Biology IB Topic 1_ Cell Biology.pdf - Topic 1 Cell Biology Introducing the Cell Theory 1 2 3 ● ● Cells are the smallest possible units of life All

Biology IB Topic 1_ Cell Biology.pdf - Topic 1 Cell Biology...

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Topic 1: Cell Biology Introducing the Cell Theory 1) Cells are the smallest possible units of life 2) All living organisms are made of cells 3) All cells come from pre-existing cells Cells consist of cytoplasm, enclosed in a plasma membrane In plant and animal cells there is usually a nucleus that contains genes Exceptions to the Cell Theory Discrepancies - cases that do not fit the theory There are some tissues and organisms that are not made of typical cells: Skeletal muscle - made up of muscle fibres, these fibres are enclosed in a membrane, larger than most cells (300+ mm), hundreds of nuclei Giant algae - can grow to a large size, but only contain a single nucleus Aseptate fungi - consist of thread-like structures called hyphae, which contain many nuclei Functions of life in Unicellular Organisms Unicellular organisms consist of only one cell, which carries out all the functions of life in that cell Paramecium Feeds on smaller organisms through endocytosis Increases in size and dry mass by accumulating matter from its food Reacts to stimuli Expels waste products of metabolism (e.g. carbon dioxide) from respiration Produce enzymes which catalyze many different chemical reactions in the cytoplasm Keeps internal condition within limits Reproduces asexually using mitosis or sexually using meiosis Chlamydomonas Produces its own food by photosynthesis Increases in size due to photosynthesis and absorption of minerals Reacts to stimuli Expels waste products of metabolism (e.g. oxygen) from photosynthesis Produce enzymes which catalyze many different chemical reactions in the cytoplasm Keeps internal condition within limits Reproduces asexually using mitosis or sexually using meiosis Multicellular Organisms As cells grow larger, surface area to volume ratio becomes smaller Rate at which materials enter or leave a cell depend on the surface area Rate at which materials are used or produced depends on the volume A cell that becomes too large may not be able to take in essential materials or excrete waste quickly enough Large organisms contain many cells (multicellular) Different groups of cells become specialized for different functions by differentiation
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Differentiation Genome - an organism’s entire set of genes In multicellular organisms, each cell has the full genome, so it has the instructions to develop into any type of cell Emergent Properties Emergent properties arise from the interaction of the component parts of a complex structure EX. each cell in a tiger’s body has a distinctive property, but when these cells work together, the properties combine and give the tiger the ability to do more complex things such as hunting Stem Cells Stem cells - cells that have the capacity to divide and differentiate along different pathways Human embryos consist entirely of stem cells in early stages
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