Download Chapter 3: Organic Compounds

Chapter 3: Organic Compounds
AP Biology
Organic Compounds
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Carbon atoms covalently bonded to each
other forming the backbone of the
molecule
More than 5 million
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Hydrocarbons can be produced in a wide
variety of shapes
Many organic compounds are large
macromolecules
Properties of Carbon
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4 valence electrons
Form 4 covalent bonds
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Can bond to another Carbon
Or another element
Carbon-Carbon bonds are strong
Not limited to single bonds (C-C)

Can form double (C=C) or triple (C=C)
bonds
Properties of Carbon

Carbon Chains can
be:
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Unbranched
Branched
Rings
Do not form in a
single plane
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3-D
Symmetrical
Properties of Carbon

Freedom of rotation around each
carbon-carbon single bond
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Organic molecules are flexible
Variety of shapes
Can link together in variety of patterns
creating even wider variety of shapes
Isomers

Compounds with the same molecular
formula but different structures
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Different properties
Different names
Cells can distinguish between isomers
Functional Groups
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Change the properties of organic
molecules
Participates in chemical reactions
Replace a hydrogen
P. 46 - 47
Functional Group
Hydroxyl -OH
Name of compounds
Functions
Alcohols
hydrophilic and polar
Aldehydes (when the =O
occurs at the end of chain)
Carbonyl -CO
Ketones (when the =O
hydrophilic and polar
occurs in the middle of chain)
Carboxyl -COOH
Amino -NH2
Carboxylic Acids
Amines
act as acids, donate protons
act as bases, pick up protons
from acids
Macromolecules Important to Life
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Carbohydrates
Lipids
Proteins
Nucleic Acids
Polymers
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Most macromolecules are polymers,
produced by linking small organic
compounds called monomers
This diversity comes from various
combinations of the 40-50 common
monomers.

(These monomers can be connected in
various combinations like the 26 letters in
the alphabet can be used to create a
great diversity of words).
Carbohydrates
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Sugars, starches, and cellulose
Used for fuel and structural materials
Carbon, Hydrogen, and Oxygen in
1:2:1 ratio

Ex.
Fig. 5.3
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Carbohydrates
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1 sugar unit: monosaccharide
2 units: disaccharide
many sugar units: polysaccharide
Pentoses – 5 carbon sugars
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Deoxyribose
Ribose
Monosaccharides
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Simple sugars
3-7 carbon atoms
Glucose and
fructose
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Glucose important
energy source for
cells
Many are ring
structures
Disaccharides
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2 monosaccharides combined
Examples: sucrose, lactose
Polysaccharides
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polymers (long chains of repeating units) of
monosaccharides
Starch and glycogen
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Starch – main storage carbohydrate of plants
Glycogen – main storage carbohydrate of animals
Starch
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Plants store starch within plastids, including
chloroplasts.
Plants can store surplus glucose in starch and
withdraw it when needed for energy or carbon.
Animals that feed on plants, especially parts rich
in starch, can also access this starch to support
their own metabolism.
Cellulose
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Most abundant polysaccharide
50% or more of all the carbon in plants
Humans cannot digest cellulose
Symbiotic Relationships - Herbivores
Fig. 5.8
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Other Polysaccharides with
Special Roles
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Chitin
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External skeletons
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Insects
Crayfish
Other arthropods
Cell walls of fungi
Tough structures
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Multiple hydrogen
bonds
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Glycoproteins
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Carbohydrates +
proteins
Outer surface of
cells
Protection
Allow cells to stick
together
Ex. mucus
Lipids
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Exception: do not have polymers, just
large molecules
Fats or fatlike
Insoluble in water (hydrophobic)
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Nonpolar covalent bonds
Mainly hydrogen and carbon, few
oxygen-containing functional groups
Lipids
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Types:
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Fats
Phospholipids
Steroids (Cholesterol & Some Hormones)
Waxes
Functions of Lipids:
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Reserve energy storage
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2x as much energy/gram than carbohydrates
Carbs and proteins can be transformed into fats
and stored in adipose tissue
Structural components of cellular
membranes
Hormones
Insulation
Cushioning
Triglycerides (fats)
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Fatty Acid + Glycerol
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Glycerol consists of a three-carbon skeleton with
a hydroxyl group attached to each.
A fatty acid consists of a carboxyl group
attached to a long carbon skeleton
Fat Molecule - Triglyceride
3 fatty acids joined to glycerol
Saturated Fats
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Contain max. possible # of
hydrogen atoms
No double bonds
Solid at room temperature
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Animal fat and solid vegetable
shortening
Not a dietary requirement
Unsaturated Fats
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Liquid at room temperature
Include double bonds
Monounsaturated – 1 double
bond
Polyunsaturated – more than 1
double bond
Some are essential nutrients that
must be obtained from food
Saturated vs. Unsaturated Fats
Phospholipids
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2 fatty acids + glycerol
Cell membranes
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Inside = hydrophobic
Outside = hydrophilic
Steroids
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Ring structure with different functional
groups attached
Cell membranes
Required to make all hormones
Proteins
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Complex structures
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Structure relates to function!
Often, function depends on its ability to
recognize and bind to another
molecule.
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Ex. Antibodies, Enzymes
Functions of Proteins (p.59)
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Support (keratin for hair and nails &
collagen for ligaments, tendons, skin)
Enzymes to catalyze reactions
Transport across cell membranes
Hemoglobin – oxygen transport
Defense from infection
Hormones (such as insulin)
Cell movement
Proteins
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Polymers made of amino acids
Amino acids are joined by peptide
bonds
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Chains are called polypeptides
Amino acids form a wide variety of
structures
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Building blocks for living tissue
20 common amino acids (monomers)
Amino Acids
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Plants and bacteria can synthesize all
amino acids
Animals can manufacture some of the
important amino acids
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If animals cannot synthesize them, they
are essential amino acids
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Must be obtained from diet
List of Amino Acids & Functions
Amino Acid Structure (Animation)
Protein Structure
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Different functional groups determine
the amino acid
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Combination of aa’s determine the protein
One or more polypeptides folded into a
complex 3-D structure
Shapes of Proteins
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Polypeptide chains are twisted or
folded to form a 3-D shape such as:
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Long fibers
Globular – tightly folded into compact,
spherical shape
Close relationship between shape and
function
Shapes of Proteins
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Primary Structure - sequence of amino
acids that form the polypeptide chain
Secondary Structure - Parts of the
polypeptide fold into local patterns (alpha
helix or pleated sheet) p.63
Tertiary Structure - the overall 3D shape
(globular or fibrous) p.64
Quaternary Structure - consists of two or
more polypeptide chains or subunits p.65
Changes to Protein Shape
A protein’s conformation can change in
response to the physical and chemical
conditions.
Alterations in pH, salt concentration,
temperature, or other factors can unravel or
denature a protein.
Nucleic Acids
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Informational polymers
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DNA (deoxyribonucleic acid)
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Contain hereditary information
Code that determines what proteins a cell
manufactures
Makes our genes
RNA (ribonucleic acid)
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Takes part in process of making proteins
Structure of DNA
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5 carbon sugar (deoxyribose)
Nitrogen base (adenine, thymine,
guanine, cytosine)
Phosphate group
All 3 of these = nucleotide (monomer)
 Complimentary base pairing: A-T, G-C
Important nucleotides
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ATP (adenosine triphosphate)
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Functions in energy storage
Composed of adenine, ribose, 3
phosphates
Table 3-3 p.68-69
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Summary of the Important Biological
Compounds
Study this table!