AP Biology
John D. O’Bryant School of
Mathematics and Science
September 17, 2012
AP Biology
Agenda
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Do Now (Quiz)
Macromolecules (review)
Qualitative Tests of Biological Macromolecules
Case Study: “A Can of Bull”
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Do Now (Quiz)
 1. Beta pleated sheets are characterized by
 A) disulfide bridges between cysteine amino acids.
 B) parallel regions of the polypeptide chain held
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together by hydrophobic interactions.
C) folds stabilized by hydrogen bonds between
segments of the polypeptide backbone.
D) membrane sheets composed of phospholipids
E) hydrogen bonds between adjacent cellulose
molecules
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Do Now (Quiz)
 2. Which of these molecules would provide the most
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energy (kcal/g) when eaten
A) glucose
B) starch
C) glycogen
D) fat
E) protein
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Do Now (Quiz)
 3. The alpha helix of proteins is
 A) part of the tertiary structure and is stabilized by
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disulfide bridges
B) a double helix
C) stabilized by hydrogen bonds and commonly found
in fibrous proteins
D) found in some regions of globular proteins and
stabilized by hydrophobic interactions
E) a complementary sequence to messenger RNA
AP Biology
Do Now (Quiz)
 4. Cows can derive nutrients from cellulose because
 A) they can produce enzymes that break the beta
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linkages between glucose molecules
B) they chew and rechew their cud so that cellulose
fibers are finally broken down
C) One of their stomachs contains bacteria that can
hydrolyze the bonds of cellulose
D) their intestinal tract contains termites, which
produce enzymes to hydrolyze cellulose
E) they can convert cellulose to starch and then
hydrolyze starch to glucose
AP Biology
Do Now (Quiz)
 5. Dehydration reactions are used in forming which of
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the following compounds?
A) triacylglycerides
B) polysaccharides
C) proteins
D) A and C only
E) A, B, and C
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Proteins
Multipurpose
molecules
AP Biology
2008-
Protein denaturation
 Unfolding a protein

In Biology,
size doesn’t matter,
SHAPE matters!
conditions that disrupt H bonds, ionic
bonds, disulfide bridges
 temperature
 pH
 salinity

alter 2° & 3° structure
 alter 3-D shape

destroys functionality
 some proteins can return to their functional shape
after denaturation, many cannot
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EAT
Let’s build
X some
Proteins!
AP Biology
2008-
Chaperonin proteins
 Guide protein folding
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
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provide shelter for folding polypeptides
keep the new protein segregated from
cytoplasmic influences
Protein models
 Protein structure visualized by
X-ray crystallography
 extrapolating from amino acid sequence
 computer modelling

lysozyme
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Nucleic acids
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2006-2007
Nucleic Acids
Information
storage
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2006-2007
Nucleic Acids
 Function:

genetic material
 stores information
 genes
 blueprint for building proteins

DNA
DNA  RNA  proteins
 transfers information
 blueprint for new cells
 blueprint for next generation
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proteins
G
C
T
A
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A
C
G
T
A
C
G
T
A
Nucleic Acids
 Examples:

RNA (ribonucleic acid)
 single helix

DNA (deoxyribonucleic acid)
 double helix
 Structure:

AP Biology
monomers = nucleotides
DNA
RNA
Nucleotides
 3 parts
nitrogen base (C-N ring)
 pentose sugar (5C)

 ribose in RNA
 deoxyribose in DNA

phosphate (PO4) group
Are nucleic acids
charged molecules?
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Nitrogen base
I’m the
A,T,C,G or U
part!
Types of nucleotides
 2 types of nucleotides
different nitrogen bases
 purines

 double ring N base
 adenine (A)
 guanine (G)

pyrimidines
 single ring N base
 cytosine (C)
 thymine (T)
 uracil (U)
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Purine = AG
Pure silver!
Nucleic polymer
 Backbone
sugar to PO4 bond
 phosphodiester bond

 new base added to sugar of
previous base
 polymer grows in one direction

N bases hang off the
sugar-phosphate backbone
Dangling bases?
Why is this important?
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Pairing of nucleotides
 Nucleotides bond between
DNA strands
H bonds
 purine :: pyrimidine
 A :: T
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 2 H bonds

G :: C
 3 H bonds
Matching bases?
Why is this important?
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DNA molecule
 Double helix

H bonds between bases
join the 2 strands
 A :: T
 C :: G
H bonds?
Why is this important?
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Copying DNA
 Replication

2 strands of DNA helix are
complementary
 have one, can build other
 have one, can rebuild the
whole
Matching halves?
Why is this
a good system?
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When does a cell copy DNA?
 When in the life of a cell does DNA have
to be copied?

cell reproduction
 mitosis

gamete production
 meiosis
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DNA replication
“It has not escaped our notice that
the specific pairing we have
postulated immediately suggests a
possible copying mechanism for the
genetic material.”
James Watson
Francis Crick
1953
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1953 | 1962
Watson and Crick … and others…
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Maurice Wilkins… and…
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1953 | 1962
Rosalind Franklin (1920-1958)
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Interesting note…
 Ratio of A-T::G-C
affects stability
of DNA molecule
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
2 H bonds vs. 3 H bonds
biotech procedures
 more G-C =
need higher T° to
separate strands

high T° organisms
 many G-C

parasites
 many A-T (don’t know why)
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Another interesting note…
 ATP
Adenosine triphosphate

modified nucleotide
 adenine (AMP) + Pi + Pi
+
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+
HELIXHELIX
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Macromolecule
Review
AP Biology
2006-2007
Carbohydrates
 Structure / monomer

monosaccharide
 Function
energy
 raw materials
 energy storage
 structural compounds

glycosidic bond
 Examples

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glucose, starch, cellulose, glycogen
Lipids
 Structure / building block

glycerol, fatty acid, cholesterol, H-C chains
 Function
energy storage
 membranes
 hormones

 Examples

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ester bond (in a fat)
fat, phospholipids, steroids
Proteins
 Structure / monomer
amino acids
 levels of structure

 Function
enzymes
 transport
 signals

defense
 structure
 receptors

peptide bond
 Examples

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digestive enzymes, membrane
channels, insulin hormone, actin
Nucleic acids
 Structure / monomer

nucleotide
 Function

information storage
& transfer
 Examples

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DNA, RNA
phosphodiester bond
Let’s build
some DNA, baby!
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Ghosts of Lectures Past
(storage)
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2007-2008
Building the polymer
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RNA & DNA
 RNA

single nucleotide chain
 DNA

double nucleotide chain
 N bases bond in pairs
across chains

spiraled in a double helix
 double helix 1st proposed as structure of DNA
in 1953 by James Watson & Francis Crick
(just celebrated 50th anniversary in 2003!)
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Information polymer
 Function

series of bases encodes information
 like the letters of a book

stored information is passed
from parent to offspring
 need to copy accurately

stored information = genes
 genetic information
Passing on information?
Why is this important?
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