Transcript Chapter 2: Chemistry of Life 2.1: Atoms, Ions, and Molecules

Chapter 2: Chemistry of Life
2.1: Atoms, Ions, and Molecules
• Warm Up: What complex things do you
know that are made up by simple units?
• Objectives: Identify elements common to
living things.
• Describe how ions form.
• Compare ionic and covalent bonding.
• Terms to Know: Atom, elements, compound,
ion, ionic bond, covalent bond, molecule.
Living things Consist of Atoms
of Different Elements
• An Atom is the
smallest basic unit of
matter.
• Millions of atoms can
fill the space of a
pencil dot on a sheet
of paper.
Atoms
• All atoms share the same
basic structure.
• Atoms consist of three
subatomic particles:
• 1. Protons – positively
charged particles in the
nucleus of the atom (+)
• 2. Neutrons – particles
in the nucleus of the atom
with NO charge (o)
• 3. Electrons – particles
surrounding the nucleus
with a negative charge (-)
Elements
• An Element is one
particular type of atom,
and it cannot be broken
down into simpler
substances by ordinary
chemical means.
• Elements are arranged
on the Periodic Table and
each has it’s own unique
characteristics.
– Ex: hydrogen, oxygen,
carbon, nitrogen,
phosphorus
Atoms and Elements
• All atoms of a given element have a specific number of protons,
neutrons and electrons.
• The number of protons and electrons is given by the Atomic
number of the element.
– Ex: Hydrogen’s atomic # is 1, so it has 1 proton and 1 electron.
– Ex: Oxygen’s atomic # is 8, so it has 8 protons and 8 electrons.
• The number of neutrons can be found by subtracting atomic number
from atomic mass.
– Ex: Hydrogen’s atomic mass is 1 so the number of neutrons is 1-1 or 0
– Ex: Oxygen’s atomic mass is 16 so the number of neutrons is 16-8 or 8
• Valence Electrons are those found in the outermost shell of an
atom.
– The magic number for valence electrons is 8.
Compounds
• A Compound is a substance
made of atoms of different
elements bonded together in a
certain ratio.
• Common compounds in living
things include water (H2O) and
carbon dioxide (CO2).
• Compounds commonly have
different properties than the
elements that make them up.
– Ex: hydrogen and oxygen are
gases but combined they for
water, a liquid.
• How are elements different
from compounds?
Ions form when Atoms Gain or
Lose Electrons
• An Ion is an atom that has gained or lost one or more
electrons.
• An Ion forms because an atom is more stable when its
outermost energy level is full; the gain or loss of electrons
allows this to occur.
• Some ions are positively charged (those that lose electrons)
• Some ions are negatively charged (those that gain electrons).
• An Ionic Bond form through the electrical force between
oppositely charged ions.
– Ex: Salt is an ionic bond between sodium and chlorine.
– Chlorine (Cl) has 7 valence electrons (needs 1) and
Sodium (Na) has 1 valence electron (need to get rid of it)
– Sodium donates its electron to chlorine forming an ionic
bond that creates salt.
Ionic Bonds
Atoms Share Pairs of Electrons
in Covalent Bonds
• Not all atoms gain or lose electrons.
• Many elements must share electrons to fill their valence
shells.
• A Covalent Bond is formed when two or more atoms
share pairs of electrons.
– Ex: Carbon has 4 valence electrons (needs 4) and Oxygen has
6 valence electrons (needs 2).
– Neither atom can donate electrons so they share pairs to fill the
valence shell.
• A Molecule is two or more atoms held together by
covalent bonds.
– Ex: Water, Carbon Dioxide, Glucose.
• What happens to electrons in outer energy levels when
two atoms form a covalent bond?
Covalent Bonds
2.2: Properties of Water
• Objectives: Recognize the importance of
hydrogen bonding.
•
Explain why many compounds
dissolve in water.
•
Compare acids and bases.
• Warm Up: Why is water so important to life?
