Photosynthetic pigments MCQs With Answer

Introduction

Photosynthetic pigments MCQs With Answer is a focused study resource designed for B. Pharm students preparing for pharmacognosy and phytochemistry exams. This concise, Student-friendly post covers chlorophylls, carotenoids, xanthophylls, bacteriochlorophylls, their structures, absorption spectra, extraction methods, degradation products and analytical techniques like spectrophotometry, TLC and HPLC. Understanding these pigments is essential for herbal drug standardization, stability studies and quality control of plant-derived medicines. Questions emphasize biochemical roles, photoprotection, pigment–protein complexes and practical laboratory identification. Clear explanations and targeted MCQs help reinforce key concepts and exam readiness. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. Which part of the chlorophyll molecule is responsible for light absorption?

• The long phytol tail
• The central magnesium-containing porphyrin ring
• The ester linkage
• The hydrocarbon side chain

Correct Answer: The central magnesium-containing porphyrin ring

Q2. Which pigment is considered the primary photosynthetic pigment in higher plants?

• Carotene
• Chlorophyll b
• Chlorophyll a
• Xanthophyll

Correct Answer: Chlorophyll a

Q3. Chlorophyll b mainly differs from chlorophyll a by which structural feature?

• Presence of an extra phytol tail
• Replacement of a methyl group with a formyl group
• Loss of the central magnesium
• Shortening of the porphyrin ring

Correct Answer: Replacement of a methyl group with a formyl group

Q4. Which wavelength region do carotenoids primarily absorb?

• 600–700 nm (red region)
• 500–600 nm (green region)
• 400–500 nm (blue–green region)
• 700–800 nm (far-red region)

Correct Answer: 400–500 nm (blue–green region)

Q5. What is the product formed when chlorophyll loses its central Mg2+ under acidic conditions?

• Chlorophyllide
• Pheophytin (pheophorbide when phytol removed)
• Carotenoid
• Prochlorophyll

Correct Answer: Pheophytin (pheophorbide when phytol removed)

Q6. Which enzyme catalyzes removal of the phytol tail from chlorophyll to form chlorophyllide?

• Chlorophyllase
• Phaeophytinase
• Carotenoid oxygenase
• Chlorophyll oxidase

Correct Answer: Chlorophyllase

Q7. In pigment analysis by spectrophotometry, chlorophyll a shows a major absorption peak near which wavelength in the red region?

• ≈430 nm
• ≈480 nm
• ≈660–665 nm
• ≈720–730 nm

Correct Answer: ≈660–665 nm

Q8. Which pigment class provides photoprotection by quenching excess energy?

• Chlorophylls
• Carotenoids (including xanthophylls)
• Anthocyanins
• Alkaloids

Correct Answer: Carotenoids (including xanthophylls)

Q9. The xanthophyll cycle involves reversible interconversion primarily among which compounds?

• Lutein, neoxanthin, violaxanthin
• Violaxanthin, antheraxanthin, zeaxanthin
• Beta-carotene, lutein, zeaxanthin
• Chlorophyll a, chlorophyll b, pheophytin

Correct Answer: Violaxanthin, antheraxanthin, zeaxanthin

Q10. Which solvent is commonly used for efficient extraction of chlorophylls from plant tissues in the laboratory?

• Petroleum ether
• Dimethyl sulfoxide (DMSO)
• 80% acetone or methanol
• Pure water

Correct Answer: 80% acetone or methanol

Q11. Bacteriochlorophylls differ from plant chlorophylls mainly by:

• Absence of a porphyrin ring
• Different absorption maxima in near-infrared region
• Being yellow rather than green
• Having no phytol chain

Correct Answer: Different absorption maxima in near-infrared region

Q12. Which technique offers separation and qualitative analysis of photosynthetic pigments using a plate and solvent system?

• HPLC
• TLC (Thin Layer Chromatography)
• Gas chromatography
• Mass spectrometry

Correct Answer: TLC (Thin Layer Chromatography)

Q13. In HPLC analysis of pigments, which detector and wavelength range is typically monitored for chlorophylls?

• Refractive index detector at 200–220 nm
• UV–Vis detector around 400–700 nm
• Fluorescence detector at 800–900 nm
• Electrochemical detector at 300–350 nm

Correct Answer: UV–Vis detector around 400–700 nm

Q14. Which pigment is predominantly responsible for the orange color of many fruits and is a precursor for vitamin A?

• Lutein
• Beta-carotene
• Chlorophyll b
• Neoxanthin

Correct Answer: Beta-carotene

Q15. Which structural component anchors chlorophyll in the thylakoid membrane?

• Porphyrin ring
• Central magnesium ion
• Phytol (hydrophobic) tail
• Formyl group

Correct Answer: Phytol (hydrophobic) tail

Q16. Photosystem II primary pigment that initiates charge separation is associated with which chlorophyll?

