Nadia Shaheen(BOTN51BFbxbddb20R042).pptx

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1. Thal University Bhakkar Presentation Topic: Functions of Chloroplast Presented To: Dr.M.Kabir Presented By: Nadia Shaheen Roll Number: BOTN51BF20R042 Semester : 7th

2. Functions • The main function of Chloroplast is photosynthesis. Photosynthesis has 2 reactions; 1. Light reaction : It is also called Hill’s reaction , Photosynthetic electron transfer reaction, Photochemical reaction. 2. Dark reaction: It is also called Calvin reaction, Photosynthetic carbon reduction reaction, Carbon- fixation reaction or thermochemical reaction.

3. Light Reaction • Light reaction is the process of photosynthesis that converts energy from sun into chemical energy In the form of NADPH and ATP. • This reaction occur in thylakoid membrane of Chloroplast. • It consist of pigments which are present in form of groups called photosystem.

4. Photosystem • Cluster we of pigments known as photosystem • There are 2types of Photosystems. 1. Photosystem1 ( P700 ): Consist of 200 molecules of chl a, and 50carotene molecules. 2. Photosystem2 ( P680 ): Consist of 200molecules of chla,200molecules of caretenols, chl a, chl c and chl d.

5. Components of Photosystem Antenna complex: Also known as light harvesting complex. It captures light and transfer to reaction centre. Reaction centre: It converts light energy into chemical energy. It contains pigments and proteins .

6. Source : http://www.hammiverse.com/lectures/10/1.html

7. Process of Light Reaction: • Requirements : CO2,Water,chlorophyll,sunlight • Products : ATP and NADPH Step 1 : Photolysis of water Water is split into hydrogen ions, electron and Oxygen The O2 diffuse out of chloroplast Formation of reduced NADPH Step2 : Phosphorylation Light energy is converted into chemical energy Which is temporarily stored in ATP.

8. Source : https://www.quora.com/What-is-the-cyclic-electron-flow-through-light-reaction-events-in-photosynthesis

9. Dark reaction • It occurs in stroma of Chloroplast. • Requirements: NADPH and ATP • Products: Glucose sugar This reaction complete in 3steps Carbon fixation Reduction Regeneration of RuBP

10. Source : ttpss://www.toppr.com/guides/biology/photosynthesis-in-higher-plants/dark-reaction-and-photorespiration/

11. Chloroplast as semiautonomus organelle 1. DNA of Chloroplast: • Ris and Plant (1962) reported DNA molecule in Chloroplast of chlamydomonas. • Later it is reported from Chloroplast of Other algae and higher plants. • Chloroplast have double helical DNA circle with average length of 45um.

12. 2. Ribosomes of Chloroplast: • Ribosomes are of 70S type and resemble to bacterial ribosome. • They consist of two ribosomal RNAs ,23S rRNA and 16S rRNA( Stutz and Noll, 1967, Bager and Hamilton 1967). • Lyttleton also separated polyribosomes from Chloroplast.

13. 3 . Protein synthesis : The mode of synthesis of proteins of chloroplasts indicates towards their semiautonomous or symbiotic nature. Chloroplast proteins may be synthesized by three avenues : (1) by an exclusive chloroplastic mechanism, (2) by a mechanism involving nuclear genes and chloroplastic ribosomes, 3) by nuclear genes and cytoplasmic ribosomes.

14. Symbiotic origin of Chloroplast • Chloroplast divide, grow and differentiate. • They contain circular DNA ,ribosomal RNA, messengar RNA • They are able to conduct protein synthesis. By visualizing these similarities between microorganisms and Chloroplast it has been suggested that chloroplast might have relationship between autotrophic organisms. But some of enzyme of Chloroplast are coded by nuclear genes so there still exist doubt about the symbiotic origin of Chloroplast(Kirk 1966).

15. References • https://www.google.com.pk/books/edition/Cell_Biology_Genetics_Molecular_Biology/dWSUZo6QUjgC?hl=en • https://www.khanacademy.org/science/ap-biology/cellular-energetics/photosynthesis/a/light-dependent-reactions • https://www.geeksforgeeks.org/c4-cycle-of-photosynthesis/.