chloroplast

1. CHLOROPLAST
Prepared by :
Fatma Ghazi
University of Zakho
Faculty of Science
Department of Biology
Supervised by :
Dr.Ahmad basher

2. What is chloroplast ?
■ Chloroplasts are specialized organelles found in most plant cells
and other eukaryotic organisms (algae) that conducts
photosynthesis.
■ Dwells in the cytosol of mesophylls :
1. Palisade mesophyll.
2. Spongy mesophyll.
■ Number of chloroplast :
Lower plant (1 to 16 /cell).
Higher plant (20 to40/cell).
■ Size range of chloroplast : diameters (5_10) width (2_4)
micrometer.

3. Structure
■ Membrane bound organelle. Inner and Outer membrane.
■ Inter membrane space is present between Inner and outer
membrane.
■ Inner membrane encloses a matrix called stroma.
■ Another membrane bound structure called Thylakoids are
present within the stroma.
■ Thylakoids are arranged as stacks to form the granum.
■ Stroma lamellae connects the granum.

5. The Envelope
■ It is composed of a system of
double membranes, each of
which is 6 and 8 nm thick and
has a unit membrane
structure.
■ The outer membrane is
separated from the inner
membrane by an
intermembrane space of about
10nm.

6. Stroma
■ The stroma fills most of the
volume of the Chloroplast.
■ It contains about 50% of the
protein of Chloroplast.
■ It contains Ribosomes and DNA
molecule.

7. Thylacoids
■ Consist of flattened and closed
vesicles arranged as membranous
network.
■ It may be stacked like a neat pile of
coins forming GRANA.
■ There may be 40-80 grana in the
matrix of a Chloroplast.
■ Thylakoids includes light-absorbing
pigments, a complex chain of electron
carriers, and an ATP-synthesizing
apparatus.

8. Plastoglobuli
■ These are osmophilic bodies lipid in stroma.

9. Shapes
Plate shaped -
chlorella
Cup shaped -
chlamydomonas
Ribbon shaped -
spirogyra
Star shaped -
Zygnema
Spherical or Ovoidal shaped
– higher plant

10. Chloroplast pigments
■ Chlorophyll (a, b, c, d, e )
Is responsible for the plant green color.
■ In addition to chlorophyll, other pigments, known as
accessory pigments are present in plants; these
include carotene, and cyanins, colors like orange &
brown.

11. Functions
■ Main function is photosynthesis. 2 phases light
reaction and dark reaction.
■ Photosystems are involved in light reaction, that
synthesize ATP and NADPH. O₂ is released.
■ Dark reaction utilizes the product of light reactions to
fix CO₂.
■ Starch synthesis occurs within the stroma.
■ Some of the intermediates are transported to cytosol
for sucrose synthesis.