Transcript ch7_sec1
Cell Structure Section 1 Section 1: Introduction to Cells Preview • • • • • • Bellringer Key Ideas The Discovery of Cells Looking at Cells Cell Features Summary Cell Structure Section 1 Bellringer After viewing the list of items on the board, work with a partner and make two new lists: those items on the list comprised of cells and those items not comprised of cells. Give a rationale for each answer. Cell Structure Section 1 Key Ideas • How were cells discovered? • Why does cell shape vary? • What enables eukaryotes to perform more specialized functions than prokaryotes? Cell Structure Section 1 The Discovery of Cells • Microscope observations of organisms led to the discovery of the basic characteristics common to all living things. • Scientists first discovered cells in the 1600s using crude microscopes. • Observations made by scientists using more powerful microscopes in the 1800s led to the formation of the cell theory. Cell Structure Section 1 Visual Concept: Cell Theory Cell Structure Section 1 Looking at Cells • Cells vary greatly in their size and shape. • A cell’s shape reflects its function. Cell size is limited by a cell’s surface area-to-volume ratio. • Cells can be branched, flat, round, or rectangular. Cell Structure Section 1 Looking at Cells, continued • All substances that enter or leave a cell must cross the surface of the cell. • A cell’s ability to move substances across its surface can be estimated by finding its surface area-to-volume ratio. • Cells with greater surface area-to-volume ratios can exchange substances more efficiently. Cell Structure Section 1 Relationship between Surface Area and Volume Cell Structure Section 1 Looking at Cells, continued • When comparing cells of the same shape, small cells have greater surface area-to-volume ratios than large cells. • So, small cells function more efficiently than large cells. Cell Structure Section 1 Cell Features • All cells share common structural features, including a cell membrane, cytoplasm, ribosomes, and DNA. • The cell membrane is the outer layer that covers a cell’s surface and acts as a barrier between the outside environment and the inside of the cell. • The cytoplasm is the region of the cell within the cell membrane. The cytoplasm includes the fluid inside the cell called the cytosol. Cell Structure Section 1 Cell Features, continued • A ribosome is a cellular structure that makes proteins. • The DNA of a cell provides instructions for making proteins, regulates cellular activities, and enables cells to reproduce. Cell Structure Section 1 Features of Prokaryotic and Eukaryotic Cells Cell Structure Section 1 Cell Features, continued Features of Prokaryotic Cells • A prokaryote is an organism made of a single prokaryotic cell. • Prokaryotic cells do not have a nucleus or other internal compartments. The genetic material of a prokaryotic cell is a single loop of DNA. • For millions of years, prokaryotes were the only organisms on Earth. Cell Structure Section 1 Cell Features, continued Features of Eukaryotic Cells • A eukaryote is an organism made up of one or more eukaryotic cells. All multicellular organisms are made of eukaryotic cells. • The DNA of a eukaryotic cell is found in an internal compartment of the cell called the nucleus. • All eukaryotic cells have membrane-bound organelles. An organelle is a small structure found in the cytoplasm that carries out specific activities inside the cell. Cell Structure Section 1 Cell Features, continued • Each organelle in a eukaryotic cell performs distinct functions. • The complex organization of eukaryotic cells enables them to carry out more specialized functions than prokaryotic cells. Cell Structure Section 1 Visual Concept: Comparing Prokaryotes and Eukaryotes Cell Structure Section 1 Comparing Prokaryotes and Eukaryotes Cell Structure Section 1 Summary • Microscope observations of organisms led to the discovery of the basic characteristics common to all living things. • A cell’s shape reflects its function. Cell size is limited by a cell’s surface area-to-volume ratio. • The complex organization of eukaryotic cells enable them to carry out more specialized functions than prokaryotic cells.