Biology

Photosynthesis in Plants

1,492 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

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

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

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'.

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

Electrons from excited chlorophyll molecule of photosystem II are accepted first by

  1. Ferredoxin

  2. Pheophytin

  3. Cytochrome b

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

When the pigment in the reaction center of PS II (P$ _{680}$) absorbs a photon, an electron in this molecule gets excited and first transferred to electron acceptor namely pheophytin then to a series of redox molecules. The electron flow goes from Photosystem II to Photosystem I. It utilizes absorbed light for electron transport from plastocyanin on the lumenal side to ferredoxin on the stromal side of the thylakoid membrane to generate NADPH and ATP. 

Thus, the correct answer is 'Pheophytin'.

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

In PS I, the reaction centre chlorophyll a has an absorption peak at

  1. 650 nm

  2. 660 nm

  3. 680 nm

  4. 700 nm
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Photosystems are the protein complexes involved in photosynthesis. Each photosystem is characterized by the wavelength of light to which its reaction centre is most reactive. Photosystem I, reaction centre pigment chlorophyll a has absorption peak at 700nm. Thus photosystem I is also known as P$ _{700}$
So, the correct answer is '700 nm'
Multiple choice photosystems photosynthesis in plants metabolism, cell respiration, and photosynthesis photosynthesis in higher plants biology

Consider the following.
a. Cytochrome $b6$
b. Cytochrome II f
c. Plastocynin
d. Plastoquinone
What is the correct sequence of these in the photo-induced electron carriers between PS$1$ to PS$2$ in photosynthesis?

  1. $4, 1, 2, 3$
  2. $3, 4, 1, 2$
  3. $1, 2, 3, 4$
  4. $2, 3, 4, 1$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In the electron transport chain of photosynthesis, electrons flow from PS2 to PS1. The sequence is Plastoquinone (4), Cytochrome b6 (1), Cytochrome f (2), and Plastocyanin (3).

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

PS II is physically located on which side of thylakoid membrane?

  1. Inner side

  2. Outer sicde

  3. Within the lumen of thylakoid

  4. Position of PS II shifts from inner to outside
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Photosystem II or Pigment system II, a multiprotein complex involved in the non cyclic electron, proton translocation and photophosphorylation. It is located in the inner side of the thylakoid membrane.

So, the correct option is ‘Inner side’.

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

Choose the correct answer from the alternatives given.
Which of the following is a strong inhibitor of PS-II in photosynthesis

  1. Dichlorophenyl dimethyl urea

  2. Ethylene

  3. Indole acetic acid

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

DCMU (Dichlorophenyl dimethyl urea) is a herbicide which most effectively inhibits PSII in photosynthesis by the stopping CO$ _2$ fixation, which is essential for photosynthesis.

Thus, the correct answer is 'Dichlorophenyl dimethyl urea.'

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

Which of the following is wrongly matched?

  1. Sorghum - Kranz anatomy

  2. PEP carboxylase - Mesophyll cells

  3. Blackman - Law of limiting factors

  4. PS II - p700
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The core of PSII consists of a pseudo-symmetric heterodimer of two homologous proteins D1 and D2. The reaction center chlorophyll (or the primary electron donor) of photosystem II that is most reactive and best in absorbing light at wavelength of 680 nm. P680 is a group of pigments that are excitonically coupled or that act as if the pigments are a single molecule when they absorb a photon.

Thus, the correct answer is 'PS II - p700.'

Multiple choice photosystems photosynthesis in plants metabolism, cell respiration, and photosynthesis photosynthesis in higher plants biology
PS II is located on ____________.

  1. Inner side of thylakoid membrane

  2. Outer side of thylakoid membrane

  3. Lumen of thylakoid membrane

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

Photosystem I (Plastocyanin-ferredoxin oxidoreductase) is located in the membrane of stroma lamellae, while PSII  (water-plastoquinone oxidoreductase) is located in the grana region that is inner side of thylacoid membrane.

So, the correct answer is 'Inner side of thylakoid membrane'