Railway Science (Biology – Cell : Basic Unit of Life)

Plant Cell - A Eukaryotic cell that makes its own food through photosynthesis. Plant Cell Structure : Cell Wall - Rigid layer which is composed of polysaccharides cellulose, pectin and hemicellulose. It is located outside the cell membrane. Nucleus - A membrane-bound structure that is present only in eukaryotic cells.

Pyruvate is broken down in two different ways : Aerobic (takes place in the mitochondria) and Anaerobic (takes place in the cytoplasm). In the mitochondria, pyruvate is broken down into carbon dioxide and water.

Nerve cells (neurons) are mainly involved in receiving and transmitting information to different parts of the body. Our body is composed of millions to billions of nerve cells. A group of neurons forms a nerve and the nervous system. Bone cells are the cells that make up bone tissue.
Bone tissue is composed of four types of cells - Osteoblasts, Osteoclasts, Osteocytes and Osteoprogenitor cells. Muscle cells are the cells that make up muscle tissue. There are 3 types of muscle cells in the human body - Cardiac, Skeletal and Smooth.

Roots - Develops underground, helps anchor the plant firmly in the soil, Absorbs water and minerals from the soil and conducts them to the stem through the xylem of the plant.
Leaves - Responsible for photosynthesis and transpiration in the plants, Develops laterally at the node, Originates from shoot apical meristems.
Shoot - The part of a plant that comes up above the ground when it is just beginning to grow, or a new part that grows on an existing plant.

It is found in capillaries, alveoli, glomeruli and other tissues where rapid diffusion is required. Plasma cells are differentiated B-lymphocyte white blood cells capable of secreting immunoglobulin or antibodies.
Cuboidal epithelial cells are cube-like in appearance, meaning they have equal width, height and depth. Mast Cells contain chemicals such as histamine, heparin, cytokines, and growth factors.

It is broken down to give carbon dioxide, water and energy. Glucose is broken down into pyruvate and energy is released in the form of ATP in the cytoplasm. Pyruvate is taken into mitochondria and then enters Krebs cycle where it is broken down into carbon dioxide and water, yielding ATP and other by-products which then enter electron transport chain to give rise to more ATPs.

Amoeba is a microscopic single-celled organism found in pond water. It has a cell membrane, a rounded, dense nucleus and many small bubble-like vacuoles in its cytoplasm. Paramecium or paramecia are single-celled protists that are naturally found in aquatic habitats. They are typically oblong or slipper-shaped and are covered with short hairy structures called cilia.

Aerobic respiration takes place in the mitochondria of all eukaryotic entities. Food molecules are completely oxidised into carbon dioxide, water, and energy is released in the presence of oxygen.
Anaerobic respiration occurs within the cytoplasm of prokaryotic entities such as yeast and bacteria. Here, lesser energy is liberated as a result of incomplete oxidation of food in the absence of oxygen.

Photosynthetic organisms contain light-absorbing molecules called pigments that absorb only specific wavelengths of visible light, while reflecting others. The set of wavelengths absorbed by a pigment is its absorption spectrum. In plants pigments which absorb light are Chlorophyll (chlorophyll a and chlorophyll b) and Carotenoids which can be found in the intrinsic part of chloroplast.

Meristematic tissue cells : Made up of a group of cells that divide continuously to form new cells. This tissue is found in the growing regions of plants such as the tips of roots, stems, and branches.
Its function is to make plants grow. The cells of meristematic tissue have thin cell walls and dense cytoplasm. On the basis of position in plants, meristematic tissues are mainly divided into three categories - Apical meristem (increases the length of the plant), Intercalary meristem (responsible for stem elongation or longitudinal growth), Lateral meristem (the increase in the girth of stem and root).