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What are the building materials of life?
The Universe
 The most abundant element in the universe is
hydrogen – the simplest atom
 The second most abundant element in the
universe is helium
The elements are forged in the stars
 http://youtu.be/uKqvjEE0wFg
 http://youtu.be/l_hF9zq4QXU
 http://youtu.be/qfRiqwQBegQ
The elements of planet
earth
1. Fe
2. O
3. Si
4. Mg
5. Ni
6. S
The elements in the body
1. O
2. C
3. H
4. N
5. Ca
6. P
7. S
the simplest atom
Atoms
 Basic units of matter
 From ATOMOS: Unable to be cut – can’t be
divided any further in any chemical or
physical change
 Defined: The smallest part of an element
that has the properties of the element.
p+ =
=
Element is
n0 =
e- =
p+ plus n0 =
=
Symbol is
Notation is
 Learning atomic
structure is just counting
p+ =
=
Element is
n0 =
e- =
p+ plus n0 =
=
Symbol is
Notation is
Learning atomic structure
is just counting.
Two versions of the same
element????
ISOTOPES!!!
Isotopes
 Atoms of the same element with different numbers of






neutrons
Only the neutrons have changed, the identity (p+
determine) & the chemical properties (e- determine) are
the same!
Only the mass is different
Isotopes can be stable or radioactive
Isotopes can be natural or man-made
All elements have one or more isotopes – usually several –
and they are present in nature in different percentages
The natural and stable isotopes are more common ( or
more abundant ) in nature
p+ =
=
Element is
n0 =
e- =
p+ plus n0 =
=
Symbol is
Notation is
 Learning atomic
structure is just
counting.
Atoms
The subatomic
particles in a helium
atom.
The nucleus contains the
p+ and n0. It is dense and
massive.
The e- move in the energy
levels outside the nucleus
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p+ =
=
Element is
n0 =
e- =
p+ plus n0 =
=
Symbol is
Notation is
 Learning atomic
structure is just
counting.
 Learning atomic
structure is just
counting.
p+ =
=
Element is
n0 =
e- =
p+ plus n0 =
=
Symbol is
Notation is
p+ =
=
Element is
n0 =
e- =
p+ plus n0 =
=
Symbol is
Notation is
 Learning atomic
structure is just
counting.
p+ =
=
Element is
n0 =
e- =
p+ plus n0 =
=
Symbol is
Notation is
 Learning atomic
structure is just
counting.
Isotopes of Carbon
6 electrons
6 protons
6
7
8 neutrons
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Elements and Isotopes
Radioactive Isotopes


Def: Some isotopes are radioactive; their
nuclei are unstable and break down at a
constant rate over time.
Although the radiation these isotopes give
off can be dangerous, they have important
scientific and practical uses.
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Elements and Isotopes
Radioactive isotopes can be used:
 to determine the ages of rocks and fossils.
 to treat cancer.
 to kill bacteria that cause food to spoil.
 as labels or “tracers” to follow the
movement of substances within an
organism.
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p+ =
=
Element is
n0 =
e- =
p+ plus n0 =
=
Symbol is
Notation is
p+ =
=
Element is
n0 =
e- =
p+ plus n0 =
=
Symbol is
Notation is
•
p+ & n0 have about the
•
p+ are positive
•
n0 have no charge
same mass and make up
the dense center of the
atom
• Strong nuclear forces hold
them together in the
nucleus
•
e- have almost no mass and
•
e- move at nearly the speed
a negative charge
of light outside the
nucleus
Quick Quiz
1. The dense center of the atom is called the
2.
3.
4.
5.
_______________.
The atomic particle with a positive charge is
the _______________.
The atomic particle with NO charge is the
_______________.
The atomic particle with a negative charge
the _______________.
The atomic particle that identifies the atom
is the _______________.
Quick Quiz
1. Why are atoms neutral?
2. T/F Isotopes of an atom are always
radioactive.
3. The atomic particle(s) that determines an
atom’s chemical properties is the
_________________.
4. T/F Isotopes of an element are found in nature
in equal amounts.
5. Why do scientists sometimes write nuclear
symbols as follows: 4He OR 12C OR 14C.
Chemical Compounds




