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Chapter 4
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AP Biology
Carbon and the Molecular Diversity of Life
Carbon: The backbone of Life? Wait, what? Isn’t it water? Well yes and no.
Water is the universal medium for life
Most living organisms are made up of chemicals that are based on the element carbon
Carbon and the Molecular Diversity of Life
Carbon enters the biosphere through the action of plants
Plants use solar energy to transform atmospheric CO2 into the molecules of life
Molecules are then passed to animals that feed on plants
Carbon and Diversity
Carbon is able to form molecules that are large, complex and diverse
It makes possible the diversity of organism that have evolved on earth
History of looking at carbon
1800’s: Theory of vitalism A belief that a life force outside of
the jurisdiction of physical and chemical laws
1950’s: U.S. Stanley Miller. Theory of mechanism
The view that physical and chemical laws govern all natural phenomena including the processes of life.
History of looking at carbon
In order to prove that spontaneous life could occur, he did an experiment
Primordial soup idea went from speculation to empirical science!
History of looking at carbon
Methane, ammonia, and hydrogen and subjected it to steam
It was then exposed to an electrical charge
This caused a chemical reaction
The result: proteins and amino acids
Back to carbon…
Carbon has 6 electrons Carbon usually shares its electrons
to complete the valence shell Creates covalent bonds Each carbon atom acts as an
intersection point and can branch off in as many as four directions
This allows carbon to form complex bonds.
Some examples
Methane Ethane Ethylene
Carbon Experiment
Balloon 40 ml of water Soft drink bottle Drinking straw Lemon juice or vinegar 1 teaspoon baking soda
Carbon experiment
Stretch out the balloon Pour 40 ml of water into the soft
drink bottle Add the teaspoon of baking soda and
stir it around with the straw till it is dissolved
Pour the vinegar or lemon juice in and quickly put the stretched balloon over the bottle
Carbon experiment
If all goes well then your balloon should inflate! Adding the lemon juice to the baking soda creates a chemical reaction. The baking soda is a base, while the lemon juice is an acid, when the two combine they create carbon dioxide (CO2). The gas rises up and escapes through the soft drink bottle, it doesn't however escape the balloon, pushing it outwards and blowing it up. If you don't have any lemons then you can substitute the lemon juice for vinegar.
