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.
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.
ROOT HAIR DEVELOPMENT IN PLANTS:
structure and development of root hairs, Initiation and molecular genetics of root hair, functions of root hairs.
complete topic from authentic websites. Essential for for all life science students.
intro-hostory and discovery-characteristics of phytochrome-chemical nature of phytochrome-mode of action-mechanism-phytochrome mediated physiological responses-phytochrome is a pigment system:some evidences-role of phytochrome
ROOT HAIR DEVELOPMENT IN PLANTS:
structure and development of root hairs, Initiation and molecular genetics of root hair, functions of root hairs.
complete topic from authentic websites. Essential for for all life science students.
intro-hostory and discovery-characteristics of phytochrome-chemical nature of phytochrome-mode of action-mechanism-phytochrome mediated physiological responses-phytochrome is a pigment system:some evidences-role of phytochrome
The term Chloroplast was first described by Nehemiah Grew and Antonie Van Leeuwenhoek.
“Chloro” means green while“ Plast” means living.
Chlorophyll pigments present in the chloroplast imparts the green colour to plants.
Chloroplasts are present in plants and other eukaryotic organisms that conducts photosynthesis
Responsible for photosynthesis, are in many respects similar to mitochondria.
Chloroplasts are larger and more complex than mitochondria, and they perform several critical tasks in addition to the generation of ATP.
Chloroplasts synthesize amino acids, fatty acids, and the lipid components of their own membranes.
The reduction of nitrite (NO2-) to ammonia (NH3), an essential step in the incorporation of nitrogen into organic compounds, also occurs in chloroplasts.
It is a process used by plants & other organisms to convert light energy into chemical energy that can be later used by organisms as a fuel. i.e; energy transformation
WHAT IS PHOTOSYNTHESIS?, IMPORTANCE OF PHOTOSYNTHESIS, STRUCTURAL FEATURE OF LEAF ADVANTAGE FOR PHOTOSYNTHESIS,LEAVES AND LEAF STRUCTURE,CHLOROPHYLL, TYPES OF REACTIONS, LIGHT REACTION AND DARK REACTION, CYCLIC AND NON-CYCLIC PHOTOPHOSPORYLATION, MECAHANISM OF ATP SYNTHESIS, SCHEMATIC PRESENTATION OF LIGHT REACTION, CRASSULACEAN ACID METABOLISM (CAM), C3 AND C4 PLANTS, FACTORS AFFECTING RATE OF PHOTOSYNTHESIS, INTERNAL FACTORS AND EXTERNAL FACTORS,
Photosynthetic organelle and its role in crop improvementSushrutMohapatra
Chloroplasts are organelles specializing in the conversion of radiant energy to chemical energy. The chloroplast is involved in photosynthesis and consequently cells that contain chloroplasts are autotrophic, which means that they are able to make their own food from inorganic molecules by using the radiant energy of sunlight. The chloroplast converts the radiant energy of the sun into chemical energy by producing organic matter from carbon dioxide and water. The individual reactions of photosynthesis span times from femtoseconds to hours and can be divided into two major groups, reactions that require light directly and reactions that do not require light directly. Chloroplasts contain the single most important pigment on earth, i.e., chlorophyll. They impart the characteristic green colour to plants and carry out photosynthesis, the ultimate source of all organic compounds. Chloroplasts are typically biconvex lens-shaped of about 5 u diameter and 3 µ thickness. However, they exhibit a large variation is size and shape. An average cell may have 20-40 chloroplasts. but some algae, e.g. Chlamydomonas, have a single chloroplast per cell. The average chemical composition of chloroplasts may be as follows: protein 50-59 per cent, lipid 21-34 per cent, chlorophyll 5-8 per cent. carotenoids 0.7-1.1 per cent, RNA 1-7.5 per cent, and DNA 0.2-1 per cent. Chlorophyll and carotenoid molecules are associated with chloroplast thylakoid membranes.
Ultrastructure and characterstic features of bacteria.Archana Shaw
Ultrastructure and characterstic features of bacteria: BACTERIA AS A MODEL ORGANISM
THIS WAS MY PRESENTATION TOPIC IN CLASS. THOUGHT OF SHARING IT AND HOPE IT HELPS.
