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Unit 10: Mini Project 2 - Practice Quiz

BTY114 — Cell Biology Laboratory 60 Questions
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1 What does TLC stand for?

TLC profiling of egg lipids from different sources Easy
A. Thin-layer chromatography
B. Thin liquid centrifugation
C. Total lipid calculation
D. Thermal layer counting

2 What is the main purpose of TLC profiling of egg lipids?

TLC profiling of egg lipids from different sources Easy
A. To separate lipid components
B. To measure egg temperature
C. To determine shell thickness
D. To count egg cells

3 What is commonly used as the stationary phase in lipid TLC?

TLC profiling of egg lipids from different sources Easy
A. Filter paper
B. Glass wool
C. Silica gel
D. Distilled water

4 What is the mobile phase in a TLC experiment?

TLC profiling of egg lipids from different sources Easy
A. The egg yolk sample
B. The iodine chamber
C. The silica coating
D. The developing solvent

5 Where should an egg lipid sample be applied on a TLC plate?

TLC profiling of egg lipids from different sources Easy
A. At the solvent front
B. On the plate edge
C. Above the chamber lid
D. Near the baseline

6 Why should the sample spot be small and concentrated?

TLC profiling of egg lipids from different sources Easy
A. To prevent plate movement
B. To reduce chamber humidity
C. To improve separation
D. To increase solvent volume

7 What causes lipid components to move different distances on a TLC plate?

TLC profiling of egg lipids from different sources Easy
A. Differences in egg color
B. Differences in plate thickness
C. Differences in sample volume
D. Differences in polarity

8 In general, a compound that travels farther on a TLC plate has a higher:

TLC profiling of egg lipids from different sources Easy
A. value
B. Plate thickness
C. Boiling point
D. Sample density

9 What does the value compare?

TLC profiling of egg lipids from different sources Easy
A. Plate length with sample volume
B. Spot distance with solvent-front distance
C. Spot color with solvent color
D. Sample mass with solvent mass

10 Which equation represents the TLC retention factor?

TLC profiling of egg lipids from different sources Easy
A.
B.
C.
D.

11 What is the solvent front?

TLC profiling of egg lipids from different sources Easy
A. The furthest point reached by solvent
B. The darkest lipid band
C. The bottom edge of the plate
D. The line where samples are spotted

12 Why is the solvent front marked immediately after development?

TLC profiling of egg lipids from different sources Easy
A. The egg lipids may boil
B. The silica may dissolve
C. The plate may become magnetic
D. The solvent may evaporate

13 What is one reason to run egg samples from different sources on the same TLC plate?

TLC profiling of egg lipids from different sources Easy
A. To compare their lipid patterns
B. To increase the egg volume
C. To remove the silica layer
D. To make all samples identical

14 If two egg samples produce spots at similar positions, what may this suggest?

TLC profiling of egg lipids from different sources Easy
A. They were collected at the same time
B. They have identical shell colors
C. They contain equal water volumes
D. They contain similar lipid components

15 What is a lipid standard used for in TLC?

TLC profiling of egg lipids from different sources Easy
A. To clean the TLC chamber
B. To help identify lipid bands
C. To increase solvent polarity
D. To measure plate hardness

16 Why are organic solvents often used to extract lipids from egg samples?

TLC profiling of egg lipids from different sources Easy
A. Organic solvents create proteins
B. Lipids dissolve in organic solvents
C. Lipids are made only of water
D. Organic solvents solidify all lipids

17 What should be avoided when applying a sample to a TLC plate?

TLC profiling of egg lipids from different sources Easy
A. Labeling the sample position
B. Allowing the spot to dry
C. Touching the silica surface
D. Using a pencil baseline

18 Why should the baseline be drawn with a pencil rather than a pen?

TLC profiling of egg lipids from different sources Easy
A. Pen ink prevents solvent evaporation
B. Pencil ink moves faster than lipids
C. Pencil marks increase lipid concentration
D. Pencil graphite does not usually dissolve

19 What is one common way to make separated lipid spots visible?

TLC profiling of egg lipids from different sources Easy
A. Adding extra water
B. Freezing the plate
C. Using iodine vapor
D. Washing with soap

20 What does a difference in the number of TLC bands between egg sources indicate?

TLC profiling of egg lipids from different sources Easy
A. Their plates had equal solvent levels
B. Their samples had identical lipids
C. Their detected lipid profiles differ
D. Their solvents had no effect

21 What is the main purpose of using TLC when comparing lipids extracted from eggs of different sources?

TLC profiling of egg lipids from different sources Medium
A. To measure egg protein concentration
B. To compare lipid composition qualitatively
C. To sterilize the lipid extracts
D. To determine the exact lipid molecular mass

22 A lipid extract produces a spot with an value of . If the solvent front traveled , how far did the spot travel?

TLC profiling of egg lipids from different sources Medium
A.
B.
C.
D.

