This PSEB 8th Class Science Notes Chapter 8 Cell Structure and Functions will help you in revision during exams.
PSEB 8th Class Science Notes Chapter 8 Cell Structure and Functions
→ All living things carry out certain basic functions.
→ Roots, stems, leaves, and flowers are the organs of plants.
→ Animals have also parts such as hands, feet, legs, etc.
→ You cannot observe small pores in your skin without the help of a magnifying lens.
→ All living organisms take and digest food, respire, and excrete waste products.
→ Each organism represents an individual of its own kind.
→ Cells in living organisms are complex structures unlike bricks in a building.
→ Cells found in living organisms show a variety of numbers, shapes, and sizes.
→ Single-celled organisms like Amoeba, Paramecium, and Bacteria are called unicellular organisms.
→ Cells in multicellular plants and animals have a variety of shapes. Cells are generally round or spherical in shape.
→ The yellow part of the hen’s egg is called yolk and it is surrounded by white albumen, yellow yolk represents a single cell.
→ All cells are bounded by a membrane called plasma membrane or cell membrane.
→ Plasma membrane encloses a liquid substance known as protoplasm.
→ The cell wall is present in plant cells which are made up of cellulose.
→ Both the plasma membrane and cell wall give shape to the cell.
→ Ostrich egg represents the largest cell visible to the unaided eye.
→ Each cell has smaller components called cell organelles.
→ Cell multiplies and organisms become multicellular and grow in size.
→ Cells in the living organism are basic structural units.
→ Different groups of cells perform a variety of functions.
→ The number of cells being less in smaller organisms does not affect the functioning of the organisms.
→ WBC in human blood is also single-celled.
→ A group of cells performing a definite function is called a tissue.
→ Each organ is made up of a number of tissues.
→ Organ: These are the smaller parts of all living organisms. Each organ is made up of a number of tissues.
→ Tissue: A group of cells performing a definite function is called a tissue.
→ Cell: It is the basic structural and functional unit of all living organisms.
→ Unicellular: Some living organisms are made up of only a single cell that performs all the metabolic functions. Such organisms are called unicellular.
→ Multicellular: Some organisms are made up of a number of cells. Such organisms are called multicellular. In these organisms, different cells perform different functions.
→ Pseudopodia: These are finger-like false feet of amoeba.
→ White Blood Cell (WBC): These are some of the components of blood cells that engulf harmful foreign materials. These are single-celled.
→ Cell Membrane or Plasma Membrane: It is a thin covering present outside the cell which gives shape to it.
→ Cytoplasm: It is a liquid portion present between the cell membrane and nucleus of a cell.
→ Organelles: These are the living components of cells present in their cytoplasm.
→ Cell Wall: It is an extra covering present around the cell membrane of only plant cells. It gives shape and rigidity to the cell.
→ Nucleus: It is the round part of the cell which is called the controlling centre of the cell.
→ Nucleolus: It is a component of the nucleus which is dense and has a spherical body.
→ Nuclear Membrane: The nucleus is separated from the cytoplasm by a membrane called the nuclear membrane.
→ Prokaryotes: The organisms whose cells are without a well-organized nucleus i.e. lacking nuclear membrane are called prokaryotes.
→ Eukaryotes: The organisms whose cells have a distinct and clear nucleus bounded by the nuclear membrane are called eukaryotes.
→ Vacuole: The fluid-filled organelles present in a cell are called vacuoles.
→ Plastids: Small coloured bodies present in plant cells only are called plastids.
→ Chloroplasts: Green plastids present in plant cells are called chloroplasts.
→ Gene: Genes are dot-like structures present on chromosomes that help in the inheritance of characters from parents to the next generation.
→ Chromosome: These are thread-like structures present in the nucleus of a cell.