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
1. Granal thylakoids
2. Stromal thylakoids
 Stroma lamellae -granum is
interconnected by stroma lamellae.

8. Chloroplast Pigments
chlorophyll a
chlorophyll b
carotenoids
xanthophyll

10. 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.

11. PHOTOSYNTHESIS

12. 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 + 6H₂O ――――――> C₆H₁₂O₆ + 6O₂

13. 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.

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

15. Phases of Photosynthesis
1) Light Reaction
2) Dark reaction

16. Light reaction
 Requires light energy & occurs in thylakoids membranes.

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