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 NUCLEUSThe 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
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-)
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
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)
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