The Chemical Building Blocks of Life
Chapter 3
1
Outline
•
Biological Molecules
– Macromolecules
 Carbohydrates
 Transport and Storage
 Lipids
 Fats and Phospholipids
 Proteins
 Structure and Denaturation
 Nucleic Acids
 DNA and RNA
2
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.
3
Biological Molecules
•
•
•
Functional groups
– specific groups of atoms attached to carbon
backbones
 retain definite chemical properties
Macromolecules.
Other than water, biomolecules fall into 4 classes
– proteins
– nucleic acids
– lipids
– carbohydrates
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
Table 3.1
6
Table 3.2
From Subunits to Macromolecules
7
Table 3.2
From Subunits to Macromolecules
8
Carbohydrates
•
•
•
•
•
•
Molecules made of C and Hydrates (H and O)
Energy packed molecules used by most life
Can also be structural molecules in life
empirical formula is Cx(H2O)y
many named with ending “ose” ( ex: sucrose)
3 basic types:
–
–
–
monosaccharides
disaccharides
polysaccharides
9
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
10
Monosaccharides
•
•
•
Are the “simple sugars”
– composed of (3-7) linked carbons
– chains of carbons with a hydroxyl
most common = 6 -----> hexoses (C6H12O6)
– examples of hexoses are glucose and
fructose
many are Isomers:
– same empirical formula but different structural
formula
– gives a different “sweetness” and solubility
11
»Do you see the 6 carbons common to each?
»Do they have the same empirical formula?
»How do they differ?
12
Disaccharides
•
•
•
•
More complex sugars
(6-14) carbons in a chain or ring (C12H22O11)
includes table sugar (sucrose) and lactose
(milk)
created by uniting two monosaccharides
through dehydration synthesis (Gee,
where have you seen those words ?!?!?)
13
Hydrolysis and Dehydration Synthesis
14
Polysaccharides
•
•
•
Huge!!!! 100’s of mono’s linked
Animal form = glycogen
– storage of energy contained in glucose
– insulin promotes conversion to glycogen for
liver
– unique structural polysaccharide is called
chitin; hydroxyl group is replaced by an
amino group
Plant forms = starch and cellulose
– starch is for energy storage
– cellulose is a structural form - not soluble
15
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
16
Structural Carbohydrates
•
•
Cellulose - plants
– alpha form or beta form of ring
Chitin - arthropods and fungi
– modified form of cellulose
17
Lipids
•
•
•
Lipids are loosely defined as groups of
molecules that are insoluble in water.
– fats and oils
C, H and O primarily (not exclusively)
non-polar therefore insoluble in water
18
More Lipids
Phospholipids form the core of all biological
membranes.
– composed of three subunits
 glycerol
 fatty acid
 phosphate group
19
•
•
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
– carbons are single bonded - solids at room
temp
– contains maximum number of H atoms (
saturated with “H” )
– straight chains
– not preferred in diet medically (beef, pork)
20
Fats and Other Lipids
Unsaturated fats - at least one double bond between
successive carbon atoms
– carbons in double or triple bonds, less H - liquids
– tend to be “kinked” chains
– if many double or triple bonds ----->
polyunsaturated
– diet preferred (fish and vegetables)
•
Polyunsaturated - contains more than one double
bond
 usually liquid at room temperature
Why would unsaturated fats be more ideal in your diet
then saturated fats? Why are trans fats bad?
(structurally)
•
21
Fatty Acid Structure
•
•
Fatty acids are long carbon chains (4-24)
with a carboxyl at the end
Why are they called fatty acids?
22
Triglycerides
•
•
Most common of all lipids
composed of 3 fatty acids joined to
glycerol through dehydration synthesis
23
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Lipid Structure
CH2
CH2
Polar
hydrophilic
heads
Choline
Nonpolar
hydrophobic
tails
O
O P O–
O
H
C CH2
O
Phosphate
Glycerol
F
a
t
t
y
F
a
t
t
y
a
c
i
d
a
c
i
d
Schematic
N+(CH3)3
H2C
O
C O CO
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH3
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH
CH
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH3
Formula
Space-filling model
Icon
24
Saturated vs Unsaturated Fats
25
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Fig.
