• A level biology,  Biology

    Defences Against Diseases

    The body has three main lines of defence against disease. These involve mechanical barriers, chemical barriers and cells. Mechanical barriers Although many bacteria live on the surface of the skin, the outer layer of the epidermis seems to act as a barrier that stops them getting into the body. But if the skin is cut or damaged, the bacteria may get into the deeper tissues and cause infection. Hairs in the nose help to filter out bacteria that are breathed in. However, if the air is breathed in through the mouth, this defence is by-passed. Chemical barriers The acid conditions in the stomach destroy most of the bacteria that may…

  • How-do-plants-know-when-to-flower
    Biology,  Botony

    How do plants know when to flower?

    Phytochrome, a blue-green pigment, is part of a switching mechanism for phototropic responses to light of red and far-red wavelengths. Its active form, Pfr might trigger the secretion of one or more hormones that induce and inhibit flowering at different times of yeat. The main environmental cue for flowering is the length of night, i.e. the hours of darkness, which vary seasonally. Different kinds of plants from flowers at different times of years, depending on their phytochrome mechanism. Products of a set of master gene govern flower formation by selectively acting on meristematic cells of floral shoots. The study of mutants of common wall cress, Arsbidopsis thaliana, supports an ABC…

  • A level biology,  Biology,  O level biology

    Sir Alexander Fleming

    (August 6 , 1881 – March 11, 1955) Early life and Education Sir Alexander Fleming was a Scottish physician, microbiologist, and pharmacologist, who was born on August 6, 1881 at Lochfield farm near Darvel, in Ayrshire, Scotland. Alexander was the third of four children of farmer Hugh Fleming (1816–1888) from his second marriage to Grace Stirling Morton (1848–1928). In December 1915, Fleming married a trained nurse, Sarah Marion McElroy of Killala, County Mayo, Ireland. Their only child, Robert Fleming (1924–2015), became a general medical practitioner. After his first wife’s death in 1949, Fleming married Dr. Amalia Koutsouri-Vourekas, a Greek colleague at St. Mary’s, on 9th April 1953; she died in…

  • Q & A on cytplasm

    Q & A on Components of Cytoplasm

    Which organelle divides and compartmentalizes the cell?  The endomembrane system, which fills the cell and divides it into compartments, and is visible only through electron microscopy. The endoplasmic reticulum (ER), a series of interconnected membranous tubes and channels in the cytoplasm, is the largest and most extensive system of the internal membranes. What is the function of the endomembrane system? The endomembrane system allows macromolecules to diffuse or be transferred from one of the components of the system to another. What is the difference between rough and smooth endoplasmic reticulum? Rough endoplasmic reticulum are regions rich in ribosomes that manufacture proteins. These regions appear to have a pebbly surface that is somewhat similar to sand-paper.…

  • Biology

    MCQ on Respiration in plant

    Q1) Out of 36 ATP molecules produced per glucose molecule during respiration(A) 2 are produced outside glycolysis and 34 during the respiratory chain.(B) 2 are produced outside mitochondria and 34 inside mitochondria.(C) 2 during glycolysis and 34 during the Krebs cycle.(D) all are formed inside mitochondria. Q2) Respiratory substrate yielding the maximum number of ATP molecule is(A) ketogenic amino acids(B) glucose(C) amylose(D) glycogen Q3) Fermentation is anaerobic production of(A) protein and acetic acid(B) alcohol, lactic acid or similar compounds(C) ethers and acetones(D) alcohol and lipoproteins Q4) In alcoholic fermentation(A) oxygen is the electron acceptor.(B) triose phosphate is the electron donor while acetaldehyde is the electron acceptor.(C) triose phosphate is the electron donor while…