chloroplast in plant cell.......................

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 : Palisade mesophyll. 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.

4. 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.

5. 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.

6. 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.

7. Plastoglobuli These are osmophilic bodies lipid in stroma .

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

9. 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.

10. 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.