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BIOLOGY Life on Earth
WITH PHYSIOLOGY Tenth Edition
Audesirk Audesirk Byers
3
Biological
Molecules
Lecture Presentations by
Carol R. Anderson
Westwood College, River Oaks Campus
© 2014 Pearson Education, Inc.
Chapter 3 At a Glance
 3.1 Why Is Carbon So Important in Biological
Molecules?
 3.2 How Are Organic Molecules Synthesized?
© 2014 Pearson Education, Inc.
3.1 Why Is Carbon So Important in Biological
Molecules?
 Organic refers to molecules containing a carbon
skeleton bonded to hydrogen atoms
 Inorganic refers to carbon dioxide and all molecules
without carbon
© 2014 Pearson Education, Inc.
3.1 Why Is Carbon So Important in Biological
Molecules?
 The unique bonding properties of carbon are key to
the complexity of organic molecules
– The carbon atom is versatile because it has four
electrons in an outermost shell that can accommodate
eight electrons
– Therefore, a carbon atom can become stable by
forming up to four bonds (single, double, or triple)
– As a result, organic molecules can assume complex
shapes, including branched chains, rings, sheets, and
helices
© 2014 Pearson Education, Inc.
Figure 3-1 Bonding patterns
H
hydrogen
carbon
nitrogen
oxygen
© 2014 Pearson Education, Inc.
C
C
N
C
N
O
C
N
O
3.1 Why Is Carbon So Important in Biological
Molecules?
 The unique bonding properties of carbon are key to
the complexity of organic molecules (continued)
– Functional groups in organic molecules determine
the characteristics and chemical reactivity of the
molecules
– Functional groups are less stable than the carbon
backbone and are more likely to participate in
chemical reactions
© 2014 Pearson Education, Inc.
Table 3-1
© 2014 Pearson Education, Inc.
3.2 How Are Organic Molecules Synthesized?
 Small organic molecules (called monomers) are
joined to form longer molecules (called polymers)
 Biomolecules are joined or broken through
dehydration synthesis or hydrolysis
© 2014 Pearson Education, Inc.
3.2 How Are Organic Molecules Synthesized?
 Biological polymers are formed by removing water
and split apart by adding water
– Monomers are joined together through dehydration
synthesis, at the site where an H and an OH are
removed, resulting in the loss of a water molecule
(H2O)
– The openings in the outer electron shells of the two
subunits are filled when the two subunits share
electrons, creating a covalent bond
© 2014 Pearson Education, Inc.
Figure 3-2 Dehydration synthesis
dehydration
synthesis
© 2014 Pearson Education, Inc.
3.2 How Are Organic Molecules Synthesized?
 Biological polymers are formed by removing water
and split apart by adding water (continued)
– Polymers are broken apart through hydrolysis
(“water cutting”)
– Water is broken into H and OH and is used to break the
bond between monomers
© 2014 Pearson Education, Inc.
© 2014 Pearson Education, Inc.
Animation: Dehydration Synthesis and Hydrolysis
Figure 3-3 Hydrolysis
hydrolysis
© 2014 Pearson Education, Inc.
3.2 How Are Organic Molecules Synthesized?
 Biological polymers are formed by removing water
and split apart by adding water (continued)
– All biological molecules fall into one of four categories
– Carbohydrates
– Lipids
– Proteins
– Nucleotides/nucleic acids
© 2014 Pearson Education, Inc.
Table 3-2
© 2014 Pearson Education, Inc.