23 Why should the origin line be drawn with a pencil rather than a pen?

TLC profiling of egg lipids from different sources Medium
A. Pencil graphite remains near the origin
B. Pencil marks attract the solvent front
C. Pen ink prevents plate development
D. Pen ink increases lipid solubility

24 Two egg extracts produce spots at the same value in the same solvent system. What is the most appropriate conclusion?

TLC profiling of egg lipids from different sources Medium
A. The spots may represent the same lipid
B. The samples contain no other lipids
C. The extracts contain identical lipid amounts
D. The lipids have identical molecular formulas

25 Why are reference lipid standards useful when analyzing egg lipid extracts by TLC?

TLC profiling of egg lipids from different sources Medium
A. They increase the mass of sample lipids
B. They eliminate the need for solvent
C. They help assign identities to sample spots
D. They prevent all spots from spreading

26 A sample spot remains at the origin while the solvent front moves normally. Which explanation is most likely?

TLC profiling of egg lipids from different sources Medium
A. The component strongly interacts with silica
B. The plate contained no stationary phase
C. The component was more volatile than solvent
D. The solvent was completely absent

27 What is the likely effect of applying an excessively large volume of egg lipid extract to the TLC plate?

TLC profiling of egg lipids from different sources Medium
A. Broad or streaked spots may form
B. All compounds will have lower mass
C. The solvent front will stop immediately
D. The silica layer will become nonpolar

28 If the solvent level is above the sample application line at the start of development, what problem can occur?

TLC profiling of egg lipids from different sources Medium
A. The sample becomes permanently fixed to silica
B. The sample can dissolve directly into the reservoir
C. The lipid spots migrate only toward the origin
D. The solvent front becomes invisible by definition

29 Why should the developing chamber be covered during TLC separation?

TLC profiling of egg lipids from different sources Medium
A. To increase the sample volume automatically
B. To prevent lipids from entering the plate
C. To maintain a solvent-saturated atmosphere
D. To make silica chemically nonpolar

30 An egg extract gives three spots, while another gives five spots under identical TLC conditions. What does this observation suggest?

TLC profiling of egg lipids from different sources Medium
A. The second extract definitely contains twice as much lipid
B. The samples may differ in detectable lipid components
C. The solvent was different for the two extracts
D. The first extract definitely contains fewer lipids by mass

31 Why should all egg extracts be spotted at the same distance from the bottom of the TLC plate?

TLC profiling of egg lipids from different sources Medium
A. To ensure every sample has equal lipid mass
B. To make all spots appear at the solvent front
C. To allow valid comparison of values
D. To prevent the standards from dissolving

32 A spot travels while the solvent front travels . What is the spot's value?

TLC profiling of egg lipids from different sources Medium
A.
B.
C.
D.

33 In a relatively nonpolar solvent system, which component would generally travel farther on a silica TLC plate?

TLC profiling of egg lipids from different sources Medium
A. A lipid with maximum silica attraction
B. A less polar lipid
C. A strongly ionized compound
D. A highly polar phospholipid

34 What is the main reason for drying the TLC plate before visualizing or staining it?

TLC profiling of egg lipids from different sources Medium
A. To convert all lipids into proteins
B. To increase the solvent front distance
C. To dissolve stationary-phase particles
D. To remove solvent that can distort spot detection

35 If two nearby lipid spots merge into one broad band, which adjustment would most directly improve separation?

TLC profiling of egg lipids from different sources Medium
A. Use a darker pencil line
B. Lower the chamber height
C. Optimize the solvent composition
D. Increase the sample spot diameter

36 Why is it important to analyze egg samples from different sources on the same TLC plate when possible?

TLC profiling of egg lipids from different sources Medium
A. It minimizes differences in experimental conditions
B. It makes all components chemically identical
C. It guarantees identical lipid concentrations
D. It removes the need for sample controls

37 A spot has an value greater than . What is the most likely cause?

TLC profiling of egg lipids from different sources Medium
A. The lipid moved faster than the solvent front
B. The sample contained no extractable lipid
C. The silica produced additional solvent
D. The distances were measured incorrectly

38 Why should the solvent front be marked immediately after removing the TLC plate?

TLC profiling of egg lipids from different sources Medium
A. The solvent may evaporate and leave no visible front
B. The silica changes into a liquid phase
C. The origin line disappears before development
D. The lipids continue moving after drying

39 A lipid spot is faint but appears at the same position in replicate samples. What is the best interpretation?

TLC profiling of egg lipids from different sources Medium
A. The spot proves the extracts are contaminated
B. The lipid must be absent from all samples
C. The compound must be the most abundant lipid
D. The lipid is likely present at a low detectable level

40 Which observation would provide the strongest evidence that two egg sources have different lipid profiles?

TLC profiling of egg lipids from different sources Medium
A. Their solvent fronts travel different distances
B. They show different spot patterns under identical conditions
C. Their extracts have different colors before development
D. One egg has a larger shell

41 Two egg-lipid extracts are analyzed on silica TLC plates using the same solvent system. A phospholipid standard has an Rf of 0.18, while one sample contains a spot at Rf 0.19 and another at Rf 0.42. What is the most defensible interpretation?

