Courses
Courses for Kids
Free study material
Offline Centres
More
Store Icon
Store
NEET 2022 | Class 12

NEET Biology Important Chapter - Photosynthesis in Higher Plants

Get plus subscription and access unlimited live and recorded courses
Photosynthesis in Higher Plants NEET Notes, Important Questions and Summary

Photosynthesis in Higher Plants NEET Notes, Important Questions and Summary


Last updated date: 09th Dec 2024
Total views: 276.6k
Views today: 4.76k

Photosynthesis in Higher Plants is a very important chapter from the NEET point of view and one must know all the basics in order to score maximum out of the chapter. Photosynthesis in Higher Plants notes for NEET carry all the important information of the chapter and, thus, can be really helpful for last-minute revision.


This article comprises the topics such as a short note on photosynthesis, where does it occur and what are the factors affecting it, how many types of pigments are involved in photosynthesis, what is a light reaction, electron transport, the use of ATP and NADPH, C₄ pathway and Photorespiration. 


Important Topics of Photosynthesis in Higher Plants

  • Photosynthesis

  • Light Reaction

  • Electron Transport Chain

  • C3 and C4 Pathways

  • Photorespiration


Important Concepts of the Chapter

Photosynthesis is a physicochemical process in which organic molecules are synthesised using sunlight. Higher plants have more processes involved in photosynthesis, however, it is essentially the same. Oxygen is released into the atmosphere as a result of this process.


The chloroplast, which is present in the mesophyll cells of the leaves, is where photosynthesis takes place. Four major pigments are involved in carrying out the process of photosynthesis, namely:

  • Chlorophyll a

  • Chlorophyll b

  • Xanthophylls

  • Carotenoids


Photosynthesis in Higher Plants

Photosynthesis in Higher Plants can be carried out using two major reactions, namely, Light reaction and Dark reaction.


Light Reaction

  • Light reaction, as the name suggests, occurs in the presence of light.

  • The pigment gathers light and converts it to ATP, which is a source of energy.

  • Light absorption, water splitting, oxygen release, and the synthesis of ATP and NADPH are the processes involved in the light reaction.

  • Within two photosystems, PS-I and PS-II, protein-bound pigment molecules create light-harvesting complexes. Each photosystem does have a reaction centre made up of chlorophyll  ‘a’ molecules, as well as antennae holding colours.

  • PS-I has a reaction centre of P-700 because chlorophyll ‘a’ has an absorption peak of 700 nm, while PS-II has a reaction centre of P-680 because chlorophyll a has an absorption peak of 680 nm.


Phosphorylation

Phosphorylation can be described as the process of the formation of ATP under sunlight. There exist two kinds of Phosphorylation, namely, Cyclic Phosphorylation, and Non-cyclic Phosphorylation.


1. Non-Cyclic Photophosphorylation

  • PS-II catches the light with a wavelength of 680 nm, causing electron excitation. An electron acceptor accepts these energised electrons and transfers them to the electron transport system.

  • The electron transport system then transmits the electrons to the PS-I. Parallelly, electrons at PS-I are stimulated by a wavelength of 700 nm.

  • NADP⁺ is reduced to NADPH + H⁺ after receiving an electron from the electron acceptor.

  • PS-II loses electrons that do not return to it, resulting in non-cyclic photophosphorylation.

  • Both photosystems are engaged in this.


2. Cyclic Photophosphorylation

  • In this process, it is just PS-I which is involved.

  • The circulation of electrons is observed happening in the photosystem which apparently leads to the cyclic flow of electrons.

  • Only the formation of ATP happens, no NADPH + H⁺ are produced.


Water Splitting

Photolysis is the light-dependent splitting of water. Manganese and chlorine play a key part in this process, which is linked to PS-II. The electrons that are lost from P680 are replaced by electrons that are created during this process. When light is absorbed by P680, a water molecule splits to release oxygen.


