Cell Biology Lab 5

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Questions and Answers

What is the primary role of 2-mercaptoethanol in the SDS-PAGE process?

To enhance protein color during staining

To stabilize protein structures

To increase the migration speed of proteins

To reduce disulfide bonds and unfold proteins (correct)

In SDS-PAGE, what is the composition of the loading buffer?

Glycine, water, and bromophenol blue

SDS, Tris, and water

Tris-HCl, SDS, glycerol, beta-mercaptoethanol, bromophenol blue (correct)

Tris-HCl, SDS, and glycine

How do proteins migrate during SDS-PAGE?

Based on their shape and color

Based on their molecular charge only

Based on their molecular weight and charge

Based on their size, moving from negative to positive pole (correct)

Which of the following components is found in the running buffer for SDS-PAGE?

Tris, glycine, and SDS Signup and view all the answers

What is the purpose of the stacking gel in SDS-PAGE?

To allow all protein samples to enter the separating gel simultaneously Signup and view all the answers

What determines the migration distance of the protein bands in SDS-PAGE?

The size of the proteins Signup and view all the answers

Which step follows the loading of samples into the SDS-PAGE gel?

Running the gel at 100V Signup and view all the answers

Which statement about the relationship between Rf value and protein size is correct?

Lower Rf values correspond to larger proteins Signup and view all the answers

What is the primary mechanism by which SDS-PAGE separates proteins?

Based on protein size Signup and view all the answers

Which component of the polyacrylamide gel acts as a cross-linking agent?

N,N'-methylene-bis-acrylamide (Bis) Signup and view all the answers

When the pore size of the polyacrylamide gel increases, what is the effect on protein migration rate?

Migration rate increases Signup and view all the answers

Which step is performed first in a two-dimensional gel electrophoresis?

Isoelectric focusing separation Signup and view all the answers

What role does sodium dodecyl sulfate (SDS) play in the SDS-PAGE process?

It unfolds and denatures proteins Signup and view all the answers

What does the variable %T represent in the context of polyacrylamide gels?

Total concentration of acrylamide and bis-acrylamide Signup and view all the answers

Which of the following components is NOT involved in the polymerization of polyacrylamide gel?

Sodium dodecyl sulfate Signup and view all the answers

Which parameter affects the pore size of the polyacrylamide gel according to %C?

Concentration of crosslinking agent Signup and view all the answers

what are the components of polyacrylamide gel?

Acrylamide: matrix material N’N’-methylene-bis-acrylamide, known as “Bis”: cross-linking agent TEMED: catalyst Ammonium persulfate: initiator Signup and view all the answers

what is polyacrylamide gel

The gel is made by the polymerization of acrylamide and bis, which forms a network of pores. Signup and view all the answers

SDS facts

difference in MW, many proteins can be analyzed bc of this, proteins have unique charges, so tx w SDS will denature it (unfolds it), SDS binds to it and cover protein, SDS is negatively charged, making all proteins similar in charge is goal so it is separated only by MW.... also treat with B-M to reduce disulfide bonds, the poly acrylamide gel has a stacking gel (top, low ph) and separating gel (bottom, high ph), top is cathode (-) and bottom is anode (+), large proteins top and smaller at bottom, then stained with coomassie blue to see band results, first well for marker proteins in kDa, Signup and view all the answers

Study Notes

BIOL 3120 - Cell Biology Lab - Lab 5: SDS-Polyacrylamide Gel Electrophoresis (SDS-PAGE)

Lab Objective: Protein separation using SDS-PAGE
Types of Protein Gel Electrophoresis:
- Native gel: separation based on size, charge, and shape
- Isoelectric focusing: separation based on isoelectric point
- SDS-PAGE: separation based on size (focus of this lab)
- 2-dimensional gel: two-step process, first step based on isoelectric point (isoelectric focusing), second step separation is size based through SDS-PAGE
Components of Polyacrylamide Gel:
- Acrylamide: matrix material
- N,N'-methylene-bis-acrylamide ("Bis"): cross-linking agent
- TEMED: catalyst
- Ammonium persulfate: initiator
- Gel formation: polymerization of acrylamide and bis creates a network of pores
- Pore size (%T): determines protein migration rate; decreases with increased %T.
- %T: total percentage of acrylamide (monomer) and bis-acrylamide (cross-linker) per 100 ml of solution.
- %C: percentage (weight) of crosslinker to acrylamide and cross-linker (weight ratio)
SDS-PAGE Procedure
- Set up precast gel (following video instructions)
- Mix 5µL protein sample with 5µL loading buffer
- Heat the sample at 95-100°C for 5 min.
- Load sample into well(s).
- Run the gel at 150V until dye front reaches the bottom.
- Stain the gel with Coomassie (CBB) stain solution
- Destain the gel with 100mL destain solution.
SDS-PAGE Components:
- Stacking gel: top of gel, lower %T, larger pore size, lower pH; all proteins line up and enter separating gel at same time.
- Separating gel: lower %T, smaller pore size, higher pH; proteins separate based on size.
- Loading buffer: Tris-HCl, SDS, glycerol, β-mercaptoethanol, bromophenol blue
- Running buffer: Tris, glycine, SDS, pH 8.3.
Protein Migration (Rf):
- Migration distance of protein from origin (bottom of well) to dye front.
- Standard curves: plot log10 molecular weight vs. Rf for protein markers to determine bands size for unknown protein bands.

Post-Lab Questions and Requirements

Calculating band size: use standard curve of known molecular weight to determine unknown bands size.
use Rf values for unknown bands in standard curve to determine molecular weight.
Lab Report Requirements (Lab 5):
- Introduction: SDS-PAGE and protein electrophoresis.
- Materials: list chemicals used and instrument.
- Methods: experimental procedure steps
- Results: protein gel analysis (figure)
- Discussion/Conclusion: improvements, result justification, conclusions.
- File name: BIOL3120_Section_LastName_FirstName_LabN; email lab report to provided email address.

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Description

Test your knowledge on SDS-PAGE and protein separation techniques in BIOL 3120. This quiz covers the various types of protein gel electrophoresis, the components involved in polyacrylamide gel formation, and the principles underlying protein migration. Perfect for students in cell biology labs and those preparing for practical applications.