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Chapter 3THE MOLECULES OF CELLS
StandardsBy the end of the unit you should be able to:
Model synthesis and hydrolysis reactions and relate the reactions to the human body
Recognize carbs, lipids, proteins and nucleic acids in formula & skeleton form, chemical structure and describe their function in the human body
Recognize monosaccharides, disaccharides and polysaccharides and relate the molecules to how they function in the body
Recognize, describe the location of, and explain the importance of the following in the human body: neutral fats, steroids and phospholipids
I can list the major functions of nucleic acids (RNA & DNA), describe their structure with accurate detail and compare these 2 molecules
I can compare the following pairs: saturated and unsaturated fats, DNA & RNA
I can differentiate among the primary, secondary, tertiary and quaternary structure of proteins and explain how these levels of structure relate to protein functions
I can relate protein structure to protein specific examples from the human body
I ca draw the general structure of the ATP molecule in its role as the “energy currency” of cells
Biological Molecules
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
Organic Molecules – contain carbon atom
and a hydrogen atom
C can bond with up to 4 other atoms
Carbon chains vary in many ways
Hydrocarbons are composed of only hydrogen and carbon
Some carbon compounds are isomers: molecules with the same molecular formula but different structures
H H
HH
H H
Ethane Propane
HH
H H
H
H
H
H
H
H
Carbon skeletons vary in length.
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
C
HHH
H H
H H
H
H
H
H H
H
H
H
H
H
H
H H
H
H
Butane Isobutane
Skeletons may be unbranched or branched.
1-Butene 2-Butene
Skeletons may have double bonds, which can vary in location.
C
C C
C
C
C
H
C
CC
C
C
C
Cyclohexane Benzene
Skeletons may be arranged in rings.
C C C C C
C C C C
C
C CC
CCCC CCCH H
Figure 3.1A
1
2
3
4
.
3.2 Functional
groups help
determine the
properties of
organic
compounds
Some examples
of functional
groups:
Table 3.2
Functional groups are particular groupings of
atoms that give organic molecules particular
properties
Female lion
Estradiol
HO
OH
OH
O
TestosteroneFigure 3.2
Male lion
Basic Vocab.
Monomer –is a small
molecule that may
become chemically
bonded to other
monomers to form a
polymer.
Polymer – a large
molecule that is made
of several monomers
bonded to each other
Reactions that form polymers &
monomers Hydrolysis and Synthesis Reactions
Reactions we will see for all biological
molecules
Cells make most of their large molecules by
joining smaller organic molecules into chains
called polymers
Cells link monomers to form polymers by a
dehydration reaction
H
OH H
OH
H O
H
Unlinked monomer
Dehydratio
n reaction
Longer polymer
Short polymer
OH H
H OH
Unlinked monomer
Dehydration
reaction
Short polymer
H2O
Figure 3.3A
Polymers are broken down to monomers by the
reverse process, hydrolysis
H
H2O
OH
HOH
OH H
Hydrolysis
Figure 3.3B
3.3 Cells make a huge number of large
molecules from a small set of small molecules
The four main classes of biological
molecules are carbohydrates, lipids,
proteins, and nucleic acids
Many of the molecules are gigantic and
are called macromolecules
CARBOHYDRATES 3.4 Monosaccharides are the simplest carbohydrates
The carbohydrate monomers are monosaccharides
A monosaccharide has a formula that is a multiple of
CH2O and contains hydroxyl groups and a carbonyl
group
Figure 3.4A
Carb Info:
Function of carbs for humans– source of
energy for the cell (cellular respiration)
CARBS contains carbon, hydrogen, and
oxygen in the ratio of 1:2:1. (empirical
formula)
The monosaccharides glucose and fructose
are isomers that contain the same atoms but in
different arrangements
C
C
C
C
C
C
C
C
C
C
H
H
H
H
H
H
H H
H
H
H
HO
H
H
H
C
O
HO
OH
OH
OH
OH OH
OH
OH
C O
OH
Glucose FructoseFigure 3.4B
Monosaccharides can also occur as ring structures
H
H
H
H
H
H H
H
HH
OC
C
C C
O
OHOH HO OH
OH
CH2OH
CH2OH
C
OH
OH
O
OH
Structural
formulaAbbreviated
structure
Simplified
structure
6
5
4
3 2
1
Figure 3.4C
3.5 Cells link two single sugars to form
disaccharides
Monosaccharides can join to form
disaccharides such as sucrose (table sugar)
and maltose (brewing sugar)
H
HH H
HH
H
H
H
H
H
H
H
H
H HH
H
H
H
OH OH
OHOHOH
HO
O O
O
OH
OH
OH
CH2OH CH2OH
CH2OH CH2OH
H2O
OH
HO
O
OH O
H
Glucose Glucose
Maltose
O
OH
Figure 3.5
CONNECTION 3.6 How sweet is sweet?