Introduction:
RNA interference (RNAi) or Post-Transcriptional Gene Silencing (PTGS) is an important biological process for modulating eukaryotic gene expression.
It is highly conserved process of posttranscriptional gene silencing by which double stranded RNA (dsRNA) causes sequence-specific degradation of mRNA sequences.
dsRNA-induced gene silencing (RNAi) is reported in a wide range of eukaryotes ranging from worms, insects, mammals and plants.
This process mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.
What are small ncRNAs?
micro RNA (miRNA)
short interfering RNA (siRNA)
Properties of small non-coding RNA:
Involved in silencing mRNA transcripts.
Called “small” because they are usually only about 21-24 nucleotides long.
Synthesized by first cutting up longer precursor sequences (like the 61nt one that Lee discovered).
Silence an mRNA by base pairing with some sequence on the mRNA.
Discovery of siRNA?
The first small RNA:
In 1993 Rosalind Lee (Victor Ambros lab) was studying a non- coding gene in C. elegans, lin-4, that was involved in silencing of another gene, lin-14, at the appropriate time in the
development of the worm C. elegans.
Two small transcripts of lin-4 (22nt and 61nt) were found to be complementary to a sequence in the 3' UTR of lin-14.
Because lin-4 encoded no protein, she deduced that it must be these transcripts that are causing the silencing by RNA-RNA interactions.
Types of RNAi ( non coding RNA)
MiRNA
Length (23-25 nt)
Trans acting
Binds with target MRNA in mismatch
Translation inhibition
Si RNA
Length 21 nt.
Cis acting
Bind with target Mrna in perfect complementary sequence
Piwi-RNA
Length ; 25 to 36 nt.
Expressed in Germ Cells
Regulates trnasposomes activity
MECHANISM OF RNAI:
First the double-stranded RNA teams up with a protein complex named Dicer, which cuts the long RNA into short pieces.
Then another protein complex called RISC (RNA-induced silencing complex) discards one of the two RNA strands.
The RISC-docked, single-stranded RNA then pairs with the homologous mRNA and destroys it.
THE RISC COMPLEX:
RISC is large(>500kD) RNA multi- protein Binding complex which triggers MRNA degradation in response to MRNA
Unwinding of double stranded Si RNA by ATP independent Helicase
Active component of RISC is Ago proteins( ENDONUCLEASE) which cleave target MRNA.
DICER: endonuclease (RNase Family III)
Argonaute: Central Component of the RNA-Induced Silencing Complex (RISC)
One strand of the dsRNA produced by Dicer is retained in the RISC complex in association with Argonaute
ARGONAUTE PROTEIN :
1.PAZ(PIWI/Argonaute/ Zwille)- Recognition of target MRNA
2.PIWI (p-element induced wimpy Testis)- breaks Phosphodiester bond of mRNA.)RNAse H activity.
MiRNA:
The Double-stranded RNAs are naturally produced in eukaryotic cells during development, and they have a key role in regulating gene expression .
A brief information about the SCOP protein database used in bioinformatics.
The Structural Classification of Proteins (SCOP) database is a comprehensive and authoritative resource for the structural and evolutionary relationships of proteins. It provides a detailed and curated classification of protein structures, grouping them into families, superfamilies, and folds based on their structural and sequence similarities.
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.
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.
Slide 1: Title Slide
Extrachromosomal Inheritance
Slide 2: Introduction to Extrachromosomal Inheritance
Definition: Extrachromosomal inheritance refers to the transmission of genetic material that is not found within the nucleus.
Key Components: Involves genes located in mitochondria, chloroplasts, and plasmids.
Slide 3: Mitochondrial Inheritance
Mitochondria: Organelles responsible for energy production.
Mitochondrial DNA (mtDNA): Circular DNA molecule found in mitochondria.
Inheritance Pattern: Maternally inherited, meaning it is passed from mothers to all their offspring.
Diseases: Examples include Leber’s hereditary optic neuropathy (LHON) and mitochondrial myopathy.
Slide 4: Chloroplast Inheritance
Chloroplasts: Organelles responsible for photosynthesis in plants.
