Photo synthesis photosynthesis
CLASS XI BIOLOGY
PHOTOSYNTHESIS
Complete Notes with
Diagrams • Flowcharts • Important Points
Easy English Notes For Board Exams & Quick Revision
Prepared by Puja Roy
, Introduction to Photosynthesis
Photosynthesis is the process by which green plants prepare their own food using
sunlight, carbon dioxide, and water in the presence of chlorophyll.
It is one of the most important biological processes because it provides food and
oxygen for almost all living organisms on Earth.
General Equation
6CO₂ + 6H₂O + Light Energy → C₆H₁₂O₆ + 6O₂
⭐ Important: The oxygen released during photosynthesis comes from water, not from
carbon dioxide.
Importance of Photosynthesis
• Produces food for plants and other organisms.
• Releases oxygen into the atmosphere.
• Maintains the balance of oxygen and carbon dioxide in nature.
• Converts solar energy into chemical energy stored in food.
• Forms the basis of almost all food chains.
Key Point
Photosynthesis is the primary source of food and oxygen on Earth, making it essential
for the survival of life.
Structure of Chloroplast
Chloroplast is the green, membrane-bound organelle where photosynthesis takes place.
It contains chlorophyll and other photosynthetic pigments that capture solar energy.
Main Parts of a Chloroplast
Easy English Notes For Board Exams & Quick Revision
Prepared by Puja Roy
, A. Outer Membrane
The outer membrane forms the protective covering of the chloroplast. It is smooth and
freely permeable to many substances.
B. Inner Membrane
The inner membrane lies just beneath the outer membrane and regulates the movement
of substances into and out of the chloroplast.
C. Stroma
The fluid-filled matrix inside the chloroplast is
called the stroma.
It contains enzymes, DNA, RNA, ribosomes, and
starch grains.
⭐ Important: The dark reaction (Calvin Cycle)
occurs in the stroma.
D. Grana
Grana are stacks of disc-shaped structures called
thylakoids.
They contain chlorophyll pigments and are the
main sites of light absorption.
⭐ Important: The light reaction takes place in
the grana.
E. Thylakoid
A thylakoid is a flattened membrane-bound sac containing photosynthetic pigments.
The thylakoid membrane contains Photosystem I (PS-I), Photosystem II (PS-II),
electron carriers, and ATP synthase.
Easy English Notes For Board Exams & Quick Revision
Prepared by Puja Roy
, F. Stroma Lamellae
The membranous connections that link one granum to another are called stroma
lamellae.
They help maintain communication between different grana.
Quick Summary
• Grana → Site of Light Reaction
• Stroma → Site of Dark Reaction
• Thylakoid Membrane → Contains chlorophyll and photosystems
• Stroma Lamellae → Connect different grana
⭐ Exam Tip: If asked about the site of the light reaction, write "Grana (Thylakoid
Membrane)." If asked about the site of the dark reaction, write "Stroma.”
Photosynthetic Pigments
Photosynthetic pigments are coloured substances that absorb light energy and use it for
photosynthesis.
These pigments are present in the thylakoid membrane of chloroplasts.
Types of Photosynthetic Pigments
A. Chlorophyll-a
Chlorophyll-a is the primary photosynthetic pigment.
It directly participates in the conversion of light energy into chemical energy.
⭐ Important: It is present in the reaction centres of both PS-I (P700) and PS-II (P680).
Easy English Notes For Board Exams & Quick Revision
Prepared by Puja Roy
CLASS XI BIOLOGY
PHOTOSYNTHESIS
Complete Notes with
Diagrams • Flowcharts • Important Points
Easy English Notes For Board Exams & Quick Revision
Prepared by Puja Roy
, Introduction to Photosynthesis
Photosynthesis is the process by which green plants prepare their own food using
sunlight, carbon dioxide, and water in the presence of chlorophyll.
It is one of the most important biological processes because it provides food and
oxygen for almost all living organisms on Earth.
General Equation
6CO₂ + 6H₂O + Light Energy → C₆H₁₂O₆ + 6O₂
⭐ Important: The oxygen released during photosynthesis comes from water, not from
carbon dioxide.
Importance of Photosynthesis
• Produces food for plants and other organisms.
• Releases oxygen into the atmosphere.
• Maintains the balance of oxygen and carbon dioxide in nature.
• Converts solar energy into chemical energy stored in food.
• Forms the basis of almost all food chains.
Key Point
Photosynthesis is the primary source of food and oxygen on Earth, making it essential
for the survival of life.
Structure of Chloroplast
Chloroplast is the green, membrane-bound organelle where photosynthesis takes place.
It contains chlorophyll and other photosynthetic pigments that capture solar energy.
Main Parts of a Chloroplast
Easy English Notes For Board Exams & Quick Revision
Prepared by Puja Roy
, A. Outer Membrane
The outer membrane forms the protective covering of the chloroplast. It is smooth and
freely permeable to many substances.
B. Inner Membrane
The inner membrane lies just beneath the outer membrane and regulates the movement
of substances into and out of the chloroplast.
C. Stroma
The fluid-filled matrix inside the chloroplast is
called the stroma.
It contains enzymes, DNA, RNA, ribosomes, and
starch grains.
⭐ Important: The dark reaction (Calvin Cycle)
occurs in the stroma.
D. Grana
Grana are stacks of disc-shaped structures called
thylakoids.
They contain chlorophyll pigments and are the
main sites of light absorption.
⭐ Important: The light reaction takes place in
the grana.
E. Thylakoid
A thylakoid is a flattened membrane-bound sac containing photosynthetic pigments.
The thylakoid membrane contains Photosystem I (PS-I), Photosystem II (PS-II),
electron carriers, and ATP synthase.
Easy English Notes For Board Exams & Quick Revision
Prepared by Puja Roy
, F. Stroma Lamellae
The membranous connections that link one granum to another are called stroma
lamellae.
They help maintain communication between different grana.
Quick Summary
• Grana → Site of Light Reaction
• Stroma → Site of Dark Reaction
• Thylakoid Membrane → Contains chlorophyll and photosystems
• Stroma Lamellae → Connect different grana
⭐ Exam Tip: If asked about the site of the light reaction, write "Grana (Thylakoid
Membrane)." If asked about the site of the dark reaction, write "Stroma.”
Photosynthetic Pigments
Photosynthetic pigments are coloured substances that absorb light energy and use it for
photosynthesis.
These pigments are present in the thylakoid membrane of chloroplasts.
Types of Photosynthetic Pigments
A. Chlorophyll-a
Chlorophyll-a is the primary photosynthetic pigment.
It directly participates in the conversion of light energy into chemical energy.
⭐ Important: It is present in the reaction centres of both PS-I (P700) and PS-II (P680).
Easy English Notes For Board Exams & Quick Revision
Prepared by Puja Roy
