Describe the cell organelle which is responsible for the synthesis of starch.
1 Answer
Answer :
The cell organelle responsible for the formation of starch is Chloroplast. It was discovered by Sachs and named by Schimper. It is usually disc shaped or Biconvex or Oval or spherical.
Structurally it consists of envelope, stroma and thylakoids. Envelope has two unit membranes known as outer membrane and inner membrane between which a cavity called periplastidial space is present. Stroma is the enzymatic region surrounded by inner membrane. It has dark reaction enzymes, circular DNA, RNA, 70S ribosomes, thylakoids and starch grains. Since it has circular DNA and ribosomes it can synthesize some of its proteins and can replicate by itself. Hence it is called as semiautonomous cell organelle. Thylakoids are flattened sac like structures present in the stroma. They have pigment molecules such as chlorophylls, carotenoids and phycobilins in their membrane associated with proteins to form Photosystems. It is involved in Light reaction. A stack of thylakoids is called granum and the unstacked thylakoids that connect the adjacent grana are called as Stroma thylakoids.