Chloroplast DNA (cpDNA): Circular DNA molecule found in chloroplasts.
Inheritance Pattern: Often maternally inherited in most plants, but can vary in some species.
Examples: Variegation in plants, where leaf color patterns are determined by chloroplast DNA.
Slide 5: Plasmid Inheritance
Plasmids: Small, circular DNA molecules found in bacteria and some eukaryotes.
Features: Can carry antibiotic resistance genes and can be transferred between cells through processes like conjugation.
Significance: Important in biotechnology for gene cloning and genetic engineering.
Slide 6: Mechanisms of Extrachromosomal Inheritance
Non-Mendelian Patterns: Do not follow Mendel’s laws of inheritance.
Cytoplasmic Segregation: During cell division, organelles like mitochondria and chloroplasts are randomly distributed to daughter cells.
Heteroplasmy: Presence of more than one type of organellar genome within a cell, leading to variation in expression.
Slide 7: Examples of Extrachromosomal Inheritance
Four O’clock Plant (Mirabilis jalapa): Shows variegated leaves due to different cpDNA in leaf cells.
Petite Mutants in Yeast: Result from mutations in mitochondrial DNA affecting respiration.
Slide 8: Importance of Extrachromosomal Inheritance
Evolution: Provides insight into the evolution of eukaryotic cells.
Medicine: Understanding mitochondrial inheritance helps in diagnosing and treating mitochondrial diseases.
Agriculture: Chloroplast inheritance can be used in plant breeding and genetic modification.
Slide 9: Recent Research and Advances
Gene Editing: Techniques like CRISPR-Cas9 are being used to edit mitochondrial and chloroplast DNA.
Therapies: Development of mitochondrial replacement therapy (MRT) for preventing mitochondrial diseases.
Slide 10: Conclusion
Summary: Extrachromosomal inheritance involves the transmission of genetic material outside the nucleus and plays a crucial role in genetics, medicine, and biotechnology.
Future Directions: Continued research and technological advancements hold promise for new treatments and applications.
Slide 11: Questions and Discussion
Invite Audience: Open the floor for any questions or further discussion on the topic.
This pdf is about the Schizophrenia.
For more details visit on YouTube; @SELF-EXPLANATORY;
https://www.youtube.com/channel/UCAiarMZDNhe1A3Rnpr_WkzA/videos
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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.
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.
2. Pioneers in chloroplast & plant
molecular biology
Discovered chloroplast
genetics (Chlamydomonas)
andDNA
Chloroplastgenes in corn;
demonstratedlight regulation
Chloroplastgene
function;nuclear control
Ruth Sager Lawrence Bogorad Jean-David
Rochaix
(Harvard) (Harvard) (Geneva)
3. THE HOUSE OF PLANT PHOTOSYNTHETIC MACHINERY-
CHLOROPLAST
4. INTRODUCTION
→ The term Chloroplast was first described
by Nehemiah Grew and Antonie Van
Leeuwenhoek.
→ “Chloro” means green while “ Plast”
meansliving.
→ Chlorophyll pigments present in the
chloroplast imparts the greencolour to plants.
→ Chloroplasts are present in plants and
other eukaryotic organisms that conducts
photosynthesis.
→ Chloroplasts are the most important
plastids found in plant cells.
Photo of Chloroplast in a
Moss Cell
7. CHLOROPLAST
Also known as the site of Photosynthesis. We all know what photosynthesis is, it is the process by
which chlorophyll containing cell synthesize carbohydrate from CO2 & H2O using the energy of
sunlight.
The green leaves are the main photosynthetic organ and chloroplast are the organelles which
function as the site of photosynthesis in higher plants.
Within the chloroplast there is a membranous system consisting of grana and stromal lamellae
and fluid matrix.
The membrane system is responsible for trapping light energy and synthesizing ATP and NADPH.
In Stroma the enzymatic reaction incorporates CO2 in the plant leading to the synthesis of sugar.
The former set of reaction are light dependent and are light reaction. The latter reaction though
dependent on the product of light i.e., ATP and NADPH can occur in dark and are called dark
reaction.
