A cell is a unit of life. In this lesson we will start cell and it's structure. We will also discuss the functions of nucleus , cytoplasm and cell membrane in a cell.
A cell consists of a mass of living matter called protoplasm. It is a complex jelly-like substance in which chemical activities are carried out. 70% of the protoplasm is water, the rest consists of mineral salts and organic compound such as carbohydrates, fats and protein. The protoplasm of the cell consists of 3 parts, nucleus, cytoplasm and cell membrane.
Nucleus:-
The nucleus consists of a nuclear envelop which separates the contents of nucleus from the contents of the cell. Thread- like structures called chromatin are enveloped inside the nuclear envelop. Nucleolus is also a part of the nucleus. The nucleus controls all the activities of the cell. There are spherical structures called nucleoli. Each nucleolus plays a part in the building up of proteins. The functions of the nucleus:
Responsible for cell reproduction.
Needed for the survival of the cell.
Also required for the repair of worn-out parts.
Cytoplasm:-
The part of the protoplasm surrounding the nucleus is called cytoplasm. It usually forms the larger part of the cell and is the place where most chemical processes occur. The cytoplasm consists of 70% of water. This part of cells contain many organelles.
Mitochondria: Small spherical or rod-shaped organelles. They are involved in the storage of released energy from food substances during cell respiration. The energy released may be stored in small molecules called ATP (adenosine triphosphate). This energy may be used by the plants to perform vital activities such as growth and reproduction. Plant cells may also contain the organelles called chloroplasts. Chloroplast is responsible to trap sunlight for the process of photosynthesis. A vacuole is present, it is a fluid-filled space enclosed by a membrane. The central vacuole of a plant cell contains a liquid called cell sap. The large vacuole is enclosed by a membrane called the tonoplast. Other little organelles in animal cells like, centrioles are present in order to ensure smooth cell division.
Cell Membrane:-
The cytoplasm is externally surrounded by a cell surface membrane also called the plasma membrane. It is a partially permeable membrane which controls the movement happening in and out of the cell. In plant cell, there is a cell wall which encloses the whole cell, The cell wall is made of cellulose.
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