Tag: light dependent or hill reaction

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Multiple choice botany metabolism, cell respiration, and photosynthesis light dependent or hill reaction phases of photosynthesis emerson's experiments & hill's reaction

In the light reactions of photosynthesis,

  1. PS I produces strong oxidant while PS II a strong reductant.
  2. PS I produces strong reductant $NADPH$ while PS II a strong oxidant.

  3. PS I emits electrons for PS II.

  4. PS I produces ATP which is not formed by PS II.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

PS I: This system produces a strong reductant which reduces ${NADP}^+$ to $NADPH$.

This system does not directly involve with the photooxidation of water and evolution of molecular oxygen.
PS II: This system is directly involved with the photooxidation of water and evolution of molecular oxygen.
It donates electrons to PS I when ${NADP}^+$ is reduced.
Hence, the correct answer is 'PS I produces strong reductant $NADPH$ while PS II a strong oxidant'.

Multiple choice botany metabolism, cell respiration, and photosynthesis light dependent or hill reaction phases of photosynthesis emerson's experiments & hill's reaction

Photosynthesis is considered as an oxidation reaction, because

  1. $CO _2$ is oxidised
  2. $H _2O$ is oxidised
  3. $O _2$ is released
  4. $(CH _2O)$ is oxidised.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A) Carbon dioxide is reduced, not oxidised. 
B) Water is oxidised to form protons and release oxygen. ${ H } _{ 2 }O\longrightarrow { O } _{ 2 }+{ 2H }^{ + }$

C) Oxygen is released after water undergoes oxidation.
D) ${ CH } _{ 2 }O$ does not undergo oxidation.
So the correct answer is '${ H } _{ 2 }O$ is oxidised'.

Multiple choice botany metabolism, cell respiration, and photosynthesis light dependent or hill reaction phases of photosynthesis emerson's experiments & hill's reaction
The absorption spectrum of chlorophyll

  1. approximates the action spectrum of photosynthesis

  2. shows that some colours of light are absorbed more than others

  3. explains why chlorophyll is a green pigment

  4. all of the above are correct
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Green plants are green because they contain a pigment called chlorophyll as in the absorption spectra, chlorophyll absorbs light in the red (long wavelength) and the blue (short wavelength) regions of the visible light spectrum. The green light is not absorbed but reflected, making the plant appear green. An absorption spectrum shows all the light typically absorbed by a leaf. An action spectrum, meanwhile, shows all the light that is actually used for photosynthesis. The similarity of the action spectrum of photosynthesis and the absorption spectrum of chlorophyll tells us that chlorophyll is the most important pigments in the process. The spectra are not identical, though, because carotenoid, which absorbs strongly in the blue, play a role as well.

So, the correct option is, 'all of the above are correct'.

Multiple choice botany metabolism, cell respiration, and photosynthesis light dependent or hill reaction phases of photosynthesis emerson's experiments & hill's reaction

Hill used a dye for his famous hill reaction is

  1. Sulphur green

  2. Eosine

  3. Methylene blue

  4. Dichlorophenol indophenol
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

In the year 1937 and 1939, Robert hill studied the light dependent reaction and revealed that oxygen evolved during photosynthesis came from water. In his experiment, he used Dichlorophenolindophenol (DCPIP) as a redox dye to measure the rate of photosynthesis. The dye is blue in oxidized state with a maximal absorption at 600 nm whereas in reduced, DCPIP is colourless.

Multiple choice botany metabolism, cell respiration, and photosynthesis light dependent or hill reaction phases of photosynthesis emerson's experiments & hill's reaction

Choose the correct answer from the alternatives given.
NADPH and ATP from the light-dependent reactions are used to

  1. cause rubisco to fix $CO _2$

  2. cause electrons to move along their pathways

  3. reform the photosystems

  4. convert PGA to PGAL
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Light-dependent reactions provide NADPH (electrons) and ATP (energy) to reduce PGA to PGAL. PGAL, the product of the Calvin Cycle can be converted into all sorts of other molecules. 2. Glucose phosphate is one result of PGAL metabolism; it is a common energy molecule
So, the correct answer is 'convert PGA to PGAL'

Multiple choice botany metabolism, cell respiration, and photosynthesis light dependent or hill reaction phases of photosynthesis emerson's experiments & hill's reaction

Which one is directly involved in light reaction of photosynthesis

  1. Chlorophyll a

  2. Chlorophyll b

  3. Carotenoids

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

Photosynthesis takes place in the green leaves of plants and other green part of plants like stem etc. The most active photosynthetic tissue in higher plants is the mesophyll of leaves. Mesophyll cells have many chloroplasts, which contain the specialised light absorbing green pigments, the chlorophylls. When chlorophyll absorbs light, it gets excited and emits electrons. Chlorophyll a is the primary photosynthetic pigment. It shows bright or blue green colour in chromatogram. Chlorophyll a is directly involved in light reaction of photosynthesis. It is present in the reaction centres of Photosystem I and Photosystem II which absorbs light energy of longer wavelength. These centres can release electron upon absorption of energy.

Multiple choice botany metabolism, cell respiration, and photosynthesis light dependent or hill reaction phases of photosynthesis emerson's experiments & hill's reaction

When chlorophyll absorbs light, it gets excited and emits (releases)

  1. Oxygen

  2. Water

  3. Electrons

  4. Energy rich compounds.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Photosynthesis takes place in the green leaves of plants and other green parts of plants like stem etc. When chlorophyll absorbs light, it gets excited and emits electrons. These chlorophylls are found in photosynthetic units called Photosystem I and Photosystem II. Each unit has a specific reaction center which contains pigment molecules. These molecules absorb light of different wavelengths and emit electrons. These electrons are picked up by an electron acceptor which passes them to an electron transport system of cytochromes.