Transcript Chapter 2_PPT - HCC Learning Web

Chapter 2
Essential Chemistry for Biology
PowerPoint® Lectures for
Campbell Essential Biology, Fifth Edition, and
Campbell Essential Biology with Physiology,
Fourth Edition
– Eric J. Simon, Jean L. Dickey, and Jane B. Reece
Lectures by Edward J. Zalisko
© 2013 Pearson Education, Inc.
Biology and Society: More Precious than Gold
• A drought is a period of abnormally dry weather that changes
the environment and one of the most devastating disasters.
• Droughts can cause
• severe crop damage, shortages of drinking water,
• dust storms, famine, habitat loss, and mass migration.
• Throughout human history, droughts have helped wipe out
societies and even whole civilizations.
• Droughts are catastrophic because life cannot exist without
water.
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Matter: Elements and Compounds
• Matter is anything that occupies space and has mass.
– found on the Earth in three physical states:
Solid, Liquid and Gas
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Matter: Elements and Compounds
• Matter is composed of chemical elements:.
– substances that cannot be broken down into other
substances.
– There are 92 naturally occurring elements on Earth.
– All of the elements are listed in the periodic table.
– Twenty-five are essential to life.
– Four make up about 96% of the weight of the
human body
– CHON: Carbon, Hydrogen, Oxygen and Nitrog
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Chemical composition
of the human body by
weight
Carbon (C): 18.5%
Oxygen (O):
65.0%
Calcium (Ca): 1.5%
Phosphorus (P): 1.0%
Potassium (K): 0.4%
Sulfur (S): 0.3%
Sodium (Na): 0.2%
Chlorine (Cl): 0.2%
Hydrogen (H):
9.5%
Nitrogen (N):
3.3%
Magnesium (Mg): 0.1%
Trace elements: less than 0.01%
Boron (B)
Chromium (Cr)
Cobalt (Co)
Copper (Cu)
Fluorine (F)
Iodine (I)
Iron (Fe)
Manganese (Mn)
Molybdenum (Mo)
Selenium (Se)
Silicon (Si)
Tin (Sn)
Vanadium (V)
Zinc (Zn)
Figure 2.2
Minor & Trace elements
Calcium
Minor
elements Ca
Phosphorus
Iodine
Trace
elements
Fluorine
Building strong bones and teeth
Found abundantly in milk & dairy
products, sardines, green & leafy
vegetables
Component of DNA
Found in eggs, beans and nuts
Essential ingredient of thyroid hormone
Found in dairy products
Deficiency leads to goiter
Needed for healthy bones and teeth
Matter: Elements and Compounds
• Trace elements
– are required in only very small amounts and
– are essential for life.
• An iodine deficiency causes goiter.
• Fluorine
– is added to dental products and drinking water and
– helps to maintain healthy bones and teeth.
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Hyper functioning thyroid (goiter)
Figure 2.3
Matter: Elements, Atoms and Compounds
• Each element consists of one kind of atom.
– An atom is the smallest unit of matter that still
retains the properties of an element.
• Elements can combine to form compounds.
– Compounds are substances that contain two or
more elements in a fixed ratio.
– Common compounds include
– NaCl (table salt) and
– H2O (water).
© 2013 Pearson Education, Inc.
Periodic table of the
elements
Atomic number
(number of protons)
6
C
Element symbol
Mass number
(number of protons
plus neutrons)
12
H
He
Li Be
B
Na Mg
Al Si P
K Ca Sc Ti
C
N
O
F Ne
S Cl Ar
V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te
I
Xe
Cs Ba La Hf Ta W Re Os Ir Pt Au Hg TI Pb Bi Po At Rn
Fr Ra Ac Rf Db Sg Bh Hs Mt Ds Rg Cn
Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr
Figure 2.1a
Periodic table of the elements
Practice
1. Ordinary oxygen has an atomic mass of 16 and an
atomic number of 8. How many neutrons does this
type of oxygen have?
2. Phosphorous has an atomic number of 15 and an
atomic weight of 30.974. How many neutrons does
this type of oxygen have?
3. Silicon has an atomic number of 14 and a mass
number of 28. How many neutrons are found in
silicon?
The Structure of Atoms
• Atoms are composed of three subatomic particles
– A proton is positively charged, mass of 1 dalton
– An element is defined by its number of protons
– A neutron is electrically neutral mass of 1 dalton
– Neutrons can vary between isotopes
– An electron is negatively charged minimal mass 1/2000th
1 dalton, found outside (orbiting) the nucleus.
• Most atoms have protons and neutrons packed tightly into
the nucleus.