TLC profiling of egg lipids from different sources Hard
A. The Rf 0.42 spot is phospholipid because it traveled farther
B. Both spots are phospholipids because they came from egg extracts
C. The Rf 0.19 spot is likely phospholipid, whereas Rf 0.42 requires identification
D. Neither spot can represent phospholipid because standards must have Rf 1.0

42 The solvent front traveled 7.5 cm. A lipid spot traveled 3.0 cm in one lane and 2.7 cm in a replicate lane. What conclusion is best supported?

TLC profiling of egg lipids from different sources Hard
A. The replicate Rf values are 0.40 and 0.36 and show moderate handling variation
B. The replicate Rf values are 0.40 and 0.36 and prove different lipid identities
C. The replicate Rf values are 2.50 and 2.78 and show solvent instability
D. The replicate Rf values are 0.40 and 0.36 and require immediate rejection

43 A lane containing an egg extract shows a broad streak from the origin through the middle of the plate instead of discrete spots. Which corrective action is most appropriate first?

TLC profiling of egg lipids from different sources Hard
A. Develop the plate farther without changing the sample load
B. Increase the sample volume to strengthen separated bands
C. Scrape the entire lane and repeat visualization only
D. Apply less concentrated extract in smaller, dried portions

44 A student compares egg sources using separate TLC plates. The same phospholipid standard has Rf values of 0.21, 0.28, and 0.34 on the three plates. What is the best experimental response?

TLC profiling of egg lipids from different sources Hard
A. Repeat development with standards and samples on one plate when possible
B. Compare only spot darkness because Rf values are never reproducible
C. Average the standard values and correct every sample by that average
D. Conclude that phospholipid composition differs among all egg sources

45 Two egg extracts produce spots at nearly identical Rf values, but one spot is much darker after staining. Which interpretation is scientifically justified?

TLC profiling of egg lipids from different sources Hard
A. The lighter spot must represent a nonlipid contaminant
B. The darker spot must have a higher molecular mass than the lighter spot
C. The darker spot may contain more detectable material but is not proven to be a different lipid
D. The darker spot necessarily migrated farther before the plate was photographed

46 A sample lane contains a spot at the same Rf as a cholesterol standard and a second spot just below it. What is the most appropriate conclusion?

TLC profiling of egg lipids from different sources Hard
A. Both spots are cholesterol because compounds in one class always cluster together
B. The matching spot is consistent with cholesterol, while the nearby spot needs an additional standard
C. Neither spot can be assigned because TLC cannot compare sample and standards
D. The lower spot is cholesterol because it interacted more strongly with silica

47 In a normal-phase silica TLC system, a less-polar neutral lipid generally travels farther than a more-polar phospholipid. What mechanism best explains this pattern?

TLC profiling of egg lipids from different sources Hard
A. The phospholipid is retained more strongly by polar silica interactions
B. The solvent selectively evaporates phospholipid before it can migrate
C. The neutral lipid reacts chemically with silica and is pushed toward the front
D. The phospholipid has greater density and therefore falls behind gravitationally

48 A solvent chamber was not equilibrated before development, and solvent levels differed slightly between lanes. Which effect is most likely?

TLC profiling of egg lipids from different sources Hard
A. The solvent front becomes exactly horizontal regardless of chamber setup
B. All lipid identities become invalid because silica cannot bind lipids
C. Uneven solvent vapor conditions can distort Rf values across the plate
D. Only spot color changes, while migration distances remain unaffected

49 An egg extract shows no visible lipid spots, but the positive control is clearly detected. The extract was prepared with a solvent that does not efficiently recover neutral lipids. What is the strongest conclusion?

TLC profiling of egg lipids from different sources Hard
A. The egg source definitively contains no neutral lipids
B. The positive control proves that every sample lipid was extracted
C. The sample must contain only phospholipids because no spots appeared
D. The sample result may reflect extraction failure rather than absence of neutral lipids

50 A lipid spot appears at the origin in every sample lane but not in the solvent blank. Which explanation is most plausible in a normal-phase system?

