Download Revised Chapter 4 and 5

• Chapter 4~
Carbon &
The Molecular
Diversity of Life
• Chapter 5~
The Structure &
Function of
Macromolecules
Organic chemistry
• Carbon
– tetravalence
– Tetrahedron
– shape determine function
Hydrocarbons
•
•
•
•
Only carbon & hydrogen (petroleum; lipid ‘tails’)
Covalent bonding; nonpolar
High energy storage
Isomers (same molecular formula, but different
structure & properties)
• structural~differing covalent bonding arrangement
• geometric~differing spatial arrangement
• enantiomers~mirror images pharmacological industry
(thalidomide)
Figure 4.6 Three types of isomers
Functional Groups, I
• Attachments that
replace one or more of
the hydrogens bonded
to the carbon skeleton
of the hydrocarbon
• Each has a unique
property from one
organic to another
• Hydroxyl Group
H bonded to O;
alcohols;
polar (oxygen);
solubility in water
• Carbonyl Group
• C double bond to O;
At end of skeleton: aldehyde
Otherwise: ketone
Functional Groups, II
• Carboxyl Group
O double bonded to C to hydroxyl;
carboxylic acids; covalent bond
between O and H; polar; dissociation,
H ion
• Amino Group
N to 2 H atoms; amines; acts as a base
(+1)
Functional Groups, III
• Sulfhydral Group
sulfur bonded to H;
thiols
• Phosphate Group
phosphate ion;
covalently attached
by 1 of its
O to
the C skeleton;
Polymers
• Covalent monomers
• Condensation reaction
(dehydration reaction):
One monomer provides a
hydroxyl group while the other
provides a hydrogen to form a
water molecule
• Hydrolysis:
bonds between monomers
are broken by adding water
(digestion)
D:\ImageLibrary1-17\05Macromolecules\05-02Macromolecules.mov
Carbohydrates, I
• Monosaccharides
√ CH2O formula;
√ multiple hydroxyl (-OH)
groups and 1 carbonyl
(C=O) group:
aldehyde (aldoses) sugar
ketone sugar
√ cellular respiration;
√ raw material for amino acids
and fatty acids
Carbohydrates
• Functions:
 Energy source
 Provide building material (structural role)
• Contain carbon, hydrogen and oxygen in a 1:2:1 ratio
• Varieties: monosaccharides, disaccharides, and
polysaccharides
Carbohydrates, II
• Disaccharides
√ glycosidic linkage (covalent
bond) between 2
monosaccharides;
√ covalent bond by dehydration
reaction
• Sucrose (table sugar)
√ most common disaccharide
Figure 5.5 Examples of disaccharide synthesis
Carbohydrates, III
• Polysaccharides
Storage:
Starch~ glucose monomers
Plants: plastids
Animals: glycogen
• Polysaccharides
Structural:
Cellulose~ most abundant
organic compound;
Chitin~ exoskeletons; cell
walls of fungi; surgical thread
Lipids
•
•
•
•
•
•
•
•
No polymers; glycerol and fatty acid
Fats, phospholipids, steroids
Hydrophobic; H bonds in water exclude fats
Carboxyl group = fatty acid
Non-polar C-H bonds in fatty acid ‘tails’
Ester linkage: 3 fatty acids to 1 glycerol
(dehydration formation)
Triacyglycerol (triglyceride)
Saturated vs. unsaturated fats; single vs. double bonds
Triglycerides: Long-Term Energy Storage
• Fatty acids are either unsaturated or saturated.
 Unsaturated - one or more double bonds between
carbons GOOD type of fat
• Tend to be liquid at room temperature
– Example: plant oils
 Saturated - no double bonds between carbons
• Tend to be solid at room temperature BAD FAT
– Examples: butter, lard
15
Phospholipids
• 2 fatty acids instead of
3 (phosphate group)
• ‘Tails’ hydrophobic;
‘heads’ hydrophilic
• Micelle (phospholipid
droplet in water)
• Bilayer (double layer);
cell membranes
Steroids
• Lipids with 4 fused carbon rings
• Ex: cholesterol:
cell membranes;
precursor for other
steroids (sex hormones)
Proteins
• Importance:
instrumental in nearly everything organisms do; 50% dry weight of cells; most
structurally sophisticated molecules known
• Monomer: amino acids (there are 20) ~
carboxyl (-COOH) group, amino group (NH2), H atom, variable group (R)….
• Variable group characteristics:
polar (hydrophilic), nonpolar (hydrophobic), acid or base
• Three-dimensional shape (conformation)
• Polypeptides (dehydration reaction):
peptide bonds~ covalent bond; carboxyl group to amino group (polar)
3.4 Proteins
• Proteins are polymers of amino acids
linked together by peptide bonds.
 A peptide bond is a covalent bond between
amino acids.
• Two or more amino acids joined together
are called peptides.
 Long chains of amino acids joined together are
called polypeptides.
• A protein is a polypeptide that has folded
into a particular shape and has function.
20
Functions of Proteins
• Metabolism
 Most enzymes are proteins that act as catalysts to accelerate
chemical reactions within cells.