In nature, most elements are found
combined with other elements in
compounds.
Defined: A chemical compound is a
substance formed by the chemical
combination of two or more elements in
definite proportions.
The physical and chemical properties of a
compound are different from the
elements from which it is formed.
In a chemical reaction a NEW substance is
formed; the atoms are rearranged.
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Chemical Bonds


The atoms in compounds are held together
by chemical bonds.
Bond formation involves only the
outermost electrons that surround each
atomic nucleus.
 These are called Valence electrons.
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Ionic Bonds




An ionic bond is formed when one or more
e- are transferred from one atom to another.
An atom that loses e- has a positive charge.
An atom that gains e- has a negative charge.
…….Ions: atoms that have a charge because
they have lost or gained electrons.
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Covalent Bonds
Sometimes e- are shared by atoms instead of
being transferred.
 Sharing e- means the moving e- travel in the
orbitals of both atoms.
 The structure that results is called a
molecule.
 A molecule is the smallest unit of compounds
that have covalent bonds.

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Polar Covalent Bonds
In a water molecule, each
hydrogen atom forms a
single covalent bond with
the oxygen atom.
Since oxygen atoms pull the
shared e- more strongly, the
sharing is not even and poles
of charge form around the
ends of the molecule
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Bonding Videos
 http://youtu.be/QXT4OVM4vXI
 http://youtu.be/PVL24HAesnc
Van der Waals Forces:
Weak attractive forces between molecules
 When molecules are close together, a slight attraction can
develop between the oppositely charged regions of nearby
molecules.
 Chemists call such intermolecular forces of attraction van
der Waals forces, after the scientist who discovered
them.
• Although van der Waals forces are not as strong
as ionic bonds or covalent bonds, they can hold
molecules together, especially when the molecules
are large.
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For example, van der Waals
forces form between the
molecules on the surface of a
gecko’s foot and the molecules
on the surface of the wall.
The van der Waals forces
allows the gecko to grip the
wall.
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2-2 Properties of Water
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The Water Molecule is POLAR
Polarity in the water molecule
 An atom of Oxygen, with 8 p+ in its nucleus, has
a stronger attraction for e- than hydrogen with
a single p+.
 The shared e- are pulled toward the oxygen
atom and away from the hydrogen atom.
 As a result, the oxygen end of the molecule has
a slight negative charge and the hydrogen end
has a slight positive charge.
 A water molecule is polar because there is an
uneven distribution of e- between the oxygen
and hydrogen atoms.
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Hydrogen “Bonds”
 The attractions between polar water molecules are so
significant we call them hydrogen bonds even though
they are not as strong as true covalent or ionic bonds.
 Because of their partial positive and negative charges,
polar molecules can attract each other.
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The Water Molecule
Hydrogen bonds form
between water
molecules.
Hydrogen bonds are
the strongest type of
Van der Waals forces.
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Special Properties of Water
Cohesion is an attraction between molecules
of the same substance.
Water's cohesion causes
molecules on the surface of
water to be drawn inward,
forming drops or beads.
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Special Properties of Water
 Cohesion
also explains why some insects and
spiders can walk on a pond's surface.
Hydrogen bonds cause the water’s surface to
act like a membrane; this is called Surface
Tension
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Special Properties of Water
Adhesion is an attraction between molecules of
different substances.
Ex: The surface of water in a graduated cylinder
forms a meniscus because adhesion between water
molecules and glass molecules is stronger than
cohesion between water molecules.
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Special Properties of Water
Adhesion causes water to rise in a narrow tube against the
force of gravity.
This effect is called capillary action.
Capillary action is one of the forces that draw water out of
the roots of a plant and up into its stems and leaves.
Cohesion holds the column of water together as it rises.
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Special Properties of Water
High Heat Capacity
Water is able to absorb a lot of heat energy
without having its temperature increase by
very much.
EX: Beach in the summer, sand is very hot
and the water feels very cool.
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Water is the universal solvent
 Water is the best solvent because it is a very polar
Ex: solutes that water can dissolve include salt,
sugar, gelatin
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MIXTURES
 A mixture is a material composed of two or more
elements or compounds that are physically mixed
but not chemically combined.