Dark Reaction

As the name says, Dark reactions are the ones that take place in the absence of light. This happens in the stroma of the chloroplasts. C₃ and C₄ cycles are the two cycles involved in this process. 


C₃ Cycle

The C₃ cycle, also called as Calvin Cycle is carried out in 3 steps, namely: carbon fixation, reduction and regeneration. 

  • Ribulose-1, 5-bisphosphate mixes with carbon dioxide to form 3-phosphoglyceric acid, a three-carbon molecule. RuBisCO, an enzyme, is involved in the process.

  • Glyceraldehyde-3-phosphate is formed when two molecules of ATP and one molecule of NADPH fix one molecule of carbon dioxide.

  • Glyceraldehyde-3-phosphate molecules undertake a series of processes to create glucose, while RuBP regenerates to keep the cycle going.


Calvin Cycle

Image: Calvin Cycle

C₄ Cycle

  • Also called Hatch and Slack Pathway, it is a cyclic pathway.

  • Mesophyll cells and Bundle Sheath cells contain the enzymes involved in the C₄ pathway.

  • The leaves with this anatomy are referred to as having 'Kranz' anatomy. The word 'kranz' means 'wreath,' and it refers to the way the cells are arranged.

  • Plants transform ambient carbon dioxide into a four-carbon-containing chemical molecule in this process.

  • The principal carbon dioxide acceptor is phosphoenolpyruvate, which is found in the mesophyll cells. Phosphoenolpyruvate carboxylase catalyses the process.

  • The mesophyll cells then produce aspartic and malic acids, which are then transferred to the bundle sheath cells. The C₄ acids break down here, releasing three-carbon molecules and CO₂.

  • The three-carbon molecules return to mesophyll cells, where they are transformed to phosphoenolpyruvate and the cycle is completed.

  • The Calvin cycle is completed when carbon dioxide enters the bundle sheath cells.


C₄ Cycle or Hatch and Slack Pathway

Image: C₄ Cycle or Hatch and Slack Pathway

Photorespiration

  • Krotkov coined the phrase.

  • Decker and Tio found photorespiration and established that the C₂-cycle occurs during the day in C₃-plants and that Rubisco acts as an oxygenase in C₃-green cells when there is a higher concentration of O₂ and a lower concentration of CO₂.

  • Light-dependent O₂ uptake and CO₂ release in a C₃ photosynthetic cell known as photorespiration.

  • Because it is not linked to ATP synthesis (instead, ATP is consumed) like typical dark respiration, it is a detrimental or wasteful C₃ cycle function.

  • It can be found in chloroplasts, peroxisomes, and mitochondria (three cell organelle reactions).


Factors Affecting Photosynthesis

External Factors

Internal Factors

Carbon Dioxide

Chlorophyll content within the leaves

Light

Accumulation of byproducts

Temperature

Leaf anatomy

Water

Age of leaf

DMCU- an inhibitor of photosynthesis

Hormones and protoplasmic factors.


Difference Between C₃ and C₄ Plants

C₃ Plants

C₄ Plants

C₃ plants do not show the Kranz Anatomy. 

C₄ plants do show the kranz anatomy. 

Mesophyll cells are the site of photosynthesis. 

Mesophyll cells and bundle sheath cells are the site of photosynthesis

Here the carbon dioxide acceptor is RuBisCO.

Here the carbon dioxide acceptor is PEP Carboxylase.

3-C compound called 3-Phosphoglyceric Acid (PGA) is the first stable compound.  

4-C Oxaloacetic acid (OAA) is the first stable compound.

These kinds of plants show a high photorespiratory loss.

Such plants represent less photorespiratory loss. 

The optimum temperature is 20-25 degrees celsius.

The optimum temperature is 35-44 degrees celsius. 


Solved Examples from Chapter

1. Rate of photosynthesis is independent of

  1. Intensity of light

  2. Duration of light

  3. Quality of light

  4. Temperature

Ans: b. Duration of light


Photosynthesis is a natural process that occurs in most green autotrophic plants and certain other animals. It involves the plant absorbing carbon dioxide, water, and light energy before converting it to chemical energy and releasing oxygen into the atmosphere. 


