Most proteins denature at both high and low pH. At high pH, the ionization of internal tyrosines is thought to be the main destabilizing influence, whereas at low pH, the protonation of buried histidines. A titration curve for the unfolding of the enzyme ribonuclease is shown in Figure. Given the relation between the titration curves for protein unfolding and histidine protonation, which of the following conclusion can be drawn correctly?

A. The sharp transition in graph indicates a highly cooperative process; when the protein starts to unfold, it completes the process rapidly

B. The sharp transition in graph indicates a highly noncooperative process

C. Several buried histidines can ionize when the chain starts to unfold, so that when one goes, they all go together due to cooperative behaviour of protein folding

D. Buried histidine (pK of 4 in this example) becomes accessible to solvent, its pK will shift toward its normal value of 6, significantly steepening its titration curve.

#Question id: 10219

#Unit 6. System Physiology – Plant

The PSII reaction center leads to easily  inactivation and damage by photoinhibition process while Photosystem I Is Protected from Active Oxygen Species, Why PSI protect from active oxygen species in compare to PSII

#Question id: 10217

#Unit 6. System Physiology – Plant

Another effect that appears to be a major factor in the stability of the photosynthetic apparatus, which occurs when excess excitation arriving at the PSII reaction center leads to its inactivation and damage is known as

#Question id: 10215

#Unit 6. System Physiology – Plant

Chloroplast movement is widespread among algae, mosses, and leaves of higher plants, what will be the orientation of chloroplast in dark as well as in light?

a.) In dark, chloroplasts gather at the cell surfaces parallel to the plane of the leaf so that they are aligned perpendicularly to the incident light

b.) Under high light, , the chloroplasts move to the cell surfaces that are parallel to the incident light, thus avoiding excess absorption of light

c.) the orientation of the chloroplasts in the dark is such that maximizes absorption of light

d.) the orientation of the chloroplasts in the high light is such that maximizes absorption of light

Which of the following statements is correct?

#Question id: 10214

#Unit 6. System Physiology – Plant

LHCII, one of the membrane-bound antenna pigment proteins, which can be phosphorylated and non-phosphorylated by a specific kinase present in thylakoid membrane. Which of the following statements are NOT TRUE ?

#Question id: 10210

#Unit 6. System Physiology – Plant

Some xanthophylls also participate in energy dissipation such as in light conversion of Violaxanthin to Zeaxanthin with antheraxanthin as the intermediate and vice-versa, which of the following statements is CORRECT?

a.) The conversion of Violaxanthin to Zeaxanthin a singlet oxygen is removed with the help of co-factor Ascorbate and violaxanthin de-epoxidase under high PPFD

b.) Zeaxanthin is oxidised into violaxanthin with the help of NADPH and oxygen under low PPFD

c.) Conversion of Violaxanthin to Zeaxanthin a singlet oxygen is removed with the help of NADPH and water under low PPFD

d.) Zeaxanthin is oxidised into violaxanthin in presence of enzyme known as violaxanthin de-epoxidase and co-factor Ascorbate under high PPFD

#Question id: 10209

#Unit 6. System Physiology – Plant

Protection against photodamage is a multilevel process, excited state of chlorophyll is not rapidly quenched by photochemistry it can react with molecular oxygen to form toxic photoproducts such as as singlet oxygen (1 O2*) what can damage if this second line of defense also fails to eliminate the reactive photoproducts?