*Class 11 Biology - Chapter 13: PHOTOSYNTHESIS IN HIGHER PLANTS* 🌞_NCERT Complete Short Notes | NEET 2027 | 3-4Q Fix = 12+ Marks_

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Class 11 Biology Chapter 13: PHOTOSYNTHESIS IN HIGHER PLANTS 🌞 ke complete NCERT Short Notes le aaya hu.

NEET 2027 walo ke liye 3-4 Questions Fix hai = 12-16 Marks Pakka 💯

Save kar lo, revision me kaam aayega ✅  

### *1. WHAT IS PHOTOSYNTHESIS* `Definition Line`

Definition = Anabolic + Endergonic + Redox Process

Equation: 6CO2 + 12H2O → C6H12O6 + 6H2O + 6O2 ↑

Discovery: O2 from H2O Not CO2 = Proved by Ruben, Hassid, Kamen = O18 Isotope

Chlorophyll = Primary Pigment = Trap Light Energy

Site = Mesophyll Cells = Chloroplast = 5-7 µm Length, 2-4 µm Width

### *2. EARLY EXPERIMENTS* `1Q Pakka`

**Scientist** **Experiment** **Conclusion** **Year**

**Joseph Priestley** Mint + Candle + Mouse in Bell Jar Plants Restore Air = O2 Release 1770

**Jan Ingenhousz** Hydrilla + Sunlight O2 Released Only in Light + Green Part 1779

**Julius von Sachs** Leaf + Iodine Test Glucose Made in Green Part = Starch Storage 1865

**T.W. Engelmann** Cladophora + Prism + Aerobic Bacteria Action Spectrum = Max O2 in Blue + Red 1888

**Cornelius van Niel** Purple + Green S-S Bacteria Study O2 from H2O, H2S = H Donor = General Eqn 1930s

General Equation: CO2 + 2H2A → Light + Chlorophyll → CH2O + H2O + 2A

H2O = H2A, So O2 Released from Water

### *3. CHLOROPLAST STRUCTURE* `Diagram = Board 5/5`

Double Membrane = Outer + Inner

Stroma = Matrix = Dark Reaction = Enzymes of Calvin Cycle + DNA + 70S Ribosome

Thylakoids = Disc = Light Reaction = Pigments + ETS + ATP Synthase

Grana = Stack of Thylakoids = 40-60 per Chloroplast

Stroma Lamellae = Connect Grana = No PS-II

Lumen = Thylakoid Space = H+ Accumulation Site

### *4. PIGMENTS* `NEET Line`

**Pigment** **Color** **Max Absorption** **Role** **Solubility**

**Chl a** Blue Green 430 nm Blue, 662 nm Red Reaction Centre = P680, P700 Ether

**Chl b** Yellow Green 453 nm, 642 nm Accessory = Antenna = LHCP Ether

**Xanthophyll** Yellow 425-475 nm Accessory + Photoprotection Ethanol

**Carotenoids** Orange 450-500 nm Accessory + Photoprotection Chloroform

*Trick*: *C*hl *a* = *C*hief, *b* = *B*odyguard  

*Action Spectrum* = Graph of O2 Evolution vs λ = Peaks at Blue + Red  

*Absorption Spectrum* = Graph of Light Absorbed vs λ = Peaks at Blue + Red  

_Both Same = Engelmann Proved_

### *5. LIGHT REACTION = Photochemical Phase* `2Q Fix`

*A. Photosystems = PS-I + PS-II*

**Feature** **PS-I** **PS-II**

**Location** Stroma Lamellae + Grana Non-appressed Grana Appressed Part

**Reaction Centre** P700 = Chl a P680 = Chl a

**Pigments** Chl a > Chl b, Carotenoids Chl a = Chl b, Xanthophyll

**Primary e- Acceptor** Fe-S Protein Pheophytin

**Photolysis** No Yes = H2O → 2H+ + 1/2 O2 + 2e-

**Function** NADPH Formation ATP + NADPH + O2 Formation

*B. Electron Transport = Z-Scheme* `Non-Cyclic`

H2O → PS-II P680 → Pheophytin → PQ → Cyt b6f → PC → PS-I P700 → Fe-S → Fd → NADP+ → NADPH

