Chapter 2 - The Cell - Lecture Notes.pdf - Chapter 2 The...

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1 Chapter 2 - The Cell - Lecture Notes Introduction to Cells cells - the smallest living units in our bodies human body - 50-100 trillion cells organelles - “little organs” ; carry on essential functions of cells cells - 3 main components plasma membrane - the outer boundary cytoplasm - contains most organelles nucleus - controls cellular activities cells differentiate through gene expression Introduction to Cells Figure 2.1 the range of cell sizes Types of Cells and Their Functions Table 2.1 Plasma Membrane plasma membrane defines the extent of the cell structure of membrane - fluid mosaic model (lipid bilayer) Plasma Membrane types of membrane lipids: phospholipids polar molecule hydrophilic head and hydrophobic tail cholesterol 20% of membrane lipids strengthens and stabilizes membrane glycolipids 5-10% of membrane lipids outside - cell-cell recognition Plasma Membrane types of membrane proteins: integral proteins firmly embedded within, or attached to lipid bilayer short chains of carbohydrates attach to integral proteins glycocalyx - cell “coat” peripheral proteins loosely attach to membrane surface “float” and move about the lipid bilayer
2 Plasma Membrane protein-specific functions transport intercellular connection anchorage for the cytoskeleton enzyme (catalytic) activity cell-cell recognition signal transduction Plasma Membrane Figure 2.4 Transport Across the Plasma Membrane simple diffusion - tendency of molecules to move down their concentration gradient osmosis - diffusion of water molecules across a membrane facilitated diffusion - movement of molecules down their concentration gradient through an integral protein active transport - integral proteins move molecules across the plasma membrane against their concentration gradient Transport Across the Plasma Membrane Figure 2.5 Exocytosis Figure 2.6 exocytosis - mechanism; moves substances out of the cell

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