• Words to Know: Hydrogen bond, cohesion,
adhesion, solution, solvent, solute, acid,
base, pH.
Water and Hydrogen Bonds
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Water is a Polar Molecule, this
means that is has a slightly
positive end and a slight negative
end (like a magnet).
Polar molecules form when atoms
in a molecule have unequal pulls
on the electrons they share.
Other molecules, called nonpolar
molecules, do not have these
charged regions.
Opposite charges of polar
molecules interact to form
Hydrogen Bonds.
A Hydrogen Bond is an attraction
between a slightly positive
hydrogen atom and a slightly
negative atom.
Hydrogen Bonding is very
common in water, but also occurs
in other molecules.
Properties Related to Hydrogen
Bonding
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Water is a liquid at the
temperature that support most life
on Earth.
Hydrogen bonds give water a high
Specific Heat, meaning water
resists changes in temperatures.
– This process is crucial to cells
where homeostasis is required.
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Cohesion is the attraction among
molecules of the same substance
(water to water).
– Ex: Water forming bead on a
window.
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Adhesion is the attraction of
molecules of different substances.
– Ex: Water sticks to glass in a
graduated cylinder.
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How are hydrogen bonds similar
to ionic bonds?
Many Compounds Dissolve in
Water
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A Solution is a mixture of substances
that is the same throughout – it is a
homogenous mixture.
A Solution is made up of two parts:
– The Solvent is the substance that
is present in the greater amount
and dissolves the other
substance.
– The Solute is the substance that
dissolves in the solvent.
– Ex: Koolaid: Solvent: water,
Solute: Koolaid
– Ex: Blood Plasma: Solvent:
water, Solute: sugars and
proteins.
Nonpolar substances such as fats and
oils, rarely dissolve in water.
Nonpolar substances will dissolve in
other nonpolar substances.
Polar substances will dissolve in water.
What are the solvent and solutes in a
beverage you drink?
Some Compounds form Acids or
Bases
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Some compounds break up into
ions when they dissolve in
water.
An Acid is a compound that
releases a proton – Hydrogen
Ion (H+) – when it dissolves in
water.
– An acid increases the
amount of H+ ions in
solution.
A Base is a compound that
remove H+ ions from solution.
– In these cases, more OHions in the solution.
A solution’s acidity, or H+
concentration is measure on a
pH Scale.
pH is usually measured between
0 – 14.
– 0 is very acidic, 14 is very
basic and 7 is neutral.
pH Scale
Buffers
• Most organisms need to keep
their pH within a very narrow
range around neutral (7).
• One way pH is regulate in
organisms is by substances
called Buffers.
• A Buffer is a compound that
can bind to an H+ ion when the
H+ ion concentration increases
and can release H+ ions when
the H+ concentration
decreases.
• Cells have higher H+
concentrations than blood.
Which has the higher pH?
Why?
2.3 Carbon-Based Molecules
• Objectives: Describe the bonding
properties of carbon atoms.
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Compare carbohydrates,
lipids, proteins, and nucleic acids.
• Warm Up: What do you think of when
you hear the word organic?
• Words to Know: Monomer, Polymer,
Carbohydrate, Lipid, Fatty Acid,
Protein, Amino Acid, Nucleic Acid
Carbon Atoms have Unique
Bonding Properties
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Carbon atoms are the basis of most molecules that make up living things.
Carbon can form covalent bonds with up to 4 other atoms, including other carbon
atoms.
Carbon-Based molecules have three fundamental structures:
1. Straight Chain
2. Branched Chain
3. Ring
Monomer – Small single units that link together to make larger molecules.
Polymer – a large molecule, or macromolecule, made of many monomers bonded
together.
Straight Chain
Branched Chain
Ring
Four Main Types of CarbonBased Molecules are Found in
Living Things
Monomer
Polymer
Examples
Monosaccharides (simple
sugars)
Polysaccharides
(Carbohydrates)
Glucose, Fructose,
Starch
Triglyceride (3 fatty acids
and a glycerol)
Lipids
Fats, oils, and waxes.
