Quiz 2 Prep - From HW and Practice Quiz Problems

When pH [</=/>] pKa (the ____ ____ ____), protonated and unprotonated forms are present in equal amounts.

=; half equivalence point

A mnemonic for memorizing the 2 polar, negatively charged amino acids is:

All - Aspartate Good - Glutamate

In a mass spectrum, the left side of the graph represents the __-terminus while the right side represents the __-terminus.

C; N

A mnemonic for memorizing the 6 polar, uncharged amino acids is:

Cys - Cysteine Threw - Threonine Me - Methionine Asparagus - Asparagine Glutes - Glutamine Ser - Serine

Which of the following are functions of amino acids? (free or in a bound form) Choose all that apply. Enzyme components Neurotransmitters Hormones Metabolic intermediates Carriers of genetic information

Enzyme components Neurotransmitters Hormones Metabolic intermediates

A mnemonic for memorizing the 3 polar, positively charged amino acids is:

H - Histidine A - Arginine L - Lysine

L-amino acids have a configuration of groups around the alpha carbon that can be related to the configuration of groups around the asymmetric carbon in __-____. This statement is true for ALL amino acids.

L-glyceraldehyde

To calculate the molecular mass of a compound from a mass spectrum where individual charges are given, use the formula:

M = [(m/z) x z] - z

To calculate the molecular mass of a compound from a mass spectrum where individual charges are not given, use the formula:

M = [(p2 - 1) x (p1 - 1)] / (p2 - p1)

____ ____ amino acids are likely to bind to molecules with lots of H bonding potential (e.g. glucose).

Polar uncharged

The following statements describe SDS-PAGE, a method used to separate proteins. Select the true statements. Assume that SDS-PAGE is performed under reducing conditions. Protein-SDS complexes have similar mass to charge ratios, therefore separation is by size. SDS-PAGE utilizes agarose gel to separate proteins. Proteins are visualized using a dye that binds to the gel matrix, but not to proteins. Smaller proteins migrate faster through the polyacrylamide gel. Sodium dodecyl sulfate binds proteins, resulting in protein-SDS complexes that are similar in size. Protein-SDS complexes migrate toward the positive electrode.

Protein-SDS complexes have similar mass to charge ratios, therefore separation is by size. Smaller proteins migrate faster through the polyacrylamide gel. Protein-SDS complexes migrate toward the positive electrode.

What is the major assumption when constructing or reading an evolutionary tree?

The more differences amino acid sequences have, the more time they have had to diverge.

A mnemonic for memorizing the 3 aromatic nonpolar amino acids is:

Try - Tryptophan Tyro - Tyrosine Phen - Phenylalanine

____ and ____ absorb UV light more than ____; ____ is responsible for most of the absorbance of ultraviolet light (ca. 280 nm) by proteins.

Tyrosine; tryptophan; phenylalanine; tryptophan

A mnemonic for memorizing the 6 aliphatic nonpolar amino acids is:

V - Valine I - Isoleucine P - Proline G - Glycine A - Alanine L - Leucine

Diethylaminoethyl cellulose is used as a(n) [anion/cation] -exchange resin in ion-exchange chromatography.

anion

Carboxymethyl cellulose is used as a(n) [anion/cation] -exchange resin in ion-exchange chromatography.

cation

Ion-exchange chromatography separates molecules by ____.

charge

In affinity chromatography, the stationary phase has a ____ bound group to which a protein in the [stationary/mobile] phase can bind.

covalently; mobile

Enantiomers react [identically/differently] with chiral molecules.

differently

Specific activity is the activity of an ____ per milligram of total ____ and has units of ____/____.

enzyme; protein; units; mg

Buffering capacity is greatest at the [equivalence/half equivalence] point, where the graph has the [steepest/shallowest] slope.

half equivalence; shallowest

At a pH > pI, an amino acid will have a [positive/negative] charge.

negative

In ion-exchange chromatography, the stationary phase may contain ____ or ____ ____ groups.

negatively; positively charged

The isoelectric point is the pH at which a particular molecule carries ____ ____ ____ ____.

no net electric charge

Enantiomers are ____ active and will rotate light in [the same/opposite] directions.

optically; opposite

The pI for an amino acid with a non-ionizable side chain is the midpoint between the two ____ values.

pKa

At a pH < pI, an amino acid will have a [positive/negative] charge.

positive

Affinity chromatography can separate molecules based on ____-____ ____.

protein-ligand binding

Size-exclusion chromatography separates molecules by ____.

size

In size-exclusion chromatography, the stationary phase contains cross-linked polymers with different pore ____.

sizes

Enantiomers have [the same/different] physical properties.

the same

To calculate the charge on the ion that makes the first peak in a series of two being considered, use the formula:

z = (p2 - 1) / (p2 - p1)

To calculate the charge on the ion that makes the second peak in a series of two being considered, use the formula:

z = [(p2 - 1) / (p2 - p1)] - 1