Download Biology: Ch. 2

Biology
Chemistry of Life
Structure of Atoms
 Atoms are made up of protons (+),
neutrons (0), and electrons (-).
 Protons and neutrons are in the
nucleus of the atom.
 Electrons are in constant motion
outside the nucleus (electron cloud).
 ELEMENTS are pure substances
consisting of one type of atom.
Section 2-1
An Element in the Periodic Table
6
C
Carbon
12.011
Go to
Section:
ISOTOPES
 Isotopes are atoms of the same element
that have a different number of neutrons.
 This results in the isotopes having the same
atomic number, but different atomic
masses.
 Carbon-12, Carbon-13, and Carbon-14 are
isotopes.
 Radioactive isotopes can be used to
determine the age of materials, treat
cancer, and to trace the movement of
substances in organisms.
Figure 2-2 Isotopes of Carbon
Section 2-1
Nonradioactive carbon-12
Nonradioactive carbon-13
6 electrons
6 protons
6 neutrons
6 electrons
6 protons
7 neutrons
Go to
Section:
Radioactive carbon-14
6 electrons
6 protons
8 neutrons
Chemical Compounds
 A chemical compound is a substance
formed by the chemical combination of two
or more elements in definite proportions.
 The chemical formula for a compound tells
the types of elements that are in it, and the
ratio in which the atoms of those elements
combine.
 Ex) H2O means two hydrogen atoms
always combine with one oxygen atom to
form a water molecule.
CHEMICAL BONDS
 Ionic bonds form when two or more
electrons are transferred from one atom to
another. Ex) NaCl
 Covalent bonds form when electrons are
shared between atoms.
Ex) water
 Van der Waals forces are slight attractions
that occur between oppositely charged
regions of nearby molecules. Not as strong
as ionic or covalent bonds.
Figure 2-3 Ionic Bonding
Section 2-1
Sodium atom (Na)
Chlorine atom (Cl)
Sodium ion (Na+)
Chloride ion (Cl-)
Transfer
of electron
Protons +11
Electrons -11
Charge
0
Go to
Section:
Protons +17
Electrons -17
Charge
0
Protons +11
Electrons -10
Charge
+1
Protons +17
Electrons -18
Charge
-1
Water, Water Everywhere
 If you have ever seen
a photograph of Earth
from space, you know
that much of the
planet is covered by
water.
 Water makes life on
Earth possible. If life
as we know it exists
on some other planet,
water must be present
to support that life.
Go to
Section:
Properties of Water
 Water molecules are neutral, but polar.
There is a slightly negative charge on
oxygen, and slightly positive charge on
the hydrogen atoms.
 Water molecules are polar because there
is an uneven distribution of electrons
between the oxygen and hydrogen
atoms.
 Water is extremely cohesive because of
its ability to form hydrogen bonds.
Cohesion vs. Adhesion
 Cohesion is the
attraction between
molecules of the same
substance. Ex) water
molecules to each other
 Adhesion is the
attraction between
molecules of different
substances. Ex) water
molecules cling to the
inside of a plant stem
Mixtures
 Mixtures are materials composed of
two or more elements or compounds
that are physically mixed together
but not chemically combined.
 Two types of mixtures made with
water are homogenous mixtures
and suspensions.
Homogenous mixtures
 Solution: Mixture of two
or more substances in
which the molecules of the
substance are evenly
distributed.
 Solvent- substance in
which a solute is dissolved
to form a solution. Ex)
water
 Solute- substance
dissolved in a solvent to
make a solution Ex) salt
Figure 2-9 NaCI Solution
Section 2-2
ClCl-
Na+
Na+
Water
Go to
Section:
Water
Suspensions
 Mixtures of water and undissolved
materials that are so small they do
not settle out.
 Examples are blood and milk.
Acids, Bases, and pH
 pH measures the concentration of
hydrogen ions (H+) in solution.
Ranges from 0 to 14.
 ACIDIC solutions have high H+
concentrations, and a pH less than 7.
 BASIC solutions have a low
concentration of H+, and a pH
greater than 7.
 Solutions with pH of 7, such as pure
water, are NEUTRAL.
 BUFFERS are weak acids and bases
that can react with strong acids or
bases to prevent sudden changes in
pH.
pH Scale
Section 2-2
Increasingly Basic
Oven cleaner
Increasingly Acidic
Neutral
Go to
Section:
Bleach
Ammonia solution
Soap
Sea water
Human blood
Pure water
Milk
Normal
rainfall
Acid rain
Tomato
juice
Lemon juice
Stomach acid
Carbon Compounds
 Carbon forms strong covalent bonds.
 Carbon atoms can bond to other
carbon atoms to form long chains.
 Carbon-carbon bonds can be single,
double, or triple bonds.
 Carbon atoms can close upon
themselves to from rings.
Figure 2-11 Carbon Compounds
Section 2-3
Methane
Go to
Section:
Acetylene
Butadiene
Benzene
Isooctane
Macromolecules
 Macromolecules are made from thousands
of smaller molecules.
 Monomers-small unit that can join with
other small units to form polymers.
 Polymers-large compound formed from
combinations of many monomers.
 Four groups of organic compounds found in
living things are carbohydrates, lipids,
nucleic acids, and proteins.
Carbohydrates
 Carbohydrates are compounds made up of
carbon, hydrogen, and oxygen atoms,
usually in a ratio of 1 : 2 : 1.
 Living things use carbohydrates as their
main source of energy. Stored as glycogen
in animals and starch in plants.
 Plants and some animals use carbohyrates
for structural purposes. Plants have
cellulose, animals have chitin.
