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Chapter 2
The Chemical
Composition of Cells
Learning Objectives- 1

Understand the Structure of the Molecular
Components of Living Organisms
 Carbohydrates, which supply and store energy and
serve as structural building blocks, include sugars and
polymers of sugars.
 Proteins, which catalyze reactions and are structural
building blocks, are polymers of amino acids.
 The nucleic acids DNA and RNA, which code and
express genetic information, are polymers of
nucleotides.
 Lipids are membrane components consisting mainly of
carbon and hydrogen atoms derived from acetates and
other molecules.
 Secondary metabolites such as phenolics, alkaloids,
and terpenoids often protect or strengthen plants.
Learning Objectives -2

To Understand Energy and Chemical Reactions
 Energy can be stored and can move or change matter .
 Chemical reactions involve either a net input or a net
output of free energy.
 The movement of electrons is the basis of energy transfer
through oxidation and reduction reactions.
 The terminal phosphate bond in ATP releases energy
when broken.
 NADH, NADPH, and FADH2 are universal carriers of
energy-rich electrons in living organisms.
Learning Objectives -3

To Understand the Nature of Chemical Reactions
and Enzymes

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
Enzymes position reactants, allowing reactions to occur
with minimal activation energy or increase in
temperature.
Cofactors such as coenzymes interact with enzymes to
assist reactions and indirectly provide energy in the form
of electrons for biochemical reactions.
Competitive and noncompetitive inhibition can slow or
stop enzymatic reactions and pathways.
Enzymatic reactions are linked together into metabolic
pathways.
Learning Objective

Know the basic structure of atom,
and know the role of ionic, covalent
and hydrogen bonds.
Key Terms: Atoms

Proton


Neutron


positive electric charge, small mass
uncharged, about same mass as proton
Electron

negative charge, extremely small mass
A Carbon Atom
Electrons


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Move around the nucleus at
different energy levels
Allow elements to combine
chemically to form chemical
compounds
Ions are atoms which tend to gain
or lose electrons
Electron Configurations
Acids and Bases


Acids dissociate in water to form
hydrogen ions (protons, H+)
Bases dissociate in water to yield
negatively charged hydroxide ions
(OH-)
pH Scale


A measure of the relative
concentrations of H+ and OH- in a
solution
A solution’s acidity or alkalinity is
expressed in terms of the pH scale
KEY TERMS

IONIC BOND

An electrostatic attraction between
oppositely charged ions
Ionic
Bonding
KEY TERMS

COVALENT BOND

A chemical bond involving one or
more shared pairs of electrons
Covalent Bonding in
Hydrogen
Covalent Bonding in
Methane
KEY TERMS

HYDROGEN BOND

An attraction between a slightly
positive hydrogen atom in one
molecule and a slightly negative
atom (usually oxygen) in another
molecule
Animation: How Atoms
Bond
CLICK
TO PLAY
LEARNING OBJECTIVE

Discuss the properties of water,
and explain the importance of
water to life
Water

Has a strong dissolving ability
Molecules form hydrogen bonds with one another
(cohesion)
 Molecules form hydrogen bonds to substances
with ionic or polar regions (adhesion)
 Adhesion & Cohesion are particularly important
for transport


All living things require water to survive
Almost all chemical reactions that sustain life
occur in aqueous solution
 High Melting & Freezing Points
 Insulation Property after freezing (e.g., lakes)

Water Structure
Animation: Structure of
Water
CLICK
TO PLAY
LEARNING OBJECTIVE

Describe the chemical
compositions and functions of
carbohydrates, lipids, proteins, and
nucleic acids
KEY TERMS

CARBOHYDRATE

An organic compound containing
carbon, hydrogen, and oxygen in
the approximate ratio of 1C:2H:1O
Carbohydrates 1

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Include sugars, starches, cellulose
Important fuel molecules,
components of molecules (nucleic
acids) and cell walls
Carbohydrates 2
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Monosaccharides
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Disaccharides
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simple sugars
two monosaccharide units
Polysaccharides

many monosaccharide units
Common
Monosaccharides
Sucrose Synthesis
Starch: A Storage
Polysaccharide
Cellulose: A Structural
Polysaccharide
KEY TERMS
LIPID
 Any of a group of organic
compounds that are insoluble in
water but soluble in fat solvents

