biochem example 1 practice
Which of the following describes the isoelectric point of an amino acid?
(pl) is the pH where an amino acid has no net charge
Which of the following wavelengths has the highest energy?
(wavelength with the smallest value= highest energy)
Three masses were taken for 160 μL of water. A value of 159.63 ± 0.05 μg was obtained. Which of the following must be true?
- density of the water is approx. equal to mass divided by volume - density os approx. 159.63/160 ~ 0.9977 - close to density of water at room temp. (1 g/ml)
Why is it important to wipe the tip of a pipette during a quantitive biochemistry experiment?
- ensures accurate volume measurements - prevents cross-contamination - maintains consistency in experiments
Why must a buffer be used in a biochemical experiment?
- maintain stable ph - ensure optimal conditions for reactions
Which of the following are reasons micropipettors are used in biochemistry and molecular biology?
- measure small volumes of liquid - prepare samples and reagents - used to add specific volume solvent to sample to dilute
Which of the following are biological functions of parvalbumin in rainbow trout?
- primarily functions as a calcium binding protein - plays a role in muscle relaxation
What are the advantages of both ion exchange and hydrophobic chromatography?
- separates molecules based on charge (ion exchange) - provides high resolution for purifying proteins and nucleic acids - separates molecules based on hydrophobicity (hydrophobic chrom.) - useful for concentrating protein and removing contaminants - both are complementary in purification processes
In part A of the Pippetting and Statics experiment, what was the reason for the low accuracy and precision of the measurements at the minimum volume?
- small changes -human error - environmental factors
Which of the following must be considered when purifying proteins or any other molecule?
- solubility of the protein - stability of the protein - size and charge of the protein - presence of contaminants - yield and activity of the protein
An amino acid has a pH value of 10.0. what must be true about the molecule at pH 7.0?
- the amino acid is in zwitterion form: carboxyl group deprotonated (coo-) and amino group protonated (nh3+)
Which of the following must be placed into a report when showing a figure or table?
- title/caption describing content - source/reference citation for data - numbering for easy reference within text
Why is centripetal force express in units of x g?
- to compare it to gravity (g is the acceleration due to gravity, x is times gravity)
An amino acid has a Pka value of 10.0. What is the concentration of the conjugate base of a 2 M solution of this amino acid at pH 10.0?
1 M
An amino acid has a pKa values of 10.0. What is the concentration of the conjugate base of a 2M solution of this amino acid at pH 10.0?
1 M
The following shows a picture of an AY100 micropippetor. What volume is it set at?
22 micro L (just read the number)
What wavelength of light is used in the Bradford assay?
595 nm
The Beer-Lambert law is described by which of the following equations?
A= ecl
What is the name of the protein that is used as a standard in the Bradford assay for the parvalbumin purification experiments?
Bovine Serum Albumin (BSA) provides a reliable reference for comparing the absorbance of the sample proteins
why does one expect a plot of mass versus volume of water to yiled a straight line with an intercept of zero (y=1.00 x)
Due to the constant density of water
Which of the following describes accuracy in quantitative sciences?
How close a result comes to the true value (based on density of water)
Which of the following describes precision in quantitative sciences?
How close a set of data points are to each other (size of standard deviation)
What is the bed (or column) volume in a chromatographic separation?
Vb= AxL (the volume of the stationary phase in the column)
What is the extinction coefficient?
a parameter that helps define how well a substance absorbs light at a specific wavelength at a particular concentration (e)
A centrifuge separates components of a solution based on which of the following physical properties?
based on density
The cut offs in the membranes used for dialysis is based on which of the following physical properties?
based on molecule size
Which amino acids does Coomassie Blue bind to to induce a color change in the Bradford assay?
basic acids: arginine, lysine, histidine aromatic acids: tryptophan, tyrosine, phenylalanine
The Bradford assay is used along with the volume of sample collected during purification to calculate which of the following?
concentration of protein in a sample
Ammonium sulfate or "salting out" takes advantage of which of the four non-covalent interactions in biochemistry?
hydrophobic interactions (to precipitate proteins by increasing strength)
What type of chromatography was used to purify parvalbumin from fish?
ion-exchange
Which of the following is the best definition of a pKa value?
it is the negative log of the acid dissociation constant (Ka) lower PKa= stronger acid
A buffer has a pKa value of 6.0. At which pH value does buffering occur?
occurs between ph 5.0 and ph 7.0
During the purification of parvalbumin what was the molecule being separated from. In other words what were the impurities found in the sample?
other impurities such as proteins, nucleic acids, and lipids
The _____ is the solid material left at the bottom of the centrifuge tube after centrifugation.
pellet
The following shows Asp (D) which has a pKa of 4.0. Which of the Following are possible pH values of the amino acid in the form shown? (note: pKa of N-terminus is ~ 9; pKa of C-terminus is ~2 and pKa of the side chain is ~ 4)
ph values: 2,4,9
A Bronsted-Lowry base is a _____________
proton acceptor
A Bronsted-Lowry acid is a _____________
proton donor
What is the physical basis for ion exchange chromatography?
separates charged molecules based on their interactions with a charged stationary phase.
What is the physical basis for size exclusion chromatography?
separates molecules based on their size by allowing smaller molecules to enter the pores of porous beads in the column, while larger molecules are excluded and elute faster.
What is the physical basis for hydrophobic chromatography?
separates molecules by their hydrophobic interactions, retaining hydrophobic molecules longer on a hydrophobic stationary phase than hydrophilic ones in a aqueous mobile phase.
What is the physical basis for affinity chromatography?
separates target molecules based on their specific binding interactions with ligands immobilized on a stationary phase, allowing for selective purification
What is actually being absorbed when using a spectrophotometer?
specific wavelengths of light
The _____ is the liquid at the top of the centrifuge tube after centrifugation.
supernatant
Which of the following is TRUE / FALSE about the R2 for a series of measurements?
the r2 value indicates how well data fits a model, with 1 being a perfect fit and 0 indicating no explanatory power. higher r2 values suggest a better fit, but do not guarantee model appropriateness due to potential overfitting
What is the purpose of the Braford assay?
to determine the concentration of protein in a solution
Why must proteins be purified from other components of the cell>
to ensure that their specific functions can be studied without interference from other cellular molecules.
What was the purpose of the 4 L of buffer students made for in the lab period where rainbow trout was homogenized?
to maintain a stable pH during the homogenization of rainbow trout
What is the void volume in a chromatographic separation?
volume of the mobile phase in the column that does not interact with the stationary phase, representing the space needed to elute a non-retained solute.
Which if the following is the rearrange equation used to solve the concertation of an unknown protein from a Bradford standard curve?
x=y-b/m (y=mx+b)
