Janet Macaulay; Week 1 MED 1011; Biochemistry
The most biologically important elements are hydrogen, oxygen, sulfur, nitrogen, carbon and phosphorus. These six elements make up 98% of living organisms.
An isotope has the same number of protons and electrons as other isotopes of the same element, but different numbers of neutrons.
Covalent bonds share electrons, ionic bonds are attractions between oppositely charged molecules. Hydrogen bonds form between molecules and within molecules due to electronegativity differences. Nonpolar substances do not interact directly with polar substances. They are held together with interactions known as van der Waal's forces.
When a substance dissolves in water it becomes an ion and forms ion-dipole intermolecular bonds with water molecules.
Combustion reactions are oxidation-reduction reactions, fuel is converted to carbon dioxide and water while energy is released as heat and light.
Water covers 75% of the Earth's surface; most active organisms are 45-95% water.
Solutions are substances dissolved in water. Concentration is the amount of a given substance in a given amount of solution, most substances are dissolved at very low concentrations
Buffers are systems of weak acids or bases that limit the change in pH when hydrogen ions are added. They are usually weak amphiprotic molecules which can accept or donate H ions as required.
Funcitonal groups make up part of a larger molecule, determine shape, polarity, reactivity, solubility: hydroxy groups are polar, allow linkage to other molecules via dehydration; aldehyde has a very reactive C-O double bond important in building molecules and energy releasing reactions; keto has C-O double bond important in carbohydrates and energy reactions; carboxyl group is acidic, ionises in living tissues to form -COO and H, enters into dehydration by giving up -OH, some carboxylic acids important in energy reactions; amino group is basic, accepts H to form NH3, enters into dehydration synthesis by giving up H; phosphate is negatively charged, enters into dehydration synthesis by giving up OH, when bound to another phosphate hydrolysis releases a lot of energy because of the strong repulsion between the groups; sulphydryl can give up H to bind two SH groups to form disulfide bridge, stabilising protein structure, found in cysteine amino acids