Cell Organization I Biological Organization 10 09 2010 Chemicals sub cellular organelles cells tissues organs organ systems organism II Metabolism sum of all chemical activities in an organism Anabolism Catabolism Hydrophilic substances synthesis of things in a cell breaking down of things in a cell are water loving and react with water molecules These substances react with water by hydrogen bonding This plays an important role in facilitating chemical reactions because the water dissolves the substances into ions Hydrophobic substances are water fearing and do not react with water These substances are especially important because of their ability to form association or structures that are not disrupted most minerals are in the form of ions Ions are important because Minerals their charge provides a basis for interaction between anions and cations Carbohydrates most are hydrophilic water loving Sugars starches and cellulose are carbohydrates Contain carbon hydrogen and oxygen Sugars and starches serve as energy sources for cells and cellulose is the main structural component of the cell walls of plant cells Lipids more hydrophobic are bridge molecules that are soluble in non polar solvents and are insoluble in water Lipids contain carbon and hydrogen with few oxygen containing functional groups making it non polar Lipids include fats phospholipids carotenoids steroids and waxes Some lipids are used for energy storage others serve as structural components of cell membranes and some are important hormones Proteins are macromolecules composed of amino acids and are the most versatile cell components Enzymes organic proteins catalyze specific chemical reactions Other proteins protect cells store nutrients transport specific substances between cells some are hormones some participate in cellular movements and some defend against foreign invaders Nucleic acids transmit hereditary information and determine what proteins a cell manufactures Two classes of nucleic acids are found in DNA and RNA III Cellular Functions Cell Theory 1 Cells are basic units of organization and function in all living organisms 2 All cells come from pre existing cells 3 All living cells have evolved from a common ancestor Viruses do not have the same structure as a cell IV Plasma Membrane Provides a cell with separation from the environment boundary that allows selective movement in and out of the cell Every cell is surrounded by a plasma membrane This helps maintain life and to maint ain the internal environment of the cell Only plant bacteria and fungi have cell walls Cell wall is outside the plasma membrane V Cell Size The surface area of a cell must be large enough relative to its volume to allow enough exchange of materials within the As a cell becomes larger its volume increases 3 fold at a faster rate than the surface area increases 2 fold Cells have microvilli finger like projections that increase surface area for absorbing environment nutrients The size of a cell is expressed in micrometers and the size of sub cellular constituents is expressed in nanometers VI Prokaryotes and Eukaryotes Prokaryotic cells were the first cells on earth They do not have a nucleus and are 1 10 micrometers Eukaryotic cells are bigger than prokaryotic cells 10 30 micrometers They evolved from prokaryotic cells In eukaryotic cells DNA is enclosed in the nucleus and has efficient systems membranous organelles to get in and out of the cell VII Research Tools Used By Cell Biologists A Microscopy o Light microscope resolution about 1 micrometer used to study stained or living things o Electron microscope resolution less than 1 nanometer is 1000X better Provide a high resolution image that can be greatly magnified o Transmission electron microscope the specimen is embedded in plastic and then cut into extraordinarily thin sections with a glass or diamond knife The image represents only a thin cross section layer or the specimen o Scanning electron microscope The recorded emission pattern of the secondary electrons give a 3 D picture of the surface The SEM provides information about the shape and external features of the specimen that cannot be obtained with the TEM o Resolution clarity o Contrast detail o Vital stains B Cell Fractionation a technique for purifying different parts of cells so that they can be studied by physical and chemical methods o To lyse a cell means to homogenize it o An Ultracentrifuge is a powerful spinning device that generates a centrifugal force of 500 thousand X G gravity that separates the extract into two fractions the pellet and the supernatant o The pellet forms at the bottom of the tube and contains heavier materials such as nuclei packed together Or if repeated with a higher spinning power the next heaviest will be in the pellet such as mitochondria and chloroplasts is the liquid above the pellet that contains o The supernatant lighter particles such as dissolved molecules and ions VII Organelles of Eukaryotes Cytoplasm Cytosol area outside the nucleus whole thing fluid component in the cytoplasm Endomembrane System In the endomembrane system vesicles are used to transport things between organelles and out of the cell The nucleus is considered part of the endomembrane system because it interacts with the rest of the cell because the ribosomes made in nucleus Prokaryotic cells do not have a nucleus or nucleoli Their ribosomes and chromosomes floats around in the cytosol of the nucleotoid nuclear area Nucleus contains chromatin DNA and protein that make up chromosomes Chromosomes contain DNA and are used in mitosis to create an identical daughter cell Contains an inner nucleolus that is the sight of ribosome assembly Nuclear envelope surrounds nucleus and contains nuclear pores allowing it to be selectively permeable Ribosomes protein synthesis machines move out of the nucleus trough these nuclear pores Endoplasmic Reticulum production of lipids and detox enzymes o Rough ER covered with ribosomes on the cytosolic side outer Synthesizes proteins o Smooth ER is not covered with ribosomes Synthesizes lipids and detoxifies Golgi Complex lumen Plasma membrane o Processes proteins synthesized by ER o Stacks of flattened membranous sacks each one has its own o Vesicles move proteins from ER to Golgi complex o Selectively permeable membrane that controls the shape of the cell and interact with other cells o Exocytosis is the process by which vesicles carry proteins made by the ER ribosomes from the Golgi