Lipids 1


Have a greasy consistency, do not
readily dissolve in water
Important fuel molecules,
components of cell membranes,
waterproof coverings over plant
surfaces, light-gathering molecules
for photosynthesis
Lipids 2

A neutral fat or oil molecule is
composed of a molecule of
glycerol plus one, two or three fatty
acids
Formation of a Neutral
Fat or Oil
KEY TERMS

PROTEIN
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A large, complex organic
compound composed of amino
acid subunits
Protein
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A macromolecule composed of
amino acids joined by peptide
bonds
Order of amino acids determines
structure and function of a protein
molecule
Enzymes: Proteins that increase
the rate of chemical reactions
Amino Acids
Peptide Bonds
Protein Synthesis
Animation

http://www.wisconline.com/objects/index_tj.asp?ob
jid=AP1302
Organization of Protein
Molecules
KEY TERMS

NUCLEIC ACID
Deoxyribonucleic acid (DNA) and
ribonucleic acid (RNA)
 Large, complex organic molecules
composed of nucleotides

Nucleic Acids
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Control the cell’s life processes
Deoxyribonucleic acid (DNA)
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Transmits information from one
generation to the next
Ribonucleic acid (RNA)

Involved in protein synthesis
Nucleotides
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Repeating units that form nucleic acids

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Order of nucleotides in a nucleic acid chain
determines the specific information encoded
Adenosine triphosphate (ATP)

A modified nucleotide compound important in
energy transfers in biological systems
Nucleic Acids
Nucleic Acids
Nucleic Acids
DNA Replication
Animation

http://www.visionlearning.com/libra
ry/module_viewer.php?mid=63&l=
&c3=
KEY TERMS

ADENOSINE TRIPHOSPHATE
(ATP)

An organic compound of prime
importance for energy transfers in
biological systems
ATP
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ATP is a nucleotide that performs many
essential roles in the cell.
It is the major energy currency of the
cell, providing the energy for most of the
energy-consuming activities of the cell.
It is one of the monomers used in the
synthesis of RNA and, after conversion
to deoxyATP (dATP), DNA.
It regulates many biochemical pathways.
LEARNING OBJECTIVE

Discuss the role of enzymes in
cells
KEY TERMS

ENZYME


An organic catalyst, produced
within an organism, that
accelerates specific chemical
reactions
ACTIVATION ENERGY

The energy required to initiate a
chemical reaction
Enzymes
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Speed up a chemical reaction by
lowering its activation energy
(energy needed to initiate the
reaction)
Most enzymes are highly specific
and catalyze only a single
chemical reaction
Without enzymes, chemical
reactions in cells would occur too
slowly to support life
Enzymes and Activation
Energy
Enzyme-Substrate
Complex
Energy & Chemical
Reactions
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Energy can be stored and can move
or change matter: Potential energy is
stored energy, while kinetic energy is
energy having to do with motion.
The first law of thermodynamics states
energy can be harnessed and
transformed but not created or
destroyed.
The second law of thermodynamics
states that every transfer of energy
increases the entropy (disorder) of
matter in the universe.
LEARNING OBJECTIVE

State the first and second laws of
thermodynamics, and describe
how each applies to plants and
other organisms
KEY TERMS

FIRST LAW OF THERMODYNAMICS
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Energy cannot be created or destroyed, although
it can be transformed from one form to another
SECOND LAW OF THERMODYNAMICS
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When energy is converted from one form to
another, some of it is degraded into a lowerquality, less useful form
Energy
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The ability to do work
Plants and other organisms cannot
create the energy they require to
live, but must capture energy from
the environment and use it to do
biological work
Potential
and Kinetic
Energy
Entropy
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Continuously increases in the
universe as usable energy is
converted to lower-quality, less
usable form (heat)
As each energy transformation
occurs in organisms, some energy
changes to heat
Given off into the surroundings
 Can never be used again for
biological work

Animation: Activation
Energy
Click To Start
Secondary Metabolites

Secondary metabolites
such as phenolics,
alkaloids, and terpenoids
often protect or strengthen
plants