Pigments involved in photo synthesis Questions in English

(A) Chlorophyll is the primary photosynthetic pigment responsible for trapping light energy.
In eukaryotic plants,chlorophyll is located within the thylakoid membranes of the chloroplast.
The thylakoids are stacked to form structures known as $Grana$ (singular: $Granum$).
Therefore,chlorophyll is specifically found in the $Grana$ of the chloroplast,where the light-dependent reactions of photosynthesis occur.

(B) Plastocyanin is a copper-containing protein that acts as an electron carrier in the photosynthetic electron transport chain.
It facilitates the transfer of electrons from the cytochrome $b_6f$ complex to Photosystem $I$ $(PSI)$.
Ferredoxin is an iron-sulfur protein,and cytochromes are heme-containing proteins (iron-porphyrin complexes).
Therefore,the correct answer is Plastocyanin.

(D) Phycobilins are water-soluble accessory pigments found in cyanobacteria and red algae.
They function as light-harvesting complexes that capture light energy and transfer it to the reaction centers of photosystems.
Phycobilins are associated with both $PS-I$ and $PS-II$ in these organisms to facilitate efficient energy transfer.
Since phycobilins are present in cyanobacteria and are associated with both photosystems,none of the given options correctly identify what they are $NOT$ associated with.
However,in the context of standard textbook questions where this is often posed,if the question implies which system they are $NOT$ exclusively part of,it is a trick question.
Given the options provided,since they are associated with $PS-I$,$PS-II$,and cyanobacteria,the correct answer is that they are associated with all of these,making the premise of the question '$NOT$ associated' invalid for the given choices.

(C) $Chlorophyll$ is a lipid-soluble pigment.
It is insoluble in water but dissolves readily in organic solvents such as $acetone$,$ether$,$alcohol$,and $chloroform$.

(B) The effectiveness of light for photosynthesis is determined by the absorption spectrum of chlorophyll pigments. Chlorophyll $a$ and $b$ absorb light most efficiently in the blue and red regions of the visible spectrum. Among these,the blue region $(430-450 \ nm)$ is generally more effective than the red region $(640-680 \ nm)$. Yellow and orange wavelengths are absorbed much less efficiently by these pigments. Therefore,the correct order of photosynthetic effectiveness is $Blue > Red > Yellow > Orange$.

(A) During the process of photosynthesis,the light-harvesting complexes $(LHC)$ contain pigment molecules.
When light energy (photons) strikes the chlorophyll molecules,the electrons in the chlorophyll absorb this energy and jump to a higher energy state,becoming 'excited'.
This excitation of chlorophyll is the primary photochemical event that initiates the light-dependent reactions of photosynthesis.

(C) Carotenes and xanthophylls are accessory pigments found in chloroplasts.
These pigments absorb light energy and transfer it to chlorophyll-$a$.
Crucially,they also protect the chlorophyll molecules from photo-oxidation by absorbing excess light energy that could otherwise damage the chlorophyll pigments.

(B) Protochlorophyll is the immediate precursor of chlorophyll in the biosynthetic pathway of plants.
In the presence of light,protochlorophyll is converted into chlorophyll by the enzyme protochlorophyllide reductase.
This process is a light-dependent step in the synthesis of chlorophyll $a$.

(A) The chlorophyll molecule consists of a porphyrin head and a phytol tail. The porphyrin head is a tetrapyrrole ring structure. At the center of this porphyrin ring,a single magnesium $(Mg^{2+})$ ion is coordinated by four nitrogen atoms from the pyrrole rings. This central magnesium atom is essential for the stability and light-harvesting function of the chlorophyll molecule.

(B) Photosynthesis primarily occurs in the red and blue regions of the visible light spectrum. Chlorophyll pigments absorb light most efficiently in these wavelengths. Green light is largely reflected or transmitted by the leaves,which is why plants appear green to our eyes. Therefore,green light is the least effective or not significantly used during the process of photosynthesis.

