Science questions in short. [3 marks ]

The function of a nerve cell is to transmit messages to the brain and also to take away messages from the brain to the receptor organs. Thus, it controls the working of different parts of the body.

The finger-like projection of varying lengths protruding out of the body of Amoeba, is called pseudopodia. These projections appear and disappear as Amoeba moves or feeds. Thus, the function of pseudopodia is to facilitates movement and help in capturing food.

Differences between a plant cell and animal cell:

Plant cell	Animal cell
A plant cell has a cell wall around its cell membrane. Blue-green algae cell.	An animal cell does not have a cell wall around it.
Plastids are present.	Plastids are absent.
A single large vacuole is present.	Vacuoles either are absent or if present, they are smaller in size.

The figure given in question, represents a plant cell. The various parts correctly labelled are as follows:

Plant and animal specimens are usually stained with dyes before observing them because they are transparent and will not be visible to naked eye. Hence, they are stained and then observed under a microscope, staining makes them clearly visible. Animal cells are stained with methylene blue and plant cells are stained with iodine.

Yes, all organisms have a cell membrane. It is one of the basic component of cell that encloses the other basic components-cytoplasm and nucleus. The cell membrane separates the cells from one another and controls the movement of materials in and out of the cell. Both plant and animals have cell membrane. In plants it is inside the cell wall and in animals it is the outer layer of the cell.

Most of cells are extremely small and cannot seen with naked eye, hence cells could not be observed and studied for thousands of years.

Although cells are living structures and bricks are non-living, the arrangement of cells is comparable to bricks of building because like buildings made of same bricks have different shapes, sizes and designs, similarly organisms are made up of same cells but are different from each other. Organism made of single cell are called unicellular organisms whereas, organisms made up of more than 1 cell are called multicellular organisms.

Cells are the basic unit of live. It is a membrane covered structure containing all the material needed for life. Cell are the smallest unit of life that carry out all the functions of living beings. Tissue is a group of cells of the same type that perform speciic function in the organism.

The muscle cells are responsible for movement in our body by contracting and relaxing.

The cell organelles like mitochondria, Golgi complex, ribosomes, nucleus, etc., have specific functions and carry out specific functions in a cell but they cannot be called as the structural and functional units of living organisms. This is because they can function only when present inside a living cell. They cannot act as independent units. The cei, on the contrary has independent existence. It is the smallest, structural and functional unit of life.

Different cells perform different functions and they have different shapes and sizes. For example, nerve cells have ibres that may be more than one meter long. Muscle cells are long and thin. This helps the muscle cells in expansion and contraction. White blood cells can change their shape, and this helps them to destroy germs. Plant cells located on the outer part of the stem have thick walls for support. Some cells in plants are used to store food, and these cells are larger than other cells.

The organisation of a multicellular organism is as follows- Cells- TissuesOrgan- Organ System- Organism. Cell are the smallest unit of life that carry out all the functions of living beings. Group of cells of the same type form tissue that perform speciic function in the organism. Several types of tissue form organ which carry out particular functions. Several organs together form organ system which work together to perform a function. All the organ systems together form a multicellular organism.

The additional layer surrounding the cell membrane of plant cells is called cell wall. Since, the plants cannot show physical movement and escape themselves from extreme climatic conditions, therefore a cell wall is needed for protection. The cell wall protects the plant cells from temperature variation, high wind speed, atmospheric moisture, etc. It also gives shape and support to plant cells.

The outermost layer of plant cells is the cell wall. Beneath which is the cell membrane. The term cytoplasm. Refers to the jelly-like substance containing all the cell organelles. The nucleus. Contains thread-like structures called chromosomes.

Cell membrane is the thin outermost layer of cells. It functions to keep the cytoplasm and organelles inside the cell. Since it is semi permeable, it regulates the entry and exit of water, soluble molecules and other materials. Cell membrane also helps in communicating with other cells & provides protection and support to the cell.

The lower levels of organisation in multicellular organism are cells, tissues and organs. Cell are the smallest unit of life that carry out all the functions of living beings. Group of cells of the same type together form tissue that perform speciic function in the organism. Several types of tissue form organ which carry out particular functions. Organ system and inally organism are the levels followed after these 3 lower levels.

Cytoplasm is a jelly-like substance present between the cell membrane and the nucleus. Cytoplasm contains many specialised cell organelles. Each of these organelles performs a specific function for the cell. Cytoplasm contains a number of minute living structure known as cell organelles. Each of these organelles performs a specific function for the cell. Most of the chemical reactions which are necessary to keep cell alive take place in the cytoplasm.

Plastids are major organelles found only in plant cells. The green coloured plastids present in plant cells, are called chloroplast. It contains photosynthetic pigment called chlorophyll which helps in the synthesis of food.

A tissue is a group of similar cells performing a specific function. Examples: Epithelial tissue, muscle tissue.

Mitochondria is the site of cellular respiration or oxidation of food in a cell. It uses glucose and oxygen to produce energy. Hence, it is knowns as “Powerhouse of the cell”.