14 Nov 2020 8:38 am
Chapter 5: Cell Structure and Organization.
EXERCISE [PAGES 57 – 58]
Balbharati, solutions, for, Biology, 11th, Standard, Maharashtra State Board, Chapter 5, Cell Structure and Organization, Exercise, [Pages 57 – 58], Answer the following questions,
Q.3. Answer the following questions,
Distinguish between smooth and rough endoplasmic reticulum.
Smooth endoplasmic reticulum (SER):
1. Depending on cell type, it helps in the synthesis of lipids for e.g. Steroid secreting cells of the cortical region of the adrenal gland, testes and ovaries.
2. Smooth endoplasmic reticulum plays a role in detoxification in the liver and storage of calcium ions (muscle cells).
Rough Endoplasmic Reticulum (RER):
1. Rough ER is primarily involved in protein synthesis. For e.g. Pancreatic cells synthesize the protein insulin in the ER.
2. These proteins are secreted by ribosomes attached to rough ER and are called secretory proteins. These proteins get wrapped in a membrane that buds off from the transitional region of ER. Such membrane-bound proteins depart from ER as transport vesicles.
3. Rough ER is also involved in the formation of membrane for the cell. The ER membrane grows in place by the addition of membrane proteins and phospholipids to its own membrane. Portions of this expanded membrane are transferred to other components of the endomembrane system.
Mitochondria are power house of the cell. Give reasons.
1. Mitochondria possess oxysomes on its inner membrane. These oxysomes take active part in synthesis of ATP molecules.
2. During cellular respiration, ATP molecules are produced and get accumulated in the mitochondria. They play an important role in cellular activities.
3. Only mitochondria can convert pyruvic acid to carbon dioxide and water during cell respiration. Therefore, mitochondria are called ‘power house of the cell’
What are the types of plastids?
1. Plastids are classified according to the pigments present in it. Three main types of plastids are leucoplasts, chromoplasts and chloroplasts.
2. Leucoplasts do not contain any photosynthetic pigments they are of various shapes and sizes. These are meant for storage of nutrients:
a. Amyloplasts store starch.
b. Elaioplasts store oils.
c. Aleuroplasts store proteins.
3. Chromoplasts contain pigments like carotene and xanthophyll etc.
a. They impart yellow, orange or red colour to flowers and fruits.
b. These plastids are found in the coloured parts of flowers and fruits.
4. Chloroplasts are plastids containing green pigment chlorophyll along with other enzymes that help in production of sugar by photosynthesis. They are present in plants, algae and few protists like Euglena.