Class 9 Science Chapter 5 MCQ

Each cell is bounded by an extremely delicate, thin elastic living membrane, called the plasma membrane. The plasma membrane is made up of two layers of liquid or fat molecules with protein molecules which is sandwitched between lipid layer. The structure of plasma membrane can be observed under and electron microscope only. It is a selectively permeable membrane which allows the flow of only some substances into the cell and out of the cell. Viruses do not have any membranes. Functions: a) It gives a definite shape to the cell. b) It provides protection to the in contents of the cell. c) It regulates entry and exit of substances in to and out of the cell. d) It can internalise solid and liquid materials by infolding or extending around them. This is the process of active intake of minerals. e) In animal cells, it is involved in adhesion, recognition and in the formation of vesicles, cilia, flagella, microvilli etc.

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

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).

Lipid molecules in the cell are synthesized by the smooth endoplasmic reticulum present in the cell.

The cell walls of adjacent cells are glued together by the plasmodesmata.

Diffusion can occur in any medium and the diffusing molecules may be solids, liquids or gases. Remember, semi-permeable membrane is not required in diffusion.

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.

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

Endoplasmic reticulum exists as a membranous network, which is connected to the outer membrane of nucleus from one side and plasma membrane to the other. It occurs in three forms (i)Cisternae-closed fluid filled sac (ii)Vesicles (iii)Tubules It is of two types, smooth endoplasmic reticulum i.e., without ribosomes on its surface and rough endoplasmic reticulum with ribosomes on its surface.

Osmosis is a spontaneous process where movement of solvent molecules occurs into a region of higher solute concentration from lower solute concentration through a partially permeable membrane, so as to tend to equalise the solute concentration on the two sides. When movement of the solvent takes place from outside to inside the all (inward movement) the process is endosmosis. It occurs in hypertonic solution and causes the swelling of cell. When the movement of solvent takes place from inside to outside of the cell (outward movement) the process is exosmosis. It occurs in hypertonic solution. It results the shrinkage of the cell. When the concentration of water both in the surrounding medium and in the cell is same, the solution in the surrounding medium is said to be isotonic and no movement of water molecules takes place.