Chemistry of Life
2-1 THE NATURE OF MATTER
• ATOMS – the basic unit of matter
– ?Candy bar breaks in ½ still a candy bar? What if you
continue breaking in ½?
– The subatomic particles that make up atoms are protons,
neutrons and electrons
– Proton mass = Neutron mass
– Protons = + charged
– Neutrons = Neutral charge
– Electrons = - charge, attracted to positively charged protons
– Electrons in a constant motion around the nucleus where
neutrons and protons are located
– Nucleus – center of the atom
– # electrons = # protons
ELEMENTS AND ISOTOPES
–
Element – is a pure substance that consists entirely of one
type of atom.
•
•
–
Periodic table
C = Carbon
# protons = # electrons = # atomic number
Isotopes – atoms of the same element that differ in the #
of neutrons
•
•
•
•
–
Example some carbon atoms have 6, 7 or 8 neutrons
Protons + Neutrons = Mass #
Isotopes are identified by their mass #’s
Because they have the same # of electrons, all isotopes of an
element have the same chemical properties
Radioactive Isotopes – nuclei are unstable and break
down at a constant rate overtime
•
Determine ages of rocks and fossils, treat cancer, kill bacteria –
follow movements with in an organism
Isotopes of Carbon
Because they have the same
number of electrons, these
isotopes of carbon have the same
chemical properties. The
difference among the isotopes is
the number of neutrons in their
nuclei.
Chemical compounds
•
– is a substance formed by the chemical
combination of 2 or more elements
indefinite proportions. Ex. H2O (
chemical formula )
–
NaCl – forms at a 1:1 ratio
•
•
•
Sodium – metal soft enough to be cut with a
knife and reacts explosively with cold H2O
Chlorine – greenish gas used in WWII to kill
soldiers but combined NaCl = table salt
Video phsuccessnet.com
Chemical Bonds
•
– how atoms in compounds are held together
–
The main types of chemical bonds are ionic bonds and
covalent bonds
Ionic bonds – is formed when 1 or more electrons are
transferred from 1 atom to another
–
•
•
•
Lose electron = +
Gain electron = Ion - + or – charged atom
–
–
Example Na+ Cl-
Covalent bonds – forms when electrons are shared
between atoms
•
Ex. H2O – 2 electrons shared
–
–
•
4 electrons shared– double bond
6 electrons shared – triple bond
Molecule – smallest unit of most compounds
–
Example H2O water molecule
Ionic Bonding
The chemical bond in which electrons are transferred
from one atom to another is called ionic bond. The
compound sodium chloride forms when sodium loses
its valence electron to chlorine. (Video ph)
Covalent Bonding
The chemical bond in which
electrons are shared between atoms
is called a covalent bond. In a water
molecule, each hydrogen atom shares two electrons with
the oxygen atom. (Video ph)
Van der Waals forces
• 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.
2-2 PROPERTIES OF WATER
•
Water molecules
–
H2O – neutral
•
–
10p+ = 10e-
Polarity
•
•
•
H2O, H is slightly positive, O is slightly negative
Polar molecule – a molecule in which the
charges are unevenly distributed
A H2O molecue is polar because there is an
uneven distribution of electrons between the
oxygen and hydrogen atoms
A Water Molecule The unequal
sharing of electrons causes a
water molecule to be polar. The
hydrogen end of the molecule is
slightly positive, and the oxygen end
is slightly negative.
Hydrogen Bonds
–
–
•
Cohesion – an attraction between molecules of the
same substance
–
–
•
•
The attraction between the hydrogen atom on 1 water molecule
and the oxygen atom on another water molecule is an example
of a hydrogen bond
Not as strong as ionic or covalent bond
ex. Water droplets form beads (extremely cohesive)
ex. bugs walking on water
Adhesion – attraction between molecules of different
substances
ex. Glass and water
Solutions and Suspensions
•
Mixture – materials composed of 2 or more elements or
compounds that are physically mixed together
constitute a mixture
–
•
Solutions – components are evenly distributed
throughout the solution
–
–
•
Example – salt and pepper, earth’s atmosphere is a mixture of
gases
» Example salt in H2O
Solute – (table salt) the substance that is dissolved
Solvent – (H2O) the substance in which the solute dissolves
Suspensions – mixture of H2O and
nondissolved material
NaCl Dissolving in Water When an
ionic compound such as sodium
chloride is placed in water, water
molecules surround and separate the
positive and negative ions.
Acids, Bases and pH
•
•
pH scale – to indicate the concentration of H+ ions in a
solution
Acids – any compounds that forms H+ ions in solution
–
•
Bases – a compound that produces (OH-) hydroxide
ions in a solution
–
•
Acidic solutions contain higher concentration of H+ ions than
pure H2O and have pH values below 7.
Basic, or alkaline solutions contain lower concentrations of H+
ions than pure water and have pH values above 7
Buffer – weak acids or bases that control pH to
maintain homeostasis
–
Can react with strong acids and bases to prevent sharp,
sudden changes in pH
The pH Scale
The concentration
of H+ Ions
determines whether
solutions are acidic
or basic. What is
the most acidic
material on this pH
scale? What is the
most basic
material?
2-3 Carbon Compounds
•
Organic chemistry – the study of
compounds that contain bonds between
carbon atoms
Chemistry of Carbon
•
–
Carbon atoms have 4 outer electrons
•
•
Bonds
Picture pg. 44
Carbon Compounds
Carbon can form single, double, or triple bonds with
other carbon atoms. Each line between atoms in a
molecular drawing represents one covalent bond. How
many covalent bonds are there between the carbon
atoms in acetylene?
