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

Gelatin is a fluid found inside the cell. Nucleus and Mitochondria are enclosed by membranes that separate them from the cytoplasm. Function : transport, maintain cell shape and structure, protect, store macromolecules and host to metabolic processes.

Mitochondria are found in most eukaryotic cells and are involved in energy metabolism, allowing them to produce some of their own proteins and replicate independently of the cell.
Plastids are a group of organelles found in plant cells that are involved in various functions such as photosynthesis, pigment synthesis, and storage of nutrients.
Both also have their own DNA and ribosomes, allowing them to produce some of their own proteins and replicate independently of the cell, apart from the nucleus of the cell.

Lysosomes (suicidal bags) are sphere-shaped cell organelle which found within the eukaryotic animal cells and has the capability of breaking down many types of biomolecules of the cell.
Ribosome - An intercellular structure made of both RNA and protein, and it is the site of protein synthesis in the cell. Golgi apparatus is a central intracellular membrane-bound organelle with key functions in trafficking, processing, and sorting of newly synthesized membrane and secretory proteins and lipids.
Endoplasmic reticulum (ER) - A large organelle composed of membranous sheets and tubules that start near the nucleus and stretch throughout the cell.

Pyruvate is taken into mitochondria and then enters Krebs cycle (a chain of reactions occurring in the mitochondria, through which almost all living cells produce energy in aerobic respiration) where it is broken down into carbon dioxide and water, yielding Adenosine triphosphate (ATP) and other by-products which then enter electron transport chain to give rise to more ATPs.

Types of Simple Permanent Tissue: Parenchyma - Helps plants in the photosynthesis process. Sclerenchyma - Don't have intercellular gaps and are found in the seed coverings, nuts, veins of leaves and vascular tissues of stems. Collenchyma - Made up of pectin and cellulose and have minuscule intercellular gaps.

Muscular tissue has the ability to contract and this is what brings about the movement of body parts. They also help to maintain body posture and position. Nervous tissue is found in the brain, spinal cord, and nerves.
It is responsible for coordinating and controlling many body activities. Epithelial tissue protects several aspects of your body. For example, skin is made up of epithelial tissue and protects the tissues deeper in the body, such as blood vessels, muscle and internal organs.

Squamous epithelial cells are a type of flat cell found throughout the body, including in the mouth, on the lips, and on the cervix. These squamous epithelium lines in the alveoli help in gas exchange. The diffusion of gases in the lungs is best accomplished by this single layer of squamous cells.
Columnar epithelial examples : Goblet cells, Pharynx, sex organs, Respiratory tract, Fallopian tubes, etc. Cuboidal epithelial examples : collecting ducts of the kidney, the pancreas, the salivary gland, the sweat glands, and the mammary glands. Ciliated columnar epithelium examples : Sperm ducts, lining the trachea, bronchi, kidney tubules, respiratory tract, and oviducts.

(Cellular Vacuoles) - Contains water, sap , excretory product and other materials not useful for the cell. Region shown by arrow 1 (Cell wall) - Helps to maintain the shape and size of the cell and provides mechanical support. Protects the cell from osmotic shocks, injuries and pathogens.
Region shown by arrow 2 (Cell membrane) - The regulation of the entry and exit of the substances in the cell. Region shown by arrow 3 (Smooth endoplasmic reticulum) lacks ribosomes and helps synthesize and concentrate various substances needed by the cell.

Cell wall surrounds the plasma membrane of plant cells, providing tensile strength against mechanical and osmotic stress. Cell wall permits the cells of plants fungi and bacteria to withstand very dilute external medium without bursting.

Diffusion helps in the movement of substances through cells. Types : Simple diffusion - Ions or molecules move from an area of high concentration to an area of low concentration.
Osmosis diffusion - Particles moving through water across a semipermeable membrane of low solute concentration to a region of high solute concentration. Example - Smoke of incense sticks spreads throughout the room, Sugar dissolves and sweetens the water.
Endocytosis - A cellular process by which a cell internalizes any material (liquid as well as solid) from the external environment. It includes pinocytosis (cell drinking) and phagocytosis (cell eating).