• A level biology,  Video Notes

    Osmosis

    If a dilute solution is separated from a concentrated solution by a partially permeable membrane, water diffuses across the membrane from the dilute to the concentrated solution. This is known as osmosis. A partially permeable membrane is porous but allows water to pass through more rapidly than dissolved substances. Since a dilute solution contains, in effect, more water molecules than a concentrated solution, there is a diffusion gradient which favours the passage of water from the dilute solution to the concentrated solution. In living cells, the cell membrane is partially permeable and the cytoplasm and vacuole (in plant cells) contain dissolved substances. As a consequence, water tends to diffuse into…

  • environmental science,  Video Notes

    Ecosystem – Structure and Function

    https://youtu.be/RlWj__29Uew The term ‘ecosystem’ was proposed by a British ecologist A.G. Tansley (1953). It represents the basic fundamental, functional unit of ecology which comprises of the biotic community together with its abiotic (non-living) environment. Ecosystem is the functional unit of nature where living organisms interact with each other and with their environment. Ecosystems can be recognized as self-regulating and self-sustaining units of landscapes that may be terrestrial or aquatic. Forests, grasslands and deserts are examples of terrestrial ecosystems. The aquatic ecosystems can be either freshwater (ponds, lakes, streams) or saltwater (marine estuaries) type. Ecosystem may be natural (forest, sea) if developed under natural conditions or artificial (garden, aquarium, agriculture) if…

  • Cell biology,  Video Notes

    CELL JUNCTION

    The cells of epithelial and other tissues are held together by various types of cell junctions, that can be categorized into 3- main groups – (I) Adhesive junctions The cells of epithelial tissue and even cardiac muscles are difficult to separate due to the presence of adhesive junctions. Such junctions are of 2-types (a) Adherens junctions (b) Desmosomes (a) Adherens junctions (Zonulae adherens) – Such junctions are common in the epithelial living of intestine where they form a ‘belt’ encircling the apical portion of cells and binding them to surrounding cells. Such junctions are formed by calcium -dependant-linkages of cadherin (protein) molecules and cement the cells for providing a pathway…

  • Botony,  Video Notes

    ANGIOSPERMS (FLOWERING PLANTS)

    https://youtu.be/XF6WSXqI-ks Angiosperms are most dominant and most evolved plants on this earth, appeared about 130 million years ago in Jurassic (dicot plant) and cretaceous (monocot plants) period of the Mesozoic era. Tertiary period of Cenozoic era is called as Age of angiosperms. Angiosperms are found in every habitat. They constitute more than 50% of the total plants on this earth. Angiosperms are seed bearing, flowering vascular plants in which seeds are enclosed in fruits. The term angiosperm means ‘enclosed seeds’ as seeds (ovules) are found enclosed in the ovary wall. Instead of a cone, angiosperms bear flowers. The flower is the most characteristic structure of the angiosperms. The flower is…

  • Video Notes

    Active Transport

    A few ions or molecules are transported across the membrane against their concentration gradient, i.e., from lower to higher concentration. Such type of transport is called active transport because it is an energy-dependent process in which ATP is utilised, e.g., Na+/K+ pump. https://youtu.be/visqfZd7Ms4 Active transport uses energy to pump molecules against a concentration gradient. Active transport is carried out by membrane-bound proteins. Hence, different proteins in the membrane play a major role in both active as well as passive transport. Cells undergoing active transport bear abundant mitochondria to provide ATP, needed to power active transport. Pumps are protein which can transport the substances. Active transport shows uphill transport because in…