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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 liquid centrifugation
B. Total lipid calculation
C. Thin-layer chromatography
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 count egg cells
C. To measure egg temperature
D. To determine shell thickness

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

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

4 What is the mobile phase in a TLC experiment?

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

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

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

6 Why should the sample spot be small and concentrated?

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

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 sample volume
C. Differences in plate thickness
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. Plate thickness
B. value
C. Sample density
D. Boiling point

9 What does the value compare?

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

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 darkest lipid band
B. The line where samples are spotted
C. The furthest point reached by solvent
D. The bottom edge of the plate

12 Why is the solvent front marked immediately after development?

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

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 increase the egg volume
B. To remove the silica layer
C. To make all samples identical
D. To compare their lipid patterns

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 contain similar lipid components
B. They contain equal water volumes
C. They have identical shell colors
D. They were collected at the same time

15 What is a lipid standard used for in TLC?

TLC profiling of egg lipids from different sources Easy
A. To increase solvent polarity
B. To clean the TLC chamber
C. To help identify lipid bands
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. Lipids are made only of water
B. Organic solvents solidify all lipids
C. Organic solvents create proteins
D. Lipids dissolve in organic solvents

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

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

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 marks increase lipid concentration
C. Pencil ink moves faster than lipids
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. Washing with soap
D. Using iodine vapor

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 samples had identical lipids
B. Their detected lipid profiles differ
C. Their plates had equal solvent levels
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 compare lipid composition qualitatively
B. To determine the exact lipid molecular mass
C. To measure egg protein concentration
D. To sterilize the lipid extracts

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 marks attract the solvent front
B. Pencil graphite remains near the origin
C. Pen ink increases lipid solubility
D. Pen ink prevents plate development

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 extracts contain identical lipid amounts
C. The lipids have identical molecular formulas
D. The samples contain no other lipids

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 prevent all spots from spreading
B. They help assign identities to sample spots
C. They eliminate the need for solvent
D. They increase the mass of sample lipids

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 plate contained no stationary phase
B. The component was more volatile than solvent
C. The solvent was completely absent
D. The component strongly interacts with silica

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. The solvent front will stop immediately
B. All compounds will have lower mass
C. Broad or streaked spots may form
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 lipid spots migrate only toward the origin
B. The sample becomes permanently fixed to silica
C. The solvent front becomes invisible by definition
D. The sample can dissolve directly into the reservoir

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 make silica chemically nonpolar
C. To prevent lipids from entering the plate
D. To maintain a solvent-saturated atmosphere

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 first extract definitely contains fewer lipids by mass
D. The solvent was different for the two extracts

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 prevent the standards from dissolving
B. To make all spots appear at the solvent front
C. To ensure every sample has equal lipid mass
D. To allow valid comparison of values

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 less polar lipid
B. A lipid with maximum silica attraction
C. A highly polar phospholipid
D. A strongly ionized compound

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 dissolve stationary-phase particles
B. To remove solvent that can distort spot detection
C. To convert all lipids into proteins
D. To increase the solvent front distance

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. Increase the sample spot diameter
B. Lower the chamber height
C. Use a darker pencil line
D. Optimize the solvent composition

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 makes all components chemically identical
B. It removes the need for sample controls
C. It minimizes differences in experimental conditions
D. It guarantees identical lipid concentrations

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 distances were measured incorrectly
B. The lipid moved faster than the solvent front
C. The silica produced additional solvent
D. The sample contained no extractable lipid

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 origin line disappears before development
B. The silica changes into a liquid phase
C. The solvent may evaporate and leave no visible front
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 compound must be the most abundant lipid
B. The lipid must be absent from all samples
C. The lipid is likely present at a low detectable level
D. The spot proves the extracts are contaminated

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 extracts have different colors before development
B. Their solvent fronts travel different distances
C. They show different spot patterns under identical conditions
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. The Rf 0.19 spot is likely phospholipid, whereas Rf 0.42 requires identification
C. Neither spot can represent phospholipid because standards must have Rf 1.0
D. Both spots are phospholipids because they came from egg extracts

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 require immediate rejection
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 show moderate handling variation

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. Increase the sample volume to strengthen separated bands
B. Apply less concentrated extract in smaller, dried portions
C. Scrape the entire lane and repeat visualization only
D. Develop the plate farther without changing the sample load

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

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

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

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 has greater density and therefore falls behind gravitationally
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 is retained more strongly by polar silica interactions

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. Only spot color changes, while migration distances remain unaffected
D. Uneven solvent vapor conditions can distort Rf values across the plate

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 sample must contain only phospholipids because no spots appeared
C. The positive control proves that every sample lipid was extracted
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 solvent front traveled backward and concentrated all compounds at the origin
B. The origin spot proves that the samples contain no extractable lipids
C. The spot must be the least polar neutral lipid in every sample
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. Convert each intensity directly into percent composition without standards
B. Normalize intensity to the amount of original egg or extract lipid applied
C. Rank the sources directly because intensity is independent of loading
D. Use only the darkest lane because faint spots are analytically unreliable

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

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

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 lipid was present below direct visibility or required derivatization for detection
B. The untreated plate proves that the compound was absent from the sample
C. The derivatization created the lipid, so the original extract contained none
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. Whole-egg samples always produce invalid TLC profiles regardless of extraction method
B. Different biological materials improve the comparison by increasing chemical diversity
C. Tissue composition is confounded with source, preventing a direct source comparison
D. Phospholipid intensity cannot be compared with neutral-lipid intensity under any conditions

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

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

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 molecular formula of silica because all sample matrices behave identically
D. The assumption that equal lipid mass guarantees equal chromatographic behavior

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 sample may contain a second component that overlaps or interacts near the standard
B. The solvent system has proven perfect resolution for that lipid class
C. The broadening demonstrates that the sample contains no detectable standard compound
D. The standard and sample must be chemically identical because the Rf values match
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