Lecture 4

Question 1

Two shapes of proteins

Answer 1

globular or fibrous

Question 2

dialysis

Answer 2

Removal of small molecules from a solution of a macromolecule by their diffusion through a semipermiable membrane into a suitably buffered solution

Question 3

chromatography

Answer 3

process in which complex mixtures of molecules are separated by many repeated partitionings between a flowing (mobile) phase and a stationary phase

Question 4

activity vs specific activity

Answer 4

activity
-international enzyme units/mL (from enzyme assay)

specific activity
enzyme units/mg of protein

as you purify, activity stays the same while protein concentration goes down (hopefully), meaning specific activity goes up

Question 5

activity

Answer 5

the true thermodynamic activity or potential of a stubstance, as distinct from its molar concentration

enzyme units / mL (from enzyme assay)

maybe maybe maybe number of micromoles of a substrate transformed by an enzyme preparation per minute

Question 6

international enzyme unit

Answer 6

–international enzyme unit is basically amount of enzyme that will convert one umol of substrate to product in one minute at 30 Celcius

Question 7

cation-exchange chromatography

Answer 7

• uses cation exchange resin
• -which has fixed negative charges (trap cations in column which can be flushed out separately)
• for isolating cations from the rest of sample

Question 8

anion-exchange chromatography

Answer 8

• uses anion-exchange resin
• –which has fixed cationic groups (trap anions in column which can be flushed out separately)
• for isolating anions from the rest of sample

Question 9

size-exclusion chromatography

Answer 9

procedure for separating molecules by size

• based on capacity of porus polymers to exclude solutes above a certain size
• also called gel filtration

-big move through faster

Question 10

compare activities of samples 1 and 2. proteins.
sample 1: total protein(mg)= 80; total activity (units): 120
sample 2: total protein: 20, toal activity: 120

Answer 10

the activities are equal

120 = 120

Question 11

compare specific activities of samples 1 and 2. proteins.
sample 1: total protein(mg)= 80; total activity (units): 120
sample 2: total protein: 20, toal activity: 120

Answer 11

specific activity (1) < specific activity (2)

1.5 units/mg < 6 units/mg

Question 12

HPLC

Answer 12

Chromatographic procedure, often conducted at relatively high pressures using automated equipment, which permits refined and highly reproducible profiles

Question 13

fractionation

Answer 13

process of separating the proteins or other components of a complex molecular mixture into fractions based on differences in properties such as solubility, net charge, molecular weight, or function

precipitate protein with:
-salt (gentle)
--(can keep changing salt conc to select for stuff once you've got some fractions)
-pH extremes
or 
-heat

Question 14

homologous proteins

Answer 14

proteins having similar sequences and functions in different species (of organisms)
ex the hemoglobins

Question 15

isoelectric focusing

Answer 15

electrophoretic (noun electrophoresis) method for separating macromolecules on the basis of isoelectric pH

Question 16

ion-exchange chromatography

Answer 16

process for separating complex mixtures of ionic compounds by many repeated partitionings between a flowing (mobile) phase and a stationary phase consisting of a polymeric resin that contains fixed-charged groups

-Two types: anion-exchange and cation-exchange

Question 17

specific activity

Answer 17

enzyme units / mg protein

Question 18

electrophoresis

Answer 18

movement of charged solutes in response to an electrical field
-often used to separate mixtures of ions, proteins, or nucleic acids