The Origin of Cells 1.5

Question 1

Essential Idea (Origin of Cells 1.5)

Answer 1

There is an unbroken chain of life from the first cells on Earth to all cells in organisms alive today

Question 2

Louis Pasteur (1822-1895)

Answer 2

• French microbiologist who disproved the theory of spontaneous generation (life could appear form combination of dust air and other factors)

Question 3

Pasteurs Experiment

Answer 3

• Boiled nutrient broth in three swan neck flasks, allowing air in one, sealing one and exposing on to other microbes
• No growth in the sealed one proving spontaneous generation does not happen on Earth

Question 4

Miller-Urey Hypothesis

Answer 4

• The first cell came from non-living material

Question 5

Miller-Urey Experiment

Answer 5

• Recreated conditions of early Earth
• Water was boiled to form vapour and was mixed with methane, ammonia and hydrogen
• Gas mixture was exposed to electrical discharge to simulate lightning
• Animo acids and complex oily hydrocarbons were found proving non-living synthesis of simple organic molecules was possible

Question 6

Early Earth Condition

Answer 6

• Reduced atmosphere (low oxygen)
• High radiation levels
• High temperatures
• Electrical storms

Question 7

Panspermia

Answer 7

Idea that life or complex polymers originated in space and came to Earth through comets and meteorites

Question 8

Four Conditions for Emergence of Life

Answer 8

• Simple organic molecules must be formed (amino acids, fatty acids, carbohydrates)
• Larger organism molecules must be assembled from simpler molecules (phospholipids, RNA, DNA)
• Organisms reproduce, so replication of nucleic acid must be possible
• Self contained structures, such as the membrane, required for biochemical reactions as they need set condition such as pH level

Question 9

Four Processes for Life

Answer 9

• Synthesis of organic molecules from inorganic compounds (H2O, CO2, CH4)
• Assembly of organic molecules into polymers, anabolic reactions creates polysaccharides proteins and RNA strands
• Formation of polymer so it can self replicate (inheritance)
• Packing of molecules into membranes

Question 10

Endosymbiotic Theory

Answer 10

• Theory of the origin of eukaryotic cells and supports the idea that the mitochondria and chloroplast from prokaryotes were taken through endocytosis instead of being digested
• Organelles found in eukaryotic cells were once independent prokaryotes

Question 11

Mitochondria Origin

Answer 11

Cells that carried out aerobic reparation and provided energy to their host cells evolved into mitochondria

Question 12

Chloroplast Origin

Answer 12

Prokaryotic cells that converted light energy to chemical energy became chloroplasts and passed on sugars produced during photosynthesis to host cell

Question 13

Endosymbiotic Meaning

Answer 13

• Endo: internal
• symbiotic: relationship depended on each other

Question 14

Origin Story of Eukaryotic Cells

Answer 14

• Aerobic prokaryotic cells could ingest other photosynthesis prokaryotic cells for nutrients
• Dtysfunctioning digestive enzymes (mutation), cause for prokaryotic to not digest
• Ingested prokaryote produced energy for the host
• Mitochondria engulfed first due to animal cells not having chloroplasts

Question 15

Evidence Supporting Endosymbiotic Theory (7)

Answer 15

• Double membranes
• Circular naked DNA
• DNA is formed as single chromosome
• Has 70S ribosomes
• Can perform protein synthesis and replicate independently
• Divide by binary fission
• Susceptible to some antibiotics

Question 16

Evidence Everyone Arose from One Cell

Answer 16

• All organisms use DNA and / or RNA as their genetic material
• Same 20 amino acids in all our proteins
• Code to translate codons to amino acids is the same for all organisms (64 codons)