Photosynthesis & chloroplast

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

1. PHOTOSYNTHESIS AND CHLOROPLAST AMRITHA S R BSC BIOTECHNOLOGY JSS UNIVERSITY MYSURU

2. Introduction Chloroplasts are double membranous organelles with thylakoid system present in plant cells & some eukaryotic organism . It is the structure in a green plant cell in which photosynthesis occurs. Animal cells do not contain chloroplasts.

3. The distribution of chloroplasts is homogenous in the cytoplasm of the cells & in certain cells chloroplasts become concentrated around the nucleus or just beneath the plasma membrane. A typical plant cell might contain about 50 chloroplasts per cell.

4. Chloroplast absorb sunlight & convert into sugar molecules & also produce free energy which is stored in the form of ATP & NADPH through photosynthesis. Chloroplasts are said to have originated from endosymbiotic bacteria.

5. Chloroplast structure They are generally biconvex or Plano convex shaped. Size varies from 4-6µ in diameter & 1-3µ in thickness.

6. Double membranous structure with the inner & outer membrane. Outer membrane- semi-porous & is permeable to small molecules & ions, which diffuse easily. Inner membrane – regulates passage of materials in & out of the chloroplast . Stroma -alkaline ,aqueous protein rich fluid .The chloroplast DNA ,ribosomes & thylakoid system are found floating in stroma.

7. Granum & Thylakoid system -is suspended in the stroma. It is a collection of membranous sacks called thylakoids. Chlorophyll is found in the thylakoids & is the sight for the process of light reaction of photosynthesis. Each granum contains around 10-20 thylakoids. Thylakoids are of two types Granal thylakoids Stromal thylakoids Stroma lamellae - granum is interconnected by stroma lamellae .

8. Chloroplast Pigments chlorophyll a chlorophyll b carotenoids xanthophyll

9. Chloroplast function Participate in plant immune system. Site of photosynthesis Light reaction takes place on the membranes of thylakoids. Dark reaction / Calvin cycle takes place in the stroma. Production of NADPH₂ & O₂.

10. PHOTOSYNTHESIS

11. Photosynthesis Photosynthesis is a physio-chemical process by which autotrophic organisms use light energy to make sugar & O₂ gas from CO₂ & H₂O in the presence of chlorophyll. 6CO₂ + 6H₂ O ――――――> C₆H₁₂O₆ + 6O₂

12. Function of photosynthesis Evolves molecular oxygen ,for use by other living organisms. Maintains the level of atmospheric oxygen. Produces carbohydrates that are used by the plants & animals. It is the only process ,which produces huge quantities of organic matter for sustaining life on earth . For e.g.: natural fibers, drugs ,vitamins, gums, rubber ,furniture etc.

13. S teps in photosynthesis In all green plants ,this process occurs in leaves . CO₂ & O₂ enter & exit the leaves from the leaves through pores called stomata. Water gets delivered to the leaves from the roots through a vascular system. The chlorophyll ,present in the chloroplasts of the leaf cells helps in absorbing sunlight. Chlorophyll & other carotenoids help in transferring light energy. Photosynthesis is carried out in two phases. The light reactions produce carbohydrates by using ATP & NADPH. The dark reaction synthesizes sugar from CO₂ with the help of ATP & NADPH.

14. Phases of Photosynthesis Light Reaction Dark reaction

15. Light reaction Requires light energy & occurs in thylakoids membranes .

16. Dark reaction It takes place in the stroma region of the chloroplast .

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