Biochem Lab Final Exam

What is the main reason for wiping the outside of the pipette tip after aspiration?

To prevent contaminating the outside of the receiving container and ensure accurate volume delivery

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Consider using positive displacement pipettes for more accurate volume transfer.

What is the recommended action if a drop of water appears at the pipette tip after holding it vertically for 20 s during leak testing?

The pipette has a leak and should be repaired or recalibrated.

What is the effect of liquid leaks caused by a poor seal between a pipette and its tip?

It adversely affects the reliability and accuracy of volume transfers.

Which pipette size requires an immersion depth of 2-4 mm for proper aspirating?

200 μL and 1000 μL pipettes

Classify this statement as true or false: An adjustable pipette should only be used within its specified volume range to ensure accuracy and prevent damage to the instrument.

True

True or False: The 'reverse pipetting' method involves pressing the plunger past the second stop before aspirating the sample.

True

What is the purpose of pre-wetting a pipette tip several times before delivering a specified sample volume?

To improve accuracy and precision by conditioning the tip walls

What is the purpose of using the ejector button on a micropipette?

To release the pipette tip safely without contact

Classify this statement as true or false: Size exclusion chromatography (SEC) columns typically operate at pressures above 1000 bar to achieve optimal separation.

False

Why is it important not to jam the column tightly into the collection tubes?

To ensure proper drainage and separation of proteins

The distribution coefficient, Kav , is calculated using the formula Kav = Ve-Vo/Vc-Vo, where Ve is elution volume, Vo is void volume, and Vc is total column volume.

True

What is the primary principle behind size exclusion chromatography?

Separates molecules based on their size

Which of the following food sources are rich in vitamin B12?

Eggs, dairy products, and meats

What is the relationship between molecule size and movement through the column for molecules below 60,000 daltons?

The smaller the molecule, the slower it moves through the column.

What is attached to the beads in affinity chromatography to bind the protein of interest?

A biomolecule that binds to the protein of interest

How does the body adapt to lower oxygen levels at high altitudes?

Increased red blood cell production

Classify this statement as true or false: Size exclusion chromatography offers high-resolution separation for molecules with nearly identical molecular weights.

False

In ion exchange chromatography, what property of the protein of interest determines which resin is used?

The charge of the protein of interest

Macrophages are crucial immune cells that _____ foreign cells and molecules and process antigens to present on their surfaces. When T cells recognize these presented antigens, the T cells _____ which enhances the overall immune response by destroying infected cells and _____ additional immune cells.

remove; activate and proliferate; recruiting

What type of immunity involves the production of T lymphocytes?

Cell-mediated immunity

Classify this statement as true or false: Killed vaccines provoke a stronger immune response compared to live vaccines.

False

What is the primary function of macrophages in the immune response?

Removing foreign cells and molecules

What is the significance of hybridoma immortalization in antibody production?

It enables the continuous, large-scale production of specific monoclonal antibodies.

What is the role of secondary antibodies in indirect detection?

To amplify the signal by binding to primary antibodies

Which type of spectroscopy is utilized in the Bradford Assay?

Absorbance spectroscopy

What is the consequence of pressing the plunger quickly and releasing it swiftly while aspirating liquid with a micropipette?

It causes incorrect sample volumes to be aspirated due to sudden pressure changes.

Why must a new disposable pipette tip be used for every sample?

To prevent cross-contamination between samples.

Why is it important to allow all sample fluids and equipment to reach room temperature before pipetting?

Because temperature differences affect liquid volume and pipetting accuracy

What is the correct way to adjust the volume on an adjustable micropipette?

Turn the volume selector to a higher volume than desired, then slowly decrease to the correct volume.

In the traditional pipetting method, what does pressing the plunger to the first stop accomplish?

It creates a vacuum in the tip to aspirate the correct volume of liquid.

What is the purpose of the plunger's 'second stop' in the reverse pipetting method?

To allow dispensing of any excess liquid by pushing the plunger past the first stop.

What is the critical precaution regarding the plunger when ejecting or withdrawing fluid with a micropipette?

Never let the plunger snap back quickly to avoid damaging the piston.

Why is it important to hold the pipette vertically or within 20° of vertical during aspiration?

To allow the piston to rise properly and aspirate the correct volume.

Classify this statement as true or false: Adding high concentrations of salt to the mobile phase in size exclusion chromatography helps minimize secondary interactions with the stationary phase.