• Support
 Keratin and collagen
• Transport
 Hemoglobin and membrane proteins
• Defense
 Antibodies
• Regulation
 Hormones are regulatory proteins that influence the metabolism of
cells.
• Motion
 Muscle proteins and microtubules
21
Synthesis and Degradation of a Peptide
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
amino group
amino acid
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
amino group
peptide bond
acidic group
dehydration reaction
hydrolysis reaction
amino acid
amino acid
dipeptide
water
Levels of Protein Structure
• Proteins cannot function properly unless they
fold into their proper shape.
 When a protein loses it proper shape, it said to be
denatured.
• Exposure of proteins to certain chemicals, a
change in pH, or high temperature can disrupt
protein structure.
• Proteins can have up to four levels of
structure:




Primary
Secondary
Tertiary
Quaternary
24
Four Levels of Protein Structure
 Primary
• The sequence of amino acids
 Secondary
• Characterized by the presence of alpha helices and
beta (pleated) sheets held in place with hydrogen
bonds
 Tertiary
• Final overall three-dimensional shape of a
polypeptide
• Stabilized by the presence of hydrophobic
interactions, hydrogen bonding, ionic bonding, and
covalent bonding
 Quaternary
• Consists of more than one polypeptide
25
Primary Structure
• Conformation:
Linear structure
• Molecular Biology:
each type of protein has a unique primary
structure of amino acids
• Ex: lysozyme
• Amino acid substitution:
hemoglobin; sickle-cell anemia
Secondary Structure
• Conformation:
coils & folds (hydrogen bonds)
• Alpha Helix:
coiling; keratin
• Pleated Sheet:
parallel; silk
Tertiary Structure
• Conformation:
irregular contortions from
R group bonding
hydrophobic
disulfide bridges
hydrogen bonds
ionic bonds
Quaternary Structure
• Conformation:
2 or more polypeptide
chains aggregated into 1
macromolecule
collagen (connective
tissue)
hemoglobin
Nucleic Acids, I
•
•
•
•
Deoxyribonucleic acid (DNA)
Ribonucleic acid (RNA)
DNA->RNA->protein
Polymers of nucleotides
(polynucleotide):
nitrogenous base
pentose sugar
phosphate group
• Nitrogenous bases:
pyrimidines~cytosine, thymine, uracil
purines~adenine, guanine
3.5 Nucleic Acids
• Nucleic acids are polymers of nucleotides.
• Two varieties of nucleic acids:
 DNA (deoxyribonucleic acid)
• Genetic material that stores information for its own
replication and for the sequence of amino acids in
proteins.
 RNA (ribonucleic acid)
• Perform a wide range of functions within cells
which include protein synthesis and regulation of
gene expression
31
Structure of a Nucleotide
• Each nucleotide is composed of three parts:
 A phosphate group
 A pentose sugar
 A nitrogen-containing (nitrogenous) base
• There are five types of nucleotides found in nucleic
acids.
 DNA contains adenine, guanine, cytosine, and thymine.
 RNA contains adenine, guanine, cytosine, and uracil.
• Nucleotides are joined together by a series of
dehydration synthesis reactions to form a linear
molecule called a strand.
32
Nucleotides
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
phosphate
P
C
O
5'
4'
S
1'
2'
3'
pentose sugar
nitrogencontaining
base
Figure 5.28 DNA
cell
RNA
protein: a diagrammatic overview of information flow in a
Nucleic Acids, II
• Pentoses:
– ribose (RNA)
– deoxyribose (DNA)
– nucleoside (base + sugar)
• Polynucleotide:
– phosphodiester linkages (covalent);
phosphate + sugar
Nucleic Acids, III
• Inheritance based on DNA
replication
• Double helix (Watson & Crick
- 1953)
H bonds~ between paired bases
van der Waals~ between stacked
bases
• A to T; C to G pairing
• Complementary
Structure of DNA and RNA
 The backbone of the nucleic acid strand is composed
of alternating sugar-phosphate molecules.
 RNA is predominately a single-stranded molecule.
 DNA is a double-stranded molecule.
• DNA is composed of two strands held together
by hydrogen bonds between the nitrogencontaining bases. The two strands twist around
each other to form a double helix.
– Adenine hydrogen bonds with thymine
– Cytosine hydrogen bonds with guanine
• The bonding between the nucleotides in DNA is
referred to as complementary base pairing.
37
A Special Nucleotide: ATP
• ATP (adenosine triphosphate) is composed of adenine,
ribose, and three phosphates.
• ATP is a high-energy molecule due to the presence of
the last two unstable phosphate bonds.
• Hydrolysis of the terminal phosphate bond yields:
 The molecule ADP (adenosine diphosphate)
 An inorganic phosphate
 Energy to do cellular work
• ATP is called the energy currency of the cell.
38
ATP
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
a.
adenosine
triphosphate
c.
NH2
NH2
N
N
N
H2O
P
N
adenosine
b.
P
P
triphosphate
ATP
N
N
N
P
N
adenosine
P
diphosphate
ADP
c: © Jennifer Loomis / Animals Animals / Earth Scenes
+
P
phosphate
+
ENERGY