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

SER (Smooth Endoplasmic Reticulum). Function - synthesis of carbohydrates, lipids and steroid hormones. It lacks ribosomes and helps synthesize and concentrate various substances needed by the cell. RER (Rough Endoplasmic reticulum). Function - production, folding, quality control and despatch of some proteins.

Upper Epidermis - Prevents water loss by providing an extra layer. Lower Epidermis - Allow carbon dioxide to enter the leaf, and oxygen and excess water to exit the leaf.
Stoma - Regulates gas exchange, controls water loss by changing the size of the stomatal pore. Air Spaces increases the efficiency of gas exchange. Chloroplast - Capture light energy and store it as fuel molecules in the plant's tissues.

The root apex, shoot apex, and many other regions produce new cells by mitotic divisions of meristematic cells. The term “meristem” was coined by Carl Wilhelm von Nägeli. Meristematic tissue contains undifferentiated cells, which serve as the foundation for specialized plant structures.
Seed germination : The embryo within the seed becomes active and grows into a new plant under favorable conditions. Main Types of Roots System : Tap Root system, Fibrous Root system.

The cell theory states that all living things are made of cells. Cells (discovered by Robert Hooke in 1665), viruses (discovered by Beijerinck in 1898). Algae are photosynthetic organisms that exist in environments ranging from oceans, rivers, and lakes to ponds, brackish waters and even snow. Fungi is a primitive organism, mushrooms, mold and mildew are examples.

Plasma membrane (selectively permeable membrane) permits the movement of only certain molecules in and out of the cells. Not all molecules are free to diffuse. Principal components of the plasma membrane - Lipids (phospholipids and cholesterol), proteins, and carbohydrate groups that are attached to some of the lipids and proteins.

Mitochondria (Powerhouse of the Cell) - Breaking down fuel molecules and capturing energy in cellular respiration. Chloroplasts - Found in plants and algae, responsible for capturing light energy to make sugars in photosynthesis. Ribosome (George E. Palade in 1955) - An intracellular structure made of both RNA and protein, and it is the site of protein synthesis in the cell.
DNA (Deoxyribonucleic acid) contains the instructions needed for an organism to develop, survive and reproduce. Plastids are also strange organelle.

Vacuoles are single membrane-bound structures. The membrane of the vacuoles is known as tonoplast. Some plants store waste material in the leaves which fall off, while some store it in the old xylem as resins and gums.

The tissues present in a plant which are dermal or vascular are called ground tissues. Types Parenchyma cells - Cells which have a thin primary wall, usually present in the pericycle, pith and medullary rays of primary stem and root. Parenchyma cells specialized to have air spaces in between them are called Aerenchyma cells. These are found in aquatic plants and aid the plant in floatation.
Collenchyma cells - Have thin primary walls with secondary thickening at corners; Provide mechanical and structural support in regions of new growth in plants. Sclerenchyma cells - Have thick and lignified secondary walls and are dead in nature; provide structural support to plants.

Conversion of glucose to pyruvate is known as Glycolysis. The glucose molecule undergoes partial oxidation and forms 2 molecules of pyruvate and a pair of ATP. Cytoplasm - The fluid inside a cell but outside the cell's nucleus. Ribosome - The organelles that help in protein synthesis. Mitochondria (Powerhouse of the cell) - They have a double membrane structure. Nucleus - the membrane-enclosed organelle within a cell that contains the chromosomes containing DNA.

Leucoplast - non-pigmented organelles (colorless), found in most of the non-photosynthetic parts of the plant (like roots). Act as a storage shed for starches, lipids, and proteins depending on the needs of the plants. Three types - Amyloplasts, Proteinoplasts, Elaioplasts.
Chloroplast - Sites for synthesizing food by the process of photosynthesis. Chromoplast - An area for all the pigments to be kept and synthesized in the plant. Protoplast (naked cells) - They are isolated cells, whose cell wall is withdrawn and are enveloped by plasmalemma.