February 11th Notes
February 11th Notes Bio 102
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This 4 page Class Notes was uploaded by Alyssa Shriver on Tuesday February 16, 2016. The Class Notes belongs to Bio 102 at University of Tennessee - Knoxville taught by Dr. Jeremy Chandler in Spring 2016. Since its upload, it has received 14 views. For similar materials see Introduction to Biology in Biology at University of Tennessee - Knoxville.
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Date Created: 02/16/16
Lecture 2/11/16 Diversity, Structure and Environments of Prokaryotes What percent of microbes can we culture in lab? o 1% The oldest microbe living is 250 million years old What is a prokaryote? o Non membrane bound organelle Eukaryotic Cell: membrane-bound organelles, including a nucleus Prokaryotic Cell: lack internal membrane-bound organelles o Instead carrying out all cellular functions in one central space. The DNA molecule floats freely in the cytoplasm What domains of life are prokaryotic? o All living organisms have evolved from a common ancestor. On the basis of genetic evidence, we can group living things into one of three domains of life, each with a distinct evolutionary history. While the Bacteria and Archaea both have prokaryotic cells, they have distinct evolutionary histories, with Archaea being genetically more closely related to Eukarya than to Bacteria. The domain Eukarya encompasses protists, plants, fungi, and animals, including humans. Morphology: Shape of the cell o Coccus (round) Streptococcus o Bacillus (rod) Eschericia coli o Spirilla (spiral) Rhodospirillum o Diplococcus Neisseria o Chains Streptococcus sp. o Grape-like clusters Staphylococcus o Tetrads Micrococcus Arrangement: grouping pattern of the cell Why does shape matter? o Microbes “care” what they look like. Why? Bacteria Structure o Spherical (cocci) o Rod-shaped (bacilli) o Spiral (spirochetes) o Flagella: tiny whip-like structures that project from the cell and help it move o Pili: shorter, hair-like appendages that enable bacteria to adhere to a surface o Capsule: sticky coating surrounding cells help adhere to surfaces and protect cells Biofilms o Specialized attached surface communities of microbes are called biofilms o Biofilms are important in almost every aspect of bacterial interaction with humans from dental biofilms to engineering considerations in water supplies Rotary Flagella o Prokaryotes that are motile generally swim by means of rotary flagella o Peritrichous cells have flagella randomly distributed around the cells o Lophotrichous cells have flagella at the ends o Monotrichous cells have a single flagellum Chemotaxis o The alternating runs and tumbles cause a “random walk” o Receptors detect attractant concentrations Sugars, amino acids, and other nutrient sources o Attractant concentration increases and prolongs run This is termed a “biased random walk” Causes a net movement of bacteria toward attractants (or away from repellents) Light Microscope o Light Microscopes can be used to explore the structures and functions of cells o When scientists examine a specimen on a microscope slide, Light passes through the specimen and Lenses enlarge, or magnify, the image Electron Microscopy o The most powerful electron microscopes can Magnify up to 100,00 0 times and Distinguish between objects 0.2 nanometers o Light microscopes are still very useful for studying living cells o Two major types Transmission electron microscopes (TEM) Electrons pass through the specimen Reveals internal structures Scanning electron microscopes (SEM) Electrons scan the specimen surface Reveals external features in 3-D What color is a microbe? o Some microbes do have pigments (ex. Chlorophyll) o Most do not and only appear colored when colonies of millions of organisms accumulate on a surface o To see microbes, we typically have to stain them How to do microbes acquire the building blocks of biomass? o All of Earth’s life-forms are based on carbon, which they acquire in different ways Autotrophs fix carbon and assemble into organic molecules (mainly sugars). (Make their food from non living material in their environment) Heterotrophs use preformed organic molecules. (Rely on other organisms as their food sources) Genomic Streamlining o Organisms often try to get rid of genes in an effort to make them more competitive Today’s Objectives o Explain how big most prokaryotes are. Explain what units we typically use to measure them. Explain what limits their size. 0.1 to 5.0 um Micrometer Surface area to volume ratio, nucleo-cytoplasmic ratio, fragility of cell membrane, and mechanical structures o Explain the main parts of functions of bacterial structures we discussed Flagella: tiny whip-like structures that project from the cell and help it move Pili: shorter, hair-like appendages that enable bacteria to adhere to a surface Capsule: sticky coating surrounding cells help adhere to surfaces and protect cells o Explain how bacteria use flagella to move towards food or away from predators Prokaryotes that are motile generally swim by the rotary flagella Bacteria either swims in a straight or clockwise/counter- clock wise pattern to either engulf food or swim away from predators o Explain what kind of microscopes we can use to identify bacteria and these smaller structures Light microscopes can be used to explore the structures and functions of cells Light passes through the specimen and the lenses magnifies the image Electron microscopes can magnify up to 100,000 times and distinguish between objects 0.2 nanometers Transmission electron microscopes- electrons pass through the specimen and reveals internal structures Scanning electron microscopes- electrons scan the specimen surface and reveals external features in 3- D
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