1 the chemical building blocks of life chapter 3
Post on 19-Dec-2015
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2
Outline
• Biological Molecules– Macromolecules
ProteinsStructure and Denaturation
Nucleic AcidsDNA and RNA
LipidsFats and Phospholipids
CarbohydratesTransport and Storage
3
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.
4
Biological Molecules
• Functional groups– specific groups of atoms
attached to carbon backbones
retain definite chemical properties
• Macromolecules.– proteins– nucleic acids– lipids– carbohydrates
Hydroxyl
Carbonyl
Carboxyl
Amino
Sulfhydryl
Phosphate
Methyl
Acetic acid
Functional Group
StructuralFormula
Example
Acetaldehyde
Alanine
-mercaptoethanol
Glycerol phosphate
Pyruvate
HS
P
O–
O
O
HC
H
H
OH
O
OHC
H
HN
CO
Ethanol
C
H
H
CH
H
H
OH
CH
H
HC
O
OH
H
CH3
OH
CCHO NH
CH
H
HHC
O
CHOH
H HS HC
H
CH
OH
HC
OH
H HOC
H
P
O
C
O
C
O
HHC
H
O–
O–
O–
O–
5
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.
6
Carbohydrates
• Carbohydrates are loosely defined as molecules that contain carbon, hydrogen, and oxygen in a 1:2:1 ratio.
– monosaccharides - simple sugars– disaccharides - two monosaccharides
joined by a covalent bond– polysaccharides - macromolecules made
of monosaccharide subunits isomers - alternative forms of the same
substance
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H H HHH
OH OH
OHO
OH H
OHO
OH
HO
O
OH
OH H
HH
HO
H H
HH
OH
H
OH
OH
OH
H
H
HO
CH2OH
HH
H
OH
O
GalactoseFructoseGlucose
RiboseGlyceraldehyde
3-carbonsugar
5-carbon sugars
6-carbon sugars
Deoxyribose
HH
H
H
H
H
OH
OH
OC
C
C4
5
1
3 2
4
4
4
4
5
5
55
666
1
1
1
1
3
3
2
233
2
2
1
3
2
CH2OH CH2OH
CH2OH CH2OH
CH2OH
H
Sucrose
OH
HO
O
HO
OH
OH
O
O
Lactose
OH
OHHO
H
H H
HH
H
H
H
H
H
HH
H
OH
OH
OH
O
H
H
OH HOH
O
GalactoseGlucose
Glucose
Glucose
Glucose
Fructose
Maltose
CH2OH
HOOHH
H H H HH HH H
H
OH
O
O
OH
OHOH
OCH2OH
CH2OH CH2OH
CH2OH
CH2OHCH2OH
CH2OH
Starch: chain of -glucose subunits
HOOH
OH HHH H
H
O O O O O
HOOH
OH HHH
HH
H
O
Cellulose: chain of - glucose subunits
OH
OH HHH H
H OH
OH HH
H H
H OH
OH HHH H
H OH
OH HHH H
H
O
Plantcell wall
H H
H
OH
OHH
OH
OHO O O
O O
14
4 1
form of glucose
form of glucose
4 1
14
H OH
HO H OH
H HO
OO H
O
HOH
HOHH
H O
CH2OH CH2OH CH2OH CH2OH
CH2OHCH2OH
CH2OH
CH2OH
CH2OH
OHHHH
C O
H C OH
OH
H C OH
H
HO C H
C OH C OH
H
Fructose
H C OH
H C OH
H C OH
H
HO C H
H C OH
H
Glucose Galactose
Structuralisomer
Stereo-isomer
H C
C O
HO C H
H C OH
H C OH
H
HO C H
H C OH
H
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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
9
Structural Carbohydrates
• Cellulose - plants– alpha form or beta form of ring
• Chitin - arthropods and fungi– modified form of cellulose
10
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
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Alanine(Ala)
Leucine(Leu)
Isoleucine(Ile)
Phenylalanine(Phe)
Tryptophan(Trp)
Tyrosine(Tyr)
Glutamine(Gln)
Asparagine(Asn)
Threonine(Thr)
Serine(Ser)
Glycine(Gly)
Glutamicacid (Glu)
Asparticacid (Asp
Histidine(His)
Lysine(Lys)
Arginine(Arg)
Charged
Polar uncharged
Nonpolar
NONAROMATIC AROMATIC
Valine(Val)
CH3
C C
H O
CH
C C
H O
C C
H O
CH
C C
H O
H C
C C C C
H O
NHC
C C
H O
OH
H C OH
C C
H O
C C
H O
C
NH2
O
CH2
C C O–
H O
OH
C
C C
H O
O
H
C C
H O
C C
H O
CO
C C
H O
NH
C
C C
H O
C C
H O
C N
HC NH+
CH
H
C C
H O
CO
CH3 CH3
CH3 CH3CH3
CH3 CH2
CH2
CH2
CH2
CH2
CH2CH2
NH2
CH3
CH2
NH2
H3N+ H3N+ H3N+ H3N+ H3N+ H3N+O–O–O–O–O–
H3N+H3N+H3N+H3N+H3N+
O–
O–
O– O– O– O– O–
CH2
CH2CH2 CH2 CH2
CH2
CH2
CH2
CH2
CH2
CH2
NH2+
NH3+
O–
H O
H3N+ H3N+ H3N+ H3N+ H3N+ H3N+O–O–O–O–O–
Proline(Pro)
CH CNH2+ O
Methionine(Met)
CH2
C C O–
H O
CH2
S
CH3
Cysteine(Cys)
H3N+ C C O–
H O
SH
SPECIAL FUNCTION
CH2
CH2CH2
CH2H3N+
O–
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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).
