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CBSE class9 Science Fundamental Unit of Life Very Short questions






Question 1 What is hypotonic solution?
Answer  A solution having solute concentration lower than that of the cell sap is called hypotonic solution.
Question 2: What is hypertonic solution?
Answer A solution having solute concentration higher than that of the cell sap is called hypertonic solution.
Question 3 What is isotonic solution?
AnswerA solution having solute concentration same as that of the cell sap is called isotonic solution.
Question 4 What is active transport?
Answer The movement of molecules across a membrane in cells against a concentration gradient with the help of ATP units is called active transport.
Question 5  Where are proteins synthesized inside the cell?
Answer Ribonsomes present in the cell synthesise proteins and are called protein factories of the cell. These may be attached on the surface of rough endoplasmic reticulum or lie freely in the cell.
Question 6 What is endocytosis?
Answer Endocytosis is the ingestion of material by folding of the membrane around it for its engulfment as seen in Amoeba.
Question 7 Define plasmolysis.
Answer It is the shrinkage of cytoplasm away from cell membrane when kept in a hypertonic medium.
Question 8 Why is endocytosis found in animals only?
Answer For endocytosis to occur, the outermost membrane should be flexible. But in plants cells, cell wall is the outermost membrane which is very rigid. Hence, no endocytosis occurs in plants.

Question 9 Differntiate between diffusion and osmosis.
Answer
           DIFFUSION
            OSMOSIS
It occurs in any medium.
It occurs in liquid medium only.
 Diffusing molecules may be solid, liquid or gaseous solutes.
It involves movement of solvent molecules only.
Semipereable membrane is not required.
Semipermeable membrane is required.
 
Question 10 How does an Amoeba obtain its food?
Answer In Amoeba, the food particles get surrounded by a cell membrane invagination called pseudopodia. The pseudopodia then merge with each other forming a food vacuole which is engulfed into the body of Amoeba. These vesicles are called phagosomes where the food is digested.
Question 11 What is membrane biogenesis? How is plasma membrane formed during  this process?
AnswerThe process of plasma membrane formation is called membrane biogenesis. 
The proteins and lipids are first synthesized in rough endoplasmic reticulum and the smooth endoplasmic reticulum, respectively. These are then transported to the Golgi complex for their modification. After modification, these are transported to the cell surface through vesicles which bud off from Golgi complex to fuse with cell membrane and form a part of the membrane.
 

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