BIOS E-1a Lecture 04 091911 annotated

BIOS E-1a Lecture 04 091911 annotated - Lecture 4: Cell...

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Lecture 4: Cell Theory Reading: Chapter 4 1
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Cell theory 1. All living organisms are composed of one or more cells 2. Cells are the smallest units of life 3. New cells come only from pre-existing cells by cell division 2
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Microscopy • Magnification – Ratio between the size of an image produced by a microscope and its actual size • Resolution – Ability to observe two adjacent objects as distinct from one another • Contrast – How different one structure looks from another – enhanced by dyes 3
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• 2 groups of microscopes based on source of illumination – Light microscope • Uses light for illumination • Resolution 0.2 μm – Electron microscope • Uses an electron beam • Resolution 2 nm 4
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1 nm 0.1 nm 10 nm 100 nm 1 mm 1 cm 0.1 m 1 m 10 m Atoms Lipids Proteins Ribosomes Viruses Mitochondria Nucleus Fish egg Bird egg Human height Electron microscope Light microscope Unaided human eye Small molecules Most bacteria Most plant and animal cells 1 μ m 10 μ m 100 μ m Smallest bacteria Visualization of various biological structures 5
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Electron microscope types • Transmission electron microscopy (TEM) – Beam of electrons transmitted through sample – Thin slices stained with heavy metals – Some electrons are scattered while others pass through to form an image • Scanning electron microscopy (SEM) – Sample coated with heavy metal – Beam scans surface to make 3D image 6
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Comparison between different types of electron microscopy (egg shown here) 7
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Life • All life can be placed into 2 categories based on cell structure 1.Prokaryotes 2.Eukaryotes 8
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Prokaryotic cells • Simple cell structure • Lack a membrane-enclosed nucleus • 2 categories: bacteria and archaea – Both small – Bacteria: abundant, most not harmful – Archaea: less common, often found in extreme environments 9
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Typical bacterial cell • Plasma membrane - barrier • Cytoplasm - contained inside plasma membrane • Nucleoid - region where genetic material found • Ribosomes - involved in protein synthesis 10
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• Many structures are located outside the plasma membrane – Cell wall - support and protection – Glycocalyx - traps water, protection • Capsule – may help evade immune system – Appendages - pilli (attachment), flagella (locomotion) 11
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(a) A typical rod-shaped bacterium (b) An electron micrograph of Escherichia coli 0.5 μm Ribosomes Cytoplasm Pili Flagella Nucleoid region Plasma membrane Cell wall Glycocalyx Prototypical prokaryotic cell 12
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Eukaryotic cells • DNA housed inside nucleus • Eukaryotic cells exhibit compartmentalization • Organelle - membrane-bound compartment with its own unique structure and function • Shape, size, and organization of cells vary considerably among different species and even among different cell types of the same species 13
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Nucleus Nuclear pore Centrosome Rough ER Smooth ER Mitochondrion Cytoskeleton Peroxisome Golgi apparatus Cytosol Plasma membrane Chromatin Ribosome Lysosome Nuclear envelope Nucleolus Prototypical animal cell 14
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Variation in morphologies of cells 15
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This note was uploaded on 02/09/2012 for the course BIOLOGY 102 taught by Professor Anderson during the Spring '11 term at Harvard.

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BIOS E-1a Lecture 04 091911 annotated - Lecture 4: Cell...

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