SDS-PAGE gel results
This page has four parts, in the order you use them. Part 1 is what you need to know. Part 2 says what to do, in plain English. Part 3 shows the work done once on a case that is not yours. Part 4 is your own work and where to turn it in.
Open your materials, follow the steps, then turn in your work.
Read an SDS-PAGE gel, a gel that sorts proteins by size, to judge the size and purity of your isolated protein.
Optional: listen or watch a unit review▸
Part 1 of 4 · Background and definitions▸
💡 Big idea: Molecular workflows use controls and complementary separation or detection steps to evaluate a target, while each band, , or remains limited by method resolution and sample quality.
- • SDS denatures proteins and gives all of them a uniform negative charge proportional to size.
- • Smaller proteins migrate farther through the gel matrix in a given time.
- • A meets the goal when it shows one major band at the expected size and no other visible band under the stain used. Meeting it supports purity but does not prove it: a different of about the same size can run in the same band, and a protein present in a tiny amount can be too faint for the stain to show.
Molecular workflows use controls and complementary separation or detection steps to evaluate a target, while each band, , or remains limited by method resolution and sample quality.
Molecular workflows use controls and complementary separation or detection steps to evaluate a target, while each band, , or remains limited by method resolution and sample quality.
Driving question: Your fractions glowed green yesterday, but did you actually purify the target, or did contaminants ride along? What do the bands on your SDS-PAGE gel say?
What you already know: Molecular workflows use controls and complementary separation or detection steps to evaluate a target, while each band, , or remains limited by method resolution and sample quality.
New idea: Molecular workflows use controls and complementary separation or detection steps to evaluate a target, while each band, , or remains limited by method resolution and sample quality.
Visual or model: No figure is attached to this lesson. The readings, the worked example and E1 to E3 carry the evidence.
- Observe or measure the relevant feature in SDS-PAGE gel results.
- Organize the observation with a stable evidence ID.
- Apply this rule: Define variables, controls, sampling, units, and the analysis plan before interpreting a result; analysis cannot repair biased or inconsistent measurement.
- Choose the option the evidence supports and state the limit of the conclusion.
Real biomedical example: Today the medical interventions team uses SDS-PAGE gel results to make a bounded evidence decision. A band, selected , or fluorescent alone does not prove identity, , correct sequence, biological activity, or clinical suitability.
What the evidence supports: E1 to E3 support the daily take-home when the response meets the stated success criteria.
What it cannot prove: The package does not support claims beyond this lesson's or any real patient diagnosis.
- • : A lab technique that separates a mixture into its parts based on how fast each component travels through a material like paper or a gel.
- • : The step in a separation method where a solvent washes the target molecule off a column or material so it can be collected in pure form.
- • : In a separation, one of the numbered portions of liquid collected one after another as it runs off a column. Each tube holds whatever came out at that moment, so the target ends up in some tubes and not others.
- • : How free a sample is from contaminating substances, often given as the percentage of the sample that is the intended compound.
- • : A specific whose presence signals a particular cell type, disease, or biological state, used to identify or track it.
- • : A lab method that uses an electric field to pull fragments through a gel so they separate by size and show up as bands.
Use it now: Choose one decision option. Cite E1 and E3, then explain how the rule connects the evidence to your choice. This is thinking practice for the one turn-in named under Turn in, not a second submission.
Go further, optional: The source links below are optional enrichment. Every fact required for today's local evidence decision appears in this lesson package.
National Center for Biotechnology Information is the source this lesson's claim is checked against:
Limit: A band, selected , or fluorescent alone does not prove identity, , correct sequence, biological activity, or clinical suitability.
Define variables, controls, sampling, units, and the analysis plan before interpreting a result; analysis cannot repair biased or inconsistent measurement.
Limit: A well-organized classroom study can still be limited by , measurement quality, confounding, and the population represented.
You can estimate size against a marker lane.
Limit: E3 defines the classroom product or success criterion. It is not independent scientific evidence and cannot justify a clinical or causal claim.
