CBSE class 8 science structure of a cell

1. CBSE class 8 Science – Structure of a cell Science is the study of life itself. Science, is a vast subject, with many sub-disciplines that concentrate on specific aspects of biology, physics and chemistry.. Learning Science could be a difficult job if you don’t create an effective method to memorize the hundreds of definitions and terminologies involved. In this Article, we are going to explain CBSE class 8 Science - Structure of a cell. A building block or basic structural unit of life. Structure of a Cell All the plant and animal cells have three main parts – cell wall (in plants) or cell membrane (in animals) and cytoplasm and Nucleus. Cell Wall – this is the most rigid, protective, outermost covering found in plant cells only. It provides shape and rigidity to the plant cell. Cell Membrane - this is also called the plasma membrane. It is a very thin layer covering the cell. There are very thin tiny holes in the cell membranes. The cell membrane or plasma membrane performs the following functions: It protects the cell It provides shape to the cell. It allows materials to enter and leave the cell through the tiny holes.

2. Cytoplasm (kytos = hollow, plasm = liquid) present inside the cell and filled with jelly-like substance. It occupies the space between the cell membrane and the nucleus. It has several different structures called cell organelles which perform the various life functions. Nucleus -This is a dense body found in the centre of the cell which control all the activities of the cell. The Nucleus is made up of the following parts:- Nuclear membrane: it is the porous membrane which separates the contents of a nucleus from the cytoplasm. Nucleoplasm: the fluid present in the nucleus is called nucleoplasm. Nucleolus: Small spherical body made up of nucleoprotein. RNA are also present in nucleolus. Chromosome: Nucleoplasm contains certain threadlike structures called chromosomes. These carry genes which are responsible for the passage of traits from one generation to another. CELL ORGANELLES These are extremely small structure present in the cytoplasm. Cytoplasm is composed of many living and non-living parts called cell organelles which are concerned with cell function. Mitochondria: Mitochondria ( singular mitochondrion) are oval or rod shaped organelles commonly called ‘Powerhouse of the cell’ because the production of energy from food takes place here. Endoplasmic Reticulum: It synthesizes, stores and transports material within the cell. Golgi Complex: it secretes enzymes, proteins and hormones. Lysosome: All cells contain enzymes which help in breaking down the various material. They are also called suicidal bags. Plant cells do not have Lysosome. Ribosomes: it is the site of protein synthesis. Valcuole: The space within the cytoplasm of the plant cell containing cell sap is called vacuoles. Prokaryotic and Eukaryotic cells The nucleus of animals and plants differ in structure. The nucleus in bacteria is not well organized. There is no nuclear membrane. Whereas in the cells of animals and plant nucleus is well defined with nuclear membrane. Prokaryotic: (Pro = primitive, karyon = nucleus) – these cells are bacteria and blue green algae. Eukaryotic: ( Eu = true, karyon = nuceus) – These cells are found in all organisms except bacteria and blue green algae.

3. The following are the major differences between plant and animal cells: Plant Cell Animal Cell A rigid cell wall is present. Chloroplasts are present. Large Vacuoles are present and occupy a large portion of the cell. Centrosomes are absent. Lysosomes are absent. The Cell wall is absent. Chloroplasts are absent. Vacuoles are either absent or very small and few in number. Centrosomes are present. Lysosomes are present. Division of a Cell and Growth Plants and human beings start their life as a single cell. This single cell produces billions of cells. A small seed grows into big plant or small baby grows into full grown human being. How does this happen? A cell grows and then divides into two, increasing the number of cells. The process is called cell division. The cells resulting from the cell division of a parent cell are called daughter cells. The daughter cells resemble the parental cell in a number of characters. Daughter cells grow in their maturity and divide again. New cells are required in our body not only for growth, but also for replacement of old worn out or damaged cells. Skin cell continues to divide throughout life. But nerve cells do not divide after a certain age. Takshilalearning offers CBSE class 8 Science and all other subjects in 2D and 3D videos lectures that contain an elaborate animated representation of the actions and reactions. Once you watch these videos and understand the occurrences of the Scientific world and stories, it will become impossible for you to forget those. Simulation helps you in learning as your all senses along with your hands involved while learning. For de,os or more details visit https://www.takshilalearning.com/demo/