Photolysis: 2H2O → 4H+ + O2 + 4e- = Mn, Cl, Ca Needed = OEC = O2 Evolving Complex

ATP Synthesis = Non-Cyclic Photophosphorylation = Chemiosmosis = H+ Gradient

Site = Thylakoid Lumen to Stroma = CF0-CF1 ATP Synthase

*C. Cyclic Photophosphorylation* `Only PS-I`

PS-I P700 → Fe-S → Fd → PQ → Cyt b6f → PC → P700

Only ATP Formed = No NADPH, No O2

Use = When NADPH High but ATP Low = C4 Plants Bundle Sheath

Location = Stroma Lamellae

*D. Chemiosmotic Hypothesis = Peter Mitchell*

H+ Pump = From Stroma to Lumen = 3 Ways

1. Photolysis of H2O = H+ Released in Lumen

2. PQ = Take H+ from Stroma + Release in Lumen

3. NADP Reductase = Use H+ in Stroma

Result = pH Lumen = 4-5, Stroma = 8 = Gradient

H+ Flow via CF0-CF1 = ATP Synthesis = 3H+ = 1 ATP

### *6. DARK REACTION = Biosynthetic Phase* `Calvin Cycle = C3`

*A. C3 Cycle = Calvin-Benson = Stroma*

Phase 1: Carboxylation = CO2 Acceptor = RuBP 5C + CO2 → 2 × 3PGA 3C = RuBisCO

Phase 2: Reduction = 3PGA + ATP + NADPH → G3P = Triose Phosphate

Phase 3: Regeneration = G3P + ATP → RuBP = 5 ATP for Regeneration

Input: 6 CO2 + 18 ATP + 12 NADPH → 1 Glucose + 18 ADP + 12 NADP+

RuBisCO = Most Abundant Protein on Earth = Carboxylase + Oxygenase

*B. C4 Pathway = Hatch & Slack = Kranz Anatomy*

Location: Mesophyll = PEP Carboxylase, Bundle Sheath = RuBisCO

Step 1: Mesophyll = PEP 3C + CO2 → OAA 4C = PEPcase = No Photorespiration

Step 2: OAA → Malate 4C → Transport to Bundle Sheath

Step 3: Malate → Pyruvate + CO2 = CO2 Released to RuBisCO = Calvin Cycle

Step 4: Pyruvate → PEP = Back to Mesophyll = 2 ATP Used

Advantage = CO2 Conc. Mechanism = No Photorespiration = High Temp, Low CO2

Example = Maize, Sugarcane, Sorghum, Amaranthus

Kranz = Wreath = Bundle Sheath = Large, Chloroplast, No Intercellular Space

*C. CAM Pathway = Crassulacean Acid Metabolism*

Succulents = Opuntia, Pineapple, Bryophyllum = Desert Plants

Night = Stomata Open = CO2 → OAA → Malic Acid = Vacuole Store = PEPcase

Day = Stomata Close = Malic Acid → CO2 → Calvin Cycle = Reduce Water Loss

Scotoactive Stomata = Night Open, Day Close

### *7. PHOTORESPIRATION = C2 Cycle* `Wasteful Process`

Condition = High O2, High Temp, Low CO2 = RuBisCO = Oxygenase Activity

Site = Chloroplast + Peroxisome + Mitochondria = 3 Organelles

Process: RuBP + O2 → RuBisCO → 1 PGA 3C + 1 Phosphoglycolate 2C

Phosphoglycolate → Glycolate → Glycine → Serine → Glycerate → 3PGA

Loss = 25% Carbon as CO2 = No ATP, No NADPH = Wasteful

C3 Plants = 25-50% Loss, C4 Plants = No Photorespiration = PEPcase No O2 Affinity

