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Unit 1 Review
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Essential Elements for Life
Which four account for 96%
of living matter?
What are the next four?
Trace elements
Table 2.1
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What IS a covalent bond?
Name
(molecular
formula)
Electronshell
diagram
(c) Water (H2O).
Two hydrogen
atoms and one
oxygen atom are
joined by covalent
bonds to produce a
molecule of water.
(d) Methane (CH4).
Four hydrogen
atoms can satisfy
the valence of
one carbon
atom, forming
methane.
Structural
formula
O
H
H
H
H
C
H
Figure 2.11 C, D
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H
Spacefilling
model
What’s this?
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What’s special about THESE bonds?
Because oxygen (O) is more electronegative than hydrogen (H),
shared electrons are pulled more toward oxygen.
d–
This results in a
partial negative
charge on the
oxygen and a
partial positive
charge on
the hydrogens.
O
Figure 2.12
d+
H
H
H2O
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d+
• The polarity of water molecules
– Allows them to form hydrogen bonds with each
other
– What important properties does this result in?
d–
+
H
+
Figure 3.2
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d–
H
d– +
d–
+
Hydrogen
bonds
1. Cohesion
• Cohesion
– Is bonding to neighboring
molecules
– Is due to H-bonding
– Helps pull water
up through the
xylem of plants
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Figure 3.3
Water conducting cells
100 µm
Ice …
– floats!
– insulates the water beneath it!
Hydrogen
bond
Figure 3.5
Ice
Liquid water
Hydrogen bonds are stable
Hydrogen bonds
constantly break and re-form
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The Solvent of Life
• The different poles of water molecules can
dissolve ionic compounds
Negative
oxygen regions
of polar water
molecules are
attracted to sodium
cations (Na+).
Positive
hydrogen regions
of water molecules
cling to chloride
anions (Cl–).
–
Na
+
+
–
–
Na
+
Cl–
+
Cl –
–
+
+
–
Figure 3.6
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–
+
+
–
–
+
+
–
–
The Solvent of Life
• Water can also interact with polar molecules
such as proteins
This oxygen is
attracted to a slight
d– positive charge on
the lysozyme
d+
molecule.
This oxygen is attracted to a slight
negative charge on the lysozyme molecule.
(a) Lysozyme molecule
in a nonaqueous
Figure 3.7
environment
(b) Lysozyme molecule (purple)
in an aqueous environment
such as tears or saliva
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(c) Ionic and polar regions on the protein’s
Surface attract water molecules.
• Water can dissociate
– Into hydronium ions and hydroxide ions
–
+
H
H
H
H
Figure on p. 53 of water
dissociating
H
H
H
Hydronium
ion (H3O+)
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+
H
Hydroxide
ion (OH–)
1
Increasingly Acidic
[H+] > [OH–]
• The pH scale and
pH values of
various aqueous
solutions
pH Scale
0
2
3
4
5
6
Neutral
[H+] = [OH–]
7
Battery acid
Digestive (stomach)
juice, lemon juice
Vinegar, beer, wine,
cola
Tomato juice
Black coffee
Rainwater
Urine
Pure water
Human blood
Increasingly Basic
[H+] < [OH–]
8
Seawater
9
10
11
Household ammonia
12
Household bleach
13
Figure
3.8Cummings
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as Benjamin
Milk of magnesia
14
Oven cleaner
The pH Scale
• The pH of a solution:
– low in an acid (0-7)
– high in a base (7-14)
– [H+] [OH-] = 10-14
• as [H+] rises, [OH-] …?
• pH = -log [H+]
– if [H+] = 10-3, pH = 3
– if [OH-] =10-3, pH = 11
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2. Carbon atoms are the most versatile
building blocks of molecules
• Carbon has FOUR unpaired valence electrons...
• Why is this important??
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Fig. 4.3
• hydroxyl group (-OH):
• polar covalent bonds improve __?
• improve solubility-esp. mono & di saccharides!
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• carbonyl group (C=O):
• “aldelhyde” if carbonyl group is on the end .
• “ketone” if elsewhere.
1
2
3
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• carboxyl group (-COOH):
• “carboxylic acids”
• acids because electronegativities of the two adjacent
oxygen atoms increase dissociation of H+.
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• amino group (-NH2):
• “amines”
• base because …
• ammonia can pick up a hydrogen ion (H+).
• Amino acids, the building blocks of proteins, have
amino and carboxyl groups.
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• sulfhydryl group (-SH):
• “thiols”
• How are these important in protein structure?
• What other functional group is similar?
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• phosphate group (-OPO32-):
• “phosphates”
• usually anions (-2) in solution.
• Functions?
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• disaccharide: two monosaccharides joined by a
dehydration reaction.
• Sucrose (table sugar) = glucose + fructose…
• the major transport form of sugars in plants.
• Maltose (malt sugar) = glucose + glucose
Fig. 5.5a
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• Starch: glucose storage polysaccharide of plants:
• Plants store carbs in this form because…
• starches are NOT _________ in water.
Fig. 5.6a
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• glycogen: glucose storage polysaccharide of
animals:
• highly branched
• vertebrates store about a one-day supply of glycogen
in the liver and muscles.
Insert Fig. 5.6b - glycogen
Fig. 5.6b
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?
Fig. 5.8
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• Chitin: used in annelid bristles (setae) and arthropod
exoskeletons (insects, spiders, crustaceans, …).
• like cellulose, but with a N-containing branch on each
monosaccharide.
• part of the cell walls of many fungi.
Fig. 5.9
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1. Fats: What are they good for?
• fatty acid: carboxyl group attached to a hydrocarbon
skeleton, often 16 to 18 carbons.
Type of reaction here?
• fat: glycerol + three fatty acids SEE NEXT SLIDE
• hydrophobic due to nonpolar C-H bonds
• The three fatty acids may differ in:
• length
• presence of C=C bonds
Fig. 5.10b
• You’ve heard lots about trans fats lately…
• produced during hydrogenation of polyunsaturated fats
• poorly metabolized cardiovascular damage
GOOD: Oleic acid
BAD: Elaidic acid
Oleic acid is a cis unsaturated fatty acid
that comprises 55-80% of olive oil.
Elaidic acid is a trans unsaturated fatty
acid often found when vegetable oils are
hydrogenated.
Which one would be solid at room temp?
These fatty acids are geometric isomers (chemically identical except for the
arrangement of the double bond).
What is this phospholipid made of?
• two fatty acids &
one charged
phosphate group
attached to a
glycerol.
• Additional small
groups may attach
to PO42-.
What am I?
• Phospholipid Bilayers form cell membranes…
• What part is hydrophilic?
• What part is hydrophobic?
?
Fig. 5.12b
What am I?
• Steroids: lipids with a carbon skeleton of four fused
carbon rings.
• Different steroids are created by?
• attachment of different functional groups.
Fig. 5.14
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1. What am I?
• Amino acids:
• What’s R?
• How many R’s are
there?
• What’s an essential
amino acid?
2
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3
MUST KNOW:The 4 levels of protein structure…
Fig. 5.24
H-bonds between
sections of the
backbone
Interactions
between R-groups
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3o : Tertiary structure due to R-group interactions…
• R to R, or R to backbone
• H-bonds
• ionic bonds
• hydrophobic
interactions
(interior)
• disulfide bridgesstrongest of these
interactions
Fig. 5.22
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2. A nucleic acid strand is a polymer of
nucleotides
• nucleotides: monomers that chain into nucleic acids.
• consist of three parts:
• a nitrogen base
• a pentose sugar
• a phosphate group.
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Fig. 5.29
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