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Structure of Atoms:
- Consist of protons, neutrons and electrons.
- Atomic nuclei have protons and neutrons (each 1 amu).
- Each element has a different number of protons, e.g.
hydrogen has 1 proton, carbon 14.
- The number of protons equals the atomic number of an
element.
- Atoms with the same number of protons but different numbers
of neutrons are isotopes.
- Cells of living organisms consist of organic and inorganic
molecules which are made up of atoms.
Electrons
- The number of electrons (e-) equals the number of protons in
the nucleus.
- Electrons move at near light speed, have both wave and
matter properties, when their energy level is raised they are
said to be in an �excited state�, emission spectra is when this
excited electron drops back to its ground state.
- Electrons orbit the nucleus at specific levels called
shells. The shell closes to the nucleus is the innermost shell
and has up to 2 electrons. Second and third shells (L and M)
have a maximum of 8 electrons. If an element has another shell
that is filled it is chemically inert.
Chemical Bonds
- Bonds are formed by gaining, loosing or sharing electrons.
- The formation of ionic or covalent bonds depends on the
differences between electronegativity in the atoms involved.
- Covalent bonds: formed when atoms share electrons and are
very strong. They are polar if they are between different types
of atoms e.g. oxygen and hydrogen as in H2O.
- Ionic Bonds: atoms become ions when they gain or lose
electrons and are weaker than covalent and dissociate in water.
- Hydrogen Bond: are weak intra or inter molecular attractions
between molecules with a net dipole. Dipoles are created when
there is unequal sharing of electrons between H and an
electronegative atom like oxygen or nitrogen.
Organic Molecules
- Molecular formulas describe the composition of a substance.
- Structural formulas describe how atoms are arranged in a
molecule.
- Nomenclature is the naming procedure for organic molecules.
- Stereochemistry are isomers that have the same molecular
formula but different structural formulas.
Nomenclature
- Single bond share one pair of electrons and name ends in
(�ane).
- Double bonds share two pairs of electrons, name ends in
(-ene).
- Triple bonds share three pairs of electrons, name ends in
(-yne).
Biological Macromolecules
- Carbohydrates: made up of monosaccharides (e.g. glucose),
stores energy, and modifies other macromolecules (glycolipids,
glycoproteins).
- Lipids fat triglycerides (glycerol), phospholipids, stores
energy, makes up cell membranes and steroid hormones.
- Proteins: single amino acids join forming peptides,
functions as structural proteins and enzymes.
- Nucleic Acids: individual nucleotides link to form genetic
material, RNA, DNA.
Acids, Bases and Buffers
- Electrolytes are substances that release ions in water.
- Acids release H+ in water.
- Bases release OH- in water.
- Strong acids and bases completely dissociate in H2O.
- pH is the concentration of hydrogen ions [H+] in solution.
At pH 7 hydrogen ion concentration equals hydroxyl
concentration, [H+] = [OH-].
- Buffers provide pH stability by resisting changes to pH when
small amounts of acid or base are added.
- Buffers are weak acids or weak bases and their salts.
Biochemical Reactions
Thermodynamics:
- First Law: Energy is always concerned and cannot be created
or destroyed.
- Second Law: Systems tend to become disordered.
- Entropy (S): describes the degree of disorder in a system.
- ΔG Gibbs Free Energy is the amount of energy available to do
work.
- ΔG= ΔH - T ΔS (ΔH is enthalpy change), ΔS entropy change,
T=temperature (K)
- If ΔG<0 spontaneous reaction, If ΔG>0 non-spontaneous
reaction, If ΔG=0 reaction is at equilibrium.
- Enzymes in biochemical reactions lower the activation
energy. Activation energy is the energy required to begin a
reaction.
- Types of enzyme reactions: oxidoreductase, transferase,
hydrolase, ligase, isomerase and ligase.
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