biology : class11 Biochemical Characters : Importance of Classification, Basis of Classification, Advantages of Classification : Need for Classification MCQ Questions and Answers
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Biochemical Characters
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MCQ Questions
1. An organism has a cell wall containing chitin, stores glycogen as reserve food, and obtains nutrients by absorption. Which biochemical profile most strongly supports its placement in Kingdom Fungi?
A.
Cellulose wall, starch reserve, and photosynthetic nutrition
B.
Chitin wall, glycogen reserve, and absorptive nutrition
C.
Peptidoglycan wall, glycogen reserve, and ingestive nutrition
D.
Silica wall, laminarin reserve, and photosynthetic nutrition
Correct Answer:
Chitin wall, glycogen reserve, and absorptive nutrition
Explanation:
Fungi are chemically characterized by chitin in the cell wall, glycogen as a reserve carbohydrate, and absorption of externally digested nutrients.
2. Which combination of biochemical characters best distinguishes typical green plants from animals in a five-kingdom classification scheme?
A.
Chitinous wall and glycogen reserve
B.
Cellulose wall, starch reserve, and chlorophyll-based photosynthesis
C.
Peptidoglycan wall and glycogen reserve
D.
No cell wall, glycogen reserve, and ingestive nutrition
Correct Answer:
Cellulose wall, starch reserve, and chlorophyll-based photosynthesis
Explanation:
Typical plants possess cellulose cell walls, commonly store food as starch, and synthesize organic matter using chlorophyll, whereas animals lack cell walls and store glycogen.
3. A unicellular organism possesses a peptidoglycan cell wall, membrane-bound respiratory enzymes, and no membrane-bound nucleus. Which biochemical character is most decisive for assigning it to the prokaryotic group?
A.
Presence of peptidoglycan in the cell wall
B.
Presence of respiratory enzymes
C.
Absence of chlorophyll pigments
D.
Ability to synthesize proteins
Correct Answer:
Presence of peptidoglycan in the cell wall
Explanation:
Peptidoglycan is a characteristic biochemical component of bacterial cell walls and is therefore a useful chemical character in recognizing typical prokaryotic bacteria.
4. Two photosynthetic organisms are compared. Organism X contains chlorophyll a and b and stores starch, whereas organism Y contains chlorophyll a and phycobilin pigments and stores cyanophycean starch. Which inference is most appropriate?
A.
Both must belong to the same photosynthetic group because both contain chlorophyll a
B.
X shows a biochemical profile typical of green plants, whereas Y shows a profile associated with cyanobacteria
C.
X is a fungus and Y is an animal because both contain accessory pigments
D.
Y must be a green plant because phycobilins are present in all green plants
Correct Answer:
X shows a biochemical profile typical of green plants, whereas Y shows a profile associated with cyanobacteria
Explanation:
Chlorophyll b with starch storage is characteristic of green plants, while phycobilins and cyanophycean starch are characteristic biochemical features of cyanobacteria.
5. Which biochemical combination is most consistent with brown algae rather than green algae?
A.
Chlorophyll a and b with starch as the chief reserve
B.
Chlorophyll a and c with fucoxanthin and laminarin as reserve food
C.
Bacteriochlorophyll with peptidoglycan and glycogen
D.
Phycobilins with cellulose-free walls and cyanophycean starch
Correct Answer:
Chlorophyll a and c with fucoxanthin and laminarin as reserve food
Explanation:
Brown algae characteristically contain fucoxanthin along with chlorophyll a and c, and commonly store food as laminarin, distinguishing them biochemically from green algae.
6. A classification system separates organisms using the chemical nature of their reserve food. Which pairing is correctly matched?
A.
Fungi—starch; animals—cellulose
B.
Green plants—glycogen; fungi—laminarin
C.
Animals—glycogen; green plants—starch
D.
Brown algae—glycogen; bacteria—cellulose
Correct Answer:
Animals—glycogen; green plants—starch
Explanation:
The nature of stored carbohydrates is a biochemical character: animals generally store glycogen, whereas green plants characteristically store starch.
7. An organism has a cell wall made of cellulose, contains chlorophyll a and c with fucoxanthin, and stores laminarin and mannitol. Which biochemical evidence most strongly prevents its classification as a typical green alga?
A.
The presence of a cell wall
B.
The presence of chlorophyll a
C.
The presence of fucoxanthin and laminarin
D.
The ability to perform photosynthesis
Correct Answer:
The presence of fucoxanthin and laminarin
Explanation:
Fucoxanthin pigment and laminarin reserve food are characteristic biochemical features of brown algae, unlike the chlorophyll b and starch profile typical of green algae.
8. Which set of biochemical characters would most reliably distinguish a fungus from a non-photosynthetic animal-like protist?
A.
Presence of glycogen alone
B.
Absence of chlorophyll alone
C.
Chitinous wall combined with absorptive nutrition
D.
Presence of mitochondria combined with aerobic respiration
Correct Answer:
Chitinous wall combined with absorptive nutrition
Explanation:
Glycogen storage and lack of chlorophyll can occur in several groups, but a chitinous wall together with absorptive nutrition provides a stronger biochemical basis for recognizing fungi.
9. A photosynthetic organism contains chlorophyll a and d, phycobilin pigments, and floridean starch stored outside the chloroplast. Which biochemical profile is most consistent with red algae?
A.
Red algal profile
B.
Green algal profile
C.
Brown algal profile
D.
Fungal profile
Correct Answer:
Red algal profile
Explanation:
Red algae characteristically possess phycobilin pigments, may contain chlorophyll d, and store floridean starch outside the chloroplast.
10. Why are biochemical characters especially useful when classifying organisms that appear similar in external form?
A.
They replace all other criteria and make morphology unnecessary
B.
They reveal differences in pigments, wall materials, and reserve foods that may remain hidden externally
C.
They classify organisms solely according to habitat
D.
They ensure that organisms with the same body shape always belong to the same kingdom
Correct Answer:
They reveal differences in pigments, wall materials, and reserve foods that may remain hidden externally
Explanation:
Biochemical characters provide evidence from substances such as pigments, cell-wall components, and storage products, helping distinguish superficially similar organisms and improving classification.
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