A typical plant cell mightcontain about 50 chloroplasts per cell.
8. Chloroplasts found in higher plants are generally biconvex or planoconvex shaped. In different
plants chloroplasts have different shapes, they vary from spheroid, filamentous saucer-shaped,
discoid or ovoid shaped.
They are vesicular and have a colorless center. Some chloroplasts are in shape of club, they have a
thin middle zone and the ends are filled with chlorophyll. In algae a single huge chloroplast is seen
that appears as a network, a spiral band or a stellate plate.
The size of the chloroplast also varies from species to species and it is constant for a given cell type.
In higher plants, the average size of chloroplast is 4-6 µm in diameter and 1-3µm in thickness.
Chloroplasts are bigger and fatter than mitochondria. That is why chloroplasts settle first when
photosynthetic cells are homogenized and centrifuged.
Like mitochondria, chloroplasts have their own DNA, termed cpDNA.
Site of photosynthesis in plants and algae.
CO2 + H2O + Sun Light ----->Sugar+ O2
Structure of Chloroplast
9.
10. The chloroplast are double membrane bound organelles and are
the site of photosynthesis The chloroplasts have a system of
three membranes: the outer membrane, the inner membrane and
the thylakoid system. The outer and the inner membrane of the
chloroplast enclose a semi-gel-like fluid known as the stroma.
This stroma makes up much of the volume of the chloroplast,
the thylakoids system floats in the stroma.
Outer membrane - It is a semi-porous membrane and is
permeable to small molecules and ions, which diffuses easily.
The outer membrane is not permeable to larger proteins.
Intermembrane Space - It is usually a thin intermembrane space
about 10-20 nanometers and it is present between the outer and
the inner membrane of the chloroplast.
Inner membrane - The inner membrane of the chloroplast forms
a border to the stroma. It regulates passage of materials in and
out of the chloroplast. In addition of regulation activity, the fatty
acids, lipids and carotenoids are synthesized in the inner
chloroplast membrane.
11. STROMA: is a alkaline, aqueous fluid which is protein rich and
is present within the inner membrane of the chloroplast. The
space outside the thylakoid space is called the stroma. The
chloroplast DNA chlroplast ribosomes and the thylakoid
sytem, starch granules and many proteins are found floating
aroundthestroma.
THYLAKOID: The thylakoid system is suspended in the
stroma. The thylakoid system is a collection of membranous
sacks called thylakoids. The chlorophyll is found in the
thylakoids and is the sight for the process of light reactions of
photosynthesis to happen. The thylakoids are arranged in
stacksknownasgrana.
Eachgranumcontainsaround10-20thylakoids.
Thylakoids are interconnected small sacks, the membranes of
these thylakoids is the site for the light reactions of the
photosynthesis to take place. The word 'thylakoid' is derived
from the Greek word "thylakos" which means 'sack'.
12. Protein complexes which carryoutlight reactionof photosynthesisare embedded inthe membranes of
the thylakoids.The PhotosystemIandthePhotosystemII are complexes thatharvest light with
chlorophyllandcarotenoids,they absorbthe light energy anduse it to energize the electrons.
The molecules present in thethylakoidmembraneuse theelectronsthatareenergized topumphydrogen
ions intothe thylakoidspace,this decrease thepHand become acidicinnature.Alargeprotein complex
knownas theATPsynthasecontrols theconcentrationgradientofthe hydrogenions inthe thylakoid
spaceto generateATP energy andthe hydrogenions flowbackintothe stroma.
Thylakoidsareof twotypes-granalthylakoidsandstromalthylakoids.Granalthylakoidsarearrangedin
the granaare pancakeshapedcircular discs,which areabout300-600nanometers in diameter. The
stromalthylakoidsarein contactwiththe stromaandare in theform ofhelicoid sheets.
The granalthylakoidscontainonly photosystemIIprotein complex, this allows them tostacktightlyand
formmany granallayers wiht granalmembrane. This structureincreases stabilityandsurface areaforthe
captureof light.
The photosystemIandATPsynthaseprotein complexes are present in thestroma.These protein
complexes acts asspacers between the sheets ofstromalthylakoids.
