Chloroplasts are green double membrane-bound organelles primarily located in the mesophyll cells of leaves, responsible for photosynthesis. They contain chlorophyll, which absorbs sunlight and drives the synthesis of carbohydrates, and various accessory pigments that assist in light absorption. The structure includes thylakoids, grana, and a stroma that houses enzymes and DNA necessary for metabolic processes.

1. CHLOROPLAST
AND
CHLOROPHYLLS

2. CHLOROPLAST

3. INTO THE INTERIOR OF
THE LEAF

7. o Leaves are the kitchen of the biosphere.
o Food is prepared in chloroplasts using sunlight.
o A pigment called chlorophyll present in the
chloroplast helps to absorb sunlight.
o Chloroplasts occurs chiefly in the mesophyll cells
of leaves.
o The shape of chloroplasts may vary with
organism.

8. STRUCTURE OF A LEAF

9. stroma
grana
Chloroplast
DNA
Ribosome
Stroma lamella
External membrane
Periplastidal space
Internal membrane
Granal thylacoids
Thylacoid membrane
3D STRACTURE OF CHLOROPLAST

10. Structure of chloroplast
• Chloroplast is a green double membrane bound
organelle.
• Chloroplasts occurs chiefly in the mesophyll
cells of leaves.
• The shape of chloroplasts may vary with
organism these are may lens shaped, oval,
spherical, discoid etc.
• It is double walled and fluid filled bag, having a
gelatinous matrix, called stroma.

11. • It consist a lamellar membrane system,
ribosomes, double-stranded circular DNA
molecules, mRNA, tRNA, starch grains, lipid
globules (plastoglobuli), enzymes, proteins,
etc.
• A number of organized flattened membranous
sacs called thylacoids are present in stroma.
• Thylacoid membranes are store houses of
photosynthetic pigments.

12. • The thylacoid system consists of some cylindrical
discs called grana (singular- granum).
• Each granum is a stock of several flattened sacs
called granal lamellae or granal thylacoid.
• A few unstacked thylacoids may also be present
they are called stromal thylacoid or stromal
lamellae.
• Stromal lamellae are flate membranous tubules
connecting the thylacoids of different grana.

13. • The membrane of the thylacoids enclose a
space called lumen.
• The stroma of the chloroplast contain
enzymes required for the synthesis of
carbohydrates and proteins.
• Stroma is the metabolic centre concern with
the fixation of CO2, and the synthesis of
nucleic acid, sugars, fatty acids etc.

15. CHLOROPHYLL

16.  Chlorophyll present in the chloroplast helps to
absorb sunlight.
 There are different types of chlorophylls in leaves
such as chlorophyll a, chlorophyll b.
 There are other pigments also give colour to
leaves.
chlorophyll a – bluish green
chlorophyll b – yellowish green
Carotenes – yellowish orange
Xanthophyll – yellow

17.  All these pigments have the ability to absorb
sunlight. But chlorophyll a alone can take part
directly in photosynthesis.
 The other pigments are called accessory
pigments.
 The accessory pigments absorb sun light and
transfer there energy to chlorophyll a.
 chlorophyll a and chlorophyll b absorb mainly the
blue and red rays of visible light.
 Since the green rays are not absorbed at all, it is
reflected making the leaves appear green.

18. Other photosynthetic pigments are,
• Chlorophyll c in brown algae, diatoms,
dinoflagellates.
• Chlorophyll d in some red algae.
• Bacteriochlorophyll in purple and green bacteria.
• Chlorobium chlorophyll (bacterioviridin) in
green bacteria.

19. • Phycoerythrin in red algae and cyanobacteria
• Phycocyanin in red algae and cyanobacteria
• Bacteriorhodopsin in halobacteria.