Today's decision · Simulated classroom evidence scenario
Your role: medical interventions team member
Decision: Your team must decide what the evidence from SDS-PAGE gel results supports before submitting the labeled and result claim named on today's page.
- • Sort the bands by natural charge and shape, because the most charged should travel fastest through the gel.
- • Load a sample from before next to yours, because one lane cannot show how many contaminants you removed.
- • Read the gel by size alone, since SDS erases charge and shape and smaller proteins migrate farther down the lane.
Response: State one choice, cite at least two evidence IDs, explain the rule that connects them, and add one limitation. Use it inside the one turn-in named under Turn in; it is not a separate submission.
Claim ceiling: Today's evidence supports a classroom claim about SDS-PAGE gel results. It cannot prove causation, diagnose a real patient, or justify action outside this room.
Reason for review: Your team must decide what the evidence from SDS-PAGE gel results supports before submitting the labeled and result claim named on today's page.
Context: Today the medical interventions team uses SDS-PAGE gel results to make a bounded evidence decision. A band, selected , or fluorescent alone does not prove identity, , correct sequence, biological activity, or clinical suitability.
- • T1: Read the gel-interpretation notes in the PLTW course shell and define the lane.
- • T2: Compare the lanes on the practice gel on this page, or your simulation gel, to the marker to estimate the 's size.
- • T3: Decide which is most pure based on how few extra bands it shows.
- • T4: Write one statement on whether the met the goal: one major band at about 27 kDa () and no other visible band under the stain used. Add one sentence on what your gel cannot rule out.
- • T5: Add your annotated gel reading to your Unit 4 PLTW tracker evidence.
- • E1: National Center for Biotechnology Information is the source this lesson's claim is checked against:
- • E2: Define variables, controls, sampling, units, and the analysis plan before interpreting a result; analysis cannot repair biased or inconsistent measurement.
- • E3: You can estimate size against a marker lane.
Measurements: Use only the measurements, units, graph, or counts supplied in today's task. No additional patient measurement is implied.
Uncertainty: This is a composite classroom scenario. Missing history, measurements, or confirmation tests remain unknown and limit the conclusion.
Rate or percent = part / comparison total x 100%. Percent change = (new - comparison) / comparison x 100%.
If 18 of 60 records meet a condition, the frequency is 18 / 60 x 100% = 30%.
Name the comparison total. A percent describes the supplied group and does not automatically predict an individual's outcome.
Use the counts in the practice data on this page to calculate one rate, risk, frequency, or percent change. Show the denominator and interpretation.
Students often think a polished answer about SDS-PAGE gel results is trustworthy even when its evidence source, comparison, or limitation is missing. The trap: Presentation quality cannot raise the evidence level. A band, selected , or fluorescent alone does not prove identity, , correct sequence, biological activity, or clinical suitability.
- CER:
- Claim, Evidence, Reasoning: make a claim, back it with evidence, explain your reasoning.
- SOP:
- Standard Operating Procedure, the exact steps to follow (especially in a lab).
- Tracker:
- Your PLTW progress log where you record completed evidence.
- myPLTW:
- The PLTW course site where you do the online activities. Find it in Clever with your Microsoft sign-in, right next to Schoology.
Tap the speaker to hear a term. Add two of these to your notebook glossary with a definition and an example in your own words.
Pick just 2 or 3 words from today and make them yours: write what each one means in your own words, name the context clue or evidence that helped, then give one example from what you actually did in SDS-PAGE gel results. Try your own words first; the glossary is there if you get stuck. This is voluntary and counts as extra credit, so keep it short.
Saved on this device. Show Mr. Mendoza or add these to your notebook glossary to claim the extra credit.
Part 2 of 4 · Directions in plain English▸
2.1 Open your materials
Use the materials named in the first step below. Open lesson resources.