Carbohydrate storage
Glycogen in an animal cell
Starch in a plant cell
Carbohydrates for structure
Chitin in animal cells—arthropod
shells and insects. Also found in
cells walls of fungi
Cellulose in plant cells
(we don’t have enzymes to digest it)
 Monosaccharides are single sugar
molecules, such as glucose.
 Polysaccharides are large
macromolecules formed from
monosaccharides, such as starch.
Figure 2-13 A Starch
Section 2-3
Starch
Glucose
Go to
Section:
Lipids
 Lipids are a group of organic
molecules made mostly of carbon and
hydrogen atoms.
 Generally not soluble in water.
 Grouped as fats, oils, and waxes.
 Used to store energy, form parts of
biological membranes, and form
waterproof coverings.
 Examples: steroids, triglycerides
 Saturated fats have the maximum
number of possible hydrogen bonds.
Tend to be solid at room temperature.
Examples: meat fat, Crisco, butter,
lard, etc.
 Unsaturated fats have at least one
carbon-carbon double bond C=C.
 Polyunsaturated fats contain C=C double
bonds, and are liquid at room
temperature, Examples: olive oil,
vegetable oils
Saturated vs. Unsaturated Fats
Nucleic acids
 Nucleic acids are macromolecules
containing hydrogen, oxygen,
nitrogen, carbon, and phosphorus
 Nucleotides have three parts: 5carbon sugar, phosphate group, and
a nitrogenous base.
 Nucleic acids store and transmit
hereditary or genetic information
 Examples: DNA (deoxyribonucleic
acid) and RNA (ribonucleic acid)
The Double Helix
Nucleotide
Nucleotide is
a sugar,
phosphate, &
nitrogen base
Hydrogen
bonds
Sugar-phosphate
backbone
Key
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
Proteins
 Proteins are macromolecules that
contain nitrogen, carbon, hydrogen,
and oxygen.
 Proteins are polymers of amino acids.
Have an amino group (--NH2) and a
carboxyl group (--COOH) at the
other.
 The amino acids form chains that fold
into complex structures.
Figure 2-16 Amino Acids
Section 2-3
Amino group
Carboxyl group
General structure
Go to
Section:
Alanine
Serine
 Proteins control the rate of reactions
and regulate cell processes.
 Proteins help form muscle and bone
tissue.
 Proteins help transport substances
into and out of cells.
 Help fight diseases.
Levels of Protein Structure
 Primary- amino acid sequence
 Secondary- regular repeated coiling and
folding of a protein’s amino acid chain
 Tertiary- 3-dimensional shape of a
protein due to bonding between side
chains
 Quaternary- results from interactions
between several polypeptide chain (protein has
subunits, like hemoglobin and collagen)
Figure 2-17 A Protein
Section 2-3
Amino
acids
Go to
Section:
Concept Map
Section 2-3
Carbon
Compounds
include
Carbohydrates
Lipids
Nucleic acids
Proteins
that consist of
that consist of
that consist of
that consist of
Sugars and
starches
Fats and oils
Nucleotides
Amino Acids
which contain
which contain
Carbon,
hydrogen,
oxygen
Go to
Section:
Carbon,
hydrogen,
oxygen
which contain
which contain
Carbon,hydrogen,
oxygen, nitrogen,
phosphorus
Carbon,
hydrogen,oxygen,
nitrogen,
Chemical reactions and enzymes
 A chemical reaction is a process that changes
one set of chemicals into another set of
chemicals.
 Chemical reactions always involve the breaking
of bonds in the reactants (starting materials)
and the formation of new bonds in the
products (results of the reaction)
 When this occurs, energy is either released or
absorbed.
 Evidence that a chemical reaction has occurred
includes heat, light, or gas being given off.
Products are different from the reactants.
Energy in Reactions
 Since chemical reactions involve changes in
chemical bonds, they also involve changes
in energy.
 Exothermic- reactions that release energy.
Often occur spontaneously.
 Endothermic- reactions that must absorb
energy to take place.
 The energy needed to get a reaction
started is called the activation energy.
Figure 2-19 Chemical Reactions
Section 2-4
Energy-Absorbing Reaction
Energy-Releasing Reaction
Activation
energy
Products
Activation energy
Reactants
Reactants
Products
Go to
Section:
Enzymes
 Enzymes are catalysts that speed up
chemical reactions that take place in cells.
 Enzymes lower the activation energy of the
reaction.
 Enzymes provide a site where substrates
(reactants) are brought together so that
the reaction can occur.
 This is often described as a “lock and key”
mechanism. Products are released. The
enzyme is not used up in the reaction.
Effect of Enzymes
Section 2-4
Reaction pathway
without enzyme
Activation energy
without enzyme
Reactants
Reaction pathway
with enzyme
Activation
energy
with enzyme
Products
Go to
Section:
Figure 2-21 Enzyme Action
Section 2-4
Enzyme
(hexokinase)
Products
Substrates
ADP
Glucose-6phosphate
Products
are released
ATP
Active site
Enzyme-substrate
complex
Substrates
are converted
into products
Go to
Section:
Glucose
Substrates
bind to
enzyme
Enzymes, cont.
 Optimal temperature and pH are
needed for most enzymes to be
effective.
 Enzymes in the human body function
best near normal body temperature:
35-400 C.
 Below the optimum temperature, the
reaction is slower or may not occur at
all.
Enzymes, cont.
 High temperatures disrupt the
chemical bonds in the enzyme and
changes it shape (denaturation).
 This occurs when the body has a very
high fever. Since denaturation is not
reversible, a temperature higher than
440 C usually causes death.
 Proteins begin to denature at 107 F.