Nerve activates contraction

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Polymer Principles Most macromolecules are
polymers Polymer (Poly many mer part)
large molecule consisting of many identical or
similar subunits connected together. Monomer
Subunit or building block molecule of a
polymer Macromolecule (Macro large) large
organic polymer Formation of macromolecules
from smaller building block molecules represents
another level in the hierarchy of biological
organization. There are four classes of
macromolecules in living organisms
Carbohydrates Lipids Proteins Nucleic
acids Polymerization reactions Chemical
reactions that link two or more small molecules
to form larger molecules with repeating
structural units. Condensation reactions
Polymerization reactions during which monomers
are covalently linked, producing net removal of a
water molecule for each covalent linkage.
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Figure 5.2 The synthesis and breakdown of
polymers
Polymerization Reaction Condensation or
Dehydration Reaction Requires energy, biological
catalysts (enzymes)
Digestive enzymes catalyze hydrolytic reactions
Unity in life--only about 40-50 common
monomers Diversity too---new properties emerge
from complex arrangements of monomers into
polymers
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Figure 5.3 The structure and classification of
some monosaccharides
Carbohydrates--sugars and their
polymers Sugars--smallest carbohydrates Simple
sugars--monomers of carbohydrates called
monosaccharides (CH2O) Major nutrients for cells
e.g. glucose Glucose can be produced by
photosynthesis from CO2, H2O, and
sunlight Store energy--cellular respiration Raw
material for other organic molecules Used as
monomers for disaccharides and
polysaccharides--condensation reactions
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5
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Asymmetrical carbon--enantiomers
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Figure 5.4 Linear and ring forms of glucose
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Figure 5.5 Examples of disaccharide synthesis
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Figure 5.6 Storage polysaccharides
Cells hydrolyze storage polysaccharidesas needed
for for energy
Starch--glucose polymer in plants Amylose--unbranc
hed polymer Amylopectin--branched polymer
Glycogen--glucose storage polysaccharide in
animals Very highly branched Stored in muscle
and liver
Most animals can digest starch potato, wheat,
corn, rice
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Figure 5.7 Starch and cellulose structures 
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Figure 5.7 Starch and cellulose structures 
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Figure 5.7x Starch and cellulose molecular
models
? Glucose
? Glucose
Cellulose
Starch
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Figure 5.8 The arrangement of cellulose in plant
cell walls
Cellulose reinforces plant walls Hydrogen bonds
Cellulose cannot be digested by most
organisms--no enzyme to break beta 1-4
linkage Insoluble fiber, digestion
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Figure 5.x1 Cellulose digestion termite and
Trichonympha
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Figure 5.x2 Cellulose digestion cow
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Figure 5.10 Chitin, a structural polysaccharide
exoskeleton and surgical thread
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Figure 5.11 The synthesis and structure of a
fat, or triacylglycerol
Carboxyl group has acid properties Hydrocarbon
chain, 16-18 carbons Nonpolar C-H bonds,
hydrophobic
(Condensation Reaction)
(bond between hydroxyl group and a carboxyl group)
Fats hydrophobic, not water soluble variation
due to fatty acid composition fatty acids
can be the same or different fatty acids
can vary in length fatty acids can vary in
the number and location of double bonds
(saturation)
A triglyceride
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Figure 5.12 Examples of saturated and
unsaturated fats and fatty acids 
Saturated fats no double bonds between carbons
in the tail saturated with hydrogen solid at
room temp most animal fats, bacon grease, lard,
butter
Unsaturated fats one or more double bonds in
tail kinks the tail so cannot pack closely
enough to solidify at room temp most plant fats
Artificial hydrogenation, peanut butter, margarine
Fats have many useful functions Energy storage
9 vs 4 Kcal/gram more compact fuel than
carbohydrates Cushions organs e.g. kidney
Insulates against heat loss
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Phospholipids Phospholipids
Compounds with molecular building blocks of
glycerol, two fatty acids, a phosphate group, and
usually, an additional small chemical group
attached to the phosphate. Differs from fat in
that the third carbon of glycerol is joined to a
negatively charged phosphate group Can have
small variable molecules (usually charged or
polar) attached to phosphate Are diverse
depending upon differences in fatty acids and in
phosphate attachments Show ambivalent behavior
toward water. Hydrocarbon tails are hydrophobic
and the polar head (phosphate group with
attachments) is hydrophilic. Cluster in water as
their hydrophobic portions turn away from water.
One such cluster, a micelle, assembles so the
hydrophobic tails turn toward the water-free
interior and the hydrophilic phosphate heads
arrange facing outward in contact with
water. Are major constituents of cell
membranes. At the cell surface, phospholipids
form a bilayer held together by hydrophobic
interactions among the hydrocarbon tails.
Phospholipids in water will spontaneously form
such a bilayer.
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Figure 5.13 The structure of a phospholipid
Phospholipids Compounds with molecular building
blocks of glycerol, two fatty acids, a phosphate
group, and usually, an additional small chemical
group attached to the phosphate.
Differs from fat in that the third carbon of
glycerol is joined to a negatively charged
phosphate group Can have small variable
molecules (usually charged or polar) attached to
phosphate Are diverse depending upon differences
in fatty acids and in phosphate attachments Show
ambivalent behavior toward water. Hydrocarbon
tails are hydrophobic and the polar head
(phosphate group with attachments) is
hydrophilic. Are major constituents of cell
membranes.
