- 1a) Sickle cell anaemia results from a substitution of a valine for a glutamate. What do you expect the effect might be if mutation were to have placed a leucine at that site? Or an aspartate?
- 2a) Which among them generates the strongest reducing agent?
- 2b) Which among them must absorb 4 photons during each round of non cyclic photophosphorylation?
- 2c) Name some accessory pigments that surround each
photosystem?
AnsWERS :-
1. There are eight amino acids with nonpolar side chains. Glycine, alanine, and proline have small, nonpolar side chains and are all weakly hydrophobic.
Phenylalanine, valine, leucine, isoleucine, and methionine have larger side chains and are more strongly hydrophobic.
Phenylalanine, valine, leucine, isoleucine, and methionine have larger side chains and are more strongly hydrophobic.
1a. Sickle cell anemia results is caused due to substitution of charged amino acid i.e glutamate (at the 6th position ) by valine which is non polar in nature hence due to the charge variance in the molecule the structure of the hemoglobin molecule changes drastically making it sickle shaped.
Leucine also has a non polar nature hence it would also result in abnormality of haemoglobin molecule.
However when you have a charged counterpart like aspartic acid which has the same equivalent charge and polar nature present in the molecule, replacing glutamate, it would not cause any abnormality in the haemoglobin molecule but would decrease the chain length by one Ch2 group which is additional in glutamate
Leucine also has a non polar nature hence it would also result in abnormality of haemoglobin molecule.
However when you have a charged counterpart like aspartic acid which has the same equivalent charge and polar nature present in the molecule, replacing glutamate, it would not cause any abnormality in the haemoglobin molecule but would decrease the chain length by one Ch2 group which is additional in glutamate
Q2. PSI generates the most negative redox potential because it involves NADP+-NADPH coupled reaction which has a standard redox potential of -0.32V as compared to PSII which involves o2-H20 coupled reaction having a standard redox potential of +0.82V
Q2. a *** very imp** The strongest reducing agent is generated by photosystem Iit produces NADPH from NADP+
(note by:strong oxidising is produced by Photosystem II since it produces oxygen from water)
(note by:strong oxidising is produced by Photosystem II since it produces oxygen from water)
Q2b.Both the photosystems must absorb four photons.
(Explanation: The production of one molecule of oxygen requires the removal of four electrons from two water molecules.The removal of electrons from water requires the absorption of four photons, one for each electron. At the same time the reduction of one molecule of NADP+ requires transfer of 2 electrons. Thus hypotectically if only one photosystem were able to transfer electrons from H2O to NADP+, four photons would be sufficient to produce two molecules of NADPH. Because two photosystems are utilized in the cell that number is doubled to eight four being utilised by PSII and four in PSI.)
(Explanation: The production of one molecule of oxygen requires the removal of four electrons from two water molecules.The removal of electrons from water requires the absorption of four photons, one for each electron. At the same time the reduction of one molecule of NADP+ requires transfer of 2 electrons. Thus hypotectically if only one photosystem were able to transfer electrons from H2O to NADP+, four photons would be sufficient to produce two molecules of NADPH. Because two photosystems are utilized in the cell that number is doubled to eight four being utilised by PSII and four in PSI.)
2 H2O + 2 NADP ----4Photons---> 1 O2 + 2 NADPH (Overall light reaction)
Q2c. Accessory Pigments are chlorophyll b (also c, d, and e in algae and protistans), xanthophylls, and carotenoids or phycobiliproteins (beta carotenoids)
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