Download CH03_Lecture

The Chemical Building
Blocks of Life
Chapter 3
Adapted by G. Cornwall, Ph.D.
From Raven’s Biology, McGraw Hill Publishing
Carbon
• Framework of biological
molecules consists primarily of
carbon bonded to
– Carbon
– O, N, S, P or H
• Can form up to 4 covalent
bonds
• Hydrocarbons – molecule
consisting only of carbon and
hydrogen
– Nonpolar
– Functional groups add chemical
properties
2
Isomers
• Molecules with the
same molecular or
empirical formula
– Structural isomers
– Stereoisomers – differ in
how groups attached
• Enantiomers
– mirror image
molecules
– chiral
– D-sugars and Lamino acids
3
Macromolecules
• Polymer – built by
linking monomers
• Monomer – small,
similar chemical
subunits
• Three things to keep
track of in all four
macromolecules
– What is the Monomer
– What is the Polymer
– What is Bond
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5
• Dehydration synthesis
– Formation of large molecules by the removal of water
– Monomers are joined to form polymers
• Hydrolysis
– Breakdown of large molecules by the addition of
water
– Polymers are broken down to monomers
6
Carbohydrates
• Molecules with a 1:2:1 ratio of carbon,
hydrogen, oxygen
• Empirical formula (CH2O)n
• C—H covalent bonds hold much energy
– Carbohydrates are good energy storage
molecules
– Examples: sugars, starch, glucose
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Monosaccharides
• Simplest carbohydrate
• 6 carbon sugars play important roles
• Glucose C6H12O6
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• Fructose is a structural isomer of glucose
• Galactose is a stereoisomer of glucose
• Enzymes that act on different sugars can
distinguish structural and stereoisomers of this
basic six-carbon skeleton
9
Disaccharides
• 2 monosaccharides linked together by
dehydration synthesis
• Used for sugar transport or energy storage
• Examples: sucrose, lactose, maltose
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Polysaccharides
• Long chains of monosaccharides
– Linked through dehydration synthesis
• Energy storage
– Plants use starch
– Animals use glycogen
11
Polysaccharides
• Structural support
– Plants use cellulose
– Arthropods and fungi use chitin
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Nucleic acids
• Polymer – nucleic acids
• Monomers – nucleotides
– sugar + phosphate +
nitrogenous base
– sugar is deoxyribose in
DNA or ribose in RNA
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– Nitrogenous bases include
• Purines: adenine and guanine
• Pyrimidines: thymine, cytosine, uracil
– Nucleotides connected by phosphodiester bonds
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Deoxyribonucleic acid (DNA)
• Encodes information for
amino acid sequence of
proteins
– Sequence of bases
• Double helix – 2
polynucleotide strands
connected by hydrogen
bonds
– Base-pairing rules
• A with T (or U in RNA)
• C with G
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Ribonucleic acid (RNA)
• RNA similar to DNA
except
– Contains ribose instead of
deoxyribose
– Contains uracil instead of
thymine
• Single polynucleotide
strand
• RNA uses information in
DNA to specify sequence
of amino acids in proteins
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Other nucleotides
• ATP adenosine triphosphate
– Primary energy currency of the cell
• NAD+ and FAD+
– Electron carriers for many cellular reactions
20
Card Quiz A
The addition of water to break a chemical bond is termed
–
 Dehydration synthesis
 Hydrolysis
 Condensation
 Disassociation
Card Quiz A
The monomers of DNA are covalently bonded together.
These bonds are called phosphodiester bonds.
 This is true
 This is false
Card Quiz A
Which of the following is not part of a nucleotide?
 5 carbon sugar
 Phosphate group
 Fatty acid chain
 Nitrogenous base
Card Quiz A
Dehydration synthesis –




Is used to link monomers
Removes water to form bonds
Is involved in protein synthesis
All of the above
Card Quiz A
If a strand of DNA has a sequence ATCCTAG, what
would be the complementary sequence?
