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Chapter 2

Chapter 2 – The origins of life.docx

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Wilfrid Laurier University
Matthew Smith

Chapter 2 – The origins of life 2.1 What is life? Seven characteristics that all forms of life share The fundamental unit of life is the cell Units of measurement relevant to cells Seven Characteristics of Life • Display order:All forms of life are arranged in a highly ordered manner, with the cell being the fundamental unit of life • Harness and utilize energy; all forms of life acquire energy from the environment and use it to maintain their highly ordered state • Reproduce:All organisms have the ability to make more of their own kind Respond to stimuli: Organisms can make adjustments to their structure, function, and • behavior in response to changes in the external environment.Aplant can adjust the size of the pore of the surface of a leaf (a stomata) to regulate gas exchange • Exhibit Homeostasis: Organisms are able to regulate their internal environment such that conditions remain relatively constant. Sweating is one way which the body attempts to remove heat and thereby maintain a constant temperature • Growth and development all organisms increase their size by increasing the size and/or number of cells. Many organisms also change overtime • Evolve: Population of living organisms change over the course of generations to become better adapted to their environment. Cell Theory i. All organisms are composed of one of more cells Single Cells from multicellular organisms can be extracted and maintained in vitro and survive The cell is the smallest unit that has the properties of life Abroken open cell cannot survive Much has been learned about cells by breaking them open and isolate organelles, ribosomes, membranes, DNAetc. Cells arise only from the growth and division of preexisting cells Acell cannot be formed by nothing, their existence is not spontaneous * Continued onto the next page* What are the 5 steps (in order) that were needed to produce life today? The correct order is: Areducing environment; Abiotic molecules Polymers (RNA, Ribozymes) Protobionts RNAreplaced by protein then DNA Chapter 2 – The origins of life ** True about life – populations of cells change throughout generations ** The Cell theory • The cell is a highly organized compartment that is bound by a thin highly flexible membrane. • Inside the membrane is a concentrated aqueous solution of molecular chemicals; the membrane is essential to the formation of the cell. What about Synthetic Cells? o “Synthetic cells” were first reported in 2010  They chemically synthesized the entire genome of a bacteria; mycoplasma  They wanted to define the minimum characteristics needed for life.  They were able to make little changes that were only present in their synthesized genomes  They grew up a similar species but with different characteristics. • They took the genome out of the bacteria that they grew in the lab; left with an empty cell and took the genome and placed it into the empty cell • This cell then began to change its shape, protein synthesis and so on to form the mycoplasma bacteria From this they wanted to be able to design vaccines Units of measurement ‐6 Micrometers (μm) or 10 meters  Light microscopy range Nanometers (nm) or 10 meters  Electron microscopy Chapter 2 – The origins of life 2.2 Chemical Origins of Life 4.6 billion years condensed into 1 year Conditions on primordial Earth• The Miller- Urey experiment The synthesis of polymers from monomers Protobionts: The first cells Primordial Earth Oparin – Haldane Hypothesis Organic molecules that formed building blocks of life could have been formed given conditions that prevailed on primitive earth (page 27) Reducing atmosphere that lacked oxygen: H S, CO2, NH , 2H , H3O (v4por2 Allows for synthesis of complex organic molecules Lightning constantly occurring pumping energy into the system Cyanobacteria were the first photosynthetic organism that were able to release oxygen into the air. Miller-UreyApparatus Simulate conditions on primordial earth Abiotic synthesis of biologically important compounds Urea, amino acids Adding HCN & CH2O created fatty acids, purines and pyrimidines, sugars and phospholipids Chapter 2 – The origins of life Deep sea vents Chapter 2 – The origins of life Hydrothermal vents and volcanoes Highly reducing environments Release methane and ammonia There are specific areas where highly reducing environments still exist such as these deep sea vents and volcanoes. There were and still are areas on earth that provide the conditions of primordial earth. Polymers from monomers Key macromolecules of life, such as proteins and nucleic acids, are polymers that were not formed by the miller-urey experiment Polymerization reactions may have occurred on solid surfaces Example clay They believe that clay was a primary solid on primordial earth Polymers can form on the surface of clay spontaneously however, the environment must be hot among other necessary conditions. There needs to be some sort of cellular compartment Protobionts: The first cells Agroup of abiotically produced organic molecules that are surrounded by a membrane or membrane like structure Primitive cell-like structures Some proteins of life May have been precursors of cells Where the vesicles were forming and the polymers were forming were in the same surface of clay. These organic molecules were being trapped in the vesicles forming the precursors of cells Chapter 2 – The origins of life 2.3 The origins of information & metabolism the origin of the information system ribozymes are biological catalysts that are not proteins the evolution of proteins and DNA Pathway of information Flow – the central dogma of cellular biology Information is stored in DNA The information in DNAis copied into RNA The information in RNA guides the production of proteins, they give everything structure and function, such as replication. There are proteins that exist solely for the purpose of replicating the DNA Ribozyme Binding – discovered in 1979 by Thomas Cech and won a Nobel peace prize 10 years later for this research Are RNAmolecules that are able to fold up on themselves, take up complex structure and catalyze specific reactions DNAand proteins may have developed from RNA Chapter 2 – The origins of life Scenario for evolution of flow of information – absence of ribosomes that are composed of protein and DNA. Ribosomes are actually ribozymes. Ribozymes can be viewed as the first proteins to perform replication. DNAis much more stable then RNAas a result of its double strands. Even if one strand undergoes a mutation, the second can acts as a template to repair the damaged strand. The evolution of DNAserving that information system would have provided an
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