Mitochondria are known as 'Power House' of the cell. They are said so because the energy required for various life activities is released by mitochondria in the form of ATP molecules. The body uses energy stored in ATP for synthesis of new compounds and for mechanical work. As ATP instantly provide energy, the are called energy currency of the cell?

Difference between unicellular and multicellular organisms are as given below:

Multicellularity provides division of labour. This helps the organisms to perform various life processes in a better way.

These are membrane-bound vesicles which bud off from Golgi apparatus. They contain powerful enzymes capable of digesting or breaking down all organic material. The enzymes present in lysosome are synthesised on RER. The membrane that bound lysosomes does not allow the enclosed enzymes to pass freely into the cell cytoplasm. Thus, protects the cell from autolysis (self-dissolution or breakdown). They are absent in RBCs and a few plant cells, for example, yeast, fungi and green algae.

The part of protoplasm which remains after excluding nucleus is known as cytoplasm. Cytoplasm contains aggregate molecules of various chemicals and cell organelles. Most of the biochemical reactions such as protein synthesis, release of energy etc. take place in cytoplasm or organelles present in the cytoplasm.

It performs the following functions in the plant cell:
(i) It gives a definite shape to the cell.
(ii) It provides rigidity and strength to the cell.
(iii) It protects the plasma membrane and inner cell organelles by bounding the cell from outside.
(iv) It allows cell of plants, fungi and bacteria to withstand very dilute external media without bursting.
(v) It helps in transport of the material in and out of the cell.
(vi) Cell wall maintains the shape of the cell when cytoplasm shrinkes away from cell wall during plasmolysis.
(vii) It prevents desiccation of cells.

The following  three things could happen:
(i) If the solution surrounding the cell is very dilute than cytoplasm, the water will move into the cell, i.e., the cell will gain water.
(ii) If the solution has exactly similar water concentration as that of cytoplasm of cell, there will be no net movement of water across the cell membrane, i.e., no gain or loss of water from the cell.
(iii) If the medium (solution) has a lower concentration of water than the cell, i.e., the solution is concentrated, the cell will lose water by osmosis.

Cells constitute various components of plants and animals. A cell is the smallest unit of life and is capable of all living functions. Cells are the building blocks of life. This is the reason why cells are referred to as the basic structural and functional units of life. All cells vary in their shape, size, and activity they perform. In fact, the shape and size of the cell is related to the specific functions they perform.