True

All elution peaks in size exclusion chromatography exhibit perfectly symmetric Gaussian shapes regardless of sample interactions.

False

What is the primary function of hemoglobin?

Transports O2 to the body's tissues

How many drops of buffer are collected into the final tube (tube 10)?

10

What is the significance of the heme group in hemoglobin?

It contains iron, which binds oxygen.

In size exclusion chromatography, what is the mobile phase?

The liquid containing dissolved molecules

What is the approximate molecular weight of hemoglobin?

65,000 Da

True or False: In size exclusion chromatography, larger molecules elute before smaller ones, resulting in a shorter elution volume for higher molecular weight species.

True

In size exclusion chromatography, what property of molecules determines their rate of travel through the column?

The size and shape of the molecules

Pure molecules of vitamin B12 must bind to what in order to be absorbed by the intestines?

A carrier protein in the intestinal tract

Classify this statement as true or false: The substrate selection in manual ELISA protocols influences the type of optical detection method used.

True

What type of immunity is characterized by the production of antibodies that circulate in the bloodstream?

Humoral immunity

Classify this statement as true or false: Humoral immunity involves the production of T lymphocytes that destroy infected cells.

False

What is the purpose of indirect detection in antibody visualization?

To visualize all antibodies produced in one type of animal

Which of the following is a major limitation of manual ELISA protocols compared to automated methods?

Lower throughput and higher variability

Classify this statement as true or false: Acquired immunity is present at birth and does not require initial exposure to pathogens to be activated.

False

Classify this statement as true or false: Immunofluorescence assays use fluorescently labeled antibodies to detect specific microorganisms.

True

In relation to optics, what role does light wavelength play in the Bradford Assay?

Specific wavelength absorption at 595 nm is used to detect the protein-dye complex.

The absorbance peak shift observed in the Bradford Assay is a direct consequence of laser-induced fluorescence.

False

Classify this statement as true or false: The Bradford Assay can be combined with optical biosensors to enable label-free detection of protein concentrations in complex biological samples.

False

True or False: The Bradford Assay exclusively uses laser light for protein detection.

False

Classify this statement as true or false: The Bradford Assay can be used directly as a diagnostic imaging technique in medicine.

False

True or False: The Bradford Assay requires a standard curve generated with a known protein to accurately determine unknown protein concentrations.

True

What is the principle behind the Bradford Assay for protein quantification?

Binding of Coomassie Brilliant Blue dye to proteins, causing a color change

What is the primary purpose of using the reverse pipetting technique?

Select one:

To adjust the volume selector on the pipette.

To aspirate extra sample volume by accident.

To improve dispensing accuracy for viscous or volatile liquids.

To eject the pipette tip after use.

To improve dispensing accuracy for viscous or volatile liquids.

What is the primary reason for never using a micropipette without attaching a disposable tip?

Select one:

To prevent damage to the pipette's piston and contamination

Because it improves the accuracy of volume selection

To reduce the volume capacity of the pipette

To make it easier to press the plunger

To prevent damage to the pipette's piston and contamination

Why is it important to pre-wet the pipette tip several times before dispensing a sample?

Select one:

a.

To condition the tip and improve accuracy by reducing sample retention

b.

To ensure the tip is properly sealed to the pipette shaft

c.

To calibrate the pipette electronically

d.

To dry the inside of the tip

To condition the tip and improve accuracy by reducing sample retention

Which method of pipetting involves pressing the plunger past the first stop to the second stop before aspirating the liquid?

Select one:

Serological pipetting

Positive displacement pipetting

Reverse pipetting

Traditional pipetting

Reverse pipetting

True or False: It is acceptable to lay a pipette on its side if there is still liquid in the attached tip.

Select one:

True

False

False

Why should micropipettes always be stored in an upright position when not in use?

Select one:

To prevent contamination or liquid from entering the piston mechanism

Because it looks tidier

To dry the tip faster

To keep volume settings from changing

To prevent contamination or liquid from entering the piston mechanism

What is the critical precaution when ejecting or withdrawing fluid with a micropipette to avoid damaging it?

Select one:

Always press the plunger to the second stop.

Never let the plunger snap back quickly after aspiration or dispensing.

Rotate the volume selector during dispensing.

Remove the tip before pressing the plunger.

Never let the plunger snap back quickly after aspiration or dispensing.

