(a) Mitochondria is called powerhouse of the cell.
(b) The energy from the food is released into the mitochondria, from where it is used by cell for various activities.
(c) Supriya is intelligent, attentive and has scientific attitude and knowledge

The structural hierarchy found in organisms starts from the cell that is the basic structural unit in all living organisms. Similar cells combine to form tissues, tissues combine to form organs, organs work together to form organ systems and all the different organ system, combine to form the organism.

It is said that the nucleus controls all the metabolic activities as well as formation of various cell organelles. Thus, if the nucleus is removed, it will adversely affect the organism. In organism such as Amoeba, removal of nucleus may even lead to death.

In a multicellular organism, all cells do not have the capability to perform all life functions. Thus, the given statement is false.
Although each cell can carry out the important functions of life, it is not capable of existing on its own, e.g. A muscle cell cannot obtain its own food or oxygen. Other specialised cells in the body collect food or oxygen.
All the cells do not perform all the jobs, different tasks or functions are divided among different groups of cells.

(a) Cytoplasm It is a jelly-like substance, present between the cell membrane and the nucleus. It encloses tiny structures called cell organelles that perform different functions. It also contains water, sugar, proteins, minerals, etc.
(b) Nucleus of a cell It is a spherical component of cell commonly located in the centre of cell. It is covered by porous nuclear membrane and contains genetic material like RNA and DNA. It also contains thread-like structures called chromosomes which carry genes. Nucleus controls various activities of the cell and play role in inheritance.

Robert Brown in 1831 discovered the nucleus in the cell.

Amoeba and Paramecium are unicellular organisms that made up of single cell.

Three important parts of a cell are cell membrane,cytoplasm and nucleus

Chloroplasts are found only in plant cells because plants synthesise their own food in the leaves. Chloroplast contains green pigment called chlorophyll which is essential for making food by the process called photosynthesis and also imparts green colour to the leaves.

Three main differences between plant and animal cells are as follows:

The size of the cells of an organism is not related to the size of organism. This can be understood with the example of an elephant and a rat.
The cells in elephant are not big in size as compared to the cells of small animal like rat. Hence, cells are not related to the size of an organism 
However, the size of a cell is related to the function that a cell performs. The nerve cells in both rat and elephant are long and branched and perform the function of transferring and receiving messages and also help in coordination of different functions of body parts 

Organelles are distinct, highly organised structures that perform specialised functions within the cell.
The organelles that are found in most cells are mitochondria, ribosomes and vacuole.
Functions of nucleus
(i) It is concerned with the transmission of hereditary traits from the parent to offspring (i.e.inheritance).
(ii) It controls all the metabolic activities of the cell (i.e. control centre of cell activities).