Chloroplast and parts of the chloroplast.

1. Presented by-
Yogendra Kumar Netam
Roll No- 19403356
MSc 3rd semester

2. STRUCTURAL ORGANIZATION OF CHLOROPLAST
 .Chloroplasts found in higher plants are generally
biconvex or planoconvex.
 .They can be found in Mesophyll cells of plant
leaves.
 .They are vesicular and have a colourless center.
The average size of the
Chloroplast is 4-6 µ in diameter
and 1-3 µ in thickness.

3. DIFFERENT STRUCTURES OF CHLOROPLAST
 The Chloroplast comprises of following structures:-
 1. Envelope or Outer membrane
2. Intermembrane space
3. Inner membrane
4. Stroma
5. Thylakoids
6. Peripheral reticulum
7. Plastoglobulli
8. Ribosomes
9. Starch granules

4. ENVELOPE OR OUTER MEMBRANE
 It is a semi-porous membrane and is permeable to small
molecules and ions, which diffuses easily. The outer
membrane is not permeable to larger proteins.
 It plays an important role as
the physical barrier between the
organelle and the cytoplasmic
environment.
The lipid composition of the outer
membrane has been found to be 48% phospholipids,
46% galactolipids and 7% sulfolipids.

5. ENVELOPE OR OUTER MEMBRANE
 The primary functions include the importation of
proteins (nuclear-encoded proteins) movement
(diffusion) of other compounds with low
molecular weight and ions, as well as such
functions as the site for biosynthesis of lipids.

6. INTERMEMBRANE SPACE
 It is usually a thin inter-membrane space about
10-20 nanometers and it is present between the
outer and the inner membrane of the chloroplast.
 The intermembrane space of the
chloroplast does not seem to have any obvious
function.

7. INNER MEMBRANE
 The inner membrane of the chloroplast forms a
border to the stroma. It regulates the passage of
materials in and out of the chloroplast. In addition
to regulation activity, fatty acids, lipids, and
carotenoids are synthesized in the inner chloroplast
membrane.
 The inner membrane of the chloroplast
is highly specialized with transport
proteins.
The inner membrane has been found
to contain 16% phospholipids, 79% galactolipids and
5% sulfolipids in spinach chloroplasts.

8.  Some of the other functions include the synthesis
of different types of metabolites and cell division
of organelles.
 It is heavier than outer membrane.

9. STROMA
 Stroma is an alkaline, aqueous fluid that is protein-
rich and is present within the inner membrane of the
chloroplast. The space outside the thylakoid space is
called the stroma. The chloroplast DNA chloroplast
ribosomes and the thylakoid system, starch granules
and many proteins are found floating around the
stroma.
 It is made of an outer membrane and an
intricate network of inner membranes,
forming stacks of disc-like structures called
grana. Different grana are connected to each
other through membranous extensions.

10. STROMA
 The stroma is essential for this because not only
does it contain the enzymes necessary for carbon
fixation, it also manages the chloroplast response
to cellular stresses and signaling between various
organelles. It plays an important role in both the
light-dependent and light-independent reactions of
photosynthesis.
 The Light dependent reaction
takes place in thyalakoid and the
end products of these reaction(ATP
and NADPH) is contained in stroma
for Light independent reaction.

11. STROMA
 Light independent reaction
takes place in stroma of
chloroplast where they
utilize the end products of
Light dependent reaction.
The first step of the light-independent reactions
involving carbon fixation.
It is a light-independent process in which sugar
molecules are formed from the carbon dioxide and
water molecules. The stroma is the site for the three
steps involved in the Calvin Cycle – carbon fixation,
reduction and regeneration.

12. STROMA
 Plants capture the carbon dioxide from the
atmosphere through stomata and proceed to
the Calvin cycle.
 In the Calvin cycle, the ATP and NADPH formed
during light reaction drives the reaction and
convert six molecules of carbon dioxide into one
sugar molecule, i.e. glucose.

13. CALVIN CYCLE PATHWAY

14. THYLAKOID
 The thylakoid system is suspended in the stroma.
The thylakoid system is a collection of
membranous sacs called thylakoids. The
chlorophyll is found in the thylakoids and is the
sight for the process of light reactions of
photosynthesis to happen. The thylakoids are
arranged in stacks known as grana. Each granum
contains around 10-20 thylakoids.
 There are three different models of
thylakoid including:- Helical model,
The form model, Paired layer.

15. THYLAKOID
 The thylakoid system is made up of lipid bi-
layers. The thylakoid membrane also encloses the
thylakoid lumen, which is a single, large aqueous
space.
 There are two types of thylakoids—granal
thylakoids, which are arranged in grana, and
stromal thylakoids, which are in contact with
the stroma.
 The light reaction is a light-dependent process
which includes a series of events such as light
absorption, hydrolysis, the release of oxygen,
formation of ATP and NADPH.

16. THYLAKOID
 The light reaction of photosynthesis initiates only when
it is supplied with light energy.
 The photosystem is the arrangement of pigments,
including chlorophyll within thylakoids.
 There are two photosystems in plants:
 Photosystem I (PS-I)
 Photosystem II (PS-II)
 Photosystem I absorbs light at a wavelength of 700 nm,
whereas Photosystem II absorbs light at a wavelength
of 680 nm.
 When the light hits, chlorophyll a get excited to higher
energy state followed by a series of reactions. This
energy is converted into energy molecules ATP and
NADPH by using PS I and PS II. Also, hydrolysis occurs
and releases oxygen

17. LIGHT DEPENDENT REACTION
 The net-reaction of all light-dependent reactions
in oxygenic photosynthesis is:
2H2O + 2NADP++ 3ADP + 3Pi → O2 + 2NADPH +3ATP

18. PERIPHERAL RETICULUM
 The chloroplasts of certain plants contain an
additional set of membranous tubules called
peripheral reticulum that originates from the
inner membrane of the envelope. Tiny vesicles
bud off from the inner membrane of the
chloroplast and assemble to form the tubules of
the peripheral reticulum.

19. PLASTOGLOBULI
 They are spherical bubbles
of lipids and proteins about 45–60 nanometers
across.
 They are surrounded by a
lipid monolayer. Plastoglubuli
contain both structural proteins
and enzymes involved in lipid
synthesis and metabolism.
They contain many types of lipids including
plastoquinone , vitamin E, carotenoids and
chorophyll.

20. RIBOSOMES
 Chloroplasts have their own ribosomes, which
they use to synthesize a small fraction of their
proteins. Chloroplast ribosomes are about two-
thirds the size of cytoplasmic ribosomes (around
17 nm vs 25 nm).They take mRNAs transcribed
from the chloroplast DNA and translate them into
protein.

21. STARCH GRANULES
Starch granules are very common in chloroplasts,
typically taking up 15% of the organelle's volume.
Starch granules appear and grow throughout the
day, as the chloroplast synthesizes sugars, and
are consumed at night to fuel respiration and
continue sugar export into the phloem, though in
mature chloroplasts, it is rare for a starch granule
to be completely consumed or for a new granule
to accumulate.

22.  THANK YOU