Key point to remember: According to Blackman, the rate of photosynthesis is independent of the length of light and is reliant on the intensity, quality, and temperature of light.


2. Which of the following statements about dark reactions is correct?

  1. They occur in darkness.

  2. They are light dependent.

  3. They are dependent upon the products synthesised during light reactions.

  4. All of these.

Ans: c. They are dependent upon the products synthesised during light reactions.


The dark reaction is reliant on the products (ATP and NADPH) created by the light reaction, but it is not reliant on light directly.


Key point to remember: ATP and NADPH are created during the light reactions.


3. The loss of water in C₄ plants compared to C₃ plants for the same amount of CO₂ fixed is:

  1. A Half

  2. One-third

  3. One-fourth

  4. Double

Ans: b. One-third


When the same amount of Carbon dioxide is fixed in both plants, the loss of water in C₄ plants is really one-third of the volume of water lost by C₃ plants. The amount of water lost by C₄ plants is smaller than that of C₃ plants because C₄ plants have a unique Kranz anatomy that allows them to retain water for longer periods of time.


Key point to remember: The amount of water lost by C₄ plants is smaller than that of C₃ plants.


4. Photorespiration is favoured by

  1. High oxygen and low carbon dioxide

  2. High carbon dioxide and low oxygen

  3. High temperature and low oxygen

  4. High humidity and temperature

Ans: a. High oxygen and low carbon dioxide


Photorespiration is a respiratory process in which higher plants take in oxygen from the light and release carbon dioxide, which is in some ways the opposite of photosynthesis. Photorespiration is favoured by atmospheric conditions with high levels of oxygen and low levels of carbon dioxide, as well as lower humidity.


Key point to remember: Along with high levels of oxygen, low levels of carbon and humidity are required for photorespiration. 


Solved Problems of Previous Years’ Question from the Chapter

1. Which of the following statements is incorrect?

  1. Grana lamellae have both PSI and PSII.

  2. Cyclic photophosphorylation involves both PS I and PS II.

  3. Both ATP and NADPH + H⁺ are non-cyclic synthesised during photophosphorylation.

  4. Stroma lamellae have PS I only and lack NADP reductase.

Ans: b. Cyclic photophosphorylation involves both PS I and PS II.


PSI is engaged in photophosphorylation, both cyclic and non-cyclic. PS II primarily participates in non-cyclic photophosphorylation. PS II is found in the grana thylakoids' appressed (inner) portion. PS I is found in grana thylakoids and stroma thylakoids' non-appressed (outer) regions.


Key point to remember: PS II involves non-cyclic Phosphorylation. 


2. The oxygenation activity of RuBisCo enzyme in photorespiration leads to the formation of:

  1. 1 molecule of the 3-C compound. 

  2. 1 molecule of the 6-C compound.

  3. 1 molecule of a 4-C compound and 1 molecule of the 2-C compound.

  4. 2 molecules of the 3-C compound

Ans: a. 1 molecule of the 3-C compound


Photorespiration is a photosensitive technique. RuBP carboxylase acts as an oxygenase at high temperatures and oxidises ribulose 1, 5-biphosphate to form a 3-carbon phosphoglyceric acid and a 2 -carbon phosphoglycolate instead of fixing carbon dioxide (C₃ cycle).


Key point to remember: RuBP carboxylase acts as an oxygenase at high temperatures.


3. In the leaves of C₄-plants, malic acid formation during CO₂ fixation occurs in the cells of

  1. Mesophyll

  2. bundle sheath

  3. Phloem

  4. epidermis

Ans: a. Mesophyll


CO₂ fixation occurs in the mesophyll of the leaf, which contains chlorophyll pigments, in C₄ plants. Malic acid is generated here during CO₂ fixation. Then it's moved to the bundle sheath, where it'll be decarboxylated and released as CO₂. After that, the enzyme RuBisCo fixes the CO₂.