– The nucleus is the atom’s central core.
– Electrons orbit the nucleus.
Electron shell or
Electron energy level
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Helium atom
2
Protons
Nucleus
Nucleus
2
Neutrons
2
Electrons
2e–
Electron cloud
Figure 2.4
Structure of an atom
Proton
• Positive charge
• Determines element
Electron
• Negative charge
• Participates in chemical
reactions
• Outer-shell electrons
determine chemical
behavior
Neutron
• No charge
• Determines isotope
Nucleus
• Consists of neutrons
and protons
Atom
Atomic and mass number
• Elements differ in the number of subatomic particles in
their atoms.
– The number of protons, the atomic number,
determines which element it is.
– Mass is a measure of the amount of material in an
object.
– An atom’s mass number is the sum of the number
of protons and neutrons in its nucleus.
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Isotopes
• Isotopes are alternate mass forms of an element.
– Isotopes have the same number of protons and electrons,
– but they have a different number of neutrons.
Radioactive Isotope
• The nucleus of a radioactive isotope decays, giving off
particles and energy.
• Radioactive isotopes have many uses in research and medicine.
– They can be used to determine the fate of atoms in living
organisms.
– They are used in PET scans to diagnose heart disorders and
some cancers.
• Uncontrolled exposure to radioactive isotopes can harm living
organisms by damaging DNA.
– The 1986 Chernobyl nuclear accident released large amounts of
radioactive isotopes.
– Naturally occurring radon gas may cause lung cancer.
Figure 2.5
Electron Arrangement and the Chemical
Properties of Atoms
• Of the three subatomic particles, only electrons are
directly involved in the chemical activity of an atom.
• Electrons orbit the nucleus of an atom in specific electron
shells.
• The farther an electron is from the nucleus, the greater its
energy.
• The number of electrons in the outermost shell (valance)
determines the chemical properties of an atom.
• Valance electrons determine how an atom
behaves when it encounter other atoms
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Atoms of the four elements
most abundant in living matter
Electron
First electron shell
(can hold 2 electrons)
Hydrogen (H)
Atomic number  1
How many electrons
can each orbital
hold?
Outer electron shell
(can hold 8 electrons)
Carbon (C)
Atomic number  6
Nitrogen (N)
Atomic number  7
Oxygen (O)
Atomic number  8
Figure 2.6
The rule really is to fill one level before you move to the next level
Practice
1. By definition all atoms of carbon have exactly six
______________ , but the number of
______________ varies from one isotope to another.
2. As two atoms approach each other, which subatomic
particles will first come into contacts?
Chemical Bonding and Molecules
• In chemical reactivity, a toms tend to
- complete a partially filled valence
or
- empty a partially filled valence
• Chemical reactions enable atoms to give up or acquire
electrons, in order to complete their outer shells.
• Chemical reactions usually result in atoms
- staying close together and
- being held together by attractions called chemical
bonds.
• EIGHT is GREAT. Will steal or share electrons to
get eight valance electrons
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Chemical bonding between atoms
Covalent bonds are formed when atoms share electrons
– Non polar covalent bonds = Equal attraction; ie: H2
– Polar covalent bonds = Assymetric attraction; ie:
HO2
Ionic bonds are attractions between ions of opposite
charge
– steal electrons from other = Unequal attraction
Hydrogen bonds form between a positively charged
hydrogen atom and any other negatively charged atom
van der Waals interactions form between negatively
charged and positively charged regions in molecules.
Ionic Bonds
• When an atom loses or gains electrons, it becomes electrically
charged.
– Charged atoms are called IONS.
– Ionic bonds are formed between oppositely charged ions.
– steal electrons from other = Unequal attraction
Outer shell
has 1 electron
The outer electron is stripped
from sodium and completes
the chlorine atom’s outer shell
Outer shell
has 7 electrons
Na
Sodium atom
Cl
Chlorine atom
Complete
outer shells
Na
Sodium ion
Cl
Chlorine ion
Sodium chloride (NaCl)
The attraction
between the
ions—an ionic
bond—holds
them together
Calcium chloride molecule is an ionic compound formed by an
ionic bond between calcium ion and two chloride ions.
Covalent Bonds
• A covalent bond forms when two atoms share one or more
pairs of outer-shell electrons.
– Non polar covalent bonds = Equal attraction (H2)
– Polar covalent bonds = Asymmetric attraction (HO2
• Covalent bonds are the strongest of the various bonds.
• Covalent bonds hold atoms together in a molecule.
• The number of covalent bonds an atom can form is equal to
the number of additional electrons needed to fill its outer
shell.
