Transcript Document

The Chemical Building Blocks of Life
Chapter 3
1
Biological Molecules
•
The framework of biological molecules
consists of carbon bonded to other carbon
molecules, or other types of atoms.
– Hydrocarbons consist of carbon and
hydrogen.
 Covalent bonds store considerable
energy.
 Make good fuels
2
Biological Molecules
•
•
Functional groups
– specific groups of atoms attached to
carbon backbones
 retain definite chemical properties
Macromolecules.
– proteins
– nucleic acids
– lipids
– carbohydrates
3
Functional
Group
Structural
Formula
Hydroxyl
OH
Carbonyl
C
O
O
Carboxyl
C
OH
H
Amino
N
H
Sulfhydryl
S H
O–
Phosphate
Methyl
Example
H H
H C C OH
H H
Ethanol
H O
H C C H
H
Acetaldehyde
H
O
H C C
OH
H
Acetic acid
O H
H
HO C C N
CH3 H
Alanine
H H
HO C C S H
H H
b-mercaptoethanol
OH OH H
O
O P O– H C C C O P O–
H H H
O–
O
Glycerol phosphate
H
O O H
O– C C C H
C H
H
H
Pyruvate
4
Macromolecules
•
Macromolecules are often polymers.
– long molecule built by linking together
small, similar subunits
 Dehydration synthesis removes OH and
H during synthesis of a new molecule.
 Hydrolysis breaks a covalent bond by
adding OH and H.
5
6
Proteins - C, H, O, N, S
A.
B.
C.
Amino acids
Peptide bonds
Polypeptide chains
H
R O
H-N- C-C
H H
Amine
Group
- OH
Acid
Group
7
Protein Function
8
Amino Acids
•
contain an amino group (-NH2), a carboxyl
group (-COOH) and a hydrogen atom, all
bonded to a central carbon atom
– twenty common amino acids grouped
into five classes based on side groups
 nonpolar amino acids
 polar uncharged amino acids
 charged amino acids
 aromatic amino acids
 special-function amino acids
9
Amino Acids
•
Peptide bond links two amino acids.
– A protein is composed of one or more long
chains of amino acids linked by peptide
bonds (polypeptides).
10
NONAROMATIC
AROMATIC
Nonpolar
CH3 CH3
CH3
CH
CH2
CH3 CH3
CH3
CH2
CH
H C
C O– H3N+ C C O– H3N+ C
H3N+ C
H O
H
Alanine
(Ala)
O
H
H3
CH3
CH2
H
C
C
H
O
O– H3N+
Glycine
(Gly)
C
C
H
O
H
O–
H3
C
N+
OH
C C
NH2
O
H3
C
C
H
O
H3
N+
C
H
O
O–
O
CH2
C
CH2
CH2
C
C
H
O
H3
N+
C
C O–
H O
Tyrosine
(Tyr)
NH2
C
H3
O–
Threonine Asparagine Glutamine
(Thr)
(Asn)
(Gln)
O–
O–
OH
CH2
C
C
N+
H O
CH2
O–
Charged
O
H O
CH2
CH2
N+
H O
Serine
(Ser)
O– H3N+ C C O– H3N+ C C O–
C
C
O–
CH2
NH2
O
O
N+
CH2
Leucine Isoleucine Phenylalanine Tryptophan
(Leu)
(Ile)
(Phe)
(Trp)
Polar uncharged
OH
CH3
C O– H3N+ C C
H O
Valine
(Val)
NH
C
H3
N+
C
HC
C
C
H O
NH+
N
H
CH
CH2
O–
H3
N+
C
C
CH2 NH3+
NH
CH2
CH2
CH2
CH2
CH2
CH2
O–
H O
Glutamic Aspartic Histidine
acid (Glu) acid (Asp
(His)
H3
N+
NH2+
C
C
O–
H O
Lysine
(Lys)
H3
N+
C
C O–
H
O
Arginine
(Arg)
11
Protein Structure


The shape of proteins is extremely important and
can determine the function
Water’s tendency to hydrophobically exclude
nonpolar molecules literally shoves the nonpolar
portions of the protein to the interior
Many shapes
 Primary – the specific amino acid sequences
 Secondary – formed by hydrogen bonding
 Alpha helix – coils
 Beta pleated sheet - foldbacks

motifs - folds or creases
 supersecondary structure
12
1 Primary structure
R
H H O
R
H H O
R
H H
C C N C C N C C N C C N C C N C
H O
H H O
H H O
R
R
R
2 Secondary
structure
b pleated sheet
b a b motif
a helix
3 Motifs
a turn a motif
13
Protein Structure