Practice SDS-PAGE gel (made-up practice data, not from this class's run)
Five lanes, stained with Coomassie. Distances are measured from the well in millimeters
| Lane | What was loaded | Bands seen (distance from the well in mm; strong or faint) |
|---|---|---|
| 1 | Marker ladder | 150 kDa at 6; 100 kDa at 11; 75 kDa at 16; 50 kDa at 24; 37 kDa at 31; 25 kDa at 40; 20 kDa at 46; 15 kDa at 53 |
| 2 | Crude lysate | Strong at 9, 18, 22, 29, 38 and 44; faint at 13, 35 and 50 |
| 3 | Flow-through | Strong at 18, 22, 29 and 44; faint at 9, 13, 35, 38 and 50 |
| 4 | Wash | Faint at 22 and 38 |
| 5 | Elution | Strong at 38; faint at 20 |
- Smaller proteins travel farther from the well. Sketch the gel from this table, then annotate it the way today's steps ask.
- Target protein: GFP, about 27 kDa. Estimate each band's size from the marker lane before you judge purity.
2.2 Start the work
Read the gel-interpretation notes in the PLTW course shell and define the protein marker lane.
Show all 5 required steps
- Read the gel-interpretation notes in the PLTW course shell and define the protein marker lane.
- Compare the fraction lanes on the practice gel on this page, or your simulation gel, to the marker to estimate the protein's size.
- Decide which fraction is most pure based on how few extra bands it shows.
- Write one QC statement on whether the purification met the purity goal: one major band at about 27 kDa (GFP) and no other visible band under the stain used. Add one sentence on what your gel cannot rule out.
- Add your annotated gel reading to your Unit 4 PLTW tracker evidence.
Lost your place? Reopen today's SDS-PAGE gel results record. Find the last completed evidence ID, check it against the claim ceiling, and continue with the first unfinished step rather than restarting the whole task.
- 0-10Read gel-interpretation notes; define marker lane and band
- 10-28Annotate gel image: label marker lane, estimate target size
- 28-45Compare lanes; count extra bands per lane
- 45-58Identify most-pure ; justify with band count
- 58-70Write statement: passed or failed goal with evidence
- 70-80Add annotated gel to tracker; check every part of today's is filled before you submit
- • You collected fractions yesterday; today you find out what is actually in them.
- • Today's target is , the green fluorescent protein, about 27 kDa. SDS-PAGE separates proteins by size, so other proteins in a usually show up as extra bands.
- • The goal: one major band at about 27 kDa, the size of , and no other band you can see with the stain used. Meeting it supports purity but does not prove it: a different of about the same size can run in the same band, and a protein present in a tiny amount can be too faint for the stain to show.
- • Gel interpretation is a core Lab SOPs skill tested on your end-of-course WebXam for this class.
PLTW connection and today's work
Open Activity 4.1.3 Protein Purification in myPLTW and interpret your SDS-PAGE gel to judge the size and purity of the isolated protein.
Today's stopping point: Fraction-collection data should be done; annotated gel and QC statement due today.
PLTW activity titles identify the course connection. If your account will not open, use the posted materials for today and tell Mr. Mendoza. Do not mark an online activity complete unless you completed it.
Course connection
- Activity 4.1.3 Protein Purification
Use the turn-in directions in Part 4 of this page. Do not create a second submission unless your teacher asks for one.
Show another explanation or a smaller first step
Need help? Choose a starting point
Finish the assigned lab safely before starting extra practice.
Part 3 of 4 · Worked example▸
This is a parallel case, not your own. Read it for the order of the work, then do your own in Part 4.
Parallel practice gel, not today's: a practice enzyme expected near 45 kDa.
How I read it: the marker lane holds proteins of known size, so it is my ruler. Smaller proteins travel farther from the well.
Reading:
- Marker bands at 100, 75, 50, 37 and 25 kDa. My target band sits between the 50 and 37 kDa bands, closer to 50, so I estimate about 45 kDa.
- Band counts: crude lysate, 9 bands; flow-through, 8 bands with only a faint band at 45; wash, 2 faint bands; elution, 1 strong band at about 45 kDa plus 1 faint band near 70 kDa.
- Most pure lane: the elution lane, because it has one dominant band at the expected size and only one faint extra band.