 CGAAGAT
 TAGGATC
 TACCGGA
 CGAAGTC
Card Quiz Answers
 Blue
 Green
 Red
 Yellow
 Red
Proteins
Protein functions include:
27
• Proteins are polymers
– Composed of 1 or more long, unbranched
chains
– Each chain is a polypeptide
• Amino acids are monomers
• Amino acid structure
– Central carbon atom
– Amino group
– Carboxyl group
– Single hydrogen
– Variable R group
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• Amino acids joined by dehydration
synthesis
– Peptide bond
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• Polypeptide chains fold in various ways to form
the final 3-D shape
• The shape of a protein determines its function
31
4 Levels of protein structure
1. Primary structure – sequence of amino
acids (beads on a string)
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1. Secondary structure – interaction of groups
in the peptide backbone
 a helix
 b sheet
33
3. Tertiary structure – final folded shape of a
globular protein
– Stabilized by a number of forces
– Final level of structure for proteins consisting
of only a single polypeptide chain
34
4. Quaternary structure – arrangement of
individual chains (subunits) in a protein
with 2 or more polypeptide chains
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Additional structural characteristics
• Motifs
– Common elements of secondary structure
seen in many polypeptides
– Useful in determining the function of unknown
proteins
37
• Domains
– Functional units within a larger structure
– Most proteins made of multiple domains that
perform different parts of the protein’s
function
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Chaperones
• Once thought newly made proteins folded
spontaneously
• Chaperone proteins help protein fold
correctly
• Deficiencies in chaperone proteins
implicated in certain diseases
– Cystic fibrosis is a hereditary disorder
• In some individuals, protein appears to have correct
amino acid sequence but fails to fold
39
Denaturation
• Protein loses
structure and function
• Due to environmental
conditions
– pH
– Temperature
– Ionic concentration of
solution
40
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41
Lipids
• Loosely defined group of molecules with
one main chemical characteristic
– They are insoluble in water
• High proportion of nonpolar C—H bonds
causes the molecule to be hydrophobic
• Fats, oils, waxes, and even some vitamins
42
Fats
• Triglycerides
– Composed of 1 glycerol and 3 fatty acids
• Fatty acids
– Need not be identical
– Chain length varies
– Saturated – no double bonds between carbon
atoms
• Higher melting point, animal origin
– Unsaturated – 1 or more double bonds
• Low melting point, plant origin
– Trans fats produced industrially
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Phospholipids
• Composed of
– Glycerol
– 2 fatty acids – nonpolar “tails”
– A phosphate group – polar “head”
• Form all biological membranes
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• Micelles – lipid molecules orient with polar
(hydrophilic) head toward water and
nonpolar (hydrophobic) tails away from
water
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• Phospholipid bilayer – more complicated
structure where 2 layers form
– Hydrophilic heads point outward
– Hydrophobic tails point inward toward each
other
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Other Kinds of Lipids
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Card Quiz B
What is the function of chaperonin proteins?
 Denaturation of polypeptides
 Assembling amino acids
 Regulation of gene expression
 Folding proteins
Card Quiz B
Which lipid forms membranes?
 Triglycerides
 Steroids
 Phospholipids
 Terpenes
Card Quiz B
Which of the following is not a function of proteins?
 Catalyzes chemical reactions
 Transport of material
 Structural components of tissues
 All of the above are protein functions
Card Quiz B
Which of the following is an amino group?
 -OH
 -C=O
 -COOH
 -NH2
Card Quiz B
Lincosamides are a class of antibiotics that inhibit
peptide bond formation. What type of biological molecule
would be effected?
 Lipids
 Proteins
 Nucleic Acids
 Carbohydrates
Card Quiz B
What happens when a lipid is hydrogenated?
 Hydrogen is added to the fatty acid chains
 The melting point is raised
 The lipid is converted into a saturated fat
 The fatty acid chain is straightened
 All of the above
Card Quiz Answers
 Yellow
 Red
 Yellow
 Red
 Yellow
 Green