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Common ways to represent molecules
Electron configuration
Structural formula
Space-filling model
Ball-and-stick model
H
H
Hydrogen gas (H2)
O
O
Oxygen gas (O2)
Double bounds
H
H
C
H
H
Methane (CH4)
Overlapping of orbitals/No + or – charges
Figure 2.8
Hydrogen Bonds
• Water is a compound in which the electrons in its covalent
bonds are shared unequally
– This causes water to be a polar molecule, one with opposite
charges on opposite ends (+ poles versus - poles)
– Oxygen has stronger “attraction” for the electrons
than hydrogen and therefore “higher
electronegativity”
slightly 
slightly 
H
H
H
H
O
O
slightly –
Hydrogen Bonds
• The polarity of water results in weak electrical attractions
between neighboring water molecules.
– These interactions are called hydrogen bonds.
Hydrogen bond
Practice
What happens when the outermost electron shell of
an element such as neon contains the maximum
number of eight electrons?
a. It becomes extremely unstable and reactive
b. It becomes stable and inert
c. It forms covalent bonds in an aqueous solution
An atom with an unfilled outer shell is
a.
b.
c.
d.
extremely unreactive
likely to bond with another atom
unable to bond with another atom
polar
Practice
The number of protons of an atom of an element
determines its
a. weight
b. isotopic status
c. mass number
d. tendency to form ionic bonds
e. atomic number
Fluorine’s atomic number is 9 and its mass number is
19. which of the following is true of fluorine?
a. It contains 9 protons and 10 neutrons
b. It contains 19 protons and 9 neutrons
c. It has no net charge when it has 19 electrons
d. It contains 9 protons and 19 neutrons
e. It is lighter than helium
Chemical Reactions
• Chemical reactions occurs when:
a. One substance combine with another
b. One substance is broken down into another
c. Chemical bonds are broken and other bonds form
• Cells constantly rearrange molecules by breaking existing
chemical bonds and forming new ones.
– Such changes in the chemical composition of matter are
called chemical reactions.
– Reaction between oxygen gas & hydrogen gas that forms water.
• Chemical reactions include reactants, the starting materials,
and products, the end materials.
• Chemical reactions can rearrange matter but cannot create or
destroy matter.
Figure 2.UN03
2 H2
Hydrogen
gas
+
O2
2 H2O
Oxygen
gas
Water
Reactants
Products
Water: The Molecule That Supports All of Life
• Water is the biological medium on Earth
- All life occurs in water
• The abundance of water is the main reason Earth is habitable
• All living organisms require water more than any other
substance
• Most cells are surrounded by water, and cells themselves are
about 70–95% water
• Water is the only common substance in the natural environmen
that exists in all three physical states of matter: solid, liquid,
and gas.
• Water is a reactant in many of the chemical reactions of life.
Figure 2.10
Water’s Life-Supporting Properties
• The polarity of water molecules and the hydrogen bonding
that results explain most of water’s life-supporting
properties.
– Water molecules stick together
– forming weak attractions between partially negative -O
and partially positive +H of another polar molecule.
– Water has a strong resistance to change in
temperature.
– Frozen water floats
– Water is a common solvent for life.
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The Cohesion of Water
• Because of small size,
bent shape and polarity,
Water molecules stick
together as a result of
hydrogen bonding
Evaporation
from the leaves
Microscopic waterconducting tubes
• This tendency of
molecules of the same
kind to stick together is
called Cohesion
Colorized
SEM
• Cohesion is vital for the
transport of water from
the roots to the leaves of
plants.
Cohesion due to
hydrogen bonds
between water
molecules
The Cohesion of Water
• Surface tension is the measure of how difficult it is to
stretch or break the surface of a liquid.
– Hydrogen bonds give water an unusually high
surface tension.
Figure 2.12
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2. How Water Moderates Temperature
• Because of hydrogen bonds water has a strong resistance to
temperature change.
• Heat and temperature are related, but different.
– Heat is the amount of energy associated with the movement of
the atoms and molecules in a body of matter.
– Temperature measures the intensity of heat.
• Water can absorb and store large amounts of heat while only
changing a few degrees in temperature.
• Water can moderate temperatures.
– Earth’s giant water supply causes temperatures to stay within
limits that permit life.
– Evaporative cooling occurs when a substance evaporates and
the surface of the liquid remaining behind cools down
– removes heat from Earth and from organisms
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Evaporative cooling
• When a substance evaporates
by changing the physical state
from a liquid to gas , the
surface of the liquid remaining
behind cools down.