What can cause damage to the micropipette's piston mechanism?

Select one:

Pre-wetting the tip

Using the correct tip

Snapping the plunger back quickly after aspiration

Slowly releasing the plunger

Snapping the plunger back quickly after aspiration

What is a critical reason for using a new pipette tip for each sample during micropipetting?

Select one:

To save money on tips

To make the pipette last longer

To speed up the pipetting process

To avoid cross-contamination between samples

To avoid cross-contamination between samples

Some individuals show signs of vitamin B12 deficiency despite adequate intake due to a genetic disorder affecting:

Select one:

intake of vitamin B12

production of red blood cells

synthesis of the carrier protein

breakdown of fats

synthesis of the carrier protein

Which molecules are excluded from the beads in the size exclusion column?

Select one:

Molecules larger than 60,000 daltons

Molecules with a positive charge

Molecules smaller than 60,000 daltons

Molecules with a negative charge

Molecules larger than 60,000 daltons

At what point is it acceptable for slight disturbances to the column bed to occur without affecting the separation?

Select one:

When all the liquid has drained from the column after adding 3 mL of buffer

When the protein mix has entered the column far enough that slight disturbances will not affect separation

When the protein mix has completely exited the column

Immediately after loading the protein mix

When the protein mix has entered the column far enough that slight disturbances will not affect separation

What is the purpose of adding column buffer to the top of the column after the protein mix has entered the column bed?

Select one:

To facilitate the movement of proteins through the column

To prevent the protein mix from drying out

To neutralize the pH of the column

To dilute the protein mix

To facilitate the movement of proteins through the column

Why should the protein mix be loaded carefully just above the top of the column bed?

Select one:

To minimize disturbance to the column bed

To prevent contamination of the protein mix

To speed up the loading process

To ensure even distribution of the protein mix

To minimize disturbance to the column bed

What action is taken after 5 drops of buffer have been collected into a tube?

Select one:

Add more column buffer

Add 10 more drops of buffer

Transfer the column to the next tube

Discard the collected buffer

Transfer the column to the next tube

All elution peaks in size exclusion chromatography exhibit perfectly symmetric Gaussian shapes regardless of sample interactions.

Select one:

True

False

False

What is the primary purpose of chromatography in biotechnology?

Select one:

Measuring the temperature of a solution

Synthesizing new chemical compounds

Separating individual components from complex mixtures

Determining the pH of a buffer

Separating individual components from complex mixtures

True or False: The stationary phase in size exclusion chromatography typically consists of cross-linked porous polymers or silica beads.

Select one:

True

False

True

What is the primary cause of sickle cell anemia?

Select one:

A viral infection

A mutation in the hemoglobin gene

A bacterial infection

Exposure to toxins

A mutation in the hemoglobin gene

True or False: Size exclusion chromatography separates molecules based on their hydrodynamic volume rather than their molecular weight.

Select one:

True

False

True

How does the oxygen affinity of fetal hemoglobin compare to that of adult hemoglobin?

Select one:

Higher affinity for oxygen

Same affinity for oxygen

No affinity for oxygen

Lower affinity for oxygen

Higher affinity for oxygen

How do molecules larger than the exclusion limit of a size exclusion column behave?

Select one:

They enter the beads and elute faster.

They bind to the beads and elute slower.

They pass around the beads and elute faster.

They are destroyed by the beads.

They pass around the beads and elute faster.

Why are pregnant women advised to avoid vigorous exercise?

Select one:

Reduced oxygen delivery to fetal hemoglobin

Enhanced muscle development

Decreased blood pressure

Increased nutrient absorption

Reduced oxygen delivery to fetal hemoglobin

What is the main advantage of using killed vaccines?

Select one:

They are easier to produce

They provoke a stronger immune response

They require fewer doses

They are safer for individuals with compromised immune systems

They are safer for individuals with compromised immune systems

Classify this statement as true or false: Indirect detection in immunological assays requires labeling every type of antibody used.

Select one:

True

False

False

What is the purpose of using secondary antibodies in indirect detection?

Select one:

To produce more primary antibodies

To bind directly to antigens

To amplify the signal around the antigen

To neutralize pathogens

To amplify the signal around the antigen

What is a potential application of recombinant DNA technology in antibody production?

