RRB NTPC Exam 2016 will test you on your knowledge of Cells – The structural and functional unit of life.
RRB NTPC Exam 2016 #Daily Infographic on General Science (Biology)
All living organisms on Earth are divided into cells. The main concept of cell theory is that cells are the basic structural unit for all organisms. Cells are small compartments that hold the biological equipment necessary to keep an organism alive and successful. Living things may be single-celled or they may be very complex such as a human being.
Plant Cell Explained
A plant cell consists of three distinct components
(i) Cell wall – Cell wall is the non-living protective layer outside the plasma membrane in the plant cells, bacteria, fungi and algae. The synthesis of cell wall in controlled by Golgi bodies. In bacteria the cell wall is composed of protein and non-cellulosic carbohydrates while in most algae, fungi and all plant cells, the cell-wall is formed of cellulose. Cell wall provides mechanical support and gives a definite shape to the cell. It protects plasma membrane and helps in imbibition’s of water and movement of solutes towards protoplasm.
(ii) Protoplasm – Protoplasm is the living, colourless, elastic, colloidal semi fluid substance present in the cell. Protoplasm with non-living inclusions is called protoplast. Water is the chief constituent of an active protoplast and normally constitutes 90% of the system. The remaining parts are organic and inorganic materials. Protoplasm consists of cytoplasm and nucleus and is externally bounded by the cell membrane or plasmalemma.
(iii) Cell membrane – It is a thin film like pliable membrane, and serves as protective covering of the cell. Cell membrane mainly consists of proteins and lipids but in certain cases, polysachharides have also been found. It facilitates the entrance of nutrients into the cells and allows exit of nitrogenous wastes, regulates the passage of materials into and out of the cells. It controls and maintains differential distribution of ions inside and outside the cell.
(iv) Cytoplasm – It is a jelly like fluid mass of protoplasm excluding the nucleus and surrounded by plasma membrane on the outside. It is semi permeable in nature. The cytoplasm is composed of matrix; the membrane bound organelles and non-living inclusions like vacuoles and granules. The living cytoplasmic organelles are the site of various important metabolic activities such as photosynthesis, respiration, protein synthesis etc.
(v) Plastids – Plastids are the largest cytoplasmic organelles bounded by double membranes.
Animal Cell Explained
Take the Quiz on Plant & Animal Cell