• Chlorophyll b
• Chlorophyll c
• P680 (chlorophyll a special pair)
• P700 (chlorophyll a special pair)

Correct Answer: P680 (chlorophyll a special pair)

Q17. Which pigment group is water-soluble and often found in vacuoles rather than membranes?

• Carotenoids
• Chlorophylls
• Anthocyanins
• Xanthophylls

Correct Answer: Anthocyanins

Q18. Which analytical parameter is commonly calculated from spectrophotometric data to estimate chlorophyll concentration?

• Retention factor (Rf)
• Beer–Lambert absorbance coefficient and specific equations
• pH value
• Melting point

Correct Answer: Beer–Lambert absorbance coefficient and specific equations

Q19. Which pigment absorbs light most efficiently in the blue region and transfers energy to chlorophyll a?

• Chlorophyll b
• Anthocyanin
• Carotenoids (e.g., beta-carotene)
• Phycobilin

Correct Answer: Carotenoids (e.g., beta-carotene)

Q20. Phycobiliproteins, such as phycocyanin, are characteristic pigments of which group?

• Cyanobacteria and red algae
• Higher plants
• Fungi
• Green algae exclusively

Correct Answer: Cyanobacteria and red algae

Q21. Which change is observed when chlorophyll is converted to pheophytin?

• Addition of a magnesium ion
• Removal of magnesium ion and color shift to olive-brown
• Lactonization of the porphyrin ring
• Formation of a glycosidic bond

Correct Answer: Removal of magnesium ion and color shift to olive-brown

Q22. Which pigment is most abundant in green leaves and is used as a marker in herbal quality control?

• Anthocyanin
• Chlorophyll a
• Phycocyanin
• Xanthophyll

Correct Answer: Chlorophyll a

Q23. Which reagent is typically used to detect chlorophyll on a TLC plate by visualizing under UV or visible light?

• Anisaldehyde spray
• Viewing under visible light; chlorophylls are naturally colored
• Dragendorff’s reagent
• Ninhydrin

Correct Answer: Viewing under visible light; chlorophylls are naturally colored

Q24. Which property of carotenoids contributes to their role in photoprotection?

• They produce singlet oxygen
• They quench triplet chlorophyll and singlet oxygen
• They bind Mg2+ strongly
• They are water-soluble

Correct Answer: They quench triplet chlorophyll and singlet oxygen

Q25. In the biosynthesis of chlorophyll, which precursor ring structure is common to both heme and chlorophyll pathways?

• Carotene
• Porphyrin (tetrapyrrole) ring
• Flavonoid skeleton
• Steroid nucleus

Correct Answer: Porphyrin (tetrapyrrole) ring

Q26. Which pigment class contains oxygenated carotenoids like lutein and zeaxanthin?

• Carotenes
• Xanthophylls
• Chlorophylls
• Phycobilins

Correct Answer: Xanthophylls

Q27. During sample preparation, why is extraction performed under low light and cool conditions?

• To accelerate pigment synthesis
• To prevent oxidative degradation and photo-bleaching of pigments
• To denature chlorophyllase selectively
• To promote esterification of pigments

Correct Answer: To prevent oxidative degradation and photo-bleaching of pigments

Q28. Which pigment shows fluorescence and is often measured to assess photosynthetic efficiency?

• Carotene
• Chlorophyll a
• Anthocyanin
• Pheophytin

Correct Answer: Chlorophyll a

Q29. The Soret band in chlorophyll absorption spectra refers to a strong peak in which region?

• Near-infrared region (700–800 nm)
• Blue region (~400–450 nm)
• Green region (~500–550 nm)
• Ultraviolet below 300 nm

Correct Answer: Blue region (~400–450 nm)

Q30. Which molecule acts as the central metal ion in chlorophyll?

• Iron (Fe2+)
• Copper (Cu2+)
• Magnesium (Mg2+)
• Zinc (Zn2+)

Correct Answer: Magnesium (Mg2+)

Q31. Which pigment is more polar: chlorophyll or carotenoid, and why?

• Carotenoid, because it has hydroxyl groups
• Chlorophyll, because of polar porphyrin ring and ester groups
• They have equal polarity
• Carotenoid, because of its conjugated double bonds

Correct Answer: Chlorophyll, because of polar porphyrin ring and ester groups

Q32. In standardization of herbal drugs, monitoring pigment content is useful because:

• Pigments determine molecular weight of the herb
• They are indicators of plant maturity, handling and storage conditions
• Pigments are the only active compounds
• They provide no useful information

Correct Answer: They are indicators of plant maturity, handling and storage conditions

Q33. Which pigment is commonly extracted using non-polar solvents like hexane for analysis?

• Chlorophyll a
• Carotenes (e.g., beta-carotene)
• Anthocyanins
• Chlorophyllide

Correct Answer: Carotenes (e.g., beta-carotene)

Q34. Which structural change converts chlorophyll to chlorophyllide?