• The molecules with the greatest
energy (hottest one) tend to
vaporize first
• Evaporative cooling removes
heat from the Earth and from
organisms.
3. The Biological Significance of Ice Floating
• When water molecules get cold enough, they move apart (the
movement of its molecules slows), forming ice.
- A chunk of ice has fewer molecules than an equal volume of liquid
water.
• Ice floats because it is less dense than the liquid water around it.
- the water molecules are spaced out more than in liquid water
• Oceans & lakes don’t freeze solid b/c surface ice insulates
water below allowing life to survive the winter
• If ice sank, ponds, lakes, & even oceans would freeze solid
• Life in water could not survive if bodies of water froze solid.
Hydrogen bond
Liquid water
Hydrogen bonds
constantly break
and re-form.
Ice
Stable hydrogen bonds
hold molecules apart,
making ice less dense
than water.
Figure 2.14
4. Water as the Solvent of Life
• A solution is a liquid consisting of a homogeneous mixture of
two or more substances.
– The dissolving agent is the solvent (medium of for chemical
reaction).
– The dissolved substance is the solute (table salt ).
• When water is the solvent, the result is an aqueous solution
 Water dissolve an enormous variety of solutes necessary for life.
 Hydrophilic substance dissolves in water, have attraction to
water (polar molecules)
 Hydrophobic substance that don’t have an attraction to water
(non- polar molecules, oil and butter)
 Water is the solvent inside all cells, in blood, and in plant sap.
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Polarity makes H2O a good solvent
polar H2O molecules surround + & - ions
Sodium ion
in solution
Chloride ion
in solution
Cl
Na
–
Cl
–
Na
Salt crystal
Figure 2.15
Practice
Surface tension and capillary action occur in water
because it
a. has hydrogen bonds
b. has ionic bonds
c. is dense
d. is nonpolar
e. is wet
In the reaction glucose + fructose
sucrose + water,
_____ is a reactant and _________ is a product.
Practice
Why does ice float on water?
a. Ice has a higher pH than water
b. Molecules of water are spaced father apart than
molecules of ice
c. Ice has a lower pH than water
d. Molecules of ice are spaced father apart than molecules
of water
Cocoa is mixed with hot water to make hot chocolate.
The cocoa is the ______, the hot water is the _____, and
the hot chocolate is the _________ .
a.
b.
c.
d.
e.
solute ……..…...solvent ……… solution
solvent ……..… solution ……..solute
solution………... solvent ………...solute
solvent ……....… solute……… solution
solute……..…... solution ….…....solvent
Practice
The hydrogen bond between two molecules arises
because water is
a.
b.
c.
d.
polar
hydrophobic
a liquid
nonpolar
Which of the following is not a property of water?
a.
b.
c.
d.
e.
polarity
a good solvent
cohesion
nonpolarity
store heat well
Practice
Which of the following pH values indicates a slightly
acidic solution?
a.
b.
c.
d.
e.
9
7
3
11
6.5
H2SO4 can ionize to yield two H+ ions and one
H2SO4 is
a.
b.
c.
d.
e.
molar
an acid
a base
a solution
a buffer
ion.
Practice
A basic solution contains
a.
b.
c.
d.
more OH- ions than H+ ions
the same number of OH- ions as H+ ions
no OH- ions
more H+ ions than OH- ions
Which of the following has
concentration of hydrogen ions?
a.
b.
c.
d.
baking soda at pH 9
Household ammoniac at pH 11
human blood at pH 7
black coffee at pH 5
the
greatest
Practice
Which of these refers to atoms with the same
atomic number but different atomic masses?
a.
b.
c.
d.
e.
these atoms are different elements
these atoms have different numbers of elements
these atoms are isomers
these atoms are isotopes
these atoms have different numbers of protons
An ionic bond involves______.
a.
b.
c.
d.
e.
the sharing of a single pair of electrons
an attraction between ions of opposite charge
no atoms other than sodium and chlorine
the unequal sharing of an electron pair
water avoidance
Practice
Which of these refers to atoms with the same
atomic number but different atomic masses?
a.
b.
c.
d.
e.
these atoms are different elements
these atoms have different numbers of elements
these atoms are isomers
these atoms are isotopes
these atoms have different numbers of protons
An ionic bond involves______.
a.
b.
c.
d.
e.
the sharing of a single pair of electrons
an attraction between ions of opposite charge
no atoms other than sodium and chlorine
the unequal sharing of an electron pair
water avoidance
Practice
What determines the types of chemical reactions that
an atom participates in ?
a.
b.
c.
d.
e.
its atomic mass
the number of electrons in the innermost electron shell
the number of electrons in the outermost electron shell
the number of protons it contains
its atomic number
An unchanged atom of boron has an atomic number of
5 and an atomic mass of 11. How many protons does
boron have?
