Transcript CHEMISTRY IN LIVING SYSTEMS

CHEMISTRY IN LIVING
SYSTEMS
CHEMISTRY IN LIVING SYSTEMS
All life processes involve living things made of matter
All matter is composed of elements
The chemical foundation for the diversity of life is
based on six elements: C, H, N, O, P, S
Organic Molecules: a carbon-containing molecule in
which carbon atoms are nearly always bonded to
each other and to hydrogen
ELEMENTS
The basic building blocks of all matter that cannot be
broken down into simpler substances by ordinary
methods
The smallest unit of each element that retains its
properties is the atom
Subatomic particles of the atom: proton, neutron,
electron
SUBATOMIC PARTICLES
ATOMIC NUCLEUS
The atomic nucleus has a positive charge and 99% of
the atom’s mass
A) Protons (+): 1.672 amu
- the number is unique for each element
- the number is determined by the atomic
number
B) Neutrons (o): 1.674 amu
SUBATOMIC PARTICLES
OUTSIDE THE ATOMIC NUCLEUS
A) Electrons (-): 0.001 amu
- travel in specific orbitals outside the nucleus
ATOMIC MASS
The sum of the masses of the particles in the atom
Atomic mass = mass of protons + mass of neutrons
STANDARD ATOMIC NOTATION
BOHR-RUTHERFORD DIAGRAMS
ISOTOPES
Atoms of the same element (same number of
protons) that have a different number of neutrons
Isotopes have different mass numbers but the same
atomic number
Ex:
RADIOISOTOPES
An unstable isotope that decays over time by
emitting radiation
Can be used in Radioisotope tracing
BIOCHEMISTRY
The field of study that bridges chemistry and biology
The understanding of the properties and interactions
of biologically important molecules and their function
in the cell and other living systems
INTERACTIONS WITHIN MOLECULES
“INTRAMOLECULAR” forces
A) Ionic Bonding: chemical bonding between metals
and non-metals (charged atoms)
- produced when one atom loses an electron(s)
and another atom gains an electron(s)
- Ions with opposite electrostatic charges
attract (Ex: Na+Cl-)
INTERACTIONS WITHIN MOLECULES
B) Covalent Bonding: Non-metal atoms share
electrons to become stable
ELECTRONEGATIVITY
An atom’s relative desire to GAIN/HOLD ON to
electrons
Highly electronegative atoms: O, N, Cl
Low electronegative atoms: H, C, P
ELECTRONEGATIVITY
POLAR COVALENT BONDS: when atoms with
significantly different electronegativities share
electrons in a covalent bond
- Electrons are more attracted to the atom with
the higher electronegativity causing a partial
negative charge
- The atom with the lower electronegativity
assumes a partial positive charge
- Forms polar molecules
- Ex: O-H bonds
ELECTRONEGATIVITY
NON-POLAR COVALENT BONDS: when covalent
bonds form between atoms with similar
electronegativities
- Electrons are shared fairly
- Forms non-polar molecules
- Ex: C-H bonds
EN DIFFERENCE:
INTERACTIONS BETWEEN MOLECULES
“INTERMOLECULAR” forces
- May also form within very large molecules
- Weaker than intramolecular forces
- Determine molecular interactions
- Responsible for many physical properties
INTERACTIONS BETWEEN MOLECULES
A) HYDROGEN BONDING: When the partial positive
charge of hydrogen is attracted to the partial
negative charge of another atom
- Represented with a dotted line
- Commonly found in biological molecules
between H and O or N
- Often used in cells to help maintain structure
and function (Ex: DNA)
- Though it is a weak force, many hydrogen
bonds together are strong
INTERACTIONS BETWEEN MOLECULES
INTERACTIONS BETWEEN MOLECULES
B) HYDROPHOBIC EFFECT: The natural clumping
together of non-polar molecules in water
Non-polar Molecules: “Hydrophobic”
Polar molecules: “Hydrophilic”
IONS IN BIOLOGICAL SYSTEMS
ION: When an atom or group of atoms gains or loses
electrons to maintain a stable valence shell
Anion: negatively charged atom that has
gained electron(s)
Cation: positively charged atom that has lost
electron(s)
IONS IN BIOLOGICAL SYSTEMS
Ions are important in living systems
Ex: H+ are critical for cellular respiration
Ionic substances are never considered in the form of
ionic compounds since almost all ions are dissociated
in water