Title: PowerLecture: Chapter 2
1PowerLectureChapter 2
2Learning Objectives
- Understand how protons, electrons, and neutrons
are arranged into atoms and ions. - Explain how the distribution of electrons in an
atom or ion determines the number and kinds of
chemical bonds that can be formed. - Know the various types of chemical bonds, the
circumstances under which each forms, and the
relative strengths of each type.
3Learning Objectives (contd)
- Understand the essential chemistry of water and
of some common substances dissolved in it. - Understand how small organic molecules can be
assembled into large macromolecules by
condensation. Understand how large macromolecules
can be broken apart into their basic subunits by
hydrolysis.
4Learning Objectives (contd)
- Memorize the functional groups presented and know
the properties they confer when attached to other
molecules. - Know the general structure of a monosaccharide
with six carbon atoms, glycerol, a fatty acid, an
amino acid, and a nucleotide. - Know the macromolecules into which these
essential building blocks can be assembled by
condensation.
5Learning Objectives (contd)
- Know where these carbon compounds tend to be
located in cells or organelles and the activities
in which they participate.
6Impacts/Issues
7Its Elemental
- Life depends on chemical reactions.
- An element is a fundamental form of matter that
has mass and takes up space. - Organisms consist mostly of carbon, oxygen,
hydrogen, and nitrogen. - Trace elements are needed only in small
quantities.
8Elements in the Human Body vs. Earths Crust
Human Body
Earths Crust
Oxygen 65 Carbon 18 Hydrogen 10 Nitrogen
3 Calcium 2 Phosphorus 1.1 Potassium 0.35 Sulfu
r 0.25 Sodium 0.15 Chlorine 0.15 Magnesium
0.05 Iron 0.004
Oxygen 46.6 Silicon 27.7 Aluminum 8.1 Iron 5.
0 Calcium 3.6 Sodium 2.8 Potassium
2.1 Magnesium 1.5
9How Would You Vote?
- To conduct an instant in-class survey using a
classroom response system, access JoinIn Clicker
Content from the PowerLecture main menu. - Many communities add fluoride to drinking water
supplies. Do you want it in yours? - a. Yes, screening lets people make informed
reproductive decisions about the risk to their
children. - b. No, therapies and medications
- for CF continue to improve a
- person with CF can live a full life.
10Section 1
- Atoms, the Starting Point
11Atoms, the Starting Point
- Atoms are composed of smaller particles.
- An atom is the smallest unit of matter that is
unique to a particular element. - Atoms are composed of three particles
- Protons (p) are part of the atomic nucleus and
have a positive charge. Their quantity is called
the atomic number (unique for each element). - Electrons (e-) have a negative charge. Their
quantity is equal to that of the protons. They
move around the nucleus. - Neutrons are also a part of the nucleus they are
neutral. Protons plus neutrons atomic mass
number.
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13Fig. 2.1, p. 16
14Atoms, the Starting Point
- Electron activity is the basis for organization
of materials and the flow of energy in living
things. - Isotopes are varying forms of atoms.
- Atoms with the same number of protons (e.g.,
carbon has six) but a different number of
neutrons (carbon can have six, seven, or eight)
are called isotopes (12C, 13C, 14C). - Some radioactive isotopes are unstable and tend
to decay into more stable atoms. - They can be used to date rocks and fossils.
- Some can be used as tracers to follow the path of
an atom in a series of reactions or to diagnose
disease.
15Section 2
- Medical Uses for Radioisotopes
16Medical Uses for Radioisotopes
- Radioisotopes have many important uses in
medicine. - Tracers are substances containing radioisotopes
that can be injected into patients to study
tissues or tissue function. - Radiation therapy uses the radiation from
isotopes to destroy or impair the activity of
cells that do not work properly, such as cancer
cells. - For safety, clinicians usually use isotopes with
short half-lives (the time it takes the isotope
to decay to a more stable isotope).
17Example of Radioactive Iodine
Figure 2.2
18Section 3
19What Is a Chemical Bond?
- Interacting atoms Electrons rule!
- In chemical reactions, an atom can share
electrons with another atom, accept extra
electrons, or donate electrons. - Electrons are attracted to protons, but are
repelled by other electrons. - Orbitals can be thought of as occupying shells
around the nucleus, representing different energy
levels.
20Electron Arrangements
Figure 2.4
21What Is a Chemical Bond?
- Chemical bonds join atoms.
