Photosynthesis converts light energy to chemical energy through light reaction. Light reaction occurs in the thylakoid membranes of chloroplasts, where photosystems use light to transfer electrons and pump protons, generating ATP and NADPH. There are two photosystems - PSII uses water as the electron donor and evolves oxygen, while PSI and cytochrome b6f complex generate a proton gradient used for ATP synthesis via ATP synthase. Both oxygenic and anoxygenic bacteria perform similar light reactions, though they use different electron donors and may contain only one photosystem. Light reaction is essential for providing the energy required for carbon fixation in photosynthesis.
what is photosynthesis?-history background-photosynthetic pigmment system-light harvesting complex-photo oxidation of water-photophosphorylation and mechanism of electron transport
what is photosynthesis?-history background-photosynthetic pigmment system-light harvesting complex-photo oxidation of water-photophosphorylation and mechanism of electron transport
Photorespiration - Introduction, why is it occur in plants, pathway of photorespiration, Enzymes names, pathway step by step explanation, Benefits of photorespiration, additional information related to photorespiration, Rubisco enzyme, Oxygenase enzyme, Oxygen concentration higher leads to photorespiration, problem to carry out calvin cycle.
Photosynthesis is a oxidation reduction process in which water is oxidized and carbon dioxide is reduced to carbohydrate level, the water and oxygen being by product.
Photosynthesis is a process used by plants and other organisms to convert light energy, normally from the sun, into chemical energy that can be used to fuel the organisms' activities. Carbohydrates, such as sugars, are synthesized from carbon dioxide and water.
Translocation of food in plants
1. Source and sink
2. Pathway of translocation
3. Source-sink relationship/interaction
4. Source-sink pathways follow patterns
5. Materials transported
6. The mechanism of phloem transport
7. The Pressure -Flow Model
8. Phloem loading and unloading
9. Summary
In this ppt, you will learn about photosystem first of photosynthesis, with video and animation such a nice presentation. electron movement by animation, see and understand the system.
this presentation contains briefing of the chapter as per NCERT syllabus in details that contains photosynthesis process, early experiments, photosynthetic pigments,photophosphorylation, light reactions and dark reactions n factors affecting photsynthesis.
Photorespiration - Introduction, why is it occur in plants, pathway of photorespiration, Enzymes names, pathway step by step explanation, Benefits of photorespiration, additional information related to photorespiration, Rubisco enzyme, Oxygenase enzyme, Oxygen concentration higher leads to photorespiration, problem to carry out calvin cycle.
Photosynthesis is a oxidation reduction process in which water is oxidized and carbon dioxide is reduced to carbohydrate level, the water and oxygen being by product.
Photosynthesis is a process used by plants and other organisms to convert light energy, normally from the sun, into chemical energy that can be used to fuel the organisms' activities. Carbohydrates, such as sugars, are synthesized from carbon dioxide and water.
Translocation of food in plants
1. Source and sink
2. Pathway of translocation
3. Source-sink relationship/interaction
4. Source-sink pathways follow patterns
5. Materials transported
6. The mechanism of phloem transport
7. The Pressure -Flow Model
8. Phloem loading and unloading
9. Summary
In this ppt, you will learn about photosystem first of photosynthesis, with video and animation such a nice presentation. electron movement by animation, see and understand the system.
this presentation contains briefing of the chapter as per NCERT syllabus in details that contains photosynthesis process, early experiments, photosynthetic pigments,photophosphorylation, light reactions and dark reactions n factors affecting photsynthesis.
Light Reactions
Light reactions or photochemical phase is directly depends on light
Light reaction phase include
Light absorption
Splitting of water molecule
Release of oxygen molecule
Formation of high energy chemical intermediates (ATP and NADPH)
Several protein complexes are involved in the process
The pigments are organised into two discrete photochemical light harvesting complexes (LHC) within the Photosystem I (PS I) and Photosystem II (PS II).
THE ELECTRON TRANSPORT
When PS Il absorbs red light of 680 nm wavelength, electrons are excited and transferred to an electron acceptor.
The electron acceptor passes them to a chain of electrons transport system.
Electron transport system consist of Pheophytin Plastoquinone Cytochrome complex Plastocyanin
This movement of electrons is downhill, in terms of redox potential scale
The electrons are transferred to the pigments of PS I.
