Carbon: the Chemical Foundation of All Living Organisms
The chemistry of carbon is called organic chemistry.
Organic chemistry derives its name from the word “organism,” since the chemistry of all living organisms is based on carbon.
There are literally millions of different compounds found in living organisms that are based on carbon.
Making sense of all these different compounds and their chemistry can be rather daunting.
We will take a look at some of the essential things a biology student should know about organic chemistry; hopefully you will see that the basics are fairly straightforward and understandable…
The Key to Carbon Chemistry
The key to understanding carbon chemistry is simple: carbon has four valence electrons, so it can form four bonds.
It can form four single bonds as shown here.
It can form double or triple bonds as well.
Part of Figure 2.9, page 28; figure 2.10(d), page 29, Campbell's Biology, 5th Edition
Carbon Diversity
Biodiversity refers to the diversity of life on Earth.
Earth originated 3.8 billion years ago with an original prokaryote.
This prokaryote evolved into the 1.7 million different species we have so far identified on earth.
Since all living things are based on the element carbon, we can think of “carbon diversity” as the diversity of carbon compounds among all living organisms.
These chains can be extremely long; they vary in length. In some cases 20 to 30 carbons can be bonded together!
They can be arranged in straight chains with single bonds (as shown immediately below) or…
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Carbon Chains Can Have Double Bonds
Double bonds are not uncommon in carbon compounds.
The location of these double bonds within the chain can vary.
Note that each carbon still has four bonds; this will always be true.
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Carbon Chains Can Branch
Carbons chains do not have to always be in straight lines; they can branch.
Here we see both unbranched (straight) and branched carbon skeletons.
Note each carbon still only has four bonds.
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Carbon Chains Can Form Rings
Carbon can also form ringed structures.
The ringed structures can have single or double bonds.
Note how the abbreviated structural formulas omit the corner carbons and the hydrogens attached to them.
Again, each carbon has only four bonds.
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Functional Groups
Why are they important?
Functional groups are generally found at the end of the carbon chain and are responsible for the way the carbon compound reacts chemically with other compounds.
Since chemistry is all about reactions, functional groups, in a large measure, determine the chemical nature of carbon-based compounds.
We need to be familiar with six different functional groups: