Page 1 - Lesson Notes

SAI International School
Subject- Biology, Class- IX
Topic- The Fundamental Unit of Life
Subtopic- Plastids, Vacuoles
Module- 7
LESSON NOTES

PLASTIDS

 Plastids are the large cell organelles found only in plants which are

specialized to synthesize and store organic substances.
 It is of two different types:
(i) Chromoplasts (colored plastids)
(ii) Leucoplasts (colorless plastids)

 Plastids containing the pigment chlorophyll are known as chloroplasts.
 Chromoplasts contain red, orange or yellow pigments and are common in
ripening fruit, flowers or autumn leaves.
 Leucoplasts mainly stored materials like starch, protein, oils, etc.
 They are known as Semi- autonomous organelle as can survive on their
own.
 They have their own DNA, RNA and proteins.
 During cell division, these organelles pass their own genetic material along
with the cellular DNA.

Figure- Types of plastids

Structure

 Double-membraned organelle. Within the double membrane is a gel-like
substance called stroma. It contains enzymes for photosynthesis.

 Suspended in the stroma are stack-like structures called grana (singular =

granum). Each granum is a stack of thylakoid discs.