Simultaneously, electrons in PS I are also excited when they receive red light of 700 nm and are transferred to another accepter molecule having a greater redox potential.
These electrons are moved downhill to a molecule of NADP+.
Iron sulphur proteins and ferredoxin helps electron reach to NADP+ Reductase. As a result, NADP+ is reduced to NADPH + H+
Transfer of electrons from PS II to PS I and finally downhill to NADP+ is called the Z scheme, due to its zigzag shape.
This shape is formed when all the carriers are placed in a sequence on a redox potential scale.
SPLITTING OF WATER
The water splitting complex in PS II is located on the inner side of the thylakoid membrane.
Water is split into H+, O and electrons.
So PS Il can supply electrons continuously by replacing electrons from water splitting.
Thus PS II provides electrons needed to replace those removed from PS I.
O2, is liberated as by-product of photosynthesis.
PHOTO - PHOSPHORYLATION
The synthesis of ATP by cells (in mitochondria & chloroplasts) is called phosphorylation.
Photo-phosphorylation is the synthesis of ATP from ADP in chloroplasts in presence of light.
It occurs in 2 ways:
Non- cyclic photo-phosphorylation
Cyclic photo-phosphorylation
Reference:-
https://rajusbiology.com/photosynthesis-in-higher-plants-class-11-notes/
Prepare for NEET with comprehensive Class 11 notes on photosynthesis in higher plants. Master the key concepts, processes, and factors affecting photosynthesis to excel in your exam preparation.
For more information, visit-www.vavaclasses.com
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
This pdf is about the Schizophrenia.
For more details visit on YouTube; @SELF-EXPLANATORY;
https://www.youtube.com/channel/UCAiarMZDNhe1A3Rnpr_WkzA/videos
Thanks...!
Richard's aventures in two entangled wonderlandsRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Richard's entangled aventures in wonderlandRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
The increased availability of biomedical data, particularly in the public domain, offers the opportunity to better understand human health and to develop effective therapeutics for a wide range of unmet medical needs. However, data scientists remain stymied by the fact that data remain hard to find and to productively reuse because data and their metadata i) are wholly inaccessible, ii) are in non-standard or incompatible representations, iii) do not conform to community standards, and iv) have unclear or highly restricted terms and conditions that preclude legitimate reuse. These limitations require a rethink on data can be made machine and AI-ready - the key motivation behind the FAIR Guiding Principles. Concurrently, while recent efforts have explored the use of deep learning to fuse disparate data into predictive models for a wide range of biomedical applications, these models often fail even when the correct answer is already known, and fail to explain individual predictions in terms that data scientists can appreciate. These limitations suggest that new methods to produce practical artificial intelligence are still needed.
In this talk, I will discuss our work in (1) building an integrative knowledge infrastructure to prepare FAIR and "AI-ready" data and services along with (2) neurosymbolic AI methods to improve the quality of predictions and to generate plausible explanations. Attention is given to standards, platforms, and methods to wrangle knowledge into simple, but effective semantic and latent representations, and to make these available into standards-compliant and discoverable interfaces that can be used in model building, validation, and explanation. Our work, and those of others in the field, creates a baseline for building trustworthy and easy to deploy AI models in biomedicine.
Bio
Dr. Michel Dumontier is the Distinguished Professor of Data Science at Maastricht University, founder and executive director of the Institute of Data Science, and co-founder of the FAIR (Findable, Accessible, Interoperable and Reusable) data principles. His research explores socio-technological approaches for responsible discovery science, which includes collaborative multi-modal knowledge graphs, privacy-preserving distributed data mining, and AI methods for drug discovery and personalized medicine. His work is supported through the Dutch National Research Agenda, the Netherlands Organisation for Scientific Research, Horizon Europe, the European Open Science Cloud, the US National Institutes of Health, and a Marie-Curie Innovative Training Network. He is the editor-in-chief for the journal Data Science and is internationally recognized for his contributions in bioinformatics, biomedical informatics, and semantic technologies including ontologies and linked data.
Cancer cell metabolism: special Reference to Lactate PathwayAADYARAJPANDEY1
Normal Cell Metabolism:
Cellular respiration describes the series of steps that cells use to break down sugar and other chemicals to get the energy we need to function.
Energy is stored in the bonds of glucose and when glucose is broken down, much of that energy is released.
Cell utilize energy in the form of ATP.
