. New York: WH Freeman.

Branden C and Tooze J (1999) Introduction to Protein Structure, 2nd edn. New York: Garland.

Connor M and Ferguson‐Smith M (1997) Essential Medical Genetics, 5th edn. Boston, MA: Blackwell Science.

Dekker LV (ed.) (2004) Protein Kinase C, 2nd edn. New York: Kluwer Academic/ Plenum Publishing.

Nelson DL and Cox MM (2008) Lehninger Principles of Biochemistry, 5th edn. New York: WH Freeman.

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Bray, Dennis(Dec 2010) Cell Macromolecules. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0001269.pub2]