Download 3.1 Life`s molecular diversity is based on the properties of carbon

3.1 Life’s molecular diversity is based on the
properties of carbon
A carbon atom can form four covalent bonds
Allowing it to build large and diverse organic compounds
Structural
formula
Ball-and-stick
model
H
H
Space-filling
model
H
H
C
C
H
H
Methane
H
H
The 4 single bonds of carbon point to the corners of a tetrahedron.
Carbon chains vary in many ways
H
H H
C C
H
H
H H H
C C C
H
H H H
H H
Ethane
Propane
Carbon skeletons vary in length.
H
H C H
H H H H
H
H
H C C C C H
H C C C H
H H H
H H H H
Butane
Isobutane
Skeletons may be unbranched or branched.
H H H H
C
C C C H
H
H
H H
H
1-Butene
2-Butene
Skeletons may have double bonds, which can vary in location.
H
H H H H
C C C C H
H
H
H
C
H
H C C
H
H
C
H C
C H
H
C
C H
H C C C H
H
H
C
H
H
H
Benzene
Cyclohexane
Skeletons may be arranged in rings.
Hydrocarbons are composed of only hydrogen and carbon
Functional groups help determine the properties of
organic compounds
– Functional groups are particular groupings of atoms
•
That give organic molecules particular properties
OH
O
The four main classes of biological molecules are
•
•
•
•
carbohydrates,
lipids,
proteins
nucleic acids
Monosaccharides are the simplest carbohydrates
The monosaccharides glucose and fructose are
isomers.
H
O
H
C
C
OH
C
O
HO
C
H
H
H
C
OH
HO
C
H
H
C
OH
H
C
OH
H
C
OH
H
C
OH
H
C
OH
H
C
OH
H
Glucose
H
Fructose
Monosaccharides can also occur as ring structures
Glucose
O
H
C
CH2OH
H
C
OH
HO
C
H
H
H
C
OH
HO
H
C
OH
H
C
OH
O
H
OH
H
H
OH
ring structure
H
Linear structure
H
O
OH
Simplified
structure
Cells link two single sugars (Monosaccharides) to
form disaccharides.
CH2OH
O
H H
OH
HO
CH2OH
O
H H
H
H
H
OH
Glucose
HO
OH
H OH
Glucose
H2O
CH2OH
CH2OH
H H
H
OH
HO
OH
H
O
OH
H
H
OH
H
H
O
O
H
H
OH
H
H
OH
OH
Maltose
Cells link two single sugars (Monosaccharides) to
form disaccharides.
Cells link two single sugars (Monosaccharides) to
form disaccharides.
Cells make most of their large molecule by joining
smaller organic molecules into chains called
polymers by a dehydration reaction.
H
OH
OH
Short polymer
OH
H
H
Unlinked monomer
Dehydration
Dehydration
reaction
reaction
H
H
H2O
OH
OH
Longer polymer
Polymers are broken down to monomers by the
reverse process, hydrolysis.
H2O
H
OH
Hydrolysis
H
OH
OH
H
Starch and glycogen are polysaccharides that store sugar
for later use
Cellulose is a polysaccharide found in plant cell walls
Glucose
monomer
STARCH
Starch granules in
potato tuber cells
O O
O
O
O
O
O
O
O
O
Glycogen
granules in
muscle
tissue
GLYCOGEN
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O O
Cellulose fibrils in a
plant cell wall
Cellulose
molecules
O
O
CELLULOSE
O
O
O
O
O
O
O
O
O
O
The orientation of the bond connecting the glucose
monomers is different between starch and cellulose
STARCH
CELLULOSE
Lipids
•Fats are lipids that are mostly energy-storage molecules
•Lipids are diverse compounds that consist mainly of carbon
and hydrogen atoms linked by nonpolar covalent bonds
C O
CH2
CH2
CH2
CH2
CH2 Fatty acid
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH3
Fats, also called triglycerides, are lipids whose main
function is energy storage
Fats consist of glycerol linked to three fatty acids
H
H
H
H
C
C
C
O
C
O
O C
H
O
O
C
O
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH3
CH3
CH
CH2
CH2
CH2
CH2
CH2
CH2
CH3
There are different types of lipids with a variety of
functions
– Phospholipids are a major component of cell membranes
– Waxes form waterproof coatings
H
H
H
– Steroids are often hormones
H C
C
H
C
Phosphate
Phospholipid
O
O
O
O
P
O C
O C
O
O
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH3
Fatty acid
CH
CH2
CH2
CH2
CH2
CH2
CH2
CH3
There are different types of lipids with a variety of
functions
– Phospholipids are a major component of cell membranes
– Waxes form waterproof coatings
– Steroids are often hormones
There are different types of lipids with a variety of
functions
– Phospholipids are a major component of cell membranes
– Waxes form waterproof coatings
– Steroids are often hormones
Steroids
There are different types of lipids with a variety of
functions
– Phospholipids are a major component of cell membranes
– Waxes form waterproof coatings
– Steroids are often hormones
Steroids
H3C
CH3
CH3
CH3
CH3
HO
Proteins
– Proteins are essential to the structures and activities of
life
– A protein is a polymer constructed from amino acid
monomers
– Proteins are made from amino acids linked by peptide
bonds
Proteins
Each protein has a different arrangement of a
common set of 20 amino acid monomers.
