THE CHLOROPLAST

 

   THE SITE OF PHOTOSYNTHESIS

 

THE FIRST PHOTOSYNTHETIC CELLS WERE PROBABLY PROKARYOTIC

 

PROBABLY USED H2S FOR A SUPPLY OF ELECTRONS NECESSARY FOR PHOTO-SYNTHESIS INSTEAD OF H2O

 

PHOTOSYNTHETIC PROKARYOTE “EATEN” BY A EUKARYOTIC CELL

 

PROKARYOTE BECOMES THE CHLOROPLAST

 

CHLOROPLAST CHARACTERISTICS

 

1.   CONTAIN CHLOROPHYLL, CAROTENES    AND XANTHOPHYLLS

 

2.   HAVE A DIAMETER OF 3 TO 10 um

 

3.   ARE LENS SHAPED IN CROSS

   SECTION

 

4. 20 TO 60 PER CELL

 

 

ULTRASTRUCTURE AND BIOCHEMICAL COMPARTMENTS

 

1.   PAIR OF OUTER LIMITING    MEMBRANES (ENVELOPE)

 

   a.   OUTER MEMBRANE IS PERMEABLE

   b.   INNER MEMBRANE IS

      SELECTIVELY PERMEABLE

 

2.   UNSTRUCTURED MATRIX CALLED THE

   STROMA

 

   a.   PREDOMINANTLY PROTEINS

  

      1.   ENZYMES RESPONSIBLE FOR

         PHOTOSYNTHETIC CARBON

         REDUCTION (LIGHT                 INDEPENDENT REACTIONS)

 

 

 

 

         a.   rubisco - RIBULOSE                  1,6-BISPHOSPHATE                   OXYGENASE/CARBOXYLASE

 

            1.   THE MOST ABUNDANT

               PROTEIN ON THE FACE             OF THE EARTH

 

         b.   DNA

         c.   RNA

        

3.   HIGHLY STRUCTURED INTERNAL

   SYSTEM OF MEMBRANES CALLED

   THYLLAKOIDS CONNECTED BY    LAMELLAE

 

   a.   THYLLAKOIDS IN STACKS ARE

      CALLED GRANA

  

   b.   HAVE PIGMENTS (CHLOROPHYLL

      AND CAROTENOIDS) EMBEDDED

 

 

 

 

 

4.   INTRATHYLLAKOID SPACE CALLED

   THE LUMEN

 

   a.   SITE OF WATER OXIDATION

 

   b.   FUNCTIONS AS A RESERVOIR       FOR PROTONS THAT ARE USED

      TO DRIVE ATP SYNTHESIS

 

5.   INTERMEMBRANE SPACE BETWEEN    THE TWO OUTER MEMBRANES

 

OTHER MISCELLANEOUS COMPONENTS

 

   1.   STARCH GRAINS

 

   2.   PLASTOGLOBULI (LIPID

      DROPLETS)

 

   3.   PHYTOFERRITIN - IRON             BINDING PROTEIN

 

 

 

 

NONPHOTOSYNTHETIC METABOLISM OF CHLOROPLASTS

 

   1.   ASSIMILATION OF NITROGEN

 

      a.   NITROGEN TAKEN UP BY

         PLANTS IN THE FORM OF

         NITRATE

 

      b.   NITRATE REDUCED TO

         AMMONIA

 

         1.   GLUTAMINE SYNHETASE             (GS)

 

         2.   GLUTAMATE SYNTHETASE

            (GOGAT)

        

   2.   ASSIMILATION OF SULFUR

 

      a.   SULPHATE REDUCED TO                CYSTEINE

 

   3.   BIOSYNTHESIS OF PROTEINS

 

 

 

   4.   BIOSYNTHESIS OF FATTY ACIDS

 

      a.   SATURATED FATTY ACIDS

 

         1.   PALMITATE

 

         2.   STEARATE

 

CHLOROPLASTS CONTAIN A COMPLETE GENOME INCLUDING DNA, RNA, RIBOSOMES AND ENZYMES NECESSARY FOR PROTEIN BIOSYNTHESIS