(D) The unit of photosynthesis is known as the $Quantasome$.
$Quantasomes$ are granular structures found in the thylakoid membranes of chloroplasts.
They contain a specific number of chlorophyll and accessory pigment molecules,which act as the functional units for capturing light energy during the light-dependent reactions of photosynthesis.

(B) The chlorophyll molecule is a porphyrin derivative. It consists of a central magnesium ion $(Mg^{2+})$ coordinated to four nitrogen atoms of the porphyrin ring. This structure is essential for the absorption of light energy during the process of photosynthesis.

(B) Quantasomes are granular structures found on the thylakoid membranes of the chloroplasts.
They are considered the photosynthetic units that contain chlorophyll and other pigments required for the light-dependent reactions of photosynthesis.
Therefore,the correct answer is $B$ (Chloroplast).

(C) Chlorophyll $a$ is the primary photosynthetic pigment.
According to the absorption spectrum of chlorophyll $a$,it shows two major absorption peaks.
The first peak is in the blue region (approximately $430-450 \ nm$) and the second peak is in the red region (approximately $640-680 \ nm$).
Among these,the absorption in the blue region is generally higher than in the red region.
Therefore,chlorophyll $a$ absorbs blue light most effectively.

(C) Chlorophyll molecules are pigments involved in photosynthesis.
Most chlorophylls,such as $Chl. \ a$,$Chl. \ b$,and $Chl. \ d$,possess a long hydrophobic phytol tail $(C_{20}H_{39}OH)$ attached to the porphyrin ring,which anchors them into the thylakoid membrane.
However,$Chl. \ c$ is unique because it lacks this phytol tail.
Instead,it has an acrylic acid group at the $C-17$ position,making it more polar than other chlorophylls.

(C) Chlorophyll molecules typically consist of a porphyrin head and a long hydrophobic phytol tail.
Chlorophyll $a$ and $b$ possess this phytol tail,which anchors the molecule into the thylakoid membrane.
However,Chlorophyll $c$,which is found in certain algae like diatoms and brown algae,lacks the phytol tail.
Instead,it has an acrylic acid side chain at the $C-17$ position,making it more polar than other chlorophylls.

(C) The extensive study of photosynthetic pigments,their structure,and their role in light absorption and energy transfer was primarily carried out by the renowned scientist $Govindjee$. His work significantly contributed to our understanding of the $Z$-scheme and the efficiency of light-harvesting complexes in plants.

(C) Chlorophyll $a$ is the primary photosynthetic pigment found in plants,algae,and cyanobacteria.
Its chemical structure consists of a porphyrin ring with a central magnesium $(Mg)$ atom and a long phytol tail.
The molecular formula for chlorophyll $a$ is $C_{55}H_{72}O_5N_4Mg$.
In contrast,chlorophyll $b$ has the formula $C_{55}H_{70}O_6N_4Mg$,where a methyl group $(-CH_3)$ in chlorophyll $a$ is replaced by an aldehyde group $(-CHO)$.

(B) Bacteriochlorophyll is a photosynthetic pigment found in certain bacteria.
It differs from chlorophyll $a$ primarily in the structure of its porphyrin ring.
In bacteriochlorophyll,one of the pyrrole rings (specifically ring $I$) is reduced,meaning it contains two additional hydrogen atoms compared to the corresponding ring in chlorophyll $a$.
Therefore,the presence of a pyrrole nucleus containing two hydrogens (a reduced pyrrole ring) is the key structural difference.

(A) Carotene is a type of carotenoid pigment found in plants.
It is a hydrocarbon pigment,meaning it consists only of carbon and hydrogen atoms.
The chemical formula for $\beta$-carotene,the most common form of carotene,is $C_{40}H_{56}$.
Therefore,the correct option is $A$.