13. Outer membrane
Permeable
Inner membrane
Selectively permeable
Transport proteins present
Ribosome (70S)
Site of protein synthesis
Intermembrane space
Circular DNA
Codes for proteins (enzymes)
- e.g. rubisco
Intergranal lamella
Granum
Stack of thylakoids (~ 100)
Large surface area
Site of light-depemdent reactions
Products – ATP + reduced NADP + O2
Stroma (fluid)
Enzymes for light-independent
(dark) reactions – Calvin cycle
Products – glucose + NADP + ADP
Starch grain (storage)
Storage polysaccharide (made of
glucose)Thylakoid membrane
• Increase surface area
• Pigments arranged in clusters
termed photosystems (PS)
• Allow maximum absorption of
light
• Electron carriers present
• Proton pumps present
• ATP synthase complex (for
ATP synthesis by
photophosphorylation)
• Photolysis (splitting) of water
• Products of light-dependant
reactions (ATP + reduced
NADP + O2) pass into stroma
Biconvex shape
Increases surface area
Lipid droplet
CHLOROPLAST
14. Chloroplasts Trap Solar Energy and Convert
it to Chemical Energy
The purpose of the chloroplast is to make sugars
that feed the cell’s machinery. Photosynthesis is
the process of a plant taking energy from the Sun
and creating sugars. When the energy from the
Sun hits a chloroplast and the chlorophyll
molecules, light energy is converted into the
chemical energy found in compounds such
as ATPandNADPH.
Those energy-rich compounds move into the
stroma where enzymes fix the carbon atoms from
carbon dioxide (CO2). The molecular reactions
eventually create sugar and oxygen (O2). Plants
and animals then use the sugars (glucose) for food
and energy. Animals also breathe the oxygen gas
thatis released.
15. Functionsof chloroplast:
Inplantsall thecells participateinplantimmune response asthey lack specialized immune cells. The
chloroplastswith the nucleus andcellmembrane andER arethe key organelles of pathogendefense.
The most importantfunctionofchloroplastis tomake foodbythe process of photosynthesis.Foodis
preparedin theformof sugars.During the process ofphotosynthesissugarandoxygen aremade
using lightenergy, water,and carbondioxide.
Lightreactionstakes place onthe membranes of thethylakoids.
Chloroplasts,like the mitochondriause thepotentialenergyof theH+ions orthe hydrogenion
gradienttogenerate energy inthe formof ATP.
The darkreactionsalso knownas theCalvin cycletakes place in the stromaof chloroplast.
ProductionofNADPH2 molecules and oxygenas a result ofphotolysisof water.
BY theutilizationof assimilatorypowers the6-carbonatomis brokenintotwomolecules of
phosphoglycericacid.
16.
17. LIGHT REACTION
What is the main purpose of the light reactions?
Input: Water, Photons of light
Output: Oxygen, ATP & NADPH
18. PhotosyntheticPigment
They are the substances that have an ability to absorb light at a
specific wavelength. There are four types of pigments:
1) Chlorophyll- a 2) Chlorophyll- b
3) Carotenes & 4) Xanthophyll.
The chloroplast pigments are broadly classified into two types: -
1) Chlorophyll - They are the green photosynthetic pigment.
A series of 5 types of chlorophyll i.e., chlorophyll a, b, c, d & e
occurs in plants other than bacteriochlorophyll.
Chlorophyll a found in all photosynthesis organism except bacteria
hence, it is known as Universal photosynthetic pigments.
Chlorophyll b and other chloroplast pigments are known as
accessory pigment. As they transfer the absorbed light energy to
chlorophyll a.
2) Carotenoids - It absorbs blue light and reflects yellow (xanthophyll)
and orange (carotene) light. They absorb light by chlorophylls – then
pass .
19. PIGMENT SYSTEM
Photosystem I (PS – I): It is a protein complex that uses light to mediate electron
transfer.
It lies on the outer surface of thylakoids and more of chlorophyll-a molecule
(P – 700).
Here, P stands for Pigment and 700 is the wavelength of light at which the
molecule absorb.
Photosystem II (PS – II): It is a pigment protein complex consisting of several
proteins and cofactors.
