Transcript Chapter 2

2
The Fundamental Building
Blocks:
Chemistry and Life
I. Introduction: Chemistry and Its Importance
in Biology (Section 2.1)
A. Why do we need to study chemistry? Because you need
to see what living organisms are composed of if you
want to understand how they function. (City composed
of bricks and mortar.) Figure 2.1
B. Also the public is increasingly responsible for health
care decisions that require knowledge of chemistry (see
“Science and Society”) (Interactive Activity 1, 2, or 3).
C. How do cells do anything? Chain of chemical
reactions, latching on, reforming, depositing, and
breaking down.
D. Look at an object, what do you see? Matter (takes
up space, has weight) and energy.
II. Nature of Matter: The Atom (Section
2.2)
A. Subatomic particles Figure 2.3
1. Nucleus—very small size compared to the
entire atom, composed of protons (positive
charge, mass) and neutrons (no charge, but
mass).
2. Electrons—orbit
the nucleus (negative charge,
negligible mass).
3. Atoms are usually
electrically neutral: Number
of electrons = number of
protons.
B. Elements: Figure 2.4. Gold—pure, cannot be
reduced into a simpler component substance
through chemical processes.
1. Difference between iron and gold? Both are
matter: Fe has 26 protons, and Au has 79
protons.
2. Atomic number = number of protons defines
elements.
Periodic Table
3. One element = one atomic number.
4. Elements are listed on periodic table by
number of protons: H = 1, He = 2.
5. What kind of elements are we composed of ?
Dirt? Figure 2.5
C. Atomic Weight and Isotopes
1. Neutrons also contribute weight, but not identity, so
different forms of the same element may have different
mass, called isotopes.
2. Mass number = number of protons + number of neutrons.
3. Atomic weight is the average mass number of isotopes for
one element.
III. Matter Is Transformed through
Chemical Bonding (Section 2.3)
A. Chemical Bonding
1. Electrons—The most important particles in
allowing atoms to interact so they can attach.
2. Electrons are found in distinct energy levels
(shells or orbitals). Figure 2.8
3. Atoms are driven to react by a desire to
become more stable (like a rock perched on a
hill).
III. Matter Is Transformed through
Chemical Bonding (Section 2.3)
A. Chemical Bonding
4. Stability—full outer electron shell or orbital
(like more energetically sound to have a full car
when you commute).
5. Nonreactive elements (inert gases like argon)
have full outer shells (cannot have any more
passengers, so will not react).
B. Covalent Bonds—Atoms that don’t have full outer
shells may want to share electrons so that they can
both have full outer shells. (Interactive Activity 4)
1. Covalent bonds between two hydrogen atoms
(each with one electron) and oxygen (with
eight) complete the shells of all three.
2. Law of conservation of mass—matter is
neither created nor destroyed.
3. Molecules = two or more atoms combined.
4. Compound = defined number of atoms in a
defined spatial relationship.
5. Nonpolar versus polar covalent bonds. Figure 2.9
a) Polar = H2O, Figure 2.11. Oxygen end of the
molecule is slightly negative, while the Hydrogen
end is slightly positive.
b)
Nonpolar = neither end is positive or negative
C. Ionic Bonds—atoms gain or lose electrons, taking on a
negative or positive charge.
1. Formation of NaCl,.
2. Ions = charged atoms after losing or gaining one
electron.
3. Ionic compounds = ions’ opposite charges attract one
another (opposites attract)
D. Hydrogen Bonds
1. Water in solution—Polar covalent bonds in
H2O generate partial negative and partial
positive charge on opposite sides.
2. Partial negative end of one water attracted to
partial positive end of another by a hydrogen
bond. Figure 2.13
3. These H-bonds
are in DNA &
water.
V. Some Qualities of Chemical Compounds
A. Three-dimensional shape,
B. Importance of shape to biology, Figures 2-15a and 2-15b
(Interactive Activity 6)
C. Solutes, Solvents, and Solutions
1. Water + salt = solution. Why?
2. Polar with polar, nonpolar with nonpolar.
The
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