Transcript Chapter 2 notes

The Chemical Level of
Organization
Chapter 2
Atoms and Molecules
 Atoms are the smallest units of matter,
they consist of protons, neutrons, and
electrons
Structure of an Atom
 An element consists entirely of atoms
with the same number of protons.
 Within an atom, an elecron cloud
surround the nucleus.
 The atomic mass of an atom is equal to the
total number of protons and neutron in its
nucleus.
 Isotopes are atoms of the same element
whose nuclei contain different number of
neutrons.
 The atomic weight of an element takes into
account the abundance of its various
isotopes.
 Electrons occupy a series of electron
shells around the nucleus.
 The number of electrons in the outer
shell determine an atom’s chemical
properties.
Chemical bonds and chemical
compounds
 An ionic bond results from the
attraction between ions: atoms that
have gained or lost electrons.
 Cations are positively charged
 Anions are negatively charged.
 Atoms can combine to form a molecule
 Combinations of atoms of different
elements form a compound
 Some atoms share electrons to form a
molecule held together by covalent
bonds.
 Sharing one pair of electron creates a
single covalent bond
 Sharing two pairs forms a double
covalent bond
 Unequal sharing of electrons creates a
polar covalent bond.
 A hydrogen bond is the attraction
between a hydrogen atom with slight
positive charge and a negatively
charged atom in another molecule or
within the same molecule
 Hydrogen bond can affect the shaes
and properties of molecules
Chemical Notation
 Chemical notation allows us to
describe reactions between reactant
tha generate one or more products.
Chemical Reactions
 Metabolisms refers to all the chemical
reaction in the body. Our cells
capture, store and use energy to
maintain homeostasis and support
essential functions.
Basic energy concepts
 Work involves movement of an object
or a change in its physical structure.
 Energy is the capacity to perform
work.
 There are two major types of energy:
knetic and potential.
 Kinetic energy is the energy of motion.
 Potential energy is stored energy that
results from the position or structre of
an object.
 Conversions from potential to kinetic
energy are not 100% efficient.
 Every energy exchange produces heat.
Types of Reactions
 A chemical reaction may be classified
as
 Decomposition
 Synthesis
 Exchange
 Exergonic reaction release heat
 Endergonic reactions absorb heat
 Cells gain energy to power their
functions by catabolism: the
breakdown of complex molecules
 Much of this energy supports
anabolism, the synthesis of new
organic molecules
Reversible Reactions
 Reversible reactions consist of
simultaneous synthesis and
decomposition reactions.
 At equilibrium the rates of these two
opposing reactions are in balance.
Acids and Bases
 A acid releases hydrogen ions
 A base removes hydrogen ions from a
solution
pH
 The pH of a solution indicates the
concentration of hydrogen ions it
contains.
 Solutions can be classified as neutral
(pH of 7)acidic (pH < 7) or basic
(alkaline) (pH > 7) on the basis of pH
 Buffers maintain pH within normal
limits (7.35-7.45 in most body fluids)
by releasing or absorbing hydrogen
ions.
Inorganic Compounds
 Nutrients and metabolites can be
broadly classified as organic or
inorganic compounds
 Living cells in the body generate
carbon dioxide and consume oxygen.
Water and it Properties
 Water is the most important inorganic
component of the body
 Water is an excellent solvent, has a
high heat capacity, and participates in
the metabolic reactions of the body.
 Many inorganic compounds will
undergo ionization, or dissociation in
water to form ions.
Inorganic Acids and Bases
 Inorganic acids found in the body
include hydrochloric acid carbonic
acid, sulfuric acid and phosphoric acid.
 Sodium hydroxide is an inorganic base
that may form within the body.
Salts
 A salt is an ionic compound whose
cation is not H+ and whose anion is not
OH Salts are electrolytes, compounds that
dissociate in water and conduct an
electrical current.
Organic Compounds
 Organic compounds contain carbon and
hydrogen, and usually oxygen as well.
 Large and complex organic molecules
include carbohydrates, lipids proteins
and nucleic acids.
Carbohydrates
 Carbohydrates are most important as
an energy source for metabolic
process.
 The three major types are
monosaccharides (simple sugars),
dissacharides and polysaccharides.
 A. the straight chain formula for
glucose
 B. The ring form
that is most
common in nature.
 An abbreviated
diagram fo the ring
form.
Lipids
 Lipids are water-insoluble molecules
that include fats, oils, and waxes.
 There are four important classes of
lipids: fatty acids, fats, steroids, and
phospholipids.
 Triglycerides (fats) consists of three
fatty acid molecules attached to a
molecule of glycerol
 Cholesterol is a precursor of steroid
hormones and is a component of cell
membranes
 Phospholipids are
the most abundant
components of cell
membranes.
Proteins
 Proteins perform a great variety of
function in the body.
 Important types of protein include
structural proteins, contractile
proteins, transport proteins, enzymes,
hormones and antibodies.
 Proteins are chains of amino acids
linked by peptide bonds.
 The sequence of amino acids and the
interactions of their R groups influence
the final shape of the protein
molecules.
 The shape of the protein determines
its function.
 Each protein works best at an optimal
combination of temperature and pH.
 Activation energy is the amount of
energy required to start a reaction.
Proteins called enzymes control many
chemical reaction within our bodies.
Enzymes are catalysts--substances that
accelerate chemical reaction without
themselves being permanently
changed.
 The reactants in an enzymatic
reaction, called substrates, interact to
form a product by bonding to the
enzyme at the active site.
Nucleic Acids
 Nucleic acids store and process
information at the molecular level.
 There are two kinds of nucleic acids:
DNA and RNA
 Nucleic acids are chains of nucleotides.
 Each nucleotide contains a sugar, a
phosphate group and a nitrogen base.
 The sugar is always ribose or
deoxyribose.
 The nitrogenous bases found in DNA are
adenine, guanine, cytosine, and
thymine. In RNA uracil replaces
thymine.
High-Energy Compounds
 Cells store energy in high-energy
compounds.
 The most important high-energy compound is
ATP
 When energy is available, cells make ATP by
adding a phosphate group to ADP
 When energy is needed ATP is broken down
to ADP and phosphate.