13
Proteins
• Protein functions:– enzyme catalysis– defense– transport– support– motion– regulation– storage
14
Protein Structure
• Protein function is determined by its shape.– Protein structure
primary - specific amino acid sequence secondary - folding of amino acid chains motifs - folds or creases
supersecondary structure
15
Protein Structure
– tertiary - final folded shape of globular protein-determines protein activity and function
– domains - functional units
– quaternary - forms when two or more polypeptide chains associate to form a functional protein
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CH2
CH3
CCC
O
O
NR
R
R
CNC C
C
H
C
H
H
C C S
CO
ON
N
C
H
H
CCSH
H
C
C O
ON
N
C
CCH3
Hydrogenbond
Disulfidebridge
Van der Waalsattraction
Hydrophobicexclusion
C
C
CC
C
O
(CH2)4
(NH3+)
CH2
O
ON
3
4
5
1
2
Ionic bondO–
CH3
CH3CH3
CH3
CH3CH3
CH3
N
Interactions that contribute to protein’s shape
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Chaperone Proteins
• Chaperone proteins are special proteins which help new proteins fold correctly.
– Chaperone deficiencies may play a role in facilitating certain diseases.
18
Unfolding Proteins
• Denaturation refers to the process of changing a protein’s shape.
– usually rendered biologically inactive salt-curing and pickling used to preserve
food
19
Nucleic Acids
• Deoxyribonucleic Acid (DNA)– Encodes information used to assemble
proteins.• Ribonucleic Acid (RNA)
– Reads DNA-encoded information to direct protein synthesis.
20
Nucleic Acid Structure
• Nucleic acids are composed of long polymers of repeating subunits, nucleotides.
– five-carbon sugar– phosphate– nitrogenous base
purines adenine and guanine
pyrimidines cytosine, thymine,
and uracil
Phosphate group
Sugar
Nitrogenous base
N
N
O
4’
5’
1’
3’ 2’
28
7 6
394
5
P CH2
O
–O
O–
OH ROH in RNA
H in DNA
O
N
NH2
N1
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The nitrogenous bases
Adenine
Guanine
CC
NN
N
C
HN
C
CH
O
H
Cytosine(both DNAand RNA)
Thymine(DNA only)
Uracil(RNA only)
HCC
NC
H
N
C
NH2
N
NCH
OCC
NC
H
N
CH
H
OCC
NC
H
N
C
O
HH3C
H
OCC
NC
H
N
C
O
HH
H
PURINES
PYRI
MIDINES
NH2
NH2
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Nucleic Acid Structure
• DNA exists as double-stranded molecules.
– double helix– complementary base
pairing hydrogen bonding
• RNA exists as a single stand.
– contains ribose instead of deoxyribose
– contains uracil in place of thymine
5’
3’
P
P
P
P
OH
5-carbonsugar
Nitrogenous base
Phosphate group
O
O
O
O
Phosphodiesterbonds
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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 fatty acid phosphate group
Schematic Formula Space-filling model Icon
Polarhydrophilic
heads
Nonpolarhydro-phobic
tails
CH2
CO O
OO
OPO
O O–
H2C CH
C
CH3
Choline
Phosphate
Glycerol
Fatty
acid
Fatty
acid
CH2
CH2
CH3
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CHCHCH2
CH2
CH2
CH2
CH2
CH2
CH2
N+(CH3)3
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
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
– Unsaturated fats - at least one double bond between successive carbon atoms
Polyunsaturated - contains more than one double bond
usually liquid at room temperature
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Saturated fat
Unsaturated fat
O
C
H
C
H
H
C
H
H
C
H
H
CH C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
O
O
C
H
CH
H
CH
H
CH
H
CH CH
H
CH
H
CH
H
CH
H
CH
H
CH
H
CH
H
CH
H
CH
H
CH
H
CH
H
CH
O
O
C
H
C
H
H
C
H
H
C
H
H
CH C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
H
CH
H
CH
H
H
C
H
H
C
H
HO
H H
C
H
H
C
H
H
O
C
H
CH C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
C
H
H
C
H
C C
H H H
H
C
H
C C
H
O
H
C
H
CH
H
CH
H
O
C
H
CH CH
H
CH
H
CH
H
CH
H
CH
H
CH
H
CH
CH
H
C
H H
CH
CH
H
C
H H
CHH
CH H
O
HH
C
H
C
H
H
C
H
H
O
C
H
CH C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
C
H
H
C
H
C
H
C
H
H
C
H
C
H
C
H H
O
H
H
H
H
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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.
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Summary
• Biological Molecules– Macromolecules
CarbohydratesTransport and Storage
ProteinsStructure and Denaturation
Nucleic AcidsDNA and RNA
LipidsFats and Phospholipids