Chapter+4 - • These early sketches revealed an important...

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Unformatted text preview: • These early sketches revealed an important relationship – Between art and biology, the most visual of the sciences The Art of Looking at Cells – Early scientists who observe cells • Made detailed sketches of what they saw INTRODUCTION TO THE CELL Microscopes provide windows to the world of the cell – The light microscope (LM) • Enables us to see the overall shape and structure of a cell Eyepiece Ocular lens Objective lens Specimen Condenser lens Light source Figure 4.1A – Light microscopes • Magnify cells, living and preserved, up to 1,000 times LM 1,000 × 1B ELECTRON MICROSCOPE (EM) • Uses a beam of electrons instead of light • Can detect individual atoms • Allows greater magnification and reveals cellular details • Use beams of electrons • Has 2 kinds: 1. Scanning Electron Microscope (SEM) 2. Transmission Electron Microscope (TEM ) ELECTRON MICROSCOPE SCANNING ELECTRON MICROSCOPE (SEM) -outside view • Can study detailed architecture of cell surfaces • Use electrons to scan the surface of a cell or group of cells that has been coated with a thin film of metal. TRANSMISSION ELECTRON MICROSCOPE (TEM) - inside view • Is used to study details of internal cell structure – Different types of light microscopes • Use different techniques to enhance contrast and selectively highlight cellular components 220 × 1,000 × Figure 4.1E Figure 4.1F Most cells are microscopic – Cells vary in size and shape Human height Length of some nerve and muscle cells Chicken egg Frog egg Unaided eye Light microscope Electron microscope 10 m 1 m 100 mm (10 cm) 10 mm (1 cm) 1 mm 100 μ m 10 μ m 1 μ m 100 nm 10 nm 1 nm 0.1 nm Atoms Proteins Small molecules Lipids Viruses Ribosome Nucleus Mycoplasmas (smallest bacteria) Most plant and animal cells Most bacteria Mitochondrion Figure 4.2A ALL CELLS • Have basic features in common: • Plasma membrane • DNA • Ribosomes PLASMA MEMBRANE All cells are surrounded by a plasma membrane. It separates the contents of the cell from its environment and regulates the passage of molecules into and out of the cell The membrane contains proteins that have a variety of functions o Membranes form the boundaries of many eukaryotic cell Cytoplasm Fluid-filled region between the nucleus and plasma membrane This EXCLUDES the nucleus Ribosomes Read the code in mRNA and synthesis of proteins according to the instructions in mRNA Are made of RNA and proteins Has subunits that are made in the nucleolus and move into the cytoplasm to form the ribosome (eukaryotic cells) The ribosome attaches to the mRNA As ribosomes move along messenger RNA (mRNA), the amino acids] are added to a growing chain to form...
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This note was uploaded on 05/12/2008 for the course BIOL 1101 taught by Professor Mason during the Spring '08 term at Middle Georgia State College.

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Chapter+4 - • These early sketches revealed an important...

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