Various types of molecules, including
nonsugars taste sweet because they bind to
“sweet” receptors on the tongue
Table 3.6
3.7 Polysaccharides are long chains of sugar units Polysaccharides are polymers of monosaccharides
linked together by dehydration reactions
Starch and glycogen are polysaccharides that store sugar for later use
Cellulose is a polysaccharide found in plant cell walls
Starch granules in
potato tuber cells
Glycogen
granules in
muscle tissue
Cellulose fibrils in
a plant cell wall
Glucose
monomer
Cellulose
molecules
STARCH
GLYCOGEN
CELLULOSE
O O
OOOOOO
O O O
O
OO
OO
OO
OO
OO
OO
O
OO
OO
OO
OO O
OOOOOO
OOOOOO
O
OH
OH
Figure 3.7
3.8 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
Lipids are grouped together because they are
hydrophobic
Figure 3.8A
LIPIDS
Fats, also called triglycerides (neutral fats) are
lipids whose main function is energy storage
Consist of glycerol linked to three fatty acids
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH3
H2O
H H
HH
OHOH OH
H
HO
C O
C C C
Fatty acid
Glycerol
H HH
H H
CH2
O O O
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH3
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH3
CH2
CH2
CH2
CH2
CH2
CH2
CH
CH
CH2
CH2
CH2
CH2
CH2
CH2
CH3
C C C OOO
C C C
H
Figure 3.8B Figure 3.8C
3.9 Phospholipids, waxes, and steroids are
lipids with a variety of functions
Phospholipids are a major component of cell
membranes
Waxes form waterproof coatings
Steroids are often hormones
HO
CH3
CH3
H3C CH3
CH3
Figure 3.9
CONNECTION 3.10 Anabolic steroids pose health risks
Anabolic steroids are synthetic variants of testosterone that can
cause serious health problems
3rd group of Bio Cules -
Proteins2 types
StructuralFunctional
Found in ligaments,
bones, tendons, skin
Ex – keratin, collagen
Enzymes – hydrolytic-
(lysosomes, digestive)
3.11 Proteins are essential to the structures and
activities of life
A protein is a polymer constructed from amino acid
monomers
Proteins are involved in almost all of a cell’s
activities
As enzymes they regulate chemical reactions.
Figure 3.11
PROTEINS
3.12 Proteins are made from amino acids linked by
peptide bonds
Protein diversity is based on different arrangements of a
common set of 20 amino acid monomers
Each amino acid contains An amino group
A carboxyl group
An R group, which distinguishes each of the 20
different amino acids
H
H
N
H
C
R
C
O
OH
Amino
group
Carboxyl (acid)
group
Figure 3.12A
Each amino acid has specific properties based on its structure
H
H
N
H
C
CH2
CH
CH3 CH3
C
O
OH
H
H
N C
H
CH2
OH
C
O
OH
H
H
N C
H
C
O
OHCH2
C
OH O
Leucine (Leu) Serine (Ser) Aspartic acid (Asp)
Hydrophobic Hydrophilic
Figure 3.12B
Cells link amino acids together by dehydration
synthesis
The bonds between amino acid monomers are
called peptide bonds
H
H
N C C
O
OH H
H
N+ C
H
R
C
O
OH
H2O
H
H
N C C N C C
R H R OH
O
Peptide
bond
DipeptideAmino acid
Dehydration
reaction
Amino
group
H
R
Amino acid
Carboxyl
group
H O H
Figure 3.12C
Peptide Bonds The N of one a.a. bonds to C of carboxyl of another
a.a.
Dipeptide – has 1 peptide bond & 2 a.a.
