The Social Microbe I Flashcards
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Pasteur and the germ theory
Sub surface origin hypothesis
Life originated at hydrothermal vents on ocean floors where the conditions were less hostile and more stable
What was the energy supply at hydrothermal vents?
Sub surface origin hypothesis
Supply of energy (reduced inorganic compounds - hydrogen and hydrogen sulphide)
What changed about Cyanobacteria’s metabolism that led to the great oxidation event?
Cyanobacteria used water instead of H2S to generate oxygen (oxygenic photosynthesis)
Why could the oxygen produced by Cyanobacteria not accumulate in the atmosphere?
It reacted spontaneously with reduced iron minerals to make iron oxides
How did the ozone layer appear?
Once all the iron was oxidised, oxygen could accumulate in the atmosphere
Define chemolithotroph
Organisms that obtain energy by oxidising inorganic compounds
Origin of eukaryotes (first event)
Endosymbiosis of a prokaryotic capable of aerobic respiration = led to mitochondria
Origin of eukaryotes (second event)
Endosymbiosis of cyanobacteria-like cell = led to photosynthesis
Who first noticed similarities between the bacteria and mitochondria ?
K. Mereschkovsky
1910
Evidence for endosymbiosis theory (8)
Mitochondria has its own DNA
Circular DNA
Double membrane suggests it was engulfed
Similar size to a bacteria
Mitochondria, bacteria and chloroplasts all have N-formal-methionine as the initiator amino acid
Antibiotic Rifampicin inhibits RNA polymerase action in bacteria and mitochondria but not in eukaryotic cells
Chloramphenicol inhibits protein synthesis in mitochondria, chloroplasts and prokaryotes but not in eukaryotes
Prokaryotes, mitochondria and chloroplasts all similarly have small ribosomes ranging from 60S - 75S.
Outer mitochondrial membrane
Protein-based pores which allow the passage of ions and molecules
Inner mitochondrial membrane
Loaded with proteins involved in electron transport and ATP synthesis
What is the initiator amino acid in mitochondria, chloroplasts and bacteria?
N-formyl-methionine
Define endocytosis
Cell Internalising material by invagination of its membrane to form a vesicle containing the material
Three types of endocytosis
- Phagocytosis
- Pinocytosis
- Receptor mediated endocytosis
Phagocytosis
Intake of solid material or food particles
Pinocytosis
Intake of mater dissolved in fluid
Receptor mediated endocytosis
Intake of molecules based on their interaction with receptors on cell surface
How are the stages of bacterial host adaption evidence for endosymbiosis theory
Self sufficient DNA, then it’s reduced because it loses genes it doesn’t need anymore once it’s in the host, eventually DNA becomes minimal.
= can see how mitochondrial DNA came to be (it’s an extreme stage obligate intracellular organelle)
Name an energy yielding organelle (alternative to a mitochondria)
Hydrogenosome
What are hydrogenosomes thought to have evolved from?
Mitochondria
How do hydrogenosomea generate energy?
Partial oxidation of pyruvate to acetate
Structure of hydrogenosomes
Double membrane
Contain own DNA
Circular