TOPIC 6 Origins of Life DAY 2 – INTRO TO MACROMOLECULES OBJECTIVES • Describe the basic molecular structure of carbohydrates, lipids, proteins, and nucleic acids. • Describe the primary function of carbohydrates, lipids, proteins, and nucleic acids. Macromolecule Where it is found What it does Protein Meat, Fish, Cheese Enzymes, structural, transportation, hormones among many other functions in living organism. Carbohydrate Sugar, Breads, Fruits, Pasta, Rice Short term energy Lipid Fats Nucleic Acid RNA and DNA Long term energy storage; an important component of the cell membrane. Carries genetic information ESSENTIAL QUESTION • You are composed of the same material as all other living things on the planet ……How is this possible? MACROMOLECULES ARE POLYMERS MADE UP OF MANY MONOMERS Monomer - small molecular subunit which joins with similar units to form a polymer. Polymer - consists of up to millions of repeated, covalently linked monomers. PROTEINS Are macromolecules that contain nitrogen as well as carbon, hydrogen, and oxygen. Made up of a repeating chain of amino acids. PROTEINS Are used to build muscle and can be found in beef, chicken, eggs, tofu, beans, and fish. Denature under exposure to heat – that’s what causes the egg to turn white! HOW DID THE FIRST ORGANIC COMPOUNDS FORM? Experiment conducted in 1953 by Staley L. Miller and Harold C. Urey Their apparatus, illustrated in the figure included a: Gas chamber containing gases present in Earth early atmosphere Electrodes supply electricity to provide energy to drive chemical reactions Water chamber substituted for the oceans and lakes. The Miller-Urey experiment produced a variety of organic compounds, including amino acids. THEORIES OF THE ORIGIN OF LIFE WHAT ARE WE LEARNING TODAY? Benchmarks Learning Objectives SC.912.L.15.8 – Describe I will describe scientific the scientific explanations explanations of the origin of of the origin of life on life on Earth. Earth. I will identify situations or conditions contributing to the origin of life on Earth. WHAT IS THE ESSENTIAL QUESTION? Scientists explain that that life arose from nonlife billions of years ago through the theory of abiogenesis. Could life arise from nonlife today? Explain. WHAT CONDITIONS MAKE EARTH UNIQUE? Only planet known to sustain life. Several conditions make Earth able to sustain life as we know it. presence of liquid water moderate temperature range free oxygen in the atmosphere adequate sunlight no toxic substances in the atmosphere absence of lethal radiation WHAT WAS EARTH LIKE? Earth’s early atmosphere probably contained hydrogen cyanide, carbon dioxide, carbon monoxide, nitrogen, hydrogen sulfide, and water. Volcanic activity probably formed it. Released great amounts of water vapor that later condensed to form oceans. Released CO 2 that warms the atmosphere by absorbing outgoing heat. How did that affect the temperature? This early atmosphere lacked oxygen, so it could not support life as we know it today. WHERE DID LIFE BEGIN? HOW DID LIFE BEGIN? WHAT DID IT LOOK LIKE? SO MANY QUESTIONS!!! WHERE DID LIFE BEGIN? Fossil Evidence Fossil evidence indicates that life on Earth appeared about 3.5 billion years ago in the oceans Provided protection from UV radiation Allowed multidirectional movement Served as a medium for essential chemical reactions. Anaerobic prokaryotes Primordial Soup Theory Proposed by Alexander Oparin and John Haldane. Early atmosphere contain NH3, CO2, H2O, H2, and CH4 At high temperatures, these gases may have formed single organic compounds. When Earth cooled and water vapor condensed, these simple organic compounds would have collected in lakes and oceans. Overtime. these compounds could have entered complex chemical reactions, fueled by energy from ultraviolet radiation, volcanic eruptions, and lighting. ABIOGENESIS VS. BIOGENESIS Abiogenesis or spontaneous generation states that life can arise from nonliving things Oparin reasoned that O2 prevents the synthesis of certain organic compounds that are necessary building blocks for the evolution of life Oparin proposed that the "spontaneous generation of life" did in fact occur once, but was now impossible because the conditions found on the early Earth had changed Oparin argued that a "primeval soup" of organic molecules could be created in an oxygen-less atmosphere. Biogenesis states that every living thing came from a pre-existing living thing. In 1668 Francesco Redi, proved that no maggots appeared in meat when flies were prevented from laying eggs. In 1768, Lazzaro Spallanzani demonstrated that microbes were present in the air, and could be killed by boiling. In 1861, Louis Pasteur performed a series of experiments which demonstrated that organisms such as bacteria and fungi do not spontaneously appear in sterile, nutrient-rich media. HOW DID LIFE BEGIN? Hydrothermal Vents Electric Spark These vents release important hydrogen-rich molecules Mineral catalysts could have made critical reactions occurs faster Can generate amino acids and sugars from an atmosphere loaded with water, methane, ammonia and hydrogen Demonstrated in the famous Miller-Urey experiment reported in 1953 New evidence suggest that it may have occurred in volcanic clouds HOW DID LIFE BEGIN? Panspermia Community Clay Life could have come from outer space in a comet or meteorite. Clay may have provided the foundation for first organic compounds. Mineral crystals in clay could have arranged organic compounds into organized patterns. Ice Earth 3 billion years ago ice might have covered the oceans. Protected from UV light, organic compounds may have formed and reacted with one another. HOW DID CELLS FORM? Sidney Fox and other scientists have done extensive research on the physical structures that may have given rise to the first cells. Cell like structures, including microspheres and coacervates, form spontaneously in certain kinds of solutions. Coacervates and microspheres like cells can take up certain substances from their surroundings. Coacervates can grow Microspheres can bud to from smaller microspheres. However, microspheres and coacervates do not have all of the properties of life. Unlike cells, microspheres and coacervates do not have hereditary material. WHEN DID ATMOSPHERIC OXYGEN APPEARED? About 2.7 b.y.a., cyanobacteria or blue-green algae began photosynthetic reactions About 1.8 b.y.a, the atmosphere contained abundant free oxygen. Allowed for the development of more complex, oxygen-breathing life forms Caused the first mass extinction of organism that had evolved in an oxygen-less planet Ended the process of chemical evolution Spirulina HOW DID THE FIRST EUKARYOTES FORMS? According to the endosymbiotic theory, eukaryotic cells formed from a symbiosis among several different prokaryotic organisms. Eukaryote provided a beneficial environment Prokaryote provided a method of energy synthesis. Did not receive much support until the 1960s, when it was championed by Lynn Margulis of Boston University. Aerobic prokaryote Anaerobic eukaryote WHAT EVIDENCE SUPPORTS THE ENDOSYMBIOTIC THEORY? Mitochondria and chloroplasts contain DNA similar to bacterial DNA. Mitochondria and chloroplasts have ribosomes whose size and structure closely resemble those of bacteria. Mitochondria and chloroplasts, like bacteria, reproduce by binary fission. Mitochondria and chloroplast replicate independently from the replication cycle of the cells that contains them. WHAT IS THE ESSENTIAL QUESTION? Scientists explain that that life arose from nonlife billions of years ago through the theory of abiogenesis. Could life arise from nonlife today? Explain.