EX: salt & pepper, salt water, chex mix, soda, air, alloys
Two types of mixtures can be made with water
1.
solutions
2. suspensions
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Solutions
All the components of a solution are evenly
distributed throughout the solution.
It
is HOMOGENEOUS – every part is exactly the same
The particles in a solution are too small to see so
usually they transmit light – you can see through
them.
In a salt–water solution, table salt is the solute —
the substance that is dissolved - and water is the
solvent —the substance in which the solute
dissolves.
The air you breathe is a solution of 20% oxygen
gas dissolved in 80% nitrogen gas.
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How Solutions Form
When a crystal of table salt is placed in warm water,
sodium and chloride ions are attracted to the polar water
molecules. Ions are pulled from the crystal and are
surrounded by water molecules. The ions are dispersed in
the water, forming a solution.
Cl
-
Cl Na+
Na+
Water
Water
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Suspensions
Some materials do not dissolve in water but separate
into pieces so small that they do not settle out.
Ex: blood. The movement of water molecules keeps
the small particles suspended.
Such mixtures of water and nondissolved material
are known as suspensions.
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Acids, Bases, and pH
 A water molecule can react to form hydrogen and
hydroxide ions:

H2O ⟷
[H+]
+
[OH-]
 Water is neutral because the number of positive
hydrogen ions (H+) produced equals the number
of negative hydroxide ions (OH-) produced.
 Chemists devised a measurement system called
the pH scale to indicate the concentration of H+
and OH- ions in solution.
 The pH scale ranges from 0 to 14.
 Each step on the scale represents a factor of 10.
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The pH Scale
At a pH of 7, the
concentration of H+ ions
and OH- ions is equal.
Pure water has a pH of 7.
Sea water
Human blood
Pure water
Normal rainfall
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Milk
The pH Scale
 An acid is any
compound that forms
H+ ions in solution.
 Solutions with a pH
below 7 are called
acidic because they
have more H+ ions
than OH- ions.
 The lower the pH,
the greater the
acidity.
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Acid rain
Tomato juice
Lemon juice
Stomach acids
 A base is a compound that
produces hydroxide ions
(OH- ions) in solution.
 Solutions with a pH
above 7 are called basic
because they have more
OH- ions than H+ ions.
 The higher the pH, the
more basic the solution.
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The pH Scale
Oven cleaner
Bleach
Ammonia solution
Soap
Acids, Bases, and pH
The pH of the fluids within most cells in the human
body must generally be kept between 6.5 and 7.5.
If the pH is lower or higher, it will affect the
chemical reactions that take place within the cells.
Controlling pH is important for maintaining
homeostasis.
One of the ways that the body controls pH is
through dissolved compounds called buffers.
Def: Buffers are weak acids or bases that can react
with strong acids or bases to prevent sharp, sudden
changes in pH.
Ex: Antacid – Milk of Magnesia
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2–3
Carbon Compounds
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Ch 2 continued
The Chemistry of Carbon
 DEF: Organic chemistry is the study of
all compounds that contain bonds between
carbon atoms.
 Living organisms are made of molecules
that consist of carbon and other
elements.
 Carbon atoms have four valence e- that
can join with other atoms to form four
strong covalent bonds
Carbon has 4 valence electrons
available for bonding
The chemistry
of carbon
 A central carbon atom can
form FOUR covalent
bonds with other elements
 Carbon bonds can form
long chains and even rings
 These bonds can be single
bonds, double bonds or
triple bonds
MACROMOLECULES
• Macromolecules are
formed by a process
known as
polymerization.
• The smaller units, or
monomers, join
together to form
polymers or large
molecules.
• Monomers in a polymer
may be identical, or
the monomers may be
different.
FOUR GROUPS OF