(D) Bacteriochlorophyll $a$ is a photosynthetic pigment found in purple bacteria.
Its molecular structure is similar to chlorophyll $a$,but it contains an acetyl group instead of a vinyl group at the $C-3$ position and a saturated bond between $C-7$ and $C-8$ in the porphyrin ring.
The chemical formula for bacteriochlorophyll $a$ is $C_{55}H_{74}O_6N_4Mg$.

(D) The chlorophyll molecule consists of a porphyrin head and a phytol tail.
The porphyrin head is a square-like structure with dimensions approximately $15 \times 15 \ \mathring{A}$ (often cited as $15 \times 10 \ \mathring{A}$ in some contexts,but $15 \times 15 \ \mathring{A}$ is the standard structural approximation for the porphyrin ring).
The phytol tail is a long hydrocarbon chain with a length of approximately $20 \ \mathring{A}$.
Therefore,the accepted dimensions are Head: $15 \times 15 \ \mathring{A}$ and Tail: $20 \ \mathring{A}$.

(C) Carotenoids are a class of pigments found in plants and microorganisms.
Chemically,they are classified as terpenoids.
Terpenoids are synthesized from $5$-carbon building blocks known as isoprene units $(C_5H_8)$.
Therefore,carotenoids are composed of repeating isoprene units.

(B) The functional unit of the chloroplast is the $Quantasome$.
$Quantasomes$ are granular structures found on the thylakoid membranes of chloroplasts.
They contain the photosynthetic pigments (chlorophylls and carotenoids) and are responsible for the light-dependent reactions of photosynthesis.
Therefore,they are considered the functional units of the chloroplast.

(C) Chlorophyll is the primary photosynthetic pigment located within the chloroplasts of plant cells.
Specifically,chlorophyll molecules are embedded in the thylakoid membranes.
The thylakoids are flattened,sac-like structures stacked to form grana.
Since the light-dependent reactions of photosynthesis occur on the thylakoid membranes,chlorophyll is essential there to capture light energy.

(B) Chloroplasts are the sites of photosynthesis in plants.
Inside the chloroplast,there is a system of flattened,sac-like structures called thylakoids.
Chlorophyll pigments are embedded within the thylakoid membranes,where they capture light energy for the light-dependent reactions of photosynthesis.
Therefore,the correct location of chlorophyll is the thylakoid.

(B) Chloroplasts are double-membrane-bound organelles found in plant cells.
Inside the chloroplast,there is a system of flattened,sac-like structures called thylakoids.
Chlorophyll pigments are embedded within the thylakoid membranes,which are responsible for capturing light energy during photosynthesis.
Therefore,the correct location of chlorophyll is the thylakoids.

(D) Hemoglobin,myoglobin,and cytochromes are all iron-containing compounds. Hemoglobin and myoglobin are heme proteins that transport or store oxygen,while cytochromes are iron-containing hemoproteins involved in the electron transport chain. Chlorophyll,the green pigment in plants,contains a magnesium $(Mg^{2+})$ ion at the center of its porphyrin ring,not iron.

(C) Chlorophyll is a complex organic molecule that acts as a pigment in plants. Chemically,it is a porphyrin derivative. It consists of a porphyrin ring (a tetrapyrrole ring) with a central magnesium $(Mg^{2+})$ ion. While it is not a carbohydrate,protein,or steroid,it is often classified as a lipid-soluble pigment. Among the given options,it is most closely associated with the structure of lipids or complex organic compounds,but strictly speaking,it is a magnesium-porphyrin complex. However,in many biological contexts,it is categorized as a specialized pigment molecule. Given the standard options provided,it does not fit perfectly into the four categories,but it is definitely not a carbohydrate,protein,or steroid. If forced to choose based on its hydrophobic nature,it is often studied alongside lipids,but it is chemically a porphyrin derivative.

(A) Chlorophyll is a pigment molecule that acts as a conjugated protein complex in photosynthetic organisms. It consists of a porphyrin ring (a prosthetic group) containing a magnesium ion at its center,which is associated with a protein structure. This complex is essential for capturing light energy during the process of photosynthesis.

