Chromoplasts - color centers
- Plastids are cells that store specific things.
- They are large cytoplasmic organelles found in the cells
of most plants, but they are not found not in animal cells..
- Plastids form small colorless bodies called proplastids.
- Once formed certain kinds of plastids can be converted
into other types.
- For ex. chlorophyll can be synthesized with a leucoplast
- There are three plastid categories- Leucoplasts (white
or colorless plastids that store starch granules) ,
Chromoplasts (colored plastids that store pigment molecules)
and Chloroplasts which are essential in the photosynthetic
- There are two main types of chromoplasts -- cartenoids
which store yellow and orange pigment and chlorophyll which
stores green pigment.
- Chloroplasts contain chlorophyll which contains green
pigment and some carotenoids which hold yellow or orange
- Chlorophyll traps radiant sun energy then manufactures
complex organic molecules(particularly glucose) from simple
raw organic materials.
Leucoplasts - energy storage
- Leucoplasts are organelles where starch, oil and protein
- The ones filled with starch are common in seeds and
storage roots and stems (i.e. carrots and potatoes).
- Starch is deposited as a grain or a group of grains
- Chloroplasts serve as the site of photosynthesis.
- Leaves have about 500,000 chloroplasts per square
millimeter of the surface. They are found primarily in
cells of the mesophyll, green tissue of the leaf's interior.
Each mesophyll cell contains 30-40 chloroplasts.
- They contain chlorophyll, the green pigment that absorbs
energy from sunlight for use in photosynthesis, which means
putting together with light. Photosynthesis is the process
by which plants make food. In green plants, sunlight
captured by chlorophyll enables carbon dioxide from the air
to unite with water and minerals from the soil and create
food. This process also releases oxygen into the air, and
people and animals must have this oxygen to breathe. Energy
from the sun splits water molecules into hydrogen and
oxygen. The hydrogen joins with carbon from the carbon
dioxide to produce sugar. The sugar--together with
nitrogen, sulfur, and phosphorus from the soil--helps a
plant make the fat, protein, starch, vitamins, and other
materials that it needs to survive.
- Chlorophyll gives plants their color.
- The chloroplasts of most plants are shaped like disks or
lenses. Under a microscope, they can be suspended in the
part of the cell called the cytoplasm. These lens shapes
measure about 2-4 um to 4-7 um. These organelles are
divided into three fundtional compartments by a system of
- a. Intermembrane Space
- i. The chloroplast is bound by a double membrane which
partitions its contents from the cytosol.
- b. Thylakoid Space
- i. Thylakoids form another membranous system within the
- ii. Chlorophyll is found in the thylakoid membranes.
- iii. Thylakoids function in the steps of photosynthesis
that initially convert light energy to chemical energy.
- iv. the thylakoid membrane segregates the interior of
the chloroplast into two compartments: Thylakoid space =
Space inside the thylakoid. Grana = stacks of thylakoids in
- c. Stroma
- i. Viscous fluid outside the thylakoids.
- ii. Those steps that use chemical energy to convert
carbon dioxide to sugar occur in the Srtoma.
- Chloroplasts are one of several types of specialized
plant-cell structures called plastids.
- There are several forms of chlorophyll. The most common
forms in plants are chlorophyll a and chlorophyll b. They
absorb most of the long wavelengths (red rays) and the short
wavelengths (blue-violet rays) of visible light. They
absorb the middle wavelengths (green rays) least