Class 9 Science Chapter 5 MCQ

Grana are stacks of membrane bounded flattened discoid sacs containing the molecules of chlorophyll.

Here, are all the statements are correct. Hence, your answer will be option [D].

Unlike eukaryotic cell, a prokaryotic cell lacks membrane bound organelles like plastids, mitochondria and endoplasmic reticulum but smaller and randomly scattered ribosomes are seen.

In 1938 Schleiden proposed the idea that plants consist of cells. Later in the year 1839, Schwann independently asserted that all animals and plants are made up of cells. This joint finding forms the basis of cell theory. The cell theory was refined further in 1855, when R. Virchow presented the idea that all cells arise from pre-existing cell. His amorphism was (Omnis Cellula-e-Cellula).

Here, are all the statements are correct. Hence, your answer will be option [D].

Plant cells, in addition to the plasma membrane, have another rigid rotor covering called the cell wall. The cell wall lies outside the plasma membrane. The plant cell wall is mainly composed of cellulose. Cellulose is a complex substance and provides structural strength to plants. Bacteria is not a plant therefore its cell wall is made up of “Peptidoglycan”.

Golgi body was first discovered by Camillo Golgi. Golgi bodies, or Golgi complex are formed by stacks of flattened (saucer-shaped) membranes or flattened sacs called cisternae. Golgi bodies are usually called dictyosomes in plants. Golgi apparatus is absent in bacteria, blue-green algae, mature sperms and red blood cells of mammals and other animals. The Golgi apparatus arises from the membrane of the smooth endoplasmic reticulum, which in turn originates from the rough endoplasmic reticulum. The proximal Golgi saccules (cisternae at cis face) are formed by fusion of ER-derived vesicles, while distal saccules (cisternae at trans face) “give their all” to vesicle formation and disappear. Thus, Golgi saccules are constantly and rapidly renewed. The main functions of Golgi apparatus are (i)They store, modify, package and condense the proteins synthesised in the ribosomes. (ii)They form the cell plate during the cell division. (iii)They set aside digestive enzymes in tiny membrane bound vesicles which later become lysosomes. (iv)They synthesise some polysaccharides for the cell membrane.

The prokaryotic cells lack true nucleus and a circular DNA lies naked in the cytoplasm. The unidentified nuclear region of the cell is called nucleoid. The prokaryotic cell lacks chromosomes and nucleolus or nuclear membrane and nucleoplasm remains undifferentiated from the cytoplasm.

The movement of water molecules through selectively permeable membrane along concentration gradient is called osmosis. It is the passage of water from region of high-water concentration through semipermeable membrane to a region of low water concentration (only through semipermeable membrane). Unicellular freshwater organisms and most plant cells tend to gain water through osmosis. Absorption of water by plant roots is also an example of osmosis.

Viruses are considered as an intermediate between living and non-living cells because they cannot metabolize and reproduce on their own. They can reproduce only when enters in a host’s body. They are an exception to all cell theory. A virus crystal is a collection of thousands of viruses. Viral crystal is a pore collection used for chemical studies.