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Phospholipid Bilayers of Cell Membranes
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Steroids Steroids Lipids which
have four fused carbon rings with various
functional groups attached. Cholesterol is an
important steroid and is the precursor to many
other steroids including vertebrate sex hormones
and bile acids. Is a common component of animal
cell membranes. Can contribute to
atherosclerosis.
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Figure 5.15 Cholesterol, a steroid    
Memebranes Bile salts--absorption of fats HDL and
LDL---triglycerides, phospholipids, cholesterol,
protein LDL receptor deficiency--more deposition
of cholesterol in arterial walls HDL--aid in
removal of cholesterol from tissues
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Polypeptide chains Polymers of amino acids that
are arranged in a specific linear sequence,
linked by peptide bonds Protein A macromolecule
consisting of one or more polypeptide chains
folded and coiled into specific
conformations Proteins make up 50 of the dry
weight of cells Proteins vary extensively in
structure, each with a unique 3-dimensional shape
(conformation) Although they vary in structure
and function, they are commonly made from only 20
amino acid monomers
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Figure 5.17 The 20 amino acids of proteins
nonpolar
Amino acid building blocks of
proteins Asymmetric carbon (alpha carbon) bonded
to H, Carboxyl group, Amino group, variable
R-group (side chain) Physical and chemical
properties of the side chain determine the
uniqueness of each amino acid At normal cellular
pH both the amino and carboxyl group are
ionized---pH determines which ionic state
predominates
Alpha carbon, asymmetric
Carboxyl
Amino
Side chain (R group)
Hydrophobic side chain
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Figure 5.17 The 20 amino acids of proteins
polar and electrically charged
Hydrophillic side chain
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Figure 5.18 Making a polypeptide chain
Peptide bond covalent bond formed by
condensation reaction
Amino
Carboxyl
Backbone has a repeating sequence N-CC-N-CC-
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Figure 5.19 Conformation of a protein, the
enzyme lysozyme
Proteins function depends on its specific
conformation Protein conformation 3-dimensional
shape Native conformation functional
conformation found under normal biological
conditions The conformation of a protein enables
it to bind specifically to another
molecular e.g. hormone/receptor,
enzyme/substrate, antibody/antigen Conformation
is a consequence of a specific linear sequence of
amino acids polypeptide chain coils and folds
spontaneously, mostly due to hydrophobic
interactions stabilized by chemical bonds and
weak interactions between neighboring regions of
the folded protein
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The primary structure of a protein
4 levels of protein structure Primary Secondary
Tertiary Quaternary
Primary structure sequence of amino
acids determined by genes slight change can
have large effect on function e.g. sickle-cell
hemoglobin sequence can be determined in the lab
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A single amino acid substitution in a protein
causes sickle-cell disease
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Sickled cells
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The secondary structure of a protein
Secondary structure regular, repeated coiling
and folding of a proteins polypeptide
backbone Contributes to final conformation Stabi
lized by H-bonds
Two major types of secondary structures Alpha
helix helical coil stabilized by H-bonds
found in fibrous proteins e.g. keratin and
collagen and some gobular proteins e.g. lysozyme
Beta pleated sheet a sheet of antiparallel
chains folded into accordion pleats held
together by H-bonds found in gobular proteins
e.g. lysozyme also in fibrous proteins e.g.
fibroin (silk)
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Spider silk a structural protein
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Examples of interactions contributing to the
tertiary structure of a protein
(Weak interaction)
Tertiary structure 3-dimensional shape due to
bonding between and among side chains and to
interactions between side chains and the aqueous
environment
(Weak interaction)
Strong interaction (covalent bond)
(Weak interaction)
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The quaternary structure of proteins
Quaternary structure structure that results
from the interactions between several polypeptide
chains
Supercoiled structure gives it strength
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Review the four levels of protein structure
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Figure 5.22 Denaturation and renaturation of a
protein
Proteins can be denatured by transfer to an
organic solvent, alters hydrophobic
interactions chemical agents that disrupt
hydrogen bonds, ionic bonds, disulfide
bridges excessive heat--disrupts weak
interactions
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Figure 5.23 A chaperonin in action
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Figure 5.24 X-ray crystallography
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Figure 5.25 DNA? RNA ? protein a diagrammatic
overview of information flow in a cell
Nucleic Acids store and transmit hereditary
information Protein conformation is determined
by primary structure Primary structure is
determined by genes Genes are hereditary units
that consist of DNA, a type of nucleic acid Two
types of nucleic acids DNA (Deoxyribonucleic
Acid) contains coded information that programs
all cell activity contains directions for its
own replication copied and passed from one
generation to the next found primarily in the
nucleus of eukaryotic cells makes up genes
that contain instructions for protein
synthesis via mRNA RNA (Ribonucleic Acid)
functions in the actual synthesis of proteins
coded for by DNA Sites of protein
synthesis are on ribosomes mRNA carries
encoded genetic messages from nucleus to
the cytoplams The flow of genetic info is from
DNA to RNA to protein
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Figure 5.26 The components of nucleic acids
Nucleic Acid polymer of nucleotides linked
together by condensation reactions Nucleotide
building block of nucleic acid made of a 5
carbon sugar, phosphate group, nitrogenous
base Nucleic acid polymers (polynucleotides) are
nucleotides linked together by phosphodiester
linkages Each gene contains a unique sequence of
nitrogenous bases which codes for a unique
sequence of amino acids in a protein
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Figure 5.27 The DNA double helix and its
replication
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Table 5.2 Polypeptide Sequence as Evidence for
Evolutionary Relationships