Explain cyclic photophosphorylation.
(N/A) When only $PS-I$ is functional,the electron is circulated within the photosystem and the phosphorylation occurs due to the cyclic flow of electrons. This is called cyclic photophosphorylation.
$A$ possible location where this occurs is in the stroma lamellae.
While the membrane or lamellae of the grana have both $PS-I$ and $PS-II$,the stroma lamellae lack $PS-II$ as well as the $NADP$ reductase enzyme.
The excited electron does not pass on to $NADP^+$.
It is cycled back to the $PS-I$ complex through the electron transport chain.
The cyclic flow,therefore,results only in the synthesis of $ATP$ but not of $NADPH + H^+$.
Cyclic photophosphorylation also occurs when only light of wavelengths beyond $680 \ nm$ is available for excitation.
$A$ possible location where this occurs is in the stroma lamellae.
While the membrane or lamellae of the grana have both $PS-I$ and $PS-II$,the stroma lamellae lack $PS-II$ as well as the $NADP$ reductase enzyme.
The excited electron does not pass on to $NADP^+$.
It is cycled back to the $PS-I$ complex through the electron transport chain.
The cyclic flow,therefore,results only in the synthesis of $ATP$ but not of $NADPH + H^+$.
Cyclic photophosphorylation also occurs when only light of wavelengths beyond $680 \ nm$ is available for excitation.
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Similar Questions
The following $(I-VI)$ are the main steps of chemiosmotic $ATP$ synthesis in the light reaction. Arrange them in the correct order:
$I$. $H^+$ concentration gradient established
$II$. $H^+$ diffuses through $ATP$ synthase
$III$. Carriers use energy from electrons to move $H^+$ across the membrane
$IV$. Electrons from $PS-II$ pass along the electron transport chain
$V$. Light excites electrons in $PS-II$
$VI$. Energy of $H^+$ flow is used by $ATP$ synthase to make $ATP$
$I$. $H^+$ concentration gradient established
$II$. $H^+$ diffuses through $ATP$ synthase
$III$. Carriers use energy from electrons to move $H^+$ across the membrane
$IV$. Electrons from $PS-II$ pass along the electron transport chain
$V$. Light excites electrons in $PS-II$
$VI$. Energy of $H^+$ flow is used by $ATP$ synthase to make $ATP$
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View SolutionRead the following four statements,$(i), (ii), (iii)$ and $(iv)$ and select the right option having both correct statements.
Statements:
$(i)$ $Z$ scheme of light reaction takes place in the presence of $PSI$ only.
$(ii)$ Only $PSI$ is functional in cyclic photophosphorylation.
$(iii)$ Cyclic photophosphorylation results in the synthesis of $ATP$ and $NADPH_2$.
$(iv)$ Stroma lamellae lack $PSII$ as well as $NADP$ reductase.
Statements:
$(i)$ $Z$ scheme of light reaction takes place in the presence of $PSI$ only.
$(ii)$ Only $PSI$ is functional in cyclic photophosphorylation.
$(iii)$ Cyclic photophosphorylation results in the synthesis of $ATP$ and $NADPH_2$.
$(iv)$ Stroma lamellae lack $PSII$ as well as $NADP$ reductase.
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