### *8. FACTORS AFFECTING PHOTOSYNTHESIS* `Blackman's Law`

*A. Blackman's Law of Limiting Factors 1905*

Rate = Controlled by Factor Nearest to its Min Value

If All Optimum, One Factor Low = Rate Controlled by That

Example: Light Low = Light Limiting, CO2 Increase No Use

*B. External Factors*

1. Light = Rate Increases till Saturation = 10% Full Sunlight = C3

   C4 = No Saturation even Full Sunlight = Higher Rate

   Light Quality = Red + Blue Max, Green Min

2. CO2 = Major Limiting = C3 Saturation = 450 µl/L, C4 = 360 µl/L

   Present = 300-400 µl/L = Below Optimum = Green House Use

3. Temperature = C4 Optimum = 30-40°C, C3 = 20-25°C

   High Temp = Enzyme Inactivation + Stomata Close + Photorespiration Up

4. Water = Indirect = Stomata Close = CO2 Low = Wilting Reduce Surface

*C. Internal Factors*

Chlorophyll Content, Protoplasmic Factor, Accumulation of Product

### *9. PYQ HOTSPOTS 2017-2024* 🔥

1. *RuBisCO* = Most Abundant Protein + Carboxylase/Oxygenase = NEET 2024

2. *C4 Plants* = Kranz Anatomy + PEPcase + No Photorespiration = NEET 2024

3. *Photolysis H2O* = Mn + Cl + Ca = O2 Evolving Complex = NEET 2023

4. *Cyclic Photophosphorylation* = Only PS-I + Only ATP + Stroma Lamellae = NEET 2023

5. *Calvin Cycle Input* = 6CO2 + 18ATP + 12NADPH = 1 Glucose = NEET 2022

6. *CAM Plants* = Night CO2 Fix + Day Stomata Close = NEET 2022

7. *P700 + P680* = PS-I + PS-II Reaction Centre = NEET 2021

8. *Van Niel* = O2 from H2O Not CO2 = H2S Bacteria = NEET 2021

9. *Engelmann* = Action Spectrum = Aerobic Bacteria + Prism = NEET 2020

10. *Chemiosmosis* = H+ Gradient + CF0-CF1 ATPase = NEET 2020

11. *Kranz Anatomy* = Bundle Sheath Chloroplast + No Intercellular Space = NEET 2019

12. *Photorespiration* = 3 Organelles + No ATP/NADPH = NEET 2019

13. *Blackman's Law* = Limiting Factor = NEET 2018

14. *PEP Carboxylase* = Mesophyll + No O2 Affinity = NEET 2018

15. *Chl a* = Reaction Centre Pigment = NEET 2017

### *10. GOOGLE SE HATKE TRICKS* 🧠

*A. C3 vs C4 vs CAM*

C3 = Calvin Only = 3C First = PGA = RuBisCO = 1 Cell = Photorespiration

C4 = Kranz = 4C First = OAA = PEPcase + RuBisCO = 2 Cell = No Photorespiration

CAM = Night Fix = 4C Malic = Day Calvin = 1 Cell = Water Save

Trick: **3** = **T**een Cell, **4** = **Ch**aar Cell, **CAM** = **C**actus **A**t **M**idnight

*B. ATP NADPH Count*

C3 = 18 ATP + 12 NADPH = 1 Glucose

C4 = 30 ATP + 12 NADPH = 1 Glucose = 12 Extra for PEP to Pyruvate

Trick: **C3** = **18+12** = **30 Total**, **C4** = **30+12** = **42 Total**

*C. PS-I vs PS-II Yaad*

PS-I = **P**ahla = **P**700 = **P**lastocyanin → P700

PS-II = **D**usra = **P**680 = **P**hotolysis = **P**heophytin

Location: PS-I = **S**troma Lamellae, PS-II = **G**rana

*D. Calvin Cycle Steps*

C = Carboxylation = CO2 + RuBP = RuBisCO

R = Reduction = 3PGA + ATP + NADPH → G3P

R = Regeneration = G3P + ATP → RuBP

Trick: **CRR** = **C**ar **R**un **R**egularly

*NEET Weightage*: 1Q Light Reaction + 1Q C3/C4 + 1Q Photorespiration + 1Q Factors = 16 Marks Pakka  

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