Proteins
Each amino acid contains
•
•
•
An amino group
A carboxyl group
An R group, which distinguishes each of the 20 different
amino acids
H
O
H
N
C
H
C
OH
R
Amino
group
Carboxyl (acid)
group
Proteins
Each amino acid contains
•
•
•
An amino group
A carboxyl group
An R group, which distinguishes each of the 20 different amino
acids
Each amino acid has specific properties
•
H
H
H
O
N
C
H
C
H
O
N
OH
CH2
H
H
C
H
C
CH
N
OH
CH2
O
C
H
OH
CH2
OH
C
CH3 CH3
OH
Leucine
(Leu)
Hydrophobic
C
Serine (Ser)
O
Aspartic acid
(Asp)
Hydrophilic
Proteins
Cells link amino acids together through peptide bonds
Carboxyl
group
Peptide
bond
Amino
group
O
N
C
R
Amino acid
O
+
OH
N
Dehydration
reaction
O
C
H
N
OH
R
Amino acid
H2O
C
C
O
N
C
R
R
Dipeptide
C
OH
Proteins
Cells link amino acids together through peptide bonds
Polypeptide
Protein
Groove
A protein’s shape depends on four levels of
structure
– primary structure
Leu
Met
Asn
Pro
Val
Cys
Gly
Gly
Thr
Glu
Ser
Lys
Lys
Ala
Val
Leu
Asp
Ala
Val
Arg
Amino acids
Gly
Pro
Ser
Val
Ala
Ile
Arg
Val
His
Phe
Val
A protein’s shape depends on four levels of
structure
– primary structure
– secondary structure
Amino acids
Alpha helix
Pleated sheet
A protein’s shape depends on four levels of
structure
– primary structure
– secondary structure
– tertiary structure
Groove
A protein’s shape depends on four levels of
structure
– primary structure
– secondary structure
– tertiary structure
– quaternary structure
Polypeptide
chain
Collagen
Nucleic acids
Nucleic acids are information-rich polymers
of nucleotides
DNA and RNA Serve as the blueprints for proteins and thus
control the life of a cell
RNA and DNA are made up of very similar nucleotides.
H
H
H
N
N
N
N
OH
O
P
N
O
CH2
!
O
Phosphate
group
O
H
H
N
Nitrogenous
base (A)
O
P
N
O
CH2
O
!
O
H
H
N
H
H
OH
H
N
Phosphate
group
H
H
H
N
Nitrogenous
base (A)
H
H
H
OH OH
Sugar
OH
H
Sugar
RNA
DNA
The sugar and phosphate form the backbone for the
nucleic acid or polynucleotide
A
T
C
G
T
Sugar-phosphate
backbone
Nucleotide
DNA consists of two polynucleotides twisted around
each other in a double helix.
C
A
C
T
G
C
G
TA
C
G
A
T
A
Base
pair
T
GC
T
A
A
T
TA
RNA, by contrast is a single-stranded polynucleotide.
C
A
C
T
G
C
G
TA
C
G
A
T
A
Base
pair
T
GC
T
A
A
TA
T
RNA consists of one polynucleotides twisted around
itself.
DNA and RNA have different functions:
•DNA encodes information in the form of genes.
•RNAs are both is both the messenger of information
•RNAs also can have enzyme activity.
C
C G
A
G
C
T
A
T
C
G
A
A
T A
T
A
Base
pair
A
T
G C
T
T