COMPOUNDS TO LEARN
Four groups of organic compounds
found in living things are:
1. carbohydrates
2. lipids
3. nucleic acids
4. proteins
Carbohydrates
 Carbohydrates are compounds made up of
C, H and O atoms, usually in a ratio 1 : 2 : 1.
 Living things use carbs for energy
 Plants use carbs for structural purposes.
 extra sugar is stored as complex
carbohydrates known as starches.
 Starches form when sugars join together
in a long chain.
CARBOHYDRATES
• the monomers of a
carbohydrate are
monosaccharides or
simple sugars.
EX: glucose,
galactose & fructose
• The polymers formed
from monosaccharides
are called
polysaccharides
EX: animal starch
(Glycogen), plant
starch (Cellulose)
LIPIDS
 Lipids are made mostly from C & H atoms.
 The monomer of a lipid is the glycerol molecule bonded to
a fatty acid.
LIPIDS
 Lipids can be used to store energy.
 Some lipids are important parts of
biological membranes and waterproof
coverings.
 Lipids are not soluble in water!
 Includes fats, oils, waxes, steroids
LIPIDS
 If each carbon atom in the chain has a single
bond the lipid is saturated: it contains the
maximum number of H atoms.
 If there are any double bonds (C = C) its is
unsaturated.
 Unsaturated fats tend to be liquid at room
temperature.
NUCLEIC ACIDS
 Nucleic acids store & transmit genetic information.
 The monomers that make up a nucleic acid are
nucleotides. Each nucleotide has a 5-carbon sugar, a
phosphate group, and a nitrogenous base.
Two kinds of nucleic acids
RNA: ribonucleic acid - contains the sugar
ribose.
DNA: deoxyribonucleic acid - contains the
sugar deoxyribose.
PROTEINS
 The monomers of a protein macromolecule are
called amino acids.
 Amino acids have a central carbon atom
attached to the following:
1. an amino group ( -NH2 ) on one end
2. a carboxyl group ( -COOH ) on the other end
3. a single Hydrogen atom
4. An “R-group”– called a side chain - that
varies
 There are about 20 different amino acids
The R group varies for each amino acid.
Amino acids are the monomers of all proteins.
Amino Acid sequence = different proteins
 DNA has instructions for arranging amino acids into many
different proteins
 Proteins are made up of chains of amino acids folded into
complex structures.
What proteins do
 Help carry out chemical reactions
 Control reaction rates (ex: enzymes)
 Regulate cell processes (ex: hormones, insulin)
 Used to form bones and build muscles
 Transport small molecules in and out of cells
 Fight diseases
2–4
Chemical Reactions and Enzymes
 Everything that happens in an organism is
based on chemical reactions.
 Def: A chemical reaction is a process that
changes one set of substances into another
set of substances.
 Atoms are not created or destroyed, just
rearranged.
 Reactants enter into the chemical reaction
 New substances produced are called
products
ENERGY IN REACTIONS
 Since bonds are breaking and new bonds are
forming, reactions always involve changes in
energy; energy is released or absorbed
 Chemical reactions that release energy often
occur spontaneously but not always.
 Chemical reactions that absorb energy will
not occur without a source of energy.
 Chemists call the energy that is needed to get a
reaction started the activation energy.
Living things need energy to survive!
Respiration in animals:
6 O2 + C6H12O6 ⟶ 6 CO2 + 6 H2O + Energy for living
 Reversing this reaction would require the addition of energy.
Photosynthesis in plants:
6 CO2 + 6 H2O + Energy from sun ⟶ 6 O2 + C6H12O6
ENZYMES & CATALYSTS
• Some reactions that
make life possible are
too slow.
• A catalyst is a
substance that speeds
up the reaction by
lowering the activation
energy
• Enzymes are proteins
that act as biological
catalysts
• Enzymes are very
specific: their name is
derived from the
reaction it works on
The Enzyme-Substrate Complex
The Enzyme-Substrate Complex
 1.The substrates bind to the active site on the
enzyme, forming an enzyme-substrate complex.
 *The fit is so precise that the active site and
substrates are often compared to a lock and key.
 2.The enzyme and substrates remain bound until
reaction is done and the substrates are
converted to products.
 3.The products of the reaction are released and
the enzyme is free to start the process again.