Tertiary - final folded shape of globular
protein (3-dimensional shape) based on
bonding of side groups
Domains – independent functional units of
the protein 100–200 amino acids long encoded by a specific DNA sequence
(exon)
Quaternary - forms when two or more
polypeptide chains associate to form a
functional protein
14
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
4 Tertiary
structure
5 Domains
Domain 1
6
Quaternary
structure
Domain 2
Domain 3
15
Chaperone Proteins
•
Chaperone proteins are special proteins
which help new proteins fold correctly.
– Chaperone deficiencies may play a role in
facilitating certain diseases.
16
•
Unfolding Proteins
Denaturation refers to the
process of changing a
protein’s shape.
– usually rendered
biologically inactive
 pH
 temperature
 Ionic concentration salt-curing and
pickling used to
preserve food
17
Nucleic Acids - C, H, O, N, P
•
•
Deoxyribonucleic Acid (DNA)
– Encodes information used to assemble
proteins.
Ribonucleic Acid (RNA)
– Reads DNA-encoded information to direct
protein synthesis.
18
Nucleic Acid Structure
•
Nucleic acids are composed
of long polymers of
repeating subunits,
nucleotides.
– five-carbon sugar
– Phosphate group
– nitrogenous base
 Purines double ringed
 adenine and
guanine
 Pyrimidines – single
ringed
 cytosine, thymine,
and uracil
19
59
Phosphate group
P
P
O
P
O
P
Cytosine
(both DNA
C C N and RNA)
C
C O
N
H
Thymine
O
(DNA only)
C
N
H
C
CN C O
NH2
H
P
P H
NC CH
N
U
Y
H
Phosphodiester R
R
O Guanine I
bonds
I
N
M
NCC N H
E H C
I H3C
C
C
NH2 D H
S
N N
I
H
H
N
5-carbon
O
E
sugar
S
C
Nitrogenous base
H C N
H CN C
O
H
H C
O
NH2 Adenine
NCC N
Uracil
(RNA only)
H
O
OH
39
20
Nucleic Acid Structure
•
•
DNA exists as double-stranded
molecules.
– double helix
– complementary base pairing
 Chargaff’s rule
 hydrogen bonding
RNA exists as a single stand.
– contains ribose instead of
deoxyribose
– contains uracil in place of
thymine
21
Structure of DNA
22
•
•
Lipids
Lipids are loosely defined as groups of
molecules that are insoluble in water.
– fats and oils
Phospholipids form the core of all biological
membranes.
– composed of three subunits
 Glycerol - backbone
 fatty acid – long tail
 phosphate group – head
 Polar head - hydrophilic
 Nonpolar tail - hydrophobic
23
Phospholipids form membranes
micelle
24
Fats and Other Lipids
•
Fats consist a of glycerol
molecule with three attached
fatty acids (triglyceride /
triglycerol).
– Saturated fats - all internal
carbon atoms are bonded
to at least two hydrogen
atoms – maximum # of H
– Unsaturated fats - at least
one double bond between
successive carbon atoms
 Polyunsaturated contains more than
one double bond
 usually liquid at
room temperature
25
Fats as Energy Storage Molecules
•
Fats, on average, yield about 9 kcal per
gram versus 4 kcal per gram for
carbohydrates.
– Animal fats are saturated while most plant
fats are unsaturated.
 Consumption of excess carbohydrates
leads to conversion into starch,
glycogen, or fats for future use.
26
Carbohydrates
•
Carbohydrates are loosely
defined as molecules that
contain carbon, hydrogen, and
oxygen in a 1:2:1 ratio.
– monosaccharides - simple
sugars
27
–
disaccharides - two monosaccharides
joined by a covalent bond
H
H
O
H
H
C
O
H
H
C
O
C
M
o
n
o
s
a
c
c
h
a
r
i
d
e
H
HH
C
C
2
X
G
l
u
c
o
s
eO
H
HO
H
HO
O
C
H
H
C
H
O
HO
HO
H
C
C
C
C
H
O
H
H
O
H
H
O
H2
O
2
H
O
H
H
C
D
i
s
a
c
c
h
a
r
i
d
e
M
a
l
t
o
s
e
C
H
O
H
H
C
O
C
H
H
C
H
O
C
HH
H
C
O
HO
H
H
C
H
C
H
HO
O
H
CO C
C
C
H
O
H
H
O
H
28
–
polysaccharides - macromolecules made
of monosaccharide subunits

isomers - alternative forms of the same
substance – Many C6H1206
29
Carbohydrate Transport and Storage
•
•
Transport disaccharides
– Humans transport glucose as a simple
monosaccharide.
– Plants transform glucose into a
disaccharide transport form.
Storage polysaccharides
– plant polysaccharides formed from
glucose – starches
 most is amylopectin
– Animal starch is glycogen
30
Structural Carbohydrates
•
Cellulose - plants
– alpha form or
beta form of ring
Chitin - arthropods
and fungi
 modified form
of cellulose
31