QC statement: the column enriched the enzyme but did not make it pure. One faint extra band remains, and a Coomassie-stained gel cannot show proteins below about 100 ng per band, so 'one strong band' describes what this stain can see, not proof that nothing else is in the tube.
| Lane | Bands seen | Reading |
|---|---|---|
| Marker | 100, 75, 50, 37, 25 kDa | the ruler |
| Crude lysate | 9 bands | everything the cells made |
| Flow-through | 8 bands, faint at 45 | unbound proteins |
| Wash | 2 faint bands | loosely bound proteins |
| Elution | strong at about 45, faint near 70 | most pure, enriched not pure |
This model shows the level of evidence and organization needed to complete: Models the gel reading on a parallel practice gel for a different protein: marker lane labeled, size estimated against the ladder, bands counted by lane, the most pure lane named, and a QC statement that states its own limit.
- Name the variables and include units.
- Enter observations without changing the raw values.
- Check labels, calculations, and patterns before interpreting the data.
Keep the structure. Replace the question, facts, measurements, and evidence. Then recheck units, vocabulary, and whether the conclusion goes beyond the evidence.
Also due today: Attach your annotated gel reading to your Unit 4 PLTW tracker and submit it in Schoology.
A research team lays out its question, variables, controls, sampling plan, measurement record, and analysis before deciding what the data support.
- Which variable is changed or compared?
- Which conditions and measurements must stay consistent?
- Which conclusion is inside the study's evidence boundary?
Define variables, controls, sampling, units, and the analysis plan before interpreting a result; analysis cannot repair biased or inconsistent measurement.
A well-organized classroom study can still be limited by , measurement quality, confounding, and the population represented.
- • Question and variable cards map to the study design.
- • Control and measurement cards map to fair, reproducible data collection.
- • The conclusion card maps to a bounded claim supported by the analysis.
Part 4 of 4 · Your work▸
Check your work before submitting
- You'll be able to estimate protein size against a marker lane.
- You'll be able to judge purity and write a QC statement from a gel.
Before lab work: read the safety rules
- No new chemical hazards today; gel image analysis is a paper or digital exercise.
- If handling a physical stained gel, wear gloves as Coomassie stain is a skin irritant.
- Dispose of any staining waste according to lab guidelines.
4.1 Turn in your work
DueCheck the Schoology assignment for this day- Hand in
- Annotated SDS-PAGE gel image with labeled marker lane, estimated protein size, band counts by fraction, most-pure fraction identified, and a QC statement.
How to submit and name your file
Submit as one PDF in Schoology.
In Schoology, open your course and the assignment for this lesson. Attach your file, select Submit, and check that it appears in the submission.
PDF upload helpYou get two school days for every day you were absent, so this deadline moves with you.
Today's lesson is in Schoology
Each school day has one lesson page in Schoology that holds everything for the day: the goal, the story so far, every table and data value, the numbered steps, and what to turn in. Open it first and work from it. The other rows for this day, if any, are the score line for a paper quiz or test and the John Carroll debate item; they do not add work. Check Schoology for each deadline.
- Checkpoint Quiz 5: proteins, pathogen identification, and laboratory records (paper, in class Fri 12/11)(taken on paper in class: this row holds the score, there is nothing to upload)
- Today's Lesson · Fri 12/11 · Wk16 · Checkpoint Quiz 5 on paper, then center, spread, and what a correlation can claim(today's lesson page: the goal, the data, the steps, and what to turn in are all on it)
Link will not open? Open Schoology, choose your course and section, and find the title shown above.
- CompleteEvery required part of the artifact is present, nothing left blank.
- AccurateThe science and the data are correct and match the evidence.
- Scientific reasoningYou explain your claim with evidence and reasoning (CER), not just an answer.
- Professional communicationClear, organized, labeled, and written the way a clinician or scientist would.
- SubmittedGo to Schoology to turn this in. Submit one PDF. Schoology attaches your name to your upload; on the page itself, write your period and code. Name the file: FirstName LastName - Assignment Title - YYYY-MM-DD.pdf. If you cannot get in, see Mr. Mendoza. Do not skip the work.
- Error analysis and method · counts doubleName a specific limit of the method and how it moved your result, and compare what you predicted to what happened. "Human error" does not count; say what about the procedure or instrument caused it.