Amino Acids
Protein
Muscle, hair, nails
Nucleotides
Nucleic Acids
DNA, and RNA
Carbohydrates
• Carbohydrates are molecules
composed of carbon,
hydrogen, and oxygen in a
1:2:1 ratio.
• These include sugars and
starches.
• Carbohydrates serve as the
Main energy source for living
things.
• The most basic carbohydrates
are simple sugars or
Monosaccharides.
– Ex: Glucose, Fructose
• Many glucose molecules can
be linked to form
Polysaccharides.
– Ex: Starches, Glycogen,
Cellulose.
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Lipids
Lipids are nonpolar molecules that include fats, oils, wax, and cholesterol.
Lipids make up the cell membrane (phospholipids).
Lipids provide protection and insulation for the cell.
Lipids can also be used as an energy source.
The main types of Lipids are Saturated and Unsaturated Fats.
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Saturated Fats – contains all single bonds and is a solid at room temperature.
Unsaturated Fats – contain at least one double bond and are liquids at room temperature.
Proteins
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The most varied of the carbon-based
molecules.
Proteins are used for structure.
A Protein is a polymer made of
monomers called amino acids.
Amino Acids are molecules that
contain Carbon, Hydrogen, Oxygen,
Nitrogen, and sometimes Sulfur.
Organisms use 20 different amino
acids to build proteins.
Amino acids are composed of: A
hydrogen atom, an amino group
(NH2), and a carboxyl group (COOH).
Amino acids only differ in their side
group of R-group.
Amino acids are held together by
peptide bonds.
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Ex: muscle, hair, nails, enzymes.
Enzymes are protein catalysts that
help speed up reactions.
Nucleic Acids
• Nucleic Acids are
polymers that are made
up of monomers called
nucleotides.
• A nucleotide is composed
of a sugar, a phosphate,
and a nitrogen base.
• Ex: DNA and RNA
• Nucleic Acids create the
detailed instructions for
creating proteins.
2.4 Chemical Reactions
• Objectives: Describe how bonds break
and reform during chemical reactions.
• Explain why chemical reactions release
or absorb energy.
• Words to Know: Chemical Reaction,
Reactant, Product, Bond Energy,
Equilibrium, Activation Energy,
Exothermic, Endothermic, Atom,
Molecule
Reactants, Products and Bond
Energy
• Reactants are the substances that go into
a chemical reaction.
• Products are the substances created by
the reaction.
• 6O2 + C6H12O6  6CO2 + 6H2O
Reactants
Products
Chemical Reactions Release or
Absorb Energy
• Activation Energy is the amount of
energy that needs to be absorbed for a
chemical reaction to start.
• An Exothermic Reaction releases
energy.
• An Endothermic Reaction absorbs
energy.
Chemical Reactions Release or Absorb
Energy
2.5 Enzymes
• Objectives: Explain the effect of a
catalyst on activation energy.
• Describe how enzymes regulate
chemical reactions.
• Words to Know: Catalyst, Enzyme,
Substrate
A Catalyst Lowers Activation
Energy
• A catalyst is a substance that decreases
the activation energy needed to start a
reaction.
• Catalysts are not considered to be a
reactant or product in the reaction.
Enzymes
• Enzymes are catalysts for
chemical reaction in living
things.
• Enzymes lower the activation
energy needed to start
chemical reactions.
• Enzymes are involved in
almost every process in living
things.
• Conditions such as
temperature and pH can effect
how well enzymes work.
• Enzyme structure is important
because each enzyme’s shape
allows only certain reactants to
bind to the enzyme.
Enzymes cont…
• The specific reactants that an enzyme acts on
are called Substrates.
• This model is called lock and key sine all
components must fit together just right for the
enzyme to work.
Enzymes cont…
• Scientists have recently discovered that the
structure of enzymes are not fixed in one place.
• Enzymes can actually bend slightly when they
are bound to their substrates.
• This is known as Induced fit.