The first step of respiration is called glycolysis. In a series of steps, glycolysis breaks glucose into two smaller molecules - a chemical called pyruvate. A small amount of ATP is formed during this process.
Most healthy cells continue the breakdown in a second process, called the Kreb's cycle. The Kreb's cycle allows cells to “burn” the pyruvates made in glycolysis to get more ATP.
The last step in the breakdown of glucose is called oxidative phosphorylation (Ox-Phos).
It takes place in specialized cell structures called mitochondria. This process produces a large amount of ATP. Importantly, cells need oxygen to complete oxidative phosphorylation.
If a cell completes only glycolysis, only 2 molecules of ATP are made per glucose. However, if the cell completes the entire respiration process (glycolysis - Kreb's - oxidative phosphorylation), about 36 molecules of ATP are created, giving it much more energy to use.
IN CANCER CELL:
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
introduction to WARBERG PHENOMENA:
WARBURG EFFECT Usually, cancer cells are highly glycolytic (glucose addiction) and take up more glucose than do normal cells from outside.
Otto Heinrich Warburg (; 8 October 1883 – 1 August 1970) In 1931 was awarded the Nobel Prize in Physiology for his "discovery of the nature and mode of action of the respiratory enzyme.
WARNBURG EFFECT : cancer cells under aerobic (well-oxygenated) conditions to metabolize glucose to lactate (aerobic glycolysis) is known as the Warburg effect. Warburg made the observation that tumor slices consume glucose and secrete lactate at a higher rate than normal tissues.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
1. PRESENTED BY-
ALAKESH DAS
PG 3RD SEMESTER
ENROLLMENT- BOT1662008
DEPARTMENT OF BOTANY
COTTON UNIVERSITY
PHOTOSYNTHESIS: THE
LIGHT REACTION
2. INTRODUCTION
Photosynthesis is a physiochemical process by which photosynthetic
organisms (either eukaryotes or prokaryotes) convert light energy into
chemical energy in the form of reducing power (as NADPH) and ATP
by using some inorganic compounds & utilize this energy to drive CO2
fixation.
SU
N
LIGHT
REACTION
NADP
H
+
ATP
DARK
REACTION
CO2
GLUCO
SE
3. TYPES
Based on the generation of Oxygen (O2) in the process, photosynthesis
can be of 2 principle types-
(a) Oxygenic: generation of O2 occurs via the photolysis/photo-oxidation
of H2O, who act as the ultimate e- donor; e.g. -
Eukaryotes- Green plants
Prokaryotes- Cyanobacteria
CO2 + 2H2O CH2O + H2O + O2
(b) Anoxygenic: light energy is harvested without evolution of O2 , where
some other inorganic molecule (e.g.- H2S) act as a electron donor;
seen only in prokaryotes. E.g.- Purple Photosynthetic Bacteria and
Green Photosynthetic Bacteria.
CO2 + 2H2S CH2O + H2O + 2S
4. SITE OF PHOTOSYNTHESIS : Structure of
Photosynthetic Apparatus
Most active photosynthetic tissue in higher plants is the “Mesophyll”
tissue having specialized organelle called “Chloroplast”, which contains
light absorbing pigments the “Chlorophylls” (for Bacteria-
Bacteriochlorophyll).
Chloroplast has a extensive system of internal membranes known as
“Thylakoids” & is the site of ‘light reaction’.
Fig: A eukaryotic
Chloroplast showing
internal machinery of
membrane system.
5. PHOTOSYNTHETIC PIGMENTS: Light absorbing
molecules.
Major Photosynthetic Pigments
(a) Chlorophyll (a, b)
(b) Bacteriochlorophyll
Fig: Structure of Chlorophylls & Bacteriochlorophyll.
6. Accessory Photosynthetic Pigments
(a) Carotenoids : are long chain conjugated hydrocarbons, further
divided into two groups-
(1) Carotenes (pure hydrocarbons)
(2) Xanthophylls (contain oxygen)
(b) Phycobilins : possess a linear non-cyclic tetrapyrrole ring structure,
similar to bile pigment ‘bilirubin’, and are 3 principle types-
(1) Phycoerythrobilin
(2) Phycocyanobilin
(3) Allophycocyanobilin
7. ABSORPTION SPECTRA : Concept of “Action Spectra”
Absorption Spectra : the light of wavelength at which absorption is
maximum by the pigment and is specific for every molecule.
