Tag: photosynthesis in plants

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

PS I is inactive at

  1. 550 nm

  2. 680 nm

  3. 690 nm

  4. 780 nm
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

A) PS I can funtion at wavelengths of 700 nm or less. So, it will be active at 550 nm. But its maximum activity is at 700 nm.
B) It will be active at 680 nm.
C) It will be active at 690 nm.

D) PS I cannot function at wavelengths greater than 700 nm.
So the correct answer is '780 nm'.

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

A photosystem Contains

  1. pigments, a reaction centre, and an electron acceptor
  2. ADP1 P1 and hydrogen ions $(H^+)$

  3. protons, photons and pigments

  4. both (b) and (C)
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Photosystems refer to PSI and PSII. Photosystem II contains chlorophyll a, as well as up to 50% chlorophyll b. It probably evolved later as a supplement to Photo I. It is needed to capture enough energy to do the biosynthetic reactions of the dark reaction. Its reaction centre is a molecule called P680 which absorbs light maximally at 680 nm. Similarly, PSI or P700 absorbs light at 700nm. A reaction centre comprises several (>10 or >11) protein subunits, that provide a scaffold for a series of cofactors. The cofactors can be pigments (like chlorophyll, pheophytin, carotenoids), quinones, or iron-sulfur clusters and electron acceptors for transduction in the electron transport chain. 

So, the correct option is, 'pigments, a reaction centre, and an electron acceptor'.

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

The active component of photosystem-I composed of

  1. chlorophyll-a with absorption peak at 680 nm

  2. chlorophyll-a with absorption peak at 700 nm

  3. chlorophyll-b with absorption peak at 680 nm

  4. chlorophyll-a chlorophyll-b with absorption peak at 700 nm
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
The reaction center of photosystem-I is composed of two chlorophyll molecules and is therefore referred to as a dimer. The dimer is composed of one chlorophyll a molecule and one chlorophyll a' molecule with absorption peak at 700 nm.
Thus, the correct answer is 'chlorophyll a with absorption peak at 700 nm.'