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Transcript
CELL STRUCTURE CELL STRUCTURE Enormous variety in the size and shape of different cells Smallest cells belong to group of organismsMycoplasma Only about 0.2 µm in diameter So small that often beyond the limit of resolution of light microscopes CELL STRUCTURE Large cells (giant amoeba)Chaos chaos About 1000 µm in diameter Larger cellsyolks of bird eggs Single cells containing stored food for the developing bird for the most part, cells are between 5 & 50 µm in diameter CELL STRUCTURE certain structures are common to most cells plants, animals, and related organisms have 3 basic structures: cell membrane-outer boundary nucleus-control center cytoplasm-material between the cell membrane and nucleus CELL MEMBRANE all cells are separated from their surroundings by a cell membrane regulates what enters and leaves the cell aids in the protection and support of the cell similar to cell walls that surround a house CELL MEMBRANE it must communicate with other cells, take in food, and water and eliminate wastes composed of several kinds of molecules lipids, proteins, cho’s LIPIDS • double layer of lipid molecules, known as a ‘bilayer’ forms the basic unit from which cell membranes are constructed PROTEIN some proteins stick to the surface of the lipid bilayer, others are free to move around within the bilayer some act as channels through which molecules can pass others act like small pumps, actively pushing molecules from one side of the membrane to the other CARBOHYDRATES cho’s are attached to proteins or lipids at the membrane surface many act like chemical id cards, allowing cells to recognize and interact with each other CELL WALL in organism such as plants, algae, and some bacteria, the cell membrane is surrounded by a cell wall helps to protect and support the cell very porouswater, oxygen, carbon dioxide, and other substances can pass through easily made up of two or more layers layers form in a series of steps PRIMARY CELL WALL 1st layer to form develops where two plant cells meet Contains a gluey substance called pectin, that helps hold the cells together Each of these cells then forms a primary cell wall on its side of this gluey layer Made up of cellulose (a fibrous material) Make the cell wall elasticstretch as it grows SECONDARY CELL WALL Plants that have woody stems, another layer secondary cell wall, develops Composed of cellulose and lignin Lignin makes cellulose more rigid Wood consists mainly of secondary cell walls NUCLEUS Nucleus-info center of the cell Seen in many cells as a large dark structure 1st described by Robert Brown Not all cells have nuclei Small unicellular organismbacteria and several other kinds of organisms, do not have nuclei PROKARYOTES / EUKARYOTES The absence or presence of a nucleus can be used to divide organisms into two categories: Prokaryotes-lack nuclei Eukaryotes-contain nuclei Karyon=nucleus Pro=before Eu=true PROKARYOTES Prokaryotic organism Bacteria and their relatives Usually small and unicellular EUKARYOTES Eukaryotic organisms Both unicellular and multicellular NUCLEUS Nucleus is the information center of the cell Contains DNA=instructions for making thousands of different molecules Directs all the activities that occur in a living cell NUCLEUS Nuclear envelope Composed of two membranes that form boundary around nucleus Insidedozens of nuclear pores Molecules move in and out of nucleus through nuclear pores NUCLEUS Nucleolus Most nuclei contain a small region called nucleolus Made up of RNA and proteins Where ribosomes are made NUCLEUS Chromosomes The DNA in the nucleus of eukaryotic cells is attached to special proteins and forms large structures called chromosomes Contain genetic information that must be passed to each new generation of cells CYTOPLASM Cytoplasm Area between the nucleus and the cell membrane Contains important structures TOMORROW We will discuss the organelles found within the cytoplasm!!!!!!!!!!!!
