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Cell structure and function The components of a cell The cell membrane: how materials get into and out of the cell Are

Cell structure and function The components of a cell The cell membrane: how materials get into and out of the cell Are all cells the same? The life and death of a cell. Trillions of cells in the human body All have DNA, organelles and membranes Cells are very different in size, shape and

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Cell structure and function The components of a cell The cell membrane: how materials get into and out of the cell Are

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  1. Cell structure and function The components of a cell The cell membrane: how materials get into and out of the cell Are all cells the same? The life and death of a cell

  2. Trillions of cells in the human body All have DNA, organelles and membranes Cells are very different in size, shape and activity- and how they are arranged in tissues Do cells mimic organ systems, or do organ systems mimic cells?

  3. Observe the “composite cell” (no cell looks like this) Cells are capable of: reproducing themselves synthesizing the organelles they need metabolism eliminating waste materials regulating movement of materials into and out of themselves

  4. What is so special about the cell membrane? Cell is in an aqueous environment phospholipid membrane provides a “selectively permeable” barrier Water and carbon dioxide move easily Ions, polar, large molecules do not. How DO these molecules get through the membrane?

  5. Membrane-bound proteins Transport proteins or channels for water- soluble molecules “Signal transduction”- cell receives a signal and responds to it Adhesion molecules Each type of protein has a specific function

  6. Structure and function of organelles • Protein synthesis • Endoplasmic reticulum • Rough- site of protein synthesis and • processing • Smooth- lipid metabolism and detoxification • Ribosomes- site of the initial steps of protein • synthesis • Golgi apparatus- the “UPS” of the cell

  7. II. Metabolism mitochondria- where most ATP is made mitochondria have their own DNA and ribosomes some cells have more than others III. The by-products of metabolism lysosomes contain enzymes that break down large molecules, recycle old organelles peroxisomes- specialized for detoxification in liver and kidney cells

  8. IV. Cytoskeleton- support and movement of the cell Microfilaments- (actin, myosin) involved in cell division, cell movement arrangement is significant in muscle cells Microtubules (tubulin) found in centrioles, flagella, cilia

  9. The nucleus and its contents Contains chromatin (material that makes up chromosomes) Nucleoli- ribosome synthesis Specialized nuclear membrane: double membrane with nuclear pores

  10. Features of the cell membrane Semi-permeable remember: membrane is phospholipid bilayer, with embedded and peripheral proteins Movement of materials across membrane is regulated: size of molecule solubility in water or lipid concentration gradient

  11. What is a concentration gradient? Molecules move spontaneously, from areas where they are highly concentrated to where they are less concentrated Equilibrium: molecules are uniformly distributed Molecules tend to seek equilibrium, i.e., diffuse

  12. Diffusion across a cell membrane occurs if: There is a concentration gradient (more of the substance on one side of the membrane than the other) The membrane is permeable to the substance No energy is required for diffusion Examples: oxygen and carbon dioxide why can they diffuse through the membrane?

  13. Facilitated diffusion The membrane is not permeable to all molecules Ion channels Specialized pores Carrier molecules

  14. Osmosis- diffusion of water Water will move through membrane when solutes cannot So cell might take on water, or lose water, if it is in a solution that is not isotonic Water will move down the concentration gradient Processes allow for filtration of body fluids

  15. Diffusion and osmosis do not require energy Active transport: substances are moved from area of low concentration to high Examples: sugars, amino acids, various ions ATP is required release of energy change in shape of transport protein Endocytosis, exocytosis

  16. The cell cycle

  17. Cell cycle is carefully controlled Cells can divide a limited number of times (Hayflick limit) Proto-oncogenes Tumor suppressors: genes that control the cell cycle If these genes are damaged cancer (tumors) may result Cell death (apoptosis) is also regulated

  18. We all started out as one cell! How do we develop so many different kinds of cells? How does cell differentiation occur? hormones, growth factors, etc. What are stem cells?

  19. Summary All living things are composed of one or more cells Eukaryotic cells contain organelles that have specialized functions Membranes (and physical laws) regulate the movement of materials into and out of cells Growth and differentiation of cells is carefully regulated

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