Practice
The unequal sharing of electrons within a water molecule
makes the water molecule __________.
In a neutral solution the concentration of _________.
a. hydrogen ions is equal to the concentration of hydroxide ions
b. water molecules is less than the concentration of hydrogen
ions
c. hydrogen ions is less than the concentration of hydroxide ions
d. water molecules is less than the concentration of hydroxide
ions
e. hydrogen ions is greater than the concentration of hydroxide
ions
Practice
Which of the following substance is a substance
that resists changes in pH?
a.
b.
c.
d.
e.
acid
buffer
base
Solvent
solution
What is the atomic number of an atom that has 6
protons, 6 neutrons, and 6 electrons?
Acids, Bases, and pH
• To describe the acidity of a
solution, chemists use the pH
scale.
• To describe the relative
amount of H+ in solutions,
we use the pH scale
OH−
−
OH−OH
− 
OH H OH−
OH− H
Basic
solution
13
Lower H concentration
• A compound that accepts H+
and removes them from
solution is a base.
Oven cleaner
Household
bleach
12
Household ammonia
11
Milk of magnesia
10
9
Seawater
8

OH− H
H
OH−
−
OH
H − 
OH H
Neutral
solution
H H

OH− H H
−
 OH
H 
H
Acidic
solution
Human blood
[H]  [OH−] 7 Pure water
6 Urine
Greater H concentration
• A chemical compound that
releases H+ to a solution is an
acid.
14
5
4
Black coffee
Tomato juice
3 Grapefruit juice,
soft drink
2 Lemon juice,
stomach acid
Battery acid
1
0
pH scale
Figure 2.17
pH 14
Lower H
concentration
Basic
Neutral

−
[H ]  [OH ]
Acidic
pH 7
H concentration equal
to OH− concentration

Greater H
concentration
pH 0
pH scale
Figure 2.UN10
Acids, Bases, and pH
• Biological fluids contain buffers which are
substances that resist pH change
 accept H+ ions when they are in excess and
 donate H+ ions when they are depleted
• Buffers & Cellular regulation
- pH of cells must be kept at ~ 7
- pH affects shape of molecules
- shape of molecules affect function
- therefore pH affects cellular function
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• Increases in
global CO2
concentrations
may lead to
- the
acidification of
the oceans and
- ecological
disasters
Figure 2.18
Can Exercise Boost Your Brain Power?
• Observation: Human brains shrink as we age.
• Question: Can aerobic exercise slow or reverse brain loss?
• Hypothesis: MRI (magnetic resonance imaging) scans
would reveal differences between people who regularly
exercised aerobically and those who did not.
• Prediction: Brains of active people would shrink less than
the brains of less active people.
• Experiment: Twenty-nine people in their 60s and 70s
exercised for three one-hour sessions per week. A control
group of 29 people engaged in non-aerobic stretching
exercises for the same periods.
• Results: The aerobic group showed significant increases in
brain volume compared to the non-aerobic group
Figure 2.UN04
The colors highlight brain
regions that grew in aerobic
exercise participants compared
to a control group of non-aerobic
exercises.
Figure 2.16
Fluoride in the Water
• Fluoride
– Is a common ingredient in Earth’s crust
– Helps maintain healthy teeth
• Fluoride prevents cavities by
– Affecting the metabolism of oral bacteria
– Promoting the replacement of lost minerals on the
tooth surface
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Evolution Connection:
The Search for Extraterrestrial Life
• If life similar to ours has evolved elsewhere in the
universe, then it too would depend upon water.
• Researchers at NASA missions have found evidence
that water was once abundant on Mars.
• Microbial life may exist below the Martian surface.
© 2013 Pearson Education, Inc.
Figure 2.UN06
Attraction between oppositely
charged ions holds the ions in
an ionic bond.
Li
F−
Lithium ion
Fluoride ion
Lithium fluoride (ionic compound)
Figure 2.UN07
Electron sharing
H
O
H
Atoms joined into a molecule
via covalent bonds
Figure 2.UN08
Hydrogen
bond
Figure 2.UN09a
Liquid water
Hydrogen bonds
constantly break
and re-form.
Figure 2.UN09b
Ice
Stable hydrogen
bonds hold molecules
apart, making ice
less dense than water.
Figure 2.UN11
Figure 2.UN12
F
K
Fluorine atom
Potassium atom