Cell theory & The nature of life Flashcards
Who coined the term cell?
Hooke
Hooke’s observations laid the foundation for cell theory.
What are the basic tenets of cell theory?
- Every organism is made of one or more cells
- Cells are the basic unit of life
- Cells arise from pre-existing cells
Virchow’s work on healing contributed to the understanding of cell lineage.
What three components do cells need?
- Membrane
- Genetic material
- Metabolism
What is the proposed origin of life timeframe?
Approximately 4 billion years ago
The exact location and process remain subjects of study, with possibilities including extraterrestrial origins.
What was the early Earth’s atmosphere composed of?
- Volcanic activity
- Little O2
- High CO2 levels
What role did UV light play in early Earth?
Catalyzed formation of precursor molecules like amino acids, sugars, and nucleobases
What type of polymer was capable of catalyzing its own formation?
RNA
RNA’s properties include being single-stranded, flexible, and having catalytic abilities.
What are some issues with synthesizing RNA?
- Dilution of organics in primordial soup
- RNA instability in water
- Hydrolysis due to high water concentration
How could hydrothermal fields contribute to RNA synthesis?
Provided clay mineral layers to concentrate organic molecules
This increased the likelihