BIO-1402- CH. 22 the Origin and History of Life Questions and Answers 100% Pass

BIO-1402- CH. 22 the Origin and History of Life Questions and Answers 100% Pass Cell Theory 1. All organisms are composed of cells 2. Cells are the smallest living things 3. Cells arise only from pre-existing cells What are the required minimal set of macromolecules protobionts must have? 1. Self- replicating lipid vesicles 2. Self-replicating genetic material. Plausible progression of Cells 1. Formation of organic molecules (spontaneous) 2. Formation of organic polymers 3. RNA-based protobionts 4. DNA/RNA/protein-based protobionts Reducing Atmosphere Hypothesis Miller-Urey Experiment (1953) It generated organic compounds from inorganic gasses and energy. Water vapor, ammonia, hydrogen gas, and methane react in the absence of oxygen to produce orgain molecules. Deep Sea Vent Hypothesis Proposed that key organic molecules may have originated in deep-sea vents, which are cracks in the Earth's surface where superheated water rich in metal ions and hydrogen sulfide mixes abruptly with cold seawater. These vents then release hot gaseous substances from the interior of the earth at temperatures that exceed 300 degrees Celsius. Fe2+ can H2S can reduce N2 to NH3. A critical building block for amino acids and nitrogenous bases. Extreme temperatures, metal ions, and H2S and NH3 interact, leading to organic molecules Extraterrestrial Hypothesis Sufficient organic molecules may have been present in the materials from asteroids and comets, that reached the surface of the earth in the forms of meteorites. Organic molecules travled to earth from meteorites. Formation of organic polymers 1. Protobionts required self-replicating genetic information like RNA. 2. Scientists have shown RNA polymers can form spontaneously on clay given ribonucleotides. 3. Simple organic molecules polymerized to form more complex organic polymers such as DNA, RNA, or proteins. Formation of protobionts Protobiont- is used to describe an aggregate of prebiotically produced molecules and macromolecules that acquired a boundary, such as a lipid bilayer, that allowed it to maintain an internal chemical environment distinct from that of its surroundings. Coacervates- droplets that form spontaneously from the association of charged polymers such as proteins, carbohydrates, or nucleic acids surrounded by water. -Alexander Oparin (1924) • Liposomes- vesicles surrounded by a phospholipid bilayer. -Phospholipid vesicles with selective permeability -Clay can catalyze liposome growth and division -Hanczyc, Fujikawa and Szostak (2003) Chemical selection -Occurs when a chemical