How this lesson connects
Keep using what you learned last class: Molecular workflows use controls and complementary separation or detection steps to evaluate a target, while each band, fraction, or colony remains limited by method resolution and sample quality. Today: Molecular workflows use controls and complementary separation or detection steps to evaluate a target, while each band, fraction, or colony remains limited by method resolution and sample quality.
Practice: try a question, then check your answer▸
Claim ceiling for this check: Today's evidence supports a classroom claim about SDS-PAGE gel results. It cannot prove causation, diagnose a real patient, or justify action outside this room.
A student treats one classroom result about SDS-PAGE gel results as proof. What must the student add before the conclusion is defensible?
Write an answer and pick a confidence to unlock the key.
Missed class or ready for more?▸
Run this before you touch the bench. It is built from the real lab procedure, so the decisions you make here are the ones you will make with the equipment in your hands.
I can name the procedure's purpose and the evidence I will record. I can name today's hazards and the control for each: If handling a physical stained gel, wear gloves as Coomassie stain is a skin irritant. My data table is ready before materials are handled.
Finish the checklist before you handle any material.
- • No new chemical hazards today; gel image analysis is a paper or digital exercise.
- • If handling a physical stained gel, wear gloves as Coomassie stain is a skin irritant.
- • Dispose of any staining waste according to lab guidelines.
- 1Before materials are handled, identify the purpose, variables or comparison, controls, measurement units, and stop-work condition.
- 2Read the gel-interpretation notes in the PLTW course shell and define the protein marker lane.
- 3Compare the fraction lanes on the practice gel on this page, or your simulation gel, to the marker to estimate the protein's size.
- 4Decide which fraction is most pure based on how few extra bands it shows.
- 5Write one QC statement on whether the purification met the purity goal: one major band at about 27 kDa (GFP) and no other visible band under the stain used. Add one sentence on what your gel cannot rule out.
- 6Add your annotated gel reading to your Unit 4 PLTW tracker evidence.
- 7Record each result in the prepared table before interpreting it. Mark missing, repeated, or invalid results truthfully.
- 8Complete the named cleanup and waste route, remove PPE safely, wash hands when required, and confirm the station is ready for the next group.
| Which trial or sample this row is | What you changed on purpose | What you measured, with units | What you saw, before you explain it | Anything that could make this reading wrong |
|---|---|---|---|---|
Before the procedure, predict the result and cite the rule behind the prediction.
After the procedure, compare the result with the prediction and name one limitation or source of uncertainty.
What today's skills lead to. These are real health-science careers this course builds toward. Tap one to see, on the US Department of Labor's O*NET site, what the job actually involves, what it pays, and how fast it is growing.
The bench work needs equipment you do not have at home. Do the thinking half now: read the procedure, write your prediction, and set up your data table so it is ready.
Back in class. Ask Mr. Mendoza for the class data set, or for a bench slot to run it yourself. Do not submit a Data table with invented numbers.
Class still runs. Complete today's work as this page describes (it is self-guided). Need the concept taught without a teacher? Use this authoritative explainer:
Genetic Science Learning Center: Genetics basics and proteinsThe optional extra-credit track is open. Complete reserved-unit work from home, including virtual labs, for extra credit. Each item shows its correct submission route.
Open the extra-credit trackSources: slides, readings, and resources▸
The deck carries the prior idea forward, lets you inspect an analogy, maps the rule to biology, and ends with the same evidence decision and exit ticket used on this page.
Classroom documents for this lesson are posted in Schoology. Open Clever, then Schoology, and find each one by the name shown on its card.
Open this when the class reaches this activity and use it to complete the required lesson artifact.
Open this when the class reaches this activity and use it to complete the required lesson artifact.
Use this if you were absent, got stuck, or need another pass before you submit the lesson artifact.
Sign in to Clever with your district Microsoft account to open Schoology or myPLTW. Follow today's posted steps. If myPLTW will not open, use the posted alternative and tell Mr. Mendoza. Turn in your completed work through the Schoology assignment.
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