Biology

Photosynthesis in Plants

1,508 Questions

Photosynthesis is the biological process by which plants convert light energy into chemical energy. This page contains practice questions covering essential topics like chlorophyll, light reactions, and the pathways specific to plants. This material is crucial for medical entrance exams and academic assessments.

Chlorophyll and pigmentsLight reactionsCalvin cycleCAM plantsElectron transportPhotosynthesis factors

Photosynthesis in Plants Questions

Multiple choice photosystems photosynthesis in plants metabolism, cell respiration, and photosynthesis photosynthesis in higher plants biology

In PS I, the carrier that picks up electrons from $P _{700}$ is

  1. Fe protein

  2. Fe-S protein

  3. Fe-Cu protein

  4. Fe-Mg protein
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A photosystem is composed of chlorophyll 'a' molecule which can absorb the wavelength of 700 nm. The chlorophyll a molecule acts as a reaction centre. PS-I is involved in a non-cyclic type of photophosphorylation where there is a chain of electron carriers and acceptors that transmits the electron from one to another. The primary electron acceptor is the ferredoxin molecule which is composed of Fe-S protein

So, the correct option is Fe-S protein'

Multiple choice photosystems photosynthesis in plants metabolism, cell respiration, and photosynthesis photosynthesis in higher plants biology

In pigment system II, active chlorophyll is

  1. $P _{680}$
  2. $P _{700}$
  3. $P _{673}$
  4. $P _{720}$.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The plant needed enough energy to do the biosynthetic reactions. Its reaction centre is a molecule called P680 which absorbs light maximally at 680 nm.

So the correct option is 'P$ _6$$ _8$$ _0$.'

Multiple choice photosystems photosynthesis in plants metabolism, cell respiration, and photosynthesis photosynthesis in higher plants biology

Pigment system- I conducts

  1. Cyclic photophosphorylation

  2. Non-cyclic photophosphorylation

  3. Both (A) and (B)

  4. None of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Z scheme of light reaction is non cyclic fow of electron from PSII through quinone, cyt b6b6 f complex and plastocyanin to NADPH via PSI; it does not return to PSII. NADP reductase enzyme is located on stromal side of PSI; Z scheme includes both PSI and PSII. Absence of PS-II leads to cyclic photophosphorylation in which electrons are passed from PS-I, via electron transfer chain, to back to PS-I with formation of ATP. Cyclic photophosphorylation does not pass electrons to NADP; rather electrons are passed back to PSI. PS I is involved in both cyclic and non cyclic photophosphorylation. Correct answer is B.

Multiple choice photosystems photosynthesis in plants metabolism, cell respiration, and photosynthesis photosynthesis in higher plants biology

Photosynthesis is least in which wavelength of light?

  1. 450 nm

  2. 550 nm

  3. 650 nm

  4. 700 nm
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Two main photosynthetic pigment chlorophyll a and chlorophyll b absorb light in violet blue (400 -500 nm) and red (620-700nm) region of visible spectrum. Neither of these pigments absorbs light between 500 to 600 nm (green light) causing least photosynthesis in this wavelegnth. Thus, the correct answer is option B.

Multiple choice photosystems photosynthesis in plants metabolism, cell respiration, and photosynthesis photosynthesis in higher plants biology

Bacterial photosynthesis contains

  1. PS I.

  2. PS II.

  3. Both PS I and PS II.

  4. None of the above.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Photosynthetic bacteria are anaerobic and only one type of photosystem is found in them but cyanobacteria or blue-green algae have both systems PSI and PSII.  It has two types of pigments bacteriochlorophyll which differs from chlorophyll a, in having one pyrrole ring with two hydrogens and bactericidin.

So the correct option is 'PS I'.

Multiple choice photosystems photosynthesis in plants metabolism, cell respiration, and photosynthesis photosynthesis in higher plants biology

In photosystem- I, the first electron acceptor is

  1. Plastocyanin

  2. An iron-sulphur protein

  3. Ferredoxin

  4. Cytochrome
Reveal answer Fill a bubble to check yourself
B,C Correct answer
Explanation

PSI passes electron to ferredoxin on stromal side of lumen. Ferredoxin (iron sulfur protein) receives electrons from PSI and reduces to NADP+ to form NADPH. This light reaction is catalyzed by the membrane-bound enzyme NADP reductase. Both B and C are correct answers. 

Multiple choice photosystems photosynthesis in plants metabolism, cell respiration, and photosynthesis photosynthesis in higher plants biology

PS II contains a non-chlorophyllous pigment in blue-green algae

  1. $\beta$-carotene

  2. Zeaxanthin

  3. Phycocyanin

  4. Cytochrome c.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Photosynthetic bacteria are anaerobic and only one type of photosystem is found in them but cyanobacteria or blue-green algae have both systems PSI and PSII. In PS I contain only one chlorophyll that is chlorophyll a while PS II contains various yellowish carotenoids and phycocyanin that differ in colour in different species.

So the correct option is 'Phycocyanin'.

Multiple choice photosystems photosynthesis in plants metabolism, cell respiration, and photosynthesis photosynthesis in higher plants biology

Which is sensitive to longer wavelengths of light

  1. PS II

  2. PS I

  3. Phosphorylation

  4. Photolysis.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Photosystems are the functional and structural unit of photosynthesis that contains chlorophyll and various electron carriers that helps in energy liberation.

