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 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

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