Origins by Baggott Jim;

Author:Baggott, Jim;
Language: eng
Format: epub
Publisher: Oxford University Press
Published: 2015-08-23T16:00:00+00:00

LIFE’S BUILDING BLOCKS

Despite the extraordinary diversity of life on Earth today, all life forms rely on broadly the same set of cellular structures and biochemical systems that are used to acquire energy, metabolize, grow, and replicate. Underpinning these fundamental biological processes is a set of bio-molecular mechanisms that are involved in (among other things) capturing, transferring, and storing energy and holding, transferring, and replicating what we have learned to think of as genetic information that specifies what kind of life it is.

In an attempt to keep things reasonably simple, I’m going to focus on two types of fundamental building blocks. These are chemicals called amino acids, the constituents of proteins, and nucleotides, involved in the complex molecular structures that carry genetic information and which code for the construction of proteins.

We’ll begin with amino acids. These form a class of chemical compounds which consist of two functional groups, an amine group (—NH2, hence ‘amino’) and a carboxylic acid group (—CO2H, hence ‘acid’). These compounds are distinguished from each other by possession of a third group which forms a side-chain, usually given the generic symbol ‘R’. With some exceptions, we can write a general formula for amino acids as H2N—CHR—CO2H.

There are about 500 known amino acids, but there is a core of just 20 that are intimately involved in biological systems.* These can be further categorized according to the nature of their side-chains, and a breakdown is provided in Figure 58.4

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