Tag: metabolism, cell respiration, and photosynthesis

Questions Related to metabolism, cell respiration, and photosynthesis

Electrons from excited chlorophyll of PS II are accepted first by

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

  1. Quinone

  2. Ferredoxin

  3. Cytochrome b

  4. Cytochrome f

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Correct Option: A
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'.

PS II accepts electrons from

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

  1. $OH^-$

  2. $O^{2-}$

  3. $H^+$

  4. Both A and C

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Correct Option: A
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.

Last electron acceptor of PS I is

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

  1. Ferredoxin

  2. Cyt $b _6$

  3. Plastocyanin

  4. Plastoquinone

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Correct Option: A
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'.

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

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

  1. Ferredoxin

  2. Pheophytin

  3. Cytochrome b

  4. Cytochrome f

Show answer
Correct Option: B
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'.

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

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

  1. 650 nm

  2. 660 nm

  3. 680 nm

  4. 700 nm

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Correct Option: D
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'

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?

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

  1. $4, 1, 2, 3$

  2. $3, 4, 1, 2$

  3. $1, 2, 3, 4$

  4. $2, 3, 4, 1$

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Correct Option: A

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

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

  1. Carotene

  2. Ferridoxin

  3. Phaeophytin

  4. Phycoerythrin

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Correct Option: A

Which pigment system is inactivated in red drop?

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

  1. PS-I and PS-II

  2. PS I

  3. PS II

  4. None

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Correct Option: C
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

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

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

  1. Inner side

  2. Outer sicde

  3. Within the lumen of thylakoid

  4. Position of PS II shifts from inner to outside

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Correct Option: A
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’.

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

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

  1. Dichlorophenyl dimethyl urea

  2. Ethylene

  3. Indole acetic acid

  4. Chloroform

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Correct Option: A
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.'