Question

can someone answer these please!! I NEED HELP!!

Of the following events from the light reactions of photosynthesis, which would be expected to occur first? While being split, electrons are taken out of water. Acceptance of electrons by Pc from the cytochrome complex Donation of electrons from reduced Pq to the cytochrome complex Light-induced reduction of the primary elecetron acceptor in the reaction center of PS Il takes place. Question 2 (2 points) The following figure depicts the absorption spectra of various photosynthetic pigments. Of the pigments listed, which has the widest absorption spectra? Chlorophyll Phycoerythrin Phycocyanin Chlorophy - Absorption W e Sala Green Wavelength (nm) Phycoerythrin Chlorophyll be Chlorophylla

Answer 1

Answer 1: Out of all, the first would be splitting of water to eject electrons out to be used further in the process.

Reason: The leaf absorbs the co2 and water, the water stored in the leaf is subjected to split and release electron, hydrogen and nascent oxygen.

H2Oà2electrons +2 hydrogens +1 oxygen (nascent oxygen)

This is catalysed by light energy and hence named photolysis i.e. splitting of water molecule by light.

The 2 electrons released by this are used by the PS2 or photosystem 2 or PS680 to restore the electrons after releasing and transporting its electrons continuously firstly to primary electron acceptor and then via electron transport systems i.e. Plastoquinone, cytochrome and plastocyanin again and again. That finally reaches to PS1 and again downhill where it forms NADPH2.

The H2 formed by the photolysis of water is used after the electron transportation from PS1 i.e. photosystem 1 (or P700) to ferredoxin and then when it reaches to NADP+ and then this H2 combines with it to form NADH2.

Second step would be, light-induced reduction from primary electron acceptor in the reaction centre of PS2 takes place. As explained above also, after splitting of water molecule the PS2 will be excited after receiving light energy and will get reduced and release electron to electron transportation system downhill gradient and so on.

Thirdly, donation of electrons from reduced PQ to cytochrome complex will occur (via electron transport systems i.e. Plastoquinone, cytochrome and plastocyanin) in this manner.

And, lastly acceptance of electrons by Plastocyanin. (via electron transport systems i.e. Plastoquinone, cytochrome and plastocyanin) in this manner.

Answer 2:

Phycoerythrin has the widest absorption spectra. It is red pigment and is present in light-harvesting systems as the accessory pigment that delivers its electron to the main primary centre i.e. P680 or P700 during the process of Photosynthesis. Absorption peaks are usually measured at 495 and 545/566 nm.

Others like Phycocyanin comes next absorbs orange and red light and is also accessory pigment.

that beta-carotene absorbs strongly between 400-500 nm and emits orange colour.

whereas, chlorophyll a and chlorophyll b are the main reaction centres and absorbs blue and green wavelengths.

Answer 3: The first step of the Calvin cycle is: Carbon fixation

Reason:

It involves only three stages:

1. Carbon fixation: In this phase, carbon dioxide combines with the ribulose-1,5-bisphosphate and forms, 3-phosphoglyceric acid (3-PGA), this is catalysed by enzyme RuBP carboxylase/oxygenase (rubisco).

2. Reduction: 3-PGA molecules converted into glyceraldehyde-3-phosphate (G3P).

3. Regeneration: When glyceraldehyde-3-phosphate (G3P) makes glucose and other molecules of it are regenerated to begin a new cycle.

Answer 4: The carotenoids are the colours orange and yellow because they absorb the colours blue and violet.

Reason: Carotenoids are accessory pigments in photosynthesis process.

As the specific colours when absorbed reflects specific colours.

Colour absorbed -Colour reflected or appeared

Yellow         -           Violet

Orange        -           Blue

Violet -            Yellow

Blue            -           Orange

Green        - Red