It occurs on the inner surface of thylakoids and have chlorophyll a,
chlorophyll b, carotenoids. Carotenoids content is higher as compared to PS
I.
PS – II has a special type of chlorophyll a molecule called P – 680.
20. LIGHT REACTION IN PHOTOSYNTHESIS
Photosynthesis is two step process in which one step is light dependent and the
other is independent.
The light reaction , a light independent reaction which occur in the grana of
chloroplast, and require the direct energy of light to make NADPH and ATP that
are used in dark reaction.
The photochemical reaction occurs in the light reaction- in this phase the solar
energy is trapped by chlorophyll stored in the form of chemical energy of ATP
and as reducing powerNADPH2. The ATP and NADPH2 together constitute the
assimilatory power of plant. O2 is exhaled in light reacts by splitting water
molecules.
Light reaction in the photosystem starts electron flow . In oxygenic
photosynthetic organisms, flow of electron is of two types: Cyclic and Non-
Cyclic.
21. Non – Cyclic Electron flow:
It is a light- induced electron transport from water to NADP+ and a concomitant evolution of oxygen.
It involves a collaboration of two photosystems: PSII and PSI. Electron move form water through PSII
and PSI and thentoNADP+.
Electron transport leads to generation of proton- motive force and synthesis of ATP. Formation of
ATP dueto lightinducednon-cyclicelectronflow iscalled Non-cyclic Phosphorylation.
Electronsreleasedduringphotolysisof water ispicked by thephotocenterof PSII calledP680.
It passes through a series of e- carrier (Phe) Phephytin, Plastoquinone (Pq), Cytochrome (B12),
Plastocyanine(PC).
By passing over to Cytohrome complex, the electrons loses sufficient energy for the synthesis of ATP.
Theelectronishanded overtothephotocenter(P700).
P700 excludes the electron passes through special chlorophyll molecule Fe- S complex, Ferrodoxine
to finally reach NADPH+. The later, combine with H+ with the help of NADP reductase to form
NADPH.Thisiscalled Z-scheme dueto Zig-Zag shape.
23. Cyclic Electron flow:
It is the process of photophosphorylation in which the electrons are expelled by the excited photo-
center is to it after passing through a series of electron carrier. It involves PSI only.
When non-cyclic phosphorylation is stopped under certain condition, cyclic photophosphorylation
occurs. The non-cyclic process can be stopped by illuminating isolated chloroplast with a lighter
wavelength greater than 680nm actives.
In cyclic electron flow , photo-excited electrons from P700 of PSI move through b6f complex and
back to P700. This cyclic electron flow is coupled to proton pumping into the thylakoid lumen. When
protons flow their electrochemical gradient through ATP synthase complexes, ATP synthesis occurs.
The formation of ATP due to light induced cyclic electron flow is called cyclic phosphorylation. There
is no transfer of electrons from PSI to NADP for acceptor as NADPH, is no longer available and there
is no release of O2.
In plants, the cyclic flow of electrons is utilized only when the concentration of NADPH is sufficient,
still needs ATP to power other activities in the chloroplast. Cyclic phosphorylation is somewhat more
productive as compared to non-cyclic photophosphorylation with regard to ATP synthesis.
25. Difference between CyclicandNon-cyclic?
Cyclic Non- cyclic
It involves PSI only It involves both PSI &
PSII
It synthesize only ATP It constitute with
synthesis of ATP &
NADPH.
It is not connected
with the photolysis of
water. Therefore, O2 is
not evolved.
It is connected with the
photolysis of water.
Therefore, O2 is
liberated.
26. DifferencebetweenPS – I & PS – II?
PS – I PS – II
Consist of pigment molecule
absorbing both longer &
shorter wavelength of light.
Consist of pigment molecule
absorb both only shorter
wavelength of light.
The reaction center is P700 The reaction center is P680
Lies on the outer surface of
Thylakoid.
Lies on the inner surface of
Thylakoid.
In this system molecular O2 is
not released.
In this system molecular O2 is
released by photolysis of
water.
Participation in both cyclic
flow of electron.
It involves only non-cyclic
flow of electron.