(B) $NADP$ stands for Nicotinamide Adenine Dinucleotide Phosphate.
It is a coenzyme that acts as an electron carrier in various metabolic reactions,particularly in photosynthesis.

(B) : Anthocyanins are water-soluble pigments that are commonly found in membrane-bound vacuoles. They are responsible for the red,purple,and blue colors of many fruits and flower petals.

(B) Chlorophyll is a green pigment found in plants that is essential for photosynthesis.
Its molecular structure consists of a porphyrin ring with a central metal ion.
The central metal ion present in the core of the chlorophyll molecule is $Mg^{2+}$ (magnesium).
Therefore,the correct option is $B$.

(A) In a photosystem,the reaction center is formed by a single molecule of chlorophyll-$a$.
All other pigments,including chlorophyll-$b$,carotenoids,and xanthophylls,are part of the light-harvesting complex $(LHC)$ or antennae complex.
These accessory pigments absorb light at different wavelengths and transfer the energy to the reaction center (chlorophyll-$a$).
Therefore,chlorophyll-$a$ is the only pigment that is not part of the antennae complex,as it acts as the reaction center.

(B) Phycobilins,which include phycocyanin and phycoerythrin,are accessory photosynthetic pigments found in cyanobacteria and red algae.
Unlike chlorophylls and carotenoids,which are lipid-soluble and associated with membranes,phycobilins are water-soluble proteins.
They are covalently bonded to specific proteins to form phycobiliproteins,which function in light harvesting.
Therefore,phycocyanin is the correct answer.

(B) The pigments involved in photosynthesis exhibit specific colors in chromatograms:
$1.$ Chlorophyll-$a$ appears bright or blue-green.
$2.$ Chlorophyll-$b$ appears yellow-green.
$3.$ Xanthophylls appear yellow.
$4.$ Carotenoids appear yellow to yellow-orange.
Matching these with the given columns:
$a.$ Yellow to yellow-orange corresponds to $3.$ Carotenoids.
$b.$ Green corresponds to $1.$ Chlorophyll-$a$.
$c.$ Yellow corresponds to $2.$ Xanthophyll.
Thus,the correct match is $(a-3), (b-1), (c-2)$.

(D) Accessory pigments are pigments that absorb light energy and transfer it to chlorophyll $a$,which is the primary pigment involved in photosynthesis.
These pigments include chlorophyll $b$,carotenoids,and xanthophylls.
They broaden the spectrum of light that can be absorbed for photosynthesis and also protect chlorophyll $a$ from photo-oxidation.
Therefore,all the given options are correct.

(B) In the light-harvesting complex of photosynthesis,the antenna molecules (pigment molecules) absorb light energy and transfer it to the reaction centre.
In the provided figure,$X$ represents the light-harvesting pigment molecules that capture light energy.
The energy is then transferred to the reaction centre,which then passes an electron to the primary electron acceptor,represented by $Y$.
Therefore,$X$ refers to pigment molecules and $Y$ refers to the primary acceptor.

(D) Photosynthetic pigments are classified into two categories: primary pigments and accessory pigments.
$1$. Primary Pigment: Chlorophyll-$a$ is the primary pigment because it is directly involved in the light reaction of photosynthesis by converting light energy into chemical energy.
$2$. Accessory Pigments: Chlorophyll-$b$,carotenoids,and xanthophylls are accessory pigments. They absorb light energy and transfer it to chlorophyll-$a$,and also protect chlorophyll-$a$ from photo-oxidation.
Therefore,chlorophyll-$a$ is not an accessory pigment.

(B) The incorrect statement is that $LHC$ are made up of pigment molecules bound to carbohydrates. In reality,the pigment molecules in the $LHC$ are bound to proteins,not carbohydrates. The $LHC$ consists of hundreds of pigment molecules bound to proteins. Each photosystem has all the pigments (except one molecule of chlorophyll $a$) forming a light-harvesting system also called antennae. These pigments help to make photosynthesis more efficient by absorbing different wavelengths of light.