- A chemical bond is a union between the electron
structures of atoms. - Having a filled outer shell is the most stable
state for atoms. - The shell closest to the nucleus has one orbital
holding a maximum of two electrons. - The next shell can have four orbitals with two
electrons each for a total of eight electrons. - Atoms with unfilled orbitals in their outermost
shell tend to be reactive with other atomsthey
want to fill their outer shell with the maximal
eight electrons allowed.
22Shell Model
Figure 2.5
23What Is a Chemical Bond?
- Atoms can combine into molecules.
- Molecules may contain more than one atom of the
same element N2 for example. - Compounds consist of two or more elements in
strict proportions. - A mixture is an intermingling of molecules in
varying proportions.
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25Section 4
- Important Bonds in Biological Molecules
26Important Bonds in Biological Molecules
- An ionic bond joins atoms that have opposite
charges. - When an atom loses or gains one or more
electrons, it becomes positively or negatively
chargedan ion. - In an ionic bond, () and () ions are linked by
mutual attraction of opposite charges, for
example, NaCl.
27Example of an Ionic Bond
Figure 2.7a
28Important Bonds in Biological Molecules
- Electrons are shared in a covalent bond.
- A covalent bond holds together two atoms that
share one or more pairs of electrons. - In a nonpolar covalent bond, atoms share
electrons equally H2 is an example. - In a polar covalent bond, because atoms share the
electron unequally, there is a slight difference
in charge (electronegativity) between the two
atoms participating in the bond water is an
example.
29Examples of Covalent Bonds
Figure 2.7b
30Important Bonds in Biological Molecules
- A hydrogen bond is a weak bond between polar
molecules. - In a hydrogen bond, a slightly negative atom of a
polar molecule interacts weakly with a hydrogen
atom already taking part in a polar covalent
bond. - These bonds impart structure to liquid water and
stabilize nucleic acids and other large
molecules.
31Example of a Hydrogen Bond
Figure 2.7c
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33Section 5
34Antioxidants
- Free radicals are formed by the process of
oxidation. - Oxidation is the process whereby an atom or
molecule loses one or more electrons. - Oxidation can produce free radicals that may
steal electrons from other molecules. - In large numbers, free radicals can damage other
molecules in a cell, such as DNA.
35Antioxidants
- Antioxidants are chemicals that can give up an
electron to a free radical before it does damage
to a DNA molecule.
Figure 2.8
36Section 6
Figure 2.9c
37Life Depends on Water
- Hydrogen bonding makes water liquid.
- Water is a polar molecule
- because of a slightly negative
- charge at the oxygen end and
- a slightly positive charge at
- the hydrogen end.
- Water molecules can form
- hydrogen bonds with each
- other.
Figure 2.9a-b
38Life Depends on Water
- Polar substances are
- hydrophilic (water loving)
- nonpolar ones are
- hydrophobic (water
- dreading) and are repelled
- by water.
39Life Depends on Water
- Water can absorb and hold heat.
- Water tends to stabilize temperature because it
has a high heat capacitythe ability to absorb
considerable heat before its temperature changes.
- This is an important property in evaporative and
freezing processes.
40Life Depends on Water
- Water is a biological solvent.
- The solvent properties of water
- are greatest with respect to
- polar molecules because
- spheres of hydration are
- formed around the solute
- (dissolved) molecules.
- For example, the Na of salt
- attracts the negative end of water molecules,
while the Cl- attracts the positive end.
Figure 2.10
41Section 7
- Acids, Bases, and Buffers Body Fluids
- in Flux
42Acids, Bases, and Buffers
- The pH scale indicates the concentration of
hydrogen ions. - pH is a measure of the H concentration in a
solution the greater the H the lower the value
on the pH scale. - The scale extends from 0 (acidic) to 7 (neutral)
to 14 (basic).
43 The pH Scale
Figure 2.11
44Acids, Bases, and Buffers
- Acids give up H and bases accept H.
- A substance that releases hydrogen ions (H) in
solution is an acidfor example, HCl. - Substances that release ions such as (OH-) that
can combine with hydrogen ions are called bases
(example baking soda). - High concentrations of
- strong acids or bases
- can disrupt living
- systems both internal
- and external to the body.
Figure 2.12
45Acids, Bases, and Buffers
- Buffers protect against shifts in pH.
- Buffer molecules combine with, or release, H to
prevent drastic changes in pH. - Bicarbonate is one of the bodys major buffers.
46Acids, Bases, and Buffers
- A salt releases other kinds of ions.