Macro Molecules
•
– giant molecules formed
by polyermization – large
compounds are built by
joining smaller ones
together
–
–
•
Monomers – smaller units
Polymers – many units
* four groups of organic
compounds found in
living things are
carbohydrates, lipids,
nucleic acids, and
proteins
Polymerization When small molecules,
called monomers, join together, they form
polymers, or large molecules.
Carbohydrates
•
– compounds made of carbon, hydrogen and
oxygen atoms – ratio 1:2:1
* living things use carbohydrates as their main
source of energy. Plants and some animals also
use carbohydrates for structural purposes
- example – starches and sugars
•
•
–
Monosaccharides – simple sugar molecules
•
–
Example – galactose (milk), fructose (sugar – fruit)
Polysaccharides – large macromolecules formed from
monosaccharides
•
Example – animals store excess sugar in polysaccharides called
glycogen or animal starch
Carbohydrates
Starches and sugars are examples of carbohydrates
that are used by living things as a source of energy.
Starches form when sugars join together in a long chain.
Lipids
•
– made mostly from carbon and hydrogen
atoms
–
•
•
•
•
Example – fats, oils and waxes
* Lipids can be used to store energy some
lipids are important parts of biological
membranes and waterproof coverings
- example – saturated – single bonds
- unsaturated – at least one double bond
- polysaturated – more than one double bond
Lipid Structure
Lipids are used to store energy. Lipid molecules are
made up of fatty acids and glycerol. Liquid lipids, such
as olive oil, contain mainly unsaturated fatty acids.
Nucleic acids
•
– macromolecules containing hydrogen,
oxygen, nitrogen, carbon, and
phosphorus
– Nucleotides – 3 parts, 1) 5 carbon sugar, 2)
phosphate, 3) nitrogenous base
•
•
•
* nucleic acids store and transmit
heredity, or genetic, information
- RNA – ribonucleic acid
- DNA – deoxyrobonucleic acid
Nucleotide Structure Nucleic acids store and
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.
Proteins
•
– macromolecules that contain nitrogen,
carbon, hydrogen, and oxygen
–
Amino Acids – a compound with an amino group
(NH2) on one end and a carboxyl group (OOH) on
the other end
•
•
•
How amino acids are arranged are determined
by the DNA
All amino acids can be joined to one another
* Some proteins control the rate of
reactions and regulate cell processes.
Some are used to form bones and
muscles. Others transport substances
into or out of cells or help fight disease
Protein Structure
Proteins help to carry out chemical reactions, transport small molecules in and out of
cells, and fight diseases. Proteins are made up of chains of amino acids folded into
complex structures.
2-4 Chemical Reactions & Enzymes
• everything based on chemical reactions –
growth, environment, reproduction,
movement
Chemical Reactions
•
•
– is a process that changes one set of chemicals
into another set of chemicals.
- chemical reactions – some fast some slow
–
–
•
•
•
Reactants – the elements or compounds that enter into a
chemical reaction
Products – the elements or compounds produced by a
chemical reaction
* Chemical reactions always involve the breaking of
bonds in reactants and the formation of new bonds
in products
- example CO2 + H2O = H2CO3
- H2CO3 = CO2+ H2O
carbon dioxide reacts with water to
produce a highly soluble compound
called carbonic acid, H2CO3.
• This reaction enables the bloodstream to carry
carbon dioxide to the lungs. In the lungs, the
reaction is reversed.
• This reverse reaction produces carbon dioxide
gas, which is released as you exhale.
Energy in Reactions
•
- energy is either released or absorbed whenever
chemical bonds form or one broken
–
•
Energy changes
* chemical reactions that release energy often occur
spontaneously. Chemical reactions that absorb
energy will not occur without a source of energy
- example 2H2 + O2 = 2H2O
- energy is released in the form of heat
- hydrogen gas explodes = light and sound
- for reaction to reverse energy is needed
•
•
•
•
–
Activation Energy – the energy that is needed to get a
reaction started
•
Example – match
Activation Energy
Chemical reactions that release energy often occur
spontaneously. Chemical reactions that absorb energy will
occur only with a source of energy. The peak of each graph
represents the energy needed for the reaction to go forward. The difference
between this required energy and the energy of the reactants is the activation
energy.
Enzymes
–
•
* works by lowering a reactions activation energy
–
•
•
•
Catalysts – a substance that speeds up the rate of
chemical reaction
Enzymes – are proteins that act as biological catalysts
* Cells use enzymes to speed up chemical reactions
that take place in cells
- Carbon dioxide CO2 + H2O = H2CO3 carbonic
acid
- very slow so slow we would have carbon dioxide
built up in our blood. But we have an enzyme which
speeds up the reactant
Effect of Enzymes Enzymes speed up
chemical reactions that take place in cells.
Notice how the addition of an enzyme lowers the
activation energy in this reaction. This action speeds up
the reaction.
(wkst)
Enzyme Action
–
For a chemical reaction to take place the
reactants must collide with enough energy so that
existing bonds will be broken and new bonds will
be formed – not enough energy the reactions will
be unchained
The enzyme – substrate complex
–
•
Enzymes provide a site where reactants can be brought
together to react. The site reduces the energy needed
for the reaction
–
–
substrates – the reactants of enzyme – catalyzed reactions
picture pg. 52
• An Enzyme-Catalyzed Reaction
• The enzyme hexokinase converts the
substrates glucose and ATP into
gluecose-6-phosphate and ADP.
– what are substrates? Gluecose and ATP
– what is an enzyme? Hexokinase
– Products? ADP and Gluecose – 6 phosphate
– Regulation of enzyme activity
• Some enzymes need
– certain pH values
– temperature
– turn off and on at critical states
– making materials the cells need
– releasing energy
– transferring information.