Biochem LAB Quiz 1

Aliquot

Small sample taken from a larger volume

Molar Solution

1M solution contains one mole in a volume of 1 liter of solution

Normal Solution

1N solution contains one equivalent of a substance per liter of solution; Used exclusively for acids and basins; Equivalent is the weight of a substance that will combine with 1 mole of H+ or OH- ions

50% w/v meaning

50 grams of a substance dissolved in 100 mL

4 fold v/v dilution

1 volume of original solution in a final volume that is 4x as great

Serial Dilution

Series of identical solutions are made in order to reduce the concentration to the desired level

Ion Product of Water

Kw = [H][OH-] = 1.0×10^-14 at 25 degrees C

Molarity vs Molality

Molarity = moles/L Molality = moles/kg

pH Indicators

Litmus paper determines if a solution is acidic or basic; Hydrion universal paper determines if a solution is neutral, and the e extent of acidity and basicity (wide range and narrow range); pH meter

As Hydrogen ions increase, Ka _____

Ka increases and acid strength increases

Buffer Solution

Weak acid and a salt of the acid; Resist changes in pH upon the addition of an acid or base (until buffer capacity is reached)

When concentration of a weak acid = concentration of conjugate base, the pH ____ the pKa

pH = pKa of weak acid

Max. Buffering Capacity

Nearest the pKa of the buffer (optimal buffer has a pKa close to the pH)

Amino Acids as Metabolic Fuels

Precursors of glucose, fatty acids, and ketone bodies (used as fuel by the cell)

Amino Acid Stereochemistry

All chiral except for glycine; Alpha carbon has a tetrahedral arrangement; Enantiomers can be formed; Alpha carbon configuration is usually D or L (L if amino group is to the left, D if amino group is to the right)

All amino acids that occur in proteins are in the ____ form

L-form

Zwitterion

Both the amino and carboxyl groups are charged; If AA lacks charged side chain, at neutral pH the zwitterion is neutral and can act as an acid or base

pK1

pH at which amino acid becomes deprotonated and changes charge; Equimolar concentration of cation and zwitterion; pH = pKa at this point

First Equivalence Point

Number of moles of base added is equal to the number of moles of amino acid present in the sample

Isoelectric Point

pH at which a molecule has no net charge (for amino acids with no ionizable side chain, this can be estimated as halfway between pK1 and pK2)

Amino acids with ionizable side chains have ___ pKa values on a titration curve

Three

Silica gel is ___ so ____ amino acids with preferentially associate with the stationary phase

Polar, Polar (via hydrogen bonding)

Amino acids with ___ side chains will travel further than amino acids with ____ side chains

Nonpolar, Polar

Polar amino acids will be expected to have Rf values close to ____, and nonpolar amino acids will be expected to have Rf values close to ____

0, 1

Ninhydrin and Proline

Ninhydrin reacts with alpha amino acids to form a purple colored product; Ninhydrin reacts with proline (secondary amine) to form a yellow colored product

TLC Tank Solution

Isopropanol, Acetic Acid, and Water in a 4:1:1 ratio

Standardizing pH Meter

pH 7, pH 4, pH 10

Will pH of a solution with [H+] > water be greater or less acidic than 7?

Less

Buffering Capacity

Moles of acid or base needed to change the pH by 1

What factors affect buffering capacity?

Volume of buffer (increased volume can neutralize more), Concentration of weak acid and conjugate base