Molecules and Cells Flashcards
what is the dissociation constant of an acid
where the acid dissociates to hydrogen ions and a base, the rate at which they dissociate to produce protons
how can the Ka be calculated
ka = conc of H x conc of OH divided by acid conc
what acids have a higher Ka
strong acids have a higher Ka as the dissociate quicker in solution
when is buffering most effective
when equilibrium is reached, so half dissociation, when pH = pKa, due to concentration of base and acid = so in equation, only pKa left
how does histidine have 3 buffering capacities
3 equilibria are involved due to the structure, at low pH NH3 can mop up H ions to increase pH, then as pH increases, has 2 groups that can donate H ions to slow the increase down - at pH 6 and 9
what is the goal of buffers
to restrict changes in pH
what acids are important in oral health
lactic acid, formic acid, acetic acid
how are acids formed in oral cavity
plaque bacteria ferments carbohydrates which releases acids
how does the production of acids result in tooth decay
acids increase concentration of H ions, this pushes the equilbrium to the right, causing solubilisation of hydroxyapatite - enamel crystals, releases free calcium and phosphate ions
what is the difference between tooth decay and erosion
erosion involves acids directly from food and drink, decay involves fermentation of carbohydrates
what are chelating agents
in certain fruit juices, mop up free calcium ions, therefore causing a shift of the equilibrium to the right to restore this concentration
what do buffers normally consist of
weak acid or weak base and one of its salts
why is bicarbonate the main buffer in saliva
pka value of around 6.7, so max buffering capacity around 7 perfect for oral cavity
what are the common secondary structures of proteins
alpha helix or beta pleated sheet
what is collagens unique structure
triple helix, 3 alpha helices wrapped around one another, rope like structure giving it strength and water insoluble
how is the tertiary structure of proteins formed and what protein is this found in
binding between R side chains, often giving globular appearance, myoglobin
describe the structure of haemoglobin
4 chains - 2 alpha chains and 2 beta sheets, alpha interacts with beta, each chain contains and Fe group, has a central open channel in the centre
what is maltose composed of
2 glucose molecules joined by an alpha 1-4 glycosidic bond
how does the structure of starch and glycogen differ
starch - composed only of 1-4 alpha glycosidic bond, glycogen also has this but is much more branched due to some 1-6 glycosidic bonds, this allows for glucose to be released more quickly
what is the structure of a di-glyceride and where can this be found
2 glycerol molecules are bounded to fatty chains, but the other is bonded to a phosphate molecule - found in cell membrane
name 3 biological roles of proteins
enzymes, receptors, movement
what is the structure of an amino acid
one central carbon, one amine group, one carboxyl group, one R side chain and one H ion
how can amino acids act as buffers
can ionise to either release H ions from COOH group or accept at NH3 group
how is a protein formed
through condensation reaction between amino acids, NH2 and COOH groups bind together to lose water
define homeostasis
the act of maintaining ideal conditions in the body to allow functions