Key point to remember: Malic acid is generated in mesophyll during CO₂ fixation.


Practice Questions

1. Which sugar of the Calvin cycle utilises ATP?

  1. Carboxylation

  2. Reduction

  3. Regeneration

  4. Both 2 and 3

Ans: d. Both 2 and 3


2. Identify the statement that is true for C₄ plants but not for C₃ plants?

  1. Initially fix carbon dioxide in mesophyll cells as 4-carbon long compounds. 

  2. Initially fix carbon dioxide in bundle sheath cells as 3- carbon long compounds. 

  3. Initially fix carbon dioxide in mesophyll cells as 3-carbon long compounds

  4. Initially fix carbon dioxide in bundle sheath cells as 4- carbon long compounds.

Ans: a. Initially fix carbon dioxide in mesophyll cells as 4-carbon long compounds. 


3. Dark reactions of photosynthesis are actually not totally independent of light as:

  1. The initial reactions occur in the presence of light.

  2. The reaction will be inhibited by the presence of light.

  3. They can occur during the day as well.

  4. They utilise the product of the light reaction.

Ans: d. They utilise the product of the light reaction.


Conclusion

The Photosynthesis in Higher Plants notes PDF can help the student with the last minute revision. The article contains the important concepts of the chapter and ends with the practice questions. The sample questions and practice questions are added to provide an understanding of the type of questions that could be asked in the NEET examination. 

See More
NEET 2024 Important Dates

NEET 2024 Important Dates

View All Dates
NEET 2024 exam date and revised schedule have been announced by the NTA. NEET 2024 will now be conducted on 5 May 2024, and the exam registration starts on 9 February 2024 and closes on 9 March 2024. You can check the complete schedule on our site. Furthermore, you can check NEET 2024 dates for application, admit card, exam, answer key, result, counselling, etc along with other relevant information.
See More
View All Dates
NEET Information

NEET Information

Application Form
Eligibility Criteria
Reservation Policy
Admit Card
NTA has announced the NEET 2024 application form release date on the official website https://neet.nta.nic.in/. The NEET 2024 Application Form is available on the official website for online registration from 9 February 2024 to 9 March 2024. Besides the NEET 2024 application form release date, learn about the application process, steps to fill out the form, how to submit it, the exam date sheet, etc online. Check our website for more details.
NEET 2024 applicants should be aware of the eligibility criteria before applying for the exam. NTA has released all the relevant information on the official website, i.e. https://neet.nta.nic.in/. NEET 2024 aspirants should have passed Class 12th or any other equivalent qualifying examination in 2023, or 2022, or students appearing in the Class 12th final exam in 2024 can also apply. For further details, visit our website.
As per the union government’s norms, NTA has released the NEET 2024 reservation criteria for different candidates’ categories (SC/ST/OBC/PwD), All India Quota, State Government Quota, Deemed Universities, and more. You can check more details on the Vedantu website.
NEET 2024 Admit Card will be released by the NTA in the 4th week of April 2024. Candidates can download the NEET admit card and hall ticket from the NEET official website i.e. https://neet.nta.nic.in/. For more details on the NEET admit card 2024, candidates can check Vedantu's official website.
NEET 2024 Study Material

NEET 2024 Study Material

View NEET Syllabus in Detail
Download full syllabus
Download full syllabus
View NEET Syllabus in Detail
NEET 2024 Study Material

NEET 2024 Study Material

View all study material for NEET
All
Physics
Chemistry
Biology
See All
NEET Question Papers

NEET Question Papers

NEET 2024 Book Solutions and PDF Download

NEET 2024 Book Solutions and PDF Download

View all NEET Important Books
Biology
NCERT Book for Class 12 Biology
Physics
NCERT Book for Class 12 Physics
Chemistry
NCERT Book for Class 12 Chemistry
Physics
H. C. Verma Solutions
See All
NEET 2024 Mock Tests