- A salt is an ionic compound formed when an acid
reacts with a base example HCl NaOH ? NaCl
H2O. - Many salts dissolve into ions that have key
functions in the body for example, Na, K, and Ca
in nerve and muscles.
47Section 8
48Molecules of Life
- Biological molecules contain carbon.
- Only living cells synthesize the molecules
characteristic of lifecarbohydrates, lipids,
proteins, and nucleic acids. - These molecules are organic compounds, meaning
they consist of atoms of carbon and one or more
other elements, held together by covalent bonds.
49Molecules of Life
- Carbons key feature versatile bonding.
- Living organisms are mostly oxygen, hydrogen, and
carbon. - Much of the hydrogen and oxygen are linked as
water. - Carbon can form four covalent bonds with other
atoms to form organic molecules of several
configurations.
50Molecules of Life
- Functional groups affect the chemical behavior of
organic compounds. - By definition a hydrocarbon has only hydrogen
atoms attached to a carbon backbone. - Functional groupsatoms or groups of atoms
covalently bonded to a carbon backboneconvey
distinct properties, such as solubility, to the
complete molecule.
51Examples of Functional Groups
Figure 2.13
52Molecules of Life
- Cells have chemical tools to assemble and break
apart biological molecules. - Enzymes speed up specific metabolic reactions.
- In condensation reactions, one molecule is
stripped of its H another is stripped of its
OH-. - The two molecule fragments join to form a new
compound the H and OH- form water (dehydration
synthesis). - Cells use series of condensation reactions to
build polymers out of smaller monomers.
53Examples of Condensation Reactions
Figure 2.14a
54Molecules of Life
- In hydrolysis reactions, the reverse happens one
molecule is split by the addition of H and OH-
(from water) to yield the individual components.
Figure 2.14b
55Section 9
- Carbohydrates Plentiful and Varied
56Carbohydrates Plentiful and Varied
- A carbohydrate can be a simple sugar or a larger
molecule composed of sugar units. - Carbohydrates are the most abundant biological
molecules. - Carbohydrates serve as energy sources or have
structural roles.
57Carbohydrates Plentiful and Varied
- Simple sugarsthe simplest carbohydrates.
- A monosaccharideone sugar unitis the simplest
carbohydrate. - Sugars are soluble in water and may be
sweet-tasting. - Ribose and deoxyribose (five-carbon backbones)
are building blocks for nucleic acids. - Glucose (six-carbon backbone) is a primary energy
source and precursor of many organic molecules.
58Carbohydrates Plentiful and Varied
- Oligosaccharides are short chains of sugar units.
- An oligosaccharide is a short chain resulting
from the covalent bonding of two or three
monosaccharides. - Lactose (milk sugar) is glucose plus galactose
sucrose (table sugar) is glucose plus fructose. - Oligosaccharides are used to modify protein
structure and have a role in the bodys defense
against disease.
59Formation of a Sucrose Molecule
Figure 2.15
60Carbohydrates Plentiful and Varied
- Polysaccharides are sugar chains that store
energy. - A polysaccharide consists of many sugar units
(same or different) covalently linked. - Glycogen is a storage form of glucose found in
animal tissues. - Starch (energy storage in plants) and cellulose
(structure of plant cell walls) are made of
glucose units but in different bonding
arrangements.
61Examples of Polysaccharides
Figure 2.16
62Section 10
- Lipids Fats and Their Chemical Kin
63Lipids Fats and Their Chemical Kin
- Lipids are composed mostly of nonpolar
hydrocarbon and are hydrophobic. - Fats are energy-storing lipids.
- Fats are lipids that have one, two, or three
fatty acids attached to glycerol. - A fatty acid is a long, unbranched hydrocarbon
with a carboxyl group (COOH) at one end. - Saturated fatty acids have only single CC bonds
in their tails, are solids at room temperature,
and are - derived from animal sources.
64Lipids Fats and Their Chemical Kin
- Unsaturated fatty acids have one or more double
- bonds between the carbons that form kinks in
the tails they tend to come from plants and are
liquid at room temperature.
Figure 2.17
65Lipids Fats and Their Chemical Kin
- Triglycerides have three fatty acids attached to
one glycerol. - They are the bodys most abundant lipids.
- On a per-weight basis, these molecules yield
twice as much energy as carbohydrates. - Trans fatty acids are partially saturated
(hydrogenated) lipids implicated in some types of
heart disease.
66Formation of a Triglyceride
Figure 2.18
67Lipids Fats and Their Chemical Kin
- Phospholipids are key building blocks of cell
membranes. - A phospholipid has a
- glycerol backbone, two
- fatty acids, a phosphate
- group, and a small
- hydrophilic group.