3.22(TE
Art)
Lipid
Structure
H
O H H H H H H H H H H H H H H H H H
H
O H H H H H H H
H H
H H H H H H
H C O C C C C C C C C C C C C C C C C C C HH C O C C C C C C C C C C C C C C C C C C H
H H H H H H H H H H H H H H H H H
H H H H H H H H
H H
H H H H H
O H H H H H H H H H H H H H H H H H
O H H H H H H H
H H H H H H H H H
H C O C C C C C C C C C C C C C C C C C C HH C O C C C C C C C C C C C C C C C C C C H
H H H H H H H H H H H H H H H H H
H H H H H H H H
H H H H H H H H
O H H H H H H H H H H H H H H H H H
O H H H H H H H
H H
H H
H H H
H C O C C C C C C C C C C C C C C C C C C H H C O C C C C C C C C C C C C C C C
C C H
H
H H H H H H H H H H H H H H H H H
H
H H H H H H H H
H H HH
H H
Saturated fat
Unsaturated fat
26
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.
27
Fats and Lipids in the Body
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•
•
Formed from excess glucose consumed
– floats in blood to be made into adipose tissue
Provide reserves e supply
More energy than carbs/proteins:



•
•
•
1 g carb -----> 4.3 kcal
1g prot-------> 4.6 kcal
1 g lipid -----> 9.0 kcal
Used after glycogen reserves gone (12 hours)
other functions: cushions, protects, insulates
tremendous diversity in types
28
Fig.
Water
3.20(TELipid
Art) Structure
Lipid head
(hydrophilic)
Lipid tail
(hydrophobic)
Micelle
Water
Phospholipid bilayer
Water
29
•
•
•
Hydrogenation of Polyunsaturates
Corn oil is a liquid polyunsaturated fat
Many double carbon bonds
Want to solidify it?
– Heat oil
– add pressurized hydrogen gas and catalyst
– carbons replaced by hydrogen
– produce a solid called “partially
hydrogenated vegetable oil” or PHVO
– called “trans fats” - once thought to be good
but now known to increase cholesterol
levels -
30
Additional Lipid Types
•
•
•
Phosolipids
– 2 fatty acids plus a phosphate
– part of cell membranes
– transports other lipids in blood
Steroids
– 4 connecting carbon rings + functional group
– cell membranes, hormones
– cholesterol (carried by other fats - too much
indicates excess fats in blood)
Waxes
– extremely hydrophobic
31
Proteins
•
•
•
Composed of C, H, O and N
Provide structure and support; transport
other molecules; act as enzymes (later discussion)
Polymers of subunits called amino acids
carboxyl
amino
•
R = variety of side groups giving rise to all
20 different amino acids (R = radical)
32
Proteins
•
Protein functions:
– enzyme catalysis
– defense
– transport
– support
– motion
– regulation
– storage
33
Many functions of Proteins
34
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
35
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).
36
Protein Structure
•
•
Solubility/charge of proteins related to nature of
side groups (R groups)
Combining amino acids
– OH removed from one carboxyl
– H removed from amino group of 2nd a.a.
– this is a dehydration synthesis reaction
37
Protein Structure
–
–
–
–
–
this is a dehydration synthesis reaction
results in bond between C of one and N of
second amino acid called a peptide bond
compound called a dipeptide
many amino acids = polypeptide (polymer)
tremendous number of polypeptides
38
Protein Structure
What type of
reaction is
illustrated here?