Tripeptide – has 2 bonds & 3 a.a
Polypeptides – many amino acids
GrooveGroove
Figure 3.13BFigure 3.13A
3.13 A protein’s specific shape determines its
function
A protein consists of one or more polypeptide
chains folded into a unique shape that
determines the protein’s function
3.14 A protein’s shape (and therefore its
function!) depends on four levels of structure
Primary Structure
A protein’s primary structure is the sequence of
amino acids forming its polypeptide chains
Levels of Protein Structure
Primary structure GlyThr
Gly GluSer Lys
Cys
Pro
Leu Met
Val
Lys
Val
Leu Asp Ala Val Arg Gly SerPro
Ala
Ile
Asn Val
Ala
ValHis
Val
Amino acids
PheArg
Figure 3.14A
Secondary structure
A protein’s secondary structure is the coiling or
folding of the chain, stabilized by hydrogen
bonding between a.a. on different parts of the
strand
Figure 3.14B
Secondary structure
C
N
O C
C
N H
O C
C
H
Hydrogen
bond
O C
N H
C
CO
N H
O C
C
N H
C
N
O C
C
N H
O C
C
N H
CO
C
H
N H
CO
H C R
HN
Alpha helix
CN
H
C C
H HO
N
R C C
O
N
H
O
CC N
H
C C
O
N
H
O
CC N
H
C
O
C N
H
O
CC N
H
C
O
O
CC
N
H
C C
O
N
H
CC
O
N
H
CC
O
N
H
CC
O
N
H
CC
O
N
H
CC
O
N
H
CC
O
H
N
C
Pleated sheet
Amino acids
Tertiary Structure
A protein’s tertiary structure is the overall three-
dimensional shape of a polypeptide
This 3D shape is the result of interactions between
the R groups of the a.a.s
Tertiary structure
Polypeptide
(single subunit
of transthyretin)
Figure 3.14C
Quaternary Structure
A protein’s quaternary structure results from the
association of two or more polypeptide chains
EX: hemoglobin
Quaternary structure
Transthyretin, with
four identical
polypeptide subunits
Figure 3.14D
Polypeptide
chain
Collagen
TALKING ABOUT SCIENCE 3.19 Linus Pauling contributed to
our understanding of the chemistry
of life
Linus Pauling made important
contributions to our understanding
of protein structure and function
Discovered the alpha helical
structure in proteins (secondary
level) and also the difference in the
structure of hemoglobin in regular
blood vs sickle cell anemia blood
Figure 3.15
NUCLEIC ACIDS 3.20 Nucleic acids are information-rich or
energy carrying polymers of nucleotides
There are 3 ex: DNA, RNA, ATP
Nucleic acids such as DNA and RNA serve as
the blueprints for proteins and thus control the
life of a cell
ATP serves as the energy currency of the cell
The monomers of nucleic acids are nucleotides
Composed of a 5 carbon sugar, phosphate,
and nitrogenous base (ATCGU)
Sugar
OH
O P O
O
CH2
H
O
H H
OH H
H
N
N
H
N
N H
HH
N
Phosphate
group
Nitrogenous
base (A)
Figure 3.16A
Different Nucleotides: Note
same basic shape!
The sugar and phosphate form the backbone
for the nucleic acid or polynucleotide
Sugar-phosphate
backbone
T
G
C
T
A Nucleotide
Figure 3.16B
DNA consists of two polynucleotides twisted
around each other in a double helix, the two
strands run antiparallel to each other Stretches of a DNA molecule called genes program the amino
acid sequences of proteins
C
TA
GC
C G
T A
C G
A T
A
G C
A T
A T
T A
Base
pair
T
Figure 3.16C
RNA, by contrast is a single-stranded
polynucleotide
RNA, when compared to DNA, is: Shorter
Single stranded
Has a U base (uracil) instead of a T base (thymine)
Has MANY more types/jobs, ex: messenger, transfer, ribosomal etc
ATP – Adenosine Triphosphate
Produced by cellular
respiration
Glucose + oxygen -
Carbon dioxide +
water + ATP
ATP – needed for
active transport
Notice – 2 high
energy bonds
Synthesis of –
ADP + Pi → ATP + H2O
Nucleic Acids Comparison
Molecule ATP DNA RNA
Structure Nucleotide Double
stranded
molecule
Single
Stranded
molecule
Sugar Ribose Deoxyribose Ribose
BASES A A,C,T,G A. C, U,G
Uses Energy Information Information,
many others