Action Spectra : the light of specific wavelength necessary for the
generation of oxygen (O2).
Fig : T.W Engelmann’s experiment with
Spirogyra filament showing action spec-
tra for the chloroplast which is blue-violet
& far-red region.
8. ORGANIZATION OF LIGHT ABSORBING PIGMENT
MOLECULES : Concept of “photosynthetic unit”
Majority of pigments serve as an antenna (mostly the accessory
pigment), collecting and transferring the light energy to the adjacent
molecules & finally releasing into the reaction centre.
Photosynthetic unit
Only one specialized Chlorophyll molecule known as “Photochemical
Reaction Centre” traps the energies from antenna and drives a series
of oxidation-reduction reactions via e- transport.
9. FATE OF THE LIGHT ENERGY ABSORBED BY
PHOTOSYNTHETIC PIGMENTS
a) Conversion of energy into Heat : through a process called
“Bioluminescence”; which may be either-
(1) Fluorescence : emits light of a longer wavelength.
(2) Phosphorescence : radioactive decaying of light.
Fig : Schematic presentation of
the process “Bioluminescence”.
10. b) Excitation Transfer : transfer of energy to the neighboring
molecules but not the e- directly, through a process called FRET
(Forster Resonance Energy Transfer) . Shown by pigment
molecules of ‘Antenna Complex’.
c) Electron Transfer : transfer of energy in the form of an e- to a
nearby molecule (e- acceptor) and in turn re-reduced by taking an e-
from an another molecule (e- donor). Shown by ‘Photochemical
reaction centre’.
11. CONCEPT OF PIGMENT SYSTEM : “Red Drop” & “Emerson
Enhancement effect”
Robert Emerson & Charlton Lewis (1943); experiments with Chlorella
pyrenoidosa.
a) Experiment 1 : alga was illuminated with visible light & O2 evolution per
photon absorbed (quantum yield) fairly constant up to 680 nm, beyond which
it sharply declined in the far red region, known as “Red Drop” effect.
b) Experiment 2 : alga was illuminated with two separate beams of light, one ≤
680 nm (red region) & one > 680 nm (far red region); resulting rate of
photosynthesis was 3-4 times greater when lights were applied
simultaneously rather than separately referred to as “Emerson Enhancement
12. PIGMENT SYSTEM / PHOTOSYSTEM
The photosynthetic unit, i.e. “antenna complex” & “photochemical reaction
centre” together with some proteins form a “pigment-protein” complex in
thylakoid membrane called “Pigment System/ Photosystem (PS)”.
o Photosynthetic organisms may carry two types of photosystem -
(a) Photosystem(PS)-I : consist of ‘Fe-S type’ of photochemical reaction
centre that mediates e- transfer from ‘Plastocyanin’ to ‘Ferredoxin’, also
known as “P700“ because of the action spectra of 700 nm; together with
the antenna complex forms ‘LHC-I(Light Harvesting Complex-I)’.
(b) Photosystem(PS)-II : consist of ‘Pheophytin-Quinone’ type reaction
centre constitutes ‘LHC-II’ together with antenna complex & activated by
the light of wavelength 680 nm, thus called “P680”.
o Various type of proteins are remain associated with these photosystems.
13. LOCATION OF PHOTOSYSTEMS IN “THYLAKOID
MEMBRANE”
PS-II : located predominantly in the “Appressed Membrane” of grana
thylakoid whose surface is in contact with the other membranes of
thylakoid.
PS-I : found almost exclusively in the “Non-Appressed Membrane”
(i.e. the exposed membranes which are not in contact with other
membranes) of stroma thylakoid & margins of grana thylakoid.
14. LIGHT REACTION : The transport of e- & protons (H+)
Carried out by four major protein complexes – PS-II, Cytochromeb6f, PS-I and
ATP Synthase; resulting in O2 evolution in the luminal side and reduces NADP+
to NADPH on the stromal side of the membrane. Two major types in oxygenic
eukaryotes-
(a) Non-cyclic pathway : mediated from H2O through a series of protein to
NADP+, which leads to the generation of PMF( Proton Motive Force) results in
ATP synthesis called “Non-cyclic photophosphorylation”.
Fig: The “Z-scheme”
mechanism of non-cyclic
e- transfer.
