Class 9 Science Chapter 5 MCQ

The Golgi apparatus is involved in formation of lysosome. Lysosomes are simple, tiny spherical sac-like structures evenly distributed in the cytoplasm each lysosome is surrounded by a double membrane and contains powerful enzymes capable of digesting or breaking down all organic material. These enzymes are made by rough endoplasmic reticulum. They perform following functions in our body: i)They help in breaking down or digesting large molecules of the cell. ii)They help in a defence against bacteria and viruses. iii)During starvation, lysosomes act on their own cellular organelles and digest them. This results in cell death. The lysosomes are also called suicide bags or demolition squads of the cell.

Golgi apparatus is absent in bacteria blue and green matches firms and red blood cells of mammals and other animals

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

Schleiden (1836) and Schwann (1834) gave the cell theory, which was further refined by R. Virchow (1855). The main postulates of cell theory are (i)All organisms are composed of cells and cell products. (ii)All metabolic reactions take place in cells. Thus, cell are structural and functional units of life. (iii)All cell arise from pre-existing cells only. No cell can originate spontaneously but they comes into being only by division of pre-existing cells. (iv) Every organism starts its life as a single cell.

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

If the medium surrounding the cell has a higher water concentration, than the cell will gain water by osmosis, such a dilute solution is called hypotonic solution.

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 volume of a cell is fairly constant for a particular cell type and is dependent to the size of an organism. For example, kidney or liver cells are approximately the same size in a bull, horse and mouse. The difference in the total mass of the organ or organisms dependent on the number, not on the volume of the cells. The cells of an elephant are not necessarily larger than those of other tiny animals or plants. The large size of an element is due to the larger number of cells present in its body.

Along with the function of secretion of various enzyme proteins and producing vacoules, Golgi apparatus is also involved in the synthesis of cell wall, plasma membrane and lysosome. Nucleus, mitochondria and plastids have their own genome (i.e., DNA) and ribosomes. They are self-replicating organelles i.e., they have power to divide and are able to synthesise their own structural protein (semi-autonomous organelles). Mitochondria is site of cellulose respiration and synthesis of energy rich compounds (ATP). Therefore, it is called as power house of the cell. The part of cell which between the plasma membrane and nuclear envelope is called the cytoplasm

Ribosomes are dense, spherical and granular particles which remains freely in the matrix or remain attached to endoplasmic reticulum. They are not bound by membrane and are present in both prokaryotic and eukaryotic cells. They play important role in synthesis of proteins. All enzymes are proteins but all hormones are not proteins.