Chapter 4 Flashcards
Living organisms, , are made up of chemicals based mostly on
the element carbon.
Carbon enters the biosphere through the action of producers—plants and other
photosynthetic organisms that use1. These molecules are then taken up by2
1 solar energy to transform atmospheric CO2 into
the carbon-based molecules of life
2 consumers,
which feed on other organisms.
For historical reasons, compounds containing carbon are said
to be organic, and their study is called
organic chemistry.
Organic
chemistry was redefined as 1
. Organic compounds range from 2
1he study of carbon compounds regardless of origin
2simple
molecules, such as methane (CH4), to colossal ones, such as
proteins, with thousands of atoms.
Conclusion of the miller urey experiment
Organic molecules, a first step in the origin of life, may
have been synthesized abiotically on the early Earth. Although new
evidence indicates that the early Earth’s atmosphere was different from
the “atmosphere” used by Miller in this experiment, recent experiments
using the revised list of chemicals also produced organic molecules
Results of the miller urey experiment
Miller identified a variety of organic molecules that are
common in organisms. These included simple compounds, such as
formaldehyde (CH2O) and hydrogen cyanide (HCN), and more complex molecules, such as amino acids and long chains of carbon and
hydrogen known as hydrocarbons
The key to an atom’s chemical characteristics is what and why
electron configuration. This configuration determines the
kinds and number of bonds an atom will form with other
atoms
describecarbons electron arrangement
Carbon has 6 electrons, with 2 in the first electron shell and
4 in the second shell; thus, it has 4 valence electrons in a shell
that can hold up to 8 electrons. A carbon atom usually completes its valence shell by sharing its 4 electrons with other
atoms so that 8 electrons are present
In organic
molecules, carbon usually forms 1 Each carbon atom acts as an 2
which a molecule can branch off in as many as four directions.
This enables carbon to form 3
1single or double covalent
bonds.
2intersection point from
3large, complex molecules.
the shape of a molecule is central to its
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The number of unpaired electrons in the valence shell
of an atom is generally equal to the atom’s
valence, the
number of covalent bonds it can form
Whether we call CO2 organic or inorganic, however, it is clearly
important to the living world as the source of 1
1carbon, via photosynthetic organisms, for all organic molecules in organisms
a carbon atom can also
use one or more 1 to form covalent bonds to
other carbon atoms, each of which can also form 2
Thus, the atoms can be linked into chains of seemingly 3
1valence electrons
2four bonds.
3infinite variety.
Such variation in carbon skeletons is one important source
of the
molecular complexity and diversity that characterize
living matter. In addition, atoms of other elements can be
bonded to the skeletons at available sites.
are hydrocarbons, organic molecules consisting of only
carbon and hydrogen. Atoms of hydrogen are attached to the
1 wherever electrons are available for covalent
bonding. Hydrocarbons are the major components of petroleum, which is called a fossil fuel because2
1carbon skeleton
2 it consists of thepartially decomposed remains of organisms that lived
millions of years ago.
Living matter, as you have learned, consists mainly of 1 These elements all form 2 Of all these elements, carbon
is the 3
1carbon,
oxygen, hydrogen, and nitrogen, with smaller amounts of
sulfur and phosphorus
2strong covalent bonds, an essential characteristic in the architecture of
complex organic molecules.
3virtuoso of the covalent bond