Select one:

Producing humanized antibodies for therapeutic use

Increasing the diversity of antibodies produced

Eliminating the need for animal testing

Creating antibodies that are recognized as foreign by the immune system

Producing humanized antibodies for therapeutic use

In a manual ELISA protocol, what is the primary purpose of the washing steps performed between incubations?

Select one:

To fix the antigen permanently to the well

To remove unbound reagents and reduce background noise

To activate the enzyme conjugate

To enhance color development

To remove unbound reagents and reduce background noise

What is a significant benefit of using recombinant DNA technology in antibody production?

Select one:

A.

It allows for the creation of antibodies that are recognized as foreign.

B.

It enables the production of humanized antibodies for therapy.

C.

It eliminates the need for any animal testing.

D.

It reduces the cost of antibody production.

It enables the production of humanized antibodies for therapy.

Macrophages are crucial immune cells that _______ foreign cells and molecules and process antigens to present on their surfaces. When T cells recognize these presented antigens, the T cells _______ which enhances the overall immune response by destroying infected cells and __________ additional immune cells

remove; activate and proliferate; recruiting

What is a characteristic of secondary immunodeficiency?

Select one:

It is more common than primary immunodeficiency

It is caused by genetic mutations

It has a genetic basis

It is always present at birth

It is more common than primary immunodeficiency

Which of the following is NOT a type of diagnostic test mentioned in the document?

Select one:

Polymerase chain reaction (PCR)

Agglutination

Microplate tests

Immunofluorescence assay (IFA)

Polymerase chain reaction (PCR)

Classify this statement as true or false: The Bradford Assay can be utilized to quantify proteins in samples that also contain high concentrations of detergents without interference.

Select one:

True

False

False

When evaluating recent biophotonics research, why is it important to understand the photophysical properties of dyes used in the Bradford Assay?

Select one:

Because dye properties affect light absorption and assay accuracy

Because such properties allow protein sequencing directly

Because dyes determine the magnetic resonance of proteins

Because the dye's fluorescence is the primary signal measured

Because dye properties affect light absorption and assay accuracy

True or False: The Bradford Assay can directly measure protein localization within a cell when combined with fluorescence microscopy.

Select one:

True

False

False

How does the Bradford Assay facilitate the study of protein interactions in a biological sample using optical biosensors?

Select one:

By measuring changes in light absorbance due to protein-dye binding

By emitting laser light to disrupt protein bonds

By producing fluorescence without any dye

By isolating proteins using magnetic fields

By measuring changes in light absorbance due to protein-dye binding

How does the principle of absorbance linearity in the Bradford Assay relate to the principles of spectroscopic quantification in optical imaging modalities?

Select one:

Bradford Assay does not relate to spectroscopic quantification principles

Both rely on Beer-Lambert law to correlate absorbance with concentration

Only optical imaging relies on absorbance measurements

Bradford uses scattering, while optical imaging uses fluorescence exclusively

Both rely on Beer-Lambert law to correlate absorbance with concentration

What chemical in the Bradford Assay is responsible for shifting its absorption spectrum upon binding to protein?

Select one:

Hematoxylin

Ethidium bromide

Fluorescein

Coomassie Brilliant Blue dye

Coomassie Brilliant Blue dye

Which optical property of protein-dye complexes is primarily measured in the Bradford Assay?

Select one:

Light scattering at 450 nm

Refractive index change

Absorbance at 595 nm

Fluorescence emission at 520 nm

Absorbance at 595 nm

When evaluating scientific literature, why is it important to understand the limitations of the Bradford Assay in biophotonic research?

Select one:

Its sensitivity and potential for interference from various chemicals can affect the accuracy of protein measurements, which in turn influences experimental conclusions.

It provides a method for imaging individual cells with high resolution.

It is the only method available for measuring DNA concentration in tissues.

It is used to directly measure the effects of laser ablation on tissue

Its sensitivity and potential for interference from various chemicals can affect the accuracy of protein measurements, which in turn influences experimental conclusions

In light-based protein assays like the Bradford Assay, how does solvent polarity potentially affect the assay's colorimetric response?

Select one:

It causes a shift in the absorption peak due to changes in dye-protein interactions.

It has no effect on the assay results.

It modifies the laser wavelength absorbed by proteins.

It changes the temperature sensitivity of the assay

It causes a shift in the absorption peak due to changes in dye-protein interactions.

True or False: Bradford Assay sensitivity can be enhanced by increasing the temperature during the staining process to accelerate dye-protein interactions.

Select one:

True

False

False