15. It all starts when PS-II transfers the e- by absorbing photon to the Pheophytin(a modified
Chl molecule). The process of Non-cyclic e- flow can be sub-divided into three steps-
(1) Photolysis of water (H2O) : mediated by PS-II and catalyzed by protein complex
OEC (Oxygenic Evolving Complex) which extracts e- from H2O and transfers to the PS-
II one at a time to re-reduce it. The reaction involves –
2H2O 4e- + 4H+ + O2
OEC cycles through five different states (S0 , S1 , S2 , S3 , S4) of a photon driven redox-
reaction which initiated a gear wheel that collects 4e- from 2 mol of H2O to release 1
mol of H2O. This is known as “S-State Mechanism” often called “Kok-Clock” (Kok et. al).
16. (2) The Q – Cycle : involve two major component – the “Plastoquinone” and the
“Cytochrome b6f complex”. The process include –
Pheophytin transfers the e- to Plastoquinone & reduces it into Plastohydroquinone(by
pumping 2 protons from outside) through it’s two forms QA & QB and finally releases the e-
into the Cyt b6f complex.
Cytochrome b6f complex contains several prosthetic groups – two Cyt-b , one Rieske Fe-
S protein and one Cyt-C(Cyt f), through which e- is passed following linear and cyclic
pathway as follows-
17. (3) Reduction of NADP+ : in this process PS-I is involved, which by absorbing photon
transfers one of it’s e- to ‘A0’ (a modified Chl molecule) and re-reduced by taking e- from
Plastocyanin (blue colored Co containing protein). Additional steps includes-
‘A0’ reduces ‘A1’ (a member of Quinone known as Phylloquinone/Vitamin K1 ).
The e- is then transferred through a series of Fe-S protein – FeSx , FeSA ,
FeSB to a water soluble protein ‘Ferredoxin’ (Fd).
At the last stage Ferredoxin reduces NADP+ to NADPH and the reaction is
catalyzed by a flavoprotein ‘Ferredoxin-NADP Reductase’ (FNR).
18. (b) Cyclic pathway : only the PS-I is involved in this process without any evolution of
oxygen(i.e. no photolysis of water) and reduction of NADP+ ; instead protons are
pumped across the membrane to generate PMF for the synthesis of ATP called ‘Cyclic
Photophosphorylation’.
Fig- Cyclic electron transport chain
19. SYNTHESIS OF ATP : The Chemiosmotic Mechanism
When there is a difference in ion concentration across membranes, ions tends to move
from higher concentration to lower concentration, creating a force PMF which is the
energy available for the synthesis of ATP (Peter Mitchell, 1979).
Catalyzed by a large enzyme complex ‘ATP Synthetase’ often known by several names
which can be divided into two parts – CF0 (hydrophobic) and CF1 (hydrophilic).
Fig- the coupling factor with it’s two
Parts CF0 and CF1 showing the synthesis
of ATP.
20. LIGHT REACTION IN OXYGENIC PROKARYOTES
Cyanobacteria are the only group of organisms that can carry out oxygenic
photosynthesis through non-cyclic and cyclic e- transport chain. Instead of
chloroplast they bear a striking resemblance to chloroplast themselves.
Almost similar to the eukaryotes, they carry PS-I , PS-II and Cyt b6f complex
and also extract e- from water.
Major differences includes-
They contain Phycobilins as their accessory pigment molecules.
Plastocyanin is replaced by an another protein complex called Cytochrome C6
Except these differences overall electron transport chain is similar to that of
eukaryotes mentioned above.
21. LIGHT REACTION IN ANOXYGENIC PROKARYOTES
Anoxygenic photosynthetic bacteria, which do no generate oxygen in the process; i.e. e-
donor is some inorganic compounds like H2S, S etc. and carry only one type of reaction
centre. Members include –
(a) Purple Photosynthetic Bacteria- ‘Pheophytin-Quinone type reaction centre’
(b) Green Photosynthetic Bacteria- ‘Phe-Q’ (if non-sulphur) & ‘Fe-S’ (if sulphur) reaction
centre.
Fig- Cyclic electron transport chain in
Purple Photosynthetic bacteria.
22. CONCLUSION
At last it can be concluded that “Light Reaction” of
photosynthesis is the powerhouse for the production of energy
necessary for the fixation of CO2.
Therefore, it simply means that without light reaction there will
be no food available for the consumers, which itself defines the
importance of light reaction in nature.