Macromolecules of Life (Part 2)

Continuing with my notes as I read and study about the underlying biochemical interactions associated with genetics and living organisms. This post focuses on large molecules that are important to life. The reference section has the list of books that I’ve read. Part two contains notes on carbohydrates, lipids and nucleic acids.

Carbohydrates have a series of carbon atoms bonded with hydrogen atoms, either an aldehyde (CHO) or ketone (COC) functional group and hydroxyl (OH) functional groups.  They are a source of stored energy, are used to transport the stored energy and serve as carbon skeletons (a pattern in which carbon atoms are bonded together in a molecule) that be re-arranged into new molecules.  there are four main categories of carbohydrates – monosaccharides or simple sugars (e.g. glucose), disaccharides – consists of two monosaccharides linked by covalent bonds (sucrose is made from a glucose and fructose monosaccharides), oligosaccharides – made of three to twenty monosaccharides (they are covalently bonded to proteins and lipids on the outer cell surfaces as recognition signals e.g. blood groups) and polysaccharides – made of many monosaccharides (e.g. starch, cellulose).  The covalent bonding are formed through condensation reactions and are called glycosidic linkages.  Glucose (blood sugar) is used to transport energy which is used by cells as an energy source by releasing stored energy and producing water and carbon dioxide (Sadava et al., 2009, p. 50).  Glucose can be straight form or in ring form but the ring form is more common since its stable.  Pentoses are 5 carbon sugars (e.g. ribose and deoxyribose forms the backbones of RNA and DNA molecules). 

Atom > Molecule > Functional Group > Monosaccharide > Disaccharide, Oligosaccharide, Polysaccharide

Parts that make up carbohydrates

Carbohydrates can be chemically modified by adding functional groups which are important intermediates in cellular energy reactions.  (e.g. sugar phosphates made by modifying glucose with a phosphate group).  When amino acids are used to modify carbohydrates, amino sugars are formed like glucosamine.  These are important in extracellular matrix where they form parts of glycoproteins which help keeping tissues together. 


Sadava, D. E., Hillis, D. M., Heller, C. H., & Berenbaum, M. (2009). Proteins, Carbohydrates and Lipids. In Life: The Science of Biology, 9th Edition (Ninth ed., pp. 39–57). W. H. Freeman.

Sadava, D. E., Hillis, D. M., Heller, C. H., & Berenbaum, M. (2009). Nucleic Acids and the Origin of Life. In Life: The Science of Biology, 9th Edition (Ninth ed., pp. 61–73). W. H. Freeman.

MilliporeSigma – Amino Acids Reference Charts. (n.d.).

ChemAxon (2020). MarvinSketch v 20.21 [Computer Software].

Pettersen, E. F., Goddard, T.D., Huang, C.C., Couch, G.S., Greenblatt, D.M., Meng, E.C., Ferrin, T.E. UCSF Chimera–a visualization system for exploratory research and analysis. J Comput Chem. 2004 Oct; 25(13):1605-12.

The Protein Data Bank H.M. Berman, J. Westbrook, Z. Feng, G. Gilliland, T.N. Bhat, H. Weissig, I.N. Shindyalov, P.E. Bourne (2000) Nucleic Acids Research28: 235-242. doi:10.1093/nar/28.1.235

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