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

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

In photosynthesis, during the operation of PS II, the cited $P680$ is rapidly photoxidised as it passes an electron _____________.

  1. Carotene

  2. Ferridoxin

  3. Phaeophytin

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

In photosystem II, photoexcited P680 transfers an electron rapidly to an primary electron acceptor, which is phaeophytin (a chlorophyll lacking a central magnesium ion).

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'

Multiple choice photosystems photosynthesis in plants metabolism, cell respiration, and photosynthesis photosynthesis in higher plants biology
During light reaction in photosynthesis, the following are formed. 

  1. ATP and sugar
  2. hydrogen,$ O _{2}$ and sugar
  3. ATP, hydrogen and $O _{2}$
  4. ATP, hydrogen and $O _{2}$ donor
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Light reactions occur inside thylakoids. It is dependent upon light. It involves photolysis of water (breaking of water into $H _{2}$ and $O _{2}$  and production of assimilation power (NADPH and ATP). Electron released during photolysis of water are  picked up by $P _{680}$ photocentre of photosystem II. From here electrons passes over series of carrier which include PQ, cytochrome b-f complex, and PC. While passing over cytochrome complex, the electron losses sufficient energy for creation of proton gradient and ATP from ADP and inorganic phosphate. From PC electron losses sufficient energy for creation of proton gradient and ATP from ADP and inorganic phosphate. From PC electron is picked by the trap center $P _{700} $of phtotsystem I, which pushes out electron after absorbing light energy. Electron passes over carriers Fes, ferredoxin and NADP reductase which gives electron to $NADP^+$ for combing with $H^+$ to produce NADPH.
$NADP^+ 2e^- + H^{+} \xrightarrow[NADP \,\, reductase]{} NADPH $ , So, the correct answer is 'ATP, hydrogen and O2'.

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

What of the following process happens in PS II?

  1. ${ CO } _{ 2 }$ fixation
  2. ${ CO } _{ 2 }$ reduction
  3. Photolysis of H$ _2$O

  4. All of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Photosystem II is the first protein complex in the light-dependent reactions of oxygenic photosynthesis and splitting of water is associated with it. Water is split into H+, [O] and electrons, creating O$ _{2}$ which is one of the net products of photosynthesis. The electrons needed to replace those removed from PS I are provided by PS II.

So, the correct option is 'Photolysis of H$ _{2}$O'.

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

The biochemical objective of PSI is to 

  1. oxidise $NADPH$
  2. hydrolyse $ATP$
  3. Phosphorylate $ADP$
  4. reduce $NADP^+$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

 The biochemical objective of PSI is to reduce NADP+ to NADPH because NADP+ is able to be reduced in NADPH by gain electron which has been excited from PSI(P700)  and also hydrogen ions from stroma. So electron required to reduce NADP+ is released from PSI so answer is option 4.

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

What do you mean by reaction centre

  1. It is located at center of photosynthetic apparatus

  2. Electron is 1st accepted by reaction centre

  3. Electron is excited from reaction centre

  4. Light is received first by reaction centre
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A photosynthetic reaction centre is a protein that is the site of the light reactions of photosynthesis. The reaction centre contains pigments such as chlorophyll and phaeophytin. These absorb light, promoting an electron to a higher energy level within the pigment which are located at centre of photosynthetic apparatus. so, 'the correct option is - It is located at centre of photosynthetic apparatus'.

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

Wavelength of visible light, which is required for photosynthesis is

  1. 200 -400 nm.

  2. 390 -780 nm.

  3. 700 -900 nm.

  4. 100 -200 nm.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
  • A very small part of the electromagnetic spectrum can be seen by the human eye i.e., between the wavelengths 390 and 780 nm.
  • This part of the electromagnetic spectrum is called a visible light spectrum.
  • Within the spectrum the longer the wavelength of the radiation, the slower the vibration of the photons and the less energy each photon contains. 
    Hence, correct option is B.
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. Quinone.

  2. Ferredoxin.

  3. Cytochrome - b.

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

Photosystem- II is involved in non-cyclic photophosphorylation with a reaction center P${ _6}$${ _8}$${ _0}$. The electrons excited from P${ _6}$${ _8}$${ _0}$ are accepted by plastoquinoine. 

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

Photosystem II occurs in

  1. Stroma

  2. Cytochrome

  3. Grana thylakoids

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

Photosystem II is the first protein complex in the light-dependent reactions of oxygenic photosynthesis. It is located in the grana of the thylakoid membrane of plants, algae, and cyanobacteria.

So, the correct option is C.