Lecture2

Lecture2 - 01.19.11 Lecture 2: How to Study Cells Light...

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01.19.11 Lecture 2: How to Study Cells
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Light microscopy led to the discovery of cells The microscope used by Robert Hook, the first person to discover cells in thin sections of cork Robert Hook (1635-1703)
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The first observation of living cells The microscope used by Robert Hook, the first person to discover cells in thin sections of cork Anton van Leeuwenkoek (1632-1723) First to visualize protists, spermatazoa, bacteria and muscle fibers
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Schwann’s Cell Theory • All organisms are made of cells • Cells are the fundamental unit of life • Cells come from other cells Theodor Schwann (1810-1882)
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Cellular Unity and Diversity • Delimiting membrane to separate inside from out • Metabolism to build complex molecules from food and energetic molecules from light (photosynthesis) or respiration • Capacity for reproduction: Genes ==> transcription ==> translation ==> structure & regulation DNA ==> mRNA ==> proteins ==> subunits & enzymes
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Cellular Unity: all cells share a set of common characteristics • Common biochemistry: all cells use the same basic building blocks (e.g. DNA, RNA, amino acids, lipids, carbohydrates) • Common macromolecules and supramolecular structures and physiology (e.g. lipid bilayers, ribosomes, use ATP as energy)
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Cellular Diversity: cells may be categorized based on their complexity Two major classes of cells based on complexity of intracellular organization: 1. Prokaryotes (no nuclear envelope) 2. Eukaryotes (nuclear envelope)
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A typical prokaryotic cell Capsule: Layer of polysaccharide (sugars) that protects the bacterial cell. Often associated with pathogenic bacteria as it serves as a barrier against phagocytosis by white blood cells. Cell wall: Composed of peptidoglycan (polysaccharides + protein). Maintains the overall shape and structure of the cell. Plasma membrane: The external membrane. Regulates selective transport into and out of the cell.
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Flagella: Stiff helical structure rotated by a rotary engine embedded in the membrane. Produces motility. Pili: Hollow, hair-like structures that allow bacrterial conjugation. Nucleoid: DNA in the bacterial cell is generally conFned to this region - not bounded by a membrane. Ribosomes:
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Lecture2 - 01.19.11 Lecture 2: How to Study Cells Light...

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