• Removal of central Mg2+
• Hydrolysis of ester bond removing the phytol tail
• Oxidation of the porphyrin ring
• Hydrogenation of double bonds

Correct Answer: Hydrolysis of ester bond removing the phytol tail

Q35. Which pigment type is commonly used as a natural colorant and has provitamin A activity?

• Chlorophylls
• Carotenoids (beta-carotene)
• Phycobilins
• Flavonoids

Correct Answer: Carotenoids (beta-carotene)

Q36. In photosynthetic membranes, pigments are bound to proteins forming:

• Free pigment micelles
• Membrane pores
• Pigment–protein complexes or light-harvesting complexes
• Cell wall complexes

Correct Answer: Pigment–protein complexes or light-harvesting complexes

Q37. Which pigment would you expect in brown algae instead of abundant chlorophyll a?

• Phycocyanin
• Fucoxanthin (a brown carotenoid)
• Anthocyanin
• Phycoerythrin

Correct Answer: Fucoxanthin (a brown carotenoid)

Q38. Which change indicates oxidative degradation of carotenoids during storage?

• Increase in chlorophyll a peak
• Formation of colorless oxidation products and loss of absorbance in 400–500 nm
• Conversion to phycobilins
• Increase in Rf value on TLC for carotenoids

Correct Answer: Formation of colorless oxidation products and loss of absorbance in 400–500 nm

Q39. Which pigment class contains linear tetrapyrroles bound to proteins in cyanobacteria and red algae?

• Chlorophylls
• Phycobilins (phycobiliproteins)
• Carotenoids
• Xanthophylls

Correct Answer: Phycobilins (phycobiliproteins)

Q40. Which parameter is NOT directly provided by UV–Vis spectroscopy of pigments?

• Absorption maxima (λmax)
• Concentration using Beer–Lambert law
• Exact molecular weight
• Relative purity based on peak shape

Correct Answer: Exact molecular weight

Q41. What is the role of accessory pigments in photosynthesis?

• They act as primary electron donors
• They expand the range of absorbed light and transfer energy to chlorophyll a
• They hydrolyze ATP
• They transport carbon dioxide

Correct Answer: They expand the range of absorbed light and transfer energy to chlorophyll a

Q42. Which structural feature is characteristic of carotenoids?

• Saturated aliphatic chains without conjugation
• Extended conjugated polyene chain of double bonds
• Porphyrin macrocycle
• Peptide backbone

Correct Answer: Extended conjugated polyene chain of double bonds

Q43. During HPLC separation, reversed-phase columns separate pigments primarily based on:

• Molecular weight only
• Polarity/hydrophobic interactions with stationary phase
• Charge interactions exclusively
• Enzymatic activity

Correct Answer: Polarity/hydrophobic interactions with stationary phase

Q44. Which pigment alteration is commonly used as an indicator of leaf senescence?

• Increase in chlorophyll content
• Decrease in chlorophyll and relative increase in carotenoids
• Formation of phycobilins
• Appearance of new chlorophyll types

Correct Answer: Decrease in chlorophyll and relative increase in carotenoids

Q45. Which laboratory precaution reduces enzymatic breakdown of chlorophyll during extraction?

• Using warm extraction solvent at 60°C
• Adding polyvinylpyrrolidone (PVP) and working cold
• Exposing samples to bright sunlight
• Using alkaline water as solvent

Correct Answer: Adding polyvinylpyrrolidone (PVP) and working cold

Q46. The pigment responsible for harvesting light in green sulfur bacteria is:

• Chlorophyll a
• Bacteriochlorophylls (e.g., BChl c, d, e)
• Beta-carotene
• Phycobiliproteins

Correct Answer: Bacteriochlorophylls (e.g., BChl c, d, e)

Q47. Which factor does NOT significantly affect pigment stability in plant extracts?

• Light exposure
• Temperature
• pH of solvent
• Sample barcode number

Correct Answer: Sample barcode number

Q48. Which pigment change is typical when leaves are boiled in acidic water (e.g., cooking)?

• Conversion of chlorophyll to pheophytin causing olive-brown color
• Increase in chlorophyll fluorescence
• Conversion of carotenoids to chlorophyll
• Formation of phycobiliproteins

Correct Answer: Conversion of chlorophyll to pheophytin causing olive-brown color

Q49. Which analytical approach provides both separation and structural information (mass) for pigments?

• TLC with iodine visualization
• HPLC coupled with mass spectrometry (HPLC–MS)
• Simple visible color observation
• Paper chromatography only

Correct Answer: HPLC coupled with mass spectrometry (HPLC–MS)

Q50. For formulation scientists in pharmacy, why is knowledge of photosynthetic pigments important?

• They are irrelevant to pharmaceuticals
• They help in herbal drug standardization, stability testing and identification of active plant constituents
• They determine tablet hardness directly
• They replace the need for microbial tests

Correct Answer: They help in herbal drug standardization, stability testing and identification of active plant constituents

G S Sachin

I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.

Mail- Sachin@pharmacyfreak.com