(D) Photosynthesis is the process by which green plants and some other organisms use sunlight to synthesize foods with the help of chlorophyll.
Chlorophyll is the primary pigment required for photosynthesis.
This pigment is located within the thylakoid membranes of the chloroplast.
Therefore,the chloroplast is the organelle where the essential material for photosynthesis is present.

(A) Chlorophyll is the primary photosynthetic pigment found in chloroplasts.
In higher plants,chloroplasts contain a system of thylakoids,which are flattened sac-like structures.
These thylakoids are stacked like coins to form structures called grana.
Chlorophyll molecules are embedded within the thylakoid membranes of the grana,where they capture light energy for the light-dependent reactions of photosynthesis.
Therefore,the correct location for chlorophyll is the grana.

(B) Chlorophyll is a green pigment found in the chloroplasts of plants,which is essential for photosynthesis.
Its molecular structure consists of a porphyrin ring with a central metal ion.
The central metal ion coordinated within the porphyrin ring of the chlorophyll molecule is $Mg^{2+}$ (Magnesium ion).
Therefore,the correct option is $B$.

(C) The chlorophyll molecule consists of a porphyrin head and a phytol tail.
The porphyrin head is a square-shaped structure with dimensions of approximately $15 \times 15 \mathring A$.
The phytol tail is a long hydrocarbon chain attached to the head,which is approximately $20 \mathring A$ in length.
Therefore,the correct dimensions are Head $15 \times 15 \mathring A$ and Tail $20 \mathring A$.

(A) Photosynthetic pigments such as chlorophyll $a$,chlorophyll $b$,xanthophylls,and carotenoids are embedded within the thylakoid membranes of the chloroplast.
These pigments are organized into photosystems ($PS-I$ and $PS-II$) which are essential for capturing light energy during the light-dependent reactions of photosynthesis.

(C) Chlorophyll $a$ is the primary photosynthetic pigment found in all oxygen-evolving photosynthetic organisms.
It acts as the reaction center in both Photosystem $I$ and Photosystem $II$.
While other pigments like chlorophyll $b$,carotenoids,and xanthophylls are accessory pigments,chlorophyll $a$ is essential for the conversion of light energy into chemical energy during the light-dependent reactions of photosynthesis.

(B) Chlorophyll $a$ $(C_{55}H_{72}O_5N_4Mg)$ is the primary photosynthetic pigment.
Its structure consists of a porphyrin head and a phytol tail.
The porphyrin head is composed of four pyrrole rings $(I, II, III, IV)$ linked by methine bridges.
In chlorophyll $a$,the carbon atom $3$ of pyrrole ring $II$ is attached to a methyl group $(-CH_3)$.
In contrast,chlorophyll $b$ has an aldehyde group $(-CHO)$ at the same position.

(A) Protochlorophyll is the immediate precursor to chlorophyll $a$ in the biosynthetic pathway of chlorophyll.
The structural difference between protochlorophyll and chlorophyll $a$ is the presence of two additional hydrogen atoms in the $IV$ pyrrole ring of the chlorophyll molecule.
Therefore,protochlorophyll lacks these $2$ hydrogen atoms compared to chlorophyll $a$ in one of its pyrrole rings.

(A) Photosynthesis is the process by which green plants convert light energy into chemical energy.
Chlorophyll is the primary photosynthetic pigment located in the thylakoid membranes of chloroplasts.
It is responsible for absorbing light energy,primarily in the blue and red regions of the electromagnetic spectrum,which then drives the light-dependent reactions of photosynthesis.

(C) The chlorophyll molecule consists of a porphyrin head and a phytol tail.
The porphyrin head is a tetrapyrrole ring structure.
At the center of this porphyrin ring,a single $Mg^{2+}$ (magnesium) ion is coordinated.
This magnesium ion is essential for the light-harvesting function of chlorophyll.