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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'.

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

Which pigment system is inactivated in red drop?

  1. PS-I and PS-II

  2. PS I

  3. PS II

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

  1. The fall in photosynthetic yield beyond the red region of the spectrum (680 runs) is called red drop.
  2. Reaction center of PS-2 is 680 while that of PA-1 is 700.
  3. So the psII system will be inactive.
So the correct option is PS II

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.'