Ferredoxin is a constituent of

PS I
PS II
Hill reaction
P₆₈₀

Plants give off oxygen because

oxygen results from the incorporation of carbon dioxide into sugars.
plants do not respire since they photosynthesize.
water is the initial proton donor, leaving oxygen as a photosynthetic by-product.
All of the above

Solution

Water is split at photosystem–II to donate electrons to the reaction centre. The resulting protons are moved across the membrane to establish the proton motive force and oxygen is given off as a by-product.

Cyclic and non-cyclic electron flow is used in plants to

Meet the ATP demands of the Calvin Benson cycle.
Avoid producing excess NADPH + H⁺
Balance ATP and NADPH + H⁺ ratios in the chloroplast.
All of the above

Solution

ATP is required at higher levels in the Calvin-Benson cycle than NADPH + H⁺. Therefore, there must be a mechanism for producing additional ATP. Cyclic electron flow provides that mechanism. If non cyclic electron flow were to be speed up to meet ATP needs,an excess of NADPH + H⁺ would result. Shifting between cyclic and non cyclic flow balances ATP/NADPH + H⁺ ratios.

Which of the following statements concerning the light reaction of photosynthesis are true ?

Photosystem I can operate independently of photosystem II.
Photosystem I and II are activated by different wavelengths of light.
Photosystems I and II transfer electrons and create proton gradients across the thylakoid membrane.
All of the above

Solution

Photosystems I and II operate depending on whether electron flow is cyclic or non cyclic. Activity is controlled by the ATP levels in the chloroplast. Photosystem II is activated by light of a higher energy level than photosystem I. Both photosystems transfer electrons and create proton gradients across the thylakoid membranes.

During the light stage of photosynthesis, the photo activated pigment removes an electron from the hydroxylation derived from the water molecule.

The fate of the free hydroxyl radical is that it

is broken down into oxygen and a free radical of hydrogen.
is used to raise the activation level of chlorophyll by donating a positive charge.
is used to produce adenosine triphosphate from adenosine diphosphate.
reduces carbon dioxide to sugar.

Solution

The water molecule is split as shown in the equation :

H₂O -> ½O₂ 2H⁺ 2e^-

forming oxygen and hydrogen radicals.

Thomas Engelmann illuminated a filament of algae with light that passed through a prism, thus exposing different segments of the algal filament to different wavelengths of light. He added aerobic bacteria and found that these bacteria congregated in the areas illuminated by red and blue light. If you ran the same experiment without passing light through a prism, what would you predict?

There would be no difference in results.
The number of bacteria would decrease along the entire length of the filament.
The bacteria would be relatively evenly distributed along the length of the filament.
The number of bacteria would increase along the entire length of the filament.

Assimilatory power refers to

Generation of ATP and NADPH₂
Reduction of CO₂
Splitting of water
Disintegration of plastids

Solution

Arnon(1965) used the term 'Assimilatory powers' for ATP and NADPH₂. (NADPH₂ alone is called reducing power).

Manganese is required in

Nucleic acid synthesis
Plant cell wall formation
Photolysis of water during photosynthesis
Chlorophyll synthesis

Ferredoxin is a component of

Hill reaction
Photosystem-I
P680
Photosystem-II

‘Z-scheme’ show the transfer of electrons involving

Bundle sheath cell
PS I
PS II
Both (b) and(c)

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