General Science Solutions Solutions for Class 8 Science Chapter 10 - Cell And Cell Organelles

Answer:

Ans 1 a. Mitochondria
b. Cell wall
c. Cell membrane
d. Mitochondria
e. Chloropyhll

Answer:

a. RBC's are a type of cells which are found in blood. Their function is to carry oxygen to different cells and tissues of the body. They do not contain mitochondria for two purposes:
firstly, it saves the space in the red blood cells and so more of oxygen can bind to it
secondly, it prevents the use of oxygen which is bounded to RBC's.

If mitochondria would have been present in RBC's, the oxygen which is carried by them will be used up by the RBC's. Thus, there will be less or no oxygen left which can be transported to the cells and tissues.

b. Mitochondria and plastids are two different structures and they have specific functions. Mitochondria are found in both plants and animals whereas plastids are found only in plants. The main role of mitochnodria is to provide energy to the cells for carrying out their various functions. If, there would have been no difference between mitochondria and plastids, there would have been no structure which would provide energy and thus all the processes which take place in the cell would cease.

c. Genes are hereditary structures which contain the information which is passed on from one generation to another. They are required for the transmission of information from one generation to another. They are responsible for the characteristics of all the living organisms. They store the information for the various processes which occur in all the living organisms.

d. Plasma membrane is selectively permeable which means it allows the entry or exit of selective materials inside and outside the cell. In its absence, the regulated movement of substances in  and out of the cell will be affected.

e. Anthocyanin is a pigment which is present in plants and imparts them purplish colour. In the absence of this pigment, the structures which usually have purple colour due to its presence would appear colourless.

Answer:

a. Plastids are the odd one out because they are organelles which are found only in plant cells. Rest all the organelles are found in both plants and animals.
b. Chlorophyll is the odd one out beacuse it is a type of pigment which is found in plants only. DNA and ribosomes are found in both plants and animals.

Answer:

a. Functions of the plasma membrane:

• It gives shape and support to the cell.
• It acts as a mechanical barrier to protect the internal contents of the cell.
• It separates the contents of the cell from its surrounding medium. 
• It performs physical activities such as diffusion and osmosis. 

b. Functions of cytoplasm:

• It is the medium for all cellular chemical reactions.
• It is a medium in which the organelles remain suspended.
• It helps in the movement of the different cellular elements. 

c. Functions of lysosomes:

• Lysosomes destroy foreign materials that enter the cell.
• Dead and worn-out organelles are removed by lysosomes.
• Cells are autolysed by lysosomes, and their contents are released within the cell.

d. Functions of vacuoles:

• The main function of vacuoles is to store food in a cell.
• They also help in storing and expelling wastes and toxic by products of metabolic reactions.
• They help in maintaining the turgidity and rigidity of a cell.

• It is the control centre of a cell as it controls all the activities of the cell.
• It also contains gene-containing chromosomes which are the units of inheritance in an organism.

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