These are divided into two in which photosystem I absorb light of wavelength 700 nm and photosystem II which absorbs light of wavelength 680 nm.
So the correct option is 'PS I'.

Multiple choice photosystems photosynthesis in plants metabolism, cell respiration, and photosynthesis photosynthesis in higher plants biology

Photo-oxidation or photolysis of water (in photosynthesis) occurs in association of

  1. Cytochrome $b _6$f

  2. Plastocyanin

  3. PS II

  4. PS I
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Photolysis of water is carried out to fulfill the need of electrons that are given by photosystem II to photosystem I in the Z scheme. The splitting of water is associated with PSII in which water is split into H$^+$, [O] and electrons and this also creates oxygen, one of the net product of photosynthesis.

So, the correct option is 'PS II'.

Multiple choice photosystems photosynthesis in plants metabolism, cell respiration, and photosynthesis photosynthesis in higher plants biology

Constituents of pigment system I are located on

  1. Granal thylakoids

  2. Stromal thylakoids

  3. Outer surface of granal and stromal thylakoids

  4. Stroma.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The constituents of PS I is located in the thylakoid membrane of stroma and the outer surface of grana, contain a number of light-harvesting complexes and a reaction centre complex, which is a protein complex with two special chlorophyll a molecules and a primary electron acceptor.

So the correct option is 'Outer surface of granal and stromal thylakoids'.

Multiple choice photosystems photosynthesis in plants metabolism, cell respiration, and photosynthesis photosynthesis in higher plants biology

Pigment system connected with oxidation of water is

  1. Photosystem I

  2. Photosystem II

  3. Phycobilisome

  4. Carotenoids
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Photosystem II (or water-plastoquinone oxidoreductase) is the first protein complex in the light-dependent reactions of oxygenic photosynthesis. It is located in the thylakoid membrane of plants, algae and cyanobacteria. Within the photosystem, enzymes capture photons of light to energize electrons that are then transferred through a variety of co-enzymes and co-factors to reduce plastoquinone to plastoquinol. The energized electrons are replaced by oxidizing water to form hydrogen ions and molecular oxygen.


So, the correct option is 'Option  B'.

Multiple choice photosystems photosynthesis in plants metabolism, cell respiration, and photosynthesis photosynthesis in higher plants biology

Reaction centre of PS I is

  1. $P _{700}$
  2. $P _{680}$
  3. $Chl _{715}$
  4. $Chl _{685}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Each photosystem is characterized by the wavelength of light at which it's reaction center absorbs maximum light i.e., 700 and 680 nanometers, respectively for PS I and PS II in chloroplasts. thus PS I is denoted by P$ _{700}$. Thus, the correct answer is 'P$ _{700}$'.

Multiple choice photosystems photosynthesis in plants metabolism, cell respiration, and photosynthesis photosynthesis in higher plants biology

Electrons from excited chlorophyll of PS II are accepted first by

  1. Quinone

  2. Ferredoxin

  3. Cytochrome b

  4. Cytochrome f
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A) Electrons from excited chlorphyll molecule of photosystem II are accepted first by Quinone.

B) Ferredoxin is an electron carrier. During photosynthesis, electrons are removed from water and transferred to ferredoxin.
C) Cytochrome b is a protein found in the mitochondria of eukaryotic cells. It functions as part of the electron transport chain.
D) Cytochrome f is the largest subunit of the cytochrome complex.  It functions as part of the electron transport chain.
So the correct answer is 'Quinone'.

Multiple choice photosystems photosynthesis in plants metabolism, cell respiration, and photosynthesis photosynthesis in higher plants biology

PS II accepts electrons from

  1. $OH^-$
  2. $O^{2-}$
  3. $H^+$

  4. Both A and C
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Water is split in chloroplasts in the light reaction of photosynthesis. Chlorophyll, acting as a photopigment, captures sunlight and transfers that energy to an electron pair of a water molecule. Water molecule is separated into 2 protons, molecular oxygen and a free electron pair, which then enters to PS II and accepted by plastoquinone and carried by variety of electron acceptors in a series of redox potential. The excited electrons are used for photolysis of water generating oxygen and protons which then used in synthesis of ATP and NADPH.

Multiple choice photosystems photosynthesis in plants metabolism, cell respiration, and photosynthesis photosynthesis in higher plants biology

Last electron acceptor of PS I is

  1. Ferredoxin
  2. Cyt $b _6$

  3. Plastocyanin

  4. Plastoquinone
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In the electron transport process, the excited electron from P$ _{680}$ is accepted by primary acceptor quinone, which sends them to an electron transport system consisting of plastoquinone, cytochrome complex and plastocyanin.

The excited electron absorbed by P$ _{700}$ reaction centre, then transfer to the ferredoxin (Fe), then the reduced Ferredoxin donates the electron to NADP$^+$.

The NADP$^+$ take an electron from ferredoxin, protons from the medium and get reduced to NADPH in presence of enzyme ferredoxin- NADP- reductase. So, the last electron acceptor of PS I is ferredoxin.

Hence, the correct answer is 'Ferredoxin'.