"CELL THEORY<br /> 1.1.1", "1. all living things are composed of cells (or cell products)<br /> 2. the cell is the smallest unit of life<br /> 3. cells only arise from pre-existing cells" "Explain why cells in multicellular organisms differentiate to carry out specialized functions by expressing some of their genes but not others.<br /> 1.1.8", "Every cell in a multicellular organisms contains all the genes of that organism. However, the genes that are activated vary from cell to cell. The reason we have different types of cells in our body (the cells in your eyes are not the same as the ones that make up your hair) is because different genes are activated in different cells." "Compare the relative sizes of molecules<br /> 1.1.4", "A molecule = 1 nm<br /> Thickness of cell membrane = 10 nm<br /> Viruses = 100 nm<br /> Bacteria = 1μm<br /> Organelles = up to 10 μm<br /> Eukaryotic cells = up to 100 μm" "State that multicellular organisms show emergent properties.<br /> 1.1.7", "Multicellular organisms show emergent properties. For example: cells form tissues, tissues form organs, organs form organ systems and organ systems form multicellular organisms. The idea is that the whole is greater than the composition of its parts. For example your lungs are made of many cells. However, the cells by themselves aren’t much use. It is the many cells working as a unit that allow the lungs to perform their function. For example, the gene that produces keratin will be active in hair and nail cells. Keratin is the protein which makes up hair and nails Genes encode for proteins and the proteins affect the cell’s structure and function so that the cell can specialise. Differentiation depends on gene expression which is regulated mostly during transcription. It is an advantage for multicellular organisms as cells can differentiate to be more efficient unlike unicellular organisms who have to carry out all of the functions within that one cell." "State that stem cells retain the capacity to divide and have the ability to differentiate along different pathways.<br /> 1.1.9", "Adults have stems cells in the tissues in their bodies that need to be frequently replaced such as the skin. Stem cells have the ability to produce a wide range of cells which means that they are pluripotent. They retain their ability to divide and produce many different cells by cell division and the process of differentiation. For example, one type of stem cells in the bone marrow produce a variety of red and white blood cells."
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