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Topic 1: Cells 1.1 Introduction to Cells Cell Theory: All living organisms are composed of cells o Cell is a basic unit of life. o It has a cytoplasm which is surrounded by a plasma membrane which contains a single nucleus Evidence: Robert Hooke: observations of cork material. Microscopes showed presence of box-like cellular structures. All cells come from pre-existing cells o Cells can be cultured outside body if nutrients and oxygen is present. o Mitochondria and chloroplast will not survive out of cell. o Viruses (though smaller than cells) do not count as they do not undergo process of life. Cells are the smallest unit of life o Evidence : Louis Pasteur broth experiment. The exceptions to the cell theory: Muscle Fibre o Multinucleate cytoplasm Giant Algae o Extremely large for a single cell Fungal Hyphae o Multinucleate organism Unicellular organisms Carry out all functions of life Chlorella, Scendesmus Not Eugena Multicellular Organisms Emergent properties (cells form tissues, tissues form organs etc.) The cell contributes to a greater task Many cells working together and world be useless alone. Functions of Life Metabolism - chemical reactions that occur Reproduction - Living things produce offspring, sex/asexually Homeostasis - maintaining constant internal environment Excretion -removal of waste materials from metabolism Response - the ability to react to changes in environment Nutrition - obtaining food to provide energy & materials for growth Topic 1: Cells 1.1 Introduction to Cells Surface Area to Volume Ratio of Cells Bigger size/volume o faster rate of using or making materials in cell (chemical activity per unit of time. Bigger surface area o faster rate of entering and exiting cell (removing waste and allowing reactants to enter) Imbalanced ratio o cell will eventually die Therefore, the cell must divide to restore a good ratio. Magnification: Unit Lengths relative to 1m m 1 cm 100 mm 1000 µm 1000000 nm 1000000000 Topic 1: Cells 1.1 Introduction to Cells Differentiation of Cells (Multicellular organism) All cells of an individual organism have identical genomes, each contains the entire set of genetic instructions for that organism Chemical signals are the instructions for the different genes to differentiate and become specialized Specialized cells are distinct from one another, and serve specific purposes Active genes are package in euchromatin, which is expanded and accessible Inactive genes are in heterochromatin, which is condensed. Stem Cells Unspecialized cells Have the ability to differentiate into a wide range of cells (pluripotent) Embryonic stem cells Blastocyst (one week after fertilization) o Outer layer = skin, nervous system, face, neck o Middle Layer = blood, bones o Inner Layer = respiratory and digestive systems Adult Stem Cells Growth, mantainence, repair Some wait for signals, others continuously repair cells which wear out Stargats disease Hereditary disease Mutation for vitamin A processing in the eye Causes light sensitive cells in the retina (esp. Macula) to deteriorate Small yellow spots, blind spots, poor colour vison, wavy vision and problems seeing with little light. Stem cell treatments Stargat's disease o Surgeon injects 150microliters of RPE cells under (temporarily detached) retina o RPE cells support retinas photoreceptors (detect light & pass on information) Leukaemia o Bone marrow transplant from healthy bone marrow is introduced to bloodstream once abnormal leukocytes are killed.