NEET 2024 Mock Tests

View all mock tests
NEET 2024 free online mock test series for exam preparation are available on the Vedantu website for free download. Practising these mock test papers of Physics, Chemistry and Biology prepared by expert teachers at Vedantu will help you to boost your confidence to face the NEET 2024 examination without any worries. The NEET test series for Physics, Chemistry and Biology that is based on the latest syllabus of NEET and also the Previous Year Question Papers.
See More
NEET 2024 Cut Off

NEET 2024 Cut Off

NEET Cut Off
NTA is responsible for the release of the NEET 2024 cut off score. The qualifying percentile score might remain the same for different categories. According to the latest trends, the expected cut-off mark for NEET 2024 is 50% for general category candidates, 45% for physically challenged candidates, and 40% for candidates from reserved categories. For the general category, NEET qualifying marks for 2024 ranged from 715-117 general category, while for OBC/SC/ST categories, they ranged from 116-93 for OBC, 116-93 for SC and 116-93 for ST category.
See More
NEET 2024 Results

NEET 2024 Results

The NEET 2024 result will be published by NTA on https://neet.nta.nic.in/ in the form of a scorecard on 14 June 2024. The scorecard will include the roll number, application number, candidate's personal details, and the percentile, marks, and rank of the candidate. Only those candidates who achieve the NEET cut-off will be considered qualified for the exam.
See More
Rank List
Counselling
Marks and Rank
NEET 2024 state rank lists will be released by the Medical Counselling Committee (MCC) for admissions to the 85% state quota and to all seats in private medical and dental colleges. NEET 2024 state rank lists are based on the marks obtained in medical entrance exams. Candidates can check the NEET 2024 state rank list on the official website or our site.
The Medical Counselling Committee (MCC) will conduct NEET 2024 counselling at www.mcc.nic.in. There will be two rounds of counselling for admission under 15% All India Quota (AIQ), deemed and central universities, AIIMS, JIPMER, ESIC, and AFMC. A mop-up round of NEET counselling will be conducted excluding 15% AIQ seats, while the dates of NEET counselling for 85% state quota seats will be announced by the respective state authorities.
As per the union government’s norms, NTA has released the NEET 2024 reservation criteria for different candidates’ categories (SC/ST/OBC/PwD), All India Quota, State Government Quota, Deemed Universities, and more. Previously, the Indian Government has provided NEET reservations to OBC (27%) and EWS (10%) candidates under All India Quota (AIQ). You can check more details on the Vedantu website.
NEET 2024 Top Colleges

NEET 2024 Top Colleges

View all NEET 2024 Top Colleges
Want to know which Engineering colleges in India accept the NEET 2024 scores for admission to Engineering? Find the list of Engineering colleges accepting NEET scores in India, compiled by Vedantu. 1990 Colleges are accepting NEET Score. It includes 706 Medical, 323 Dental, 914 AYUSH, and 47 BVSc & AH colleges. Also find more details on Fees, Ranking, Admission, and Placement.
See More
question-image

FAQs on NEET Biology Important Chapter - Photosynthesis in Higher Plants

FAQ

1. What is the total percentage of weightage the unit Plant Physiology makes in the NEET examination? 

The unit Plant Physiology is really important and makes the 6 percent weightage in NEET examination.

2. What are the chapters involved in unit Plant Physiology and how many questions are asked from each chapter.

The unit Plant Physiology involves a total of 5 chapters, and the below-given table shows the bifurcation:

Plant Physiology

Transport in Plants

1-2

Mineral Nutrition

1-2

Photosynthesis in Higher Plants

2

Respiration in Plants

1

Plant Growth and Development

1-2

3. Is chapter Photosynthesis in Higher plants difficult?

The chapter Photosynthesis in Higher plants is interesting to study and has many concepts that are to be thoroughly remembered. Such concepts make the chapter a bit difficult and thus the student is suggested to pay major attention to learning the basics.