- They are important
- components of cell
- membranes.
Figure 2.19a-c
68Lipids Fats and Their Chemical Kin
- Sterols are building blocks of cholesterol and
steroids. - Steroids have a backbone of four carbon rings,
but no fatty acids. - Cholesterol is an
- essential component
- of cell membranes in
- animals and can be
- modified to form sex
- hormones.
Figure 2.19d-e
69Section 11
- Proteins Biological Molecules with
- Many Roles
70Proteins
- Because they are the most diverse of the large
biological molecules, proteins function as
enzymes, in cell movements, as storage and
transport agents, as hormones, as antidisease
agents, and as structural material throughout the
body.
Figure 2.20
71Proteins
- Proteins are built from amino acids.
- Amino acids are small organic molecules with an
amino group, an acid group, a hydrogen atom, and
one of 20 varying R groups. - They form large polymers called proteins.
Figures 2.20 and 2.21
72Proteins
- The sequence of amino acids is a proteins
primary structure. - Primary structure is defined as the chain
(polypeptide) of amino acids. - The amino acids are linked together in a definite
sequence by peptide bonds between an amino group
of one and an acid group of another. - The final shape and function of any given protein
is determined by its primary structure.
73Formation of Peptide Bonds in Proteins
Figure 2.22
74Section 12
- A Proteins Function Depends on Its Shape
75A Proteins Function Depends on Its Shape
- Primary structure determines the shape and
function of proteins by positioning different
amino acids so that hydrogen bonds can form
between them and by putting R groups in positions
that force them to interact.
Figure 2.23a
76A Proteins Function Depends on Its Shape
- Many proteins fold two or three times.
- Secondary structure is the helical coil or
sheetlike array that will result from hydrogen
bonding of side groups on the amino acid chains. - Tertiary structure is caused by interactions
among R groups, resulting in a complex
three-dimensional shape.
77Figure 2.23b-c
78Fig. 2.23, p. 34
Stepped Art
79A Proteins Function Depends on Its Shape
- Proteins can have more than one polypeptide
chain. - Hemoglobin, the oxygen-carrying protein in the
blood, is an example of a protein with quaternary
structurethe complexing of two or more
polypeptide chains to form globular or fibrous
proteins. - Hemoglobin has four polypeptide chains (globins),
each coiled and folded with a heme group at the
center.
80Figure 2.24
81A Proteins Function Depends on Its Shape
- Glycoproteins have sugars attached lipoproteins
have lipids. - Certain proteins combine with triglycerides,
cholesterol, and phospholipids to form
lipoproteins for transport in the body. - Glycoproteins form when oligosaccharides are
added to proteins.
82A Proteins Function Depends on Its Shape
- Disrupting a proteins shape denatures it.
- High temperatures or chemicals can cause the
three-dimensional shape to be disrupted. - Normal functioning is lost upon denaturation,
which is often irreversible.
Figure 2.25
83Section 13
- Nucleotides and
- Nucleic Acids
84Nucleotides and Nucleic Acids
- Nucleotides energy carriers and other roles.
- Each nucleotide has a five-carbon sugar (ribose
or deoxyribose), a nitrogen-containing base, and
a phosphate group. - ATP molecules link cellular reactions that
transfer energy. - Other nucleotides include the coenzymes, which
accept and transfer hydrogen atoms and electrons
during cellular reactions, and chemical
messengers
85Figure 2.26
86Nucleotides and Nucleic Acids
- Nucleic acids include DNA and RNA.
- In nucleic acids, nucleotides are bonded together
to form large single- or double-stranded
molecules. - DNA (deoxyribonucleic acid) is double-stranded
genetic messages are encoded in its base
sequences. - RNA (ribonucleic acid) is single-stranded it
functions in the assembly of proteins.
87Figure 2.27
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89Section 14
- Food Production and a Chemical Arms Race
90Food Production and a Chemical Arms Race
- Nearly half of the food grown each year around
the world is lost to disease or insects. - Natural plant defenses have been augmented by the
development of synthetic toxins designed to kill
pests and increase crop yields. - Herbicides kill unwanted plants (weeds).
- Insecticides kill insects.
- Fungicides kill or inhibit the growth of harmful
mold or fungi.
91Food Production and a Chemical Arms Race
- Synthetic chemicals are not without dangers some
kill good insects and plants while others harm
humans through exposure. -