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Chapter 2

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BIOL 1000
Michael Gadsden

Chapter 2: Origins of Life 10/21/2010 1:25:00 PM 2.1 What Is Life? Life is in all living and non-living things because both have atoms and molecules in them. All forms of life share (1) display order (have cells, & distinct arrangements), (2) use energy, (3) reproduce, (4) response to stimuli/environment, (5) exhibit/maintain a homeostasis, (6) grow & develop, and (7) evolve. Viruses are not considered alive because they need to live off a metabolism of a living cell in order to reproduce. There are 3 principles to the cell theory, which consist of (1) all organisms being composed of one (unicellular) or more (multi-cellular) cells, (2) The cell is the smallest unit that holds the properties of life, and (3) Cells arise only from growth and division of pre-existing cells. 2.3 The Origins of Information & Metabolism There are two critical events for the development of life (1) the development of the storage, replication, and translation of information for protein synthesis, and (2) the development of metabolic pathways (capturing/harnessing of energy). All organisms have DNA (Deoxyribonucleic acid). DNA is a doubled stranded, stair-like molecule; it carries information for assembling many important components for living organisms. The information found in DNA is copied onto RNA (ribonucleic acid) molecules where it directs the production of protein molecules. Each coding is unique. Enzyme (causes reaction)  Replication of DNA  Transcription of DNA into RNA  Translation of RNA = protein This is how from generation to generation DNA is able to direct its own replications in an offspring that receive same information as parents have, nonetheless, there are always change in DNA that contribute to evolution. RNA molecules called, ribozyme’s, act as catalyst, to do so, they need the original RNA molecules to achieve their own synthesis (need the information). Ribozyme are able to carry information and act as a catalyst. Ribozyme needs a certain shape from the RNA to be able to catalyze (increase reaction) of the translation of RNA to protein. DNA is better in storing information than RNA because of (1) each strand of DNA is chemically more stable than RNA, (2) RNA base uracil is not found in DNA (damaged cytosine), and (3) DNA is double stranded (if damaged has another strand). Thus this tells us that DNA is better at storing and processing genetic information. Energy needs energy to breakdown molecules, and so, we need food. Food when broken down to its simplest forms release energy (which are a bunch of compounds). The reaction of the break down of food is called redox reaction (oxidation reduction reactions). Redox reactions are inefficient because they use up too much energy, and the cell evolve to create and add ATP to make redox reactions more efficient. 2.4 Early Life (Refer to Fig. 2.15) Earliest life is found in stromatolites, are thin layers of rock formed by prokaryotic organisms (e.g. cyanobacteria) that bind the sediments together. Panspermia is the theory on which extraterrestrial life is believed to have been present and seeded early on Earth. Its believed that they do exist because we have found fossil evidence, and prokaryotic, and simple eukaryotic organisms (spores) can withstand all extreme types of temperature, pressure and nutrients, where they can chose to lie dormant. Prokaryotes come in two domains Archaea, and bacteria. Although they lack a nucleus to keep their chromosomes in, they have nucleoids, and have many similar structures, like the plasma membrane. The plasma membrane is used to keep the cytoplasm safe. In the cytoplasm, you can find the cytosol which is the organelles, water, salts, and other organic molecules found. Plasma membranes help in the incoming and outgoing of materials in the cell. In the plasma membrane they have sites of photosynthetic e.t.c. (electron transport chain) which harvests light energy for synthesizing ATP. They are very flexible in their use of energy, carbon sources, and synthesize almost all required organic molecules. EXAMPLE Cyanobacteria can thrive anywhere there was sunlight, due to the fact, they use oxygenic photosynthesis (the use of harnessing electrons from water). As oxygenic photosynthesis occurs it releases the electrons and protons, “splitting the water molecules” which formed O2 slowly accumulating in the atmosphere. 2.5 Eukaryotic Cells (Refer to Fig. 2.18) Eukaryotic cells are distinguished by (1) the separation of DNA and cytoplasm
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