TLC profiling of egg lipids from different sources Hard
A. The spot must be the least polar neutral lipid in every sample
B. The origin spot proves that the samples contain no extractable lipids
C. The solvent front traveled backward and concentrated all compounds at the origin
D. A strongly retained polar component or overloaded sample remained near the origin

51 Three egg sources yield phospholipid spot intensities of 80, 160, and 240 arbitrary units, but different extract volumes were spotted. Which comparison is most appropriate?

TLC profiling of egg lipids from different sources Hard
A. Use only the darkest lane because faint spots are analytically unreliable
B. Normalize intensity to the amount of original egg or extract lipid applied
C. Convert each intensity directly into percent composition without standards
D. Rank the sources directly because intensity is independent of loading

52 A sample spot has an Rf of 0.50, while standards for lipid A and lipid B have Rf values of 0.48 and 0.52. What is the best identification strategy?

TLC profiling of egg lipids from different sources Hard
A. Identify the spot as a mixture only because all intermediate values are mixtures
B. Assign the spot to lipid B because higher Rf indicates greater purity
C. Assign the spot to lipid A because its Rf is numerically slightly closer
D. Treat the spot as unresolved and co-run standards or use a second solvent system

53 A sample was spotted before the pencil origin line had fully dried after marking. Several lanes show diffuse lower bands. What is the likely consequence?

TLC profiling of egg lipids from different sources Hard
A. The solvent front becomes unusable because pencil marks dissolve completely
B. The wet pencil line chemically converts phospholipids into neutral lipids
C. Moisture increases silica activity uniformly and guarantees sharper bands
D. Residual moisture can alter sample spreading and initial migration behavior

54 A source-specific spot appears only after chemical derivatization, while the untreated plate showed no visible band. How should this result be reported?

TLC profiling of egg lipids from different sources Hard
A. The derivatization created the lipid, so the original extract contained none
B. The lipid was present below direct visibility or required derivatization for detection
C. The untreated plate proves that the compound was absent from the sample
D. The spot is automatically identified because derivatization is class-specific

55 A blank solvent lane develops a faint spot at the same Rf as a major sample spot. What should be done before attributing that spot to egg lipids?

TLC profiling of egg lipids from different sources Hard
A. Identify the sample spot confidently because matching Rf proves sample origin
B. Subtract or investigate the blank contribution before assigning the sample spot
C. Increase sample concentration until the blank spot is visually overwhelmed
D. Ignore the blank because only sample lanes are relevant to lipid profiling

56 Egg samples from two sources show different ratios of phospholipid to neutral-lipid spot intensities. However, one source was extracted from yolk and the other from whole egg. What is the primary limitation?

TLC profiling of egg lipids from different sources Hard
A. Phospholipid intensity cannot be compared with neutral-lipid intensity under any conditions
B. Whole-egg samples always produce invalid TLC profiles regardless of extraction method
C. Tissue composition is confounded with source, preventing a direct source comparison
D. Different biological materials improve the comparison by increasing chemical diversity

57 The solvent front is irregular, rising 6.0 cm on one side and 7.0 cm on the other. How should Rf values be calculated for spots on the plate?

TLC profiling of egg lipids from different sources Hard
A. Use the larger 7.0 cm value for every lane to standardize the calculation
B. Use the origin-to-spot distance alone because the front is not uniform
C. Use the local solvent-front distance measured in the same lane as each spot
D. Use the average front distance and report all spots as equally reliable

58 A researcher wants to claim that one egg source has a unique lipid not found in the others because a faint spot appears only in that source. Which additional evidence is most important?

TLC profiling of egg lipids from different sources Hard
A. The unique claim is justified if the spot appears once at a plausible Rf
B. Replicate extractions and a matched blank should confirm the reproducible spot
C. The plate should be photographed with increased contrast until the spot dominates
D. A larger sample volume should be spotted only for the source with the spot

59 Two egg extracts have equal total lipid mass applied, but one produces severe streaking and the other gives sharp bands. Which factor should be investigated first?

TLC profiling of egg lipids from different sources Hard
A. Differences in extract concentration, solvent compatibility, or sample matrix
B. The plate color because sharp bands are caused primarily by visual contrast
C. The assumption that equal lipid mass guarantees equal chromatographic behavior
D. The molecular formula of silica because all sample matrices behave identically

60 A sample spot and a standard spot have the same Rf in one solvent system, but their co-spot produces a broadened or asymmetric band. What does this most strongly suggest?

TLC profiling of egg lipids from different sources Hard
A. The broadening demonstrates that the sample contains no detectable standard compound
B. The standard and sample must be chemically identical because the Rf values match
C. The solvent system has proven perfect resolution for that lipid class
D. The sample may contain a second component that overlaps or interacts near the standard
Previous MCQ
Unit 9