39
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
40
Protein Structure
•
Linear order of amino acids ----> primary
structure
–
•
•
•
(order determined by information in DNA)
bonds cause the protein to fold, kink or pleat and
results in ----> secondary structure
protein undergoes more complex twisting and
turning producing ----> tertiary structure
some proteins composed of two or more separable
polypeptide chains to
produce ---->
quaternary structure
–
many metabolic enzymes are 4 to 6 intertwined
proteins or protein complex
41
Protein Structure
–
–
–
tertiary - final folded shape of globular
protein
domains - functional units
 Large portions (sequence) of or on a
protein
quaternary - forms when two or more
polypeptide chains associate to form a
functional protein
42
Protein
Structure
•
•
•
The complexity and
specificity of the
molecule increases
from primary structure
to quaternary structure
THE SHAPE OF A
PROTEIN
DETERMINES IT
FUNCTION(S)!!
For real…..know this &
understand this
43
Chaperonins
•
Special chemicals involved with helping
proteins assume final shape
– Assist proteins as they go from linear
chains to some 3-dimensional entity
– inhibit misfolded states
– refold as a kind of proofreading function
– maintain unfolded state for protein
import/export
44
Chaperone Proteins
•
Chaperone proteins are special proteins
which help new proteins fold correctly.
– Chaperone deficiencies may play a role in
facilitating certain diseases.
45
Protein Structure
•
Denaturation refers to the process of changing a
protein’s shape.
distortion of protein structure due to heat,
detergents, pH
– molecule loses ability to do its ordinary job
For proteins, structure determines function
–
•
–
•
•
usually rendered biologically inactive
 salt-curing and pickling used to preserve food
Why do you cook meat before you eat it?
What evolutionary advantage would cooking meat
have to a species?
46
Unfolding Proteins
47
What kind of proteins are in each picture?
•
•
•
•
•
a) keratin
b) fibrin;
blood clot
c) collagen
d) silk
e) keratin
48
Information Molecules
•
The biochemical activity of a cell depends on the
production of a large number of very specifically
sequenced proteins (You are what you are
because of your proteins!)
–
Nucleic Acids direct this production!



Information storage devices (how to
make proteins)
Templates to produce exact copies of
themselves
Two kinds found in living organisms
DNA (deoxyribonucleic acid)
 RNA (ribonucleic acid)

49
Basic Nucleic Acid Structure
•
•
Composed of units called nucleotides
Each nucleic acid made of a:
–
–
–
Five carbon sugar (look at picture for
subtle difference in RNA and DNA on
next slide)
Phosphate
Nitrogen containing base (two types)
 Purines (Adenine and Guanine –
often “A” and “G”)
 Pyrimidines (Cytosine, Thymine
and Uracil – “C”, “T” and “U”)
50
Purines and Pyrimidines
51
Comparing Molecules of Life
52
Nucleic Acids
•
•
Deoxyribonucleic Acid (DNA)
– Encodes information used to assemble
proteins.
Ribonucleic Acid (RNA)
– Reads DNA-encoded information to direct
protein synthesis.
53
Differences in RNA and DNA
54
DNA
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•
•
•
•
•
•
Found in ALL living things
“Blueprints” for an organism’s development and
growth (hereditary information)
Exists as a twisted staircase, or double helix
The sides of the ladder are alternating sugars
and phosphates
The steps are composed of base pairs
Bases are complementary paired (A-T, G-C)
Bases held together by hydrogen bonds from
attracted base pairs (weak bonds)
55
Structure of DNA
56
Simple DNA Structure
•
Very simplified
diagram
57
DNA Structure
•
More detailed structure
58
DNA Structure
•
Notice the
different
number of Hbonds
between the
different base
pairs.
59
DNA Molecular Model
60
DNA Structure
•
Stick model
61
RNA
•
•
•
Carries message of DNA from nucleus to
cytoplasm of cell on how to put together a
protein (construction foreman)
Several ‘types’ exist
Different from DNA in a few ways
– Sugar is ribose, not deoxyribose
– No thymine present, uracil replaces it
– Is half a ladder, a single stranded molecule
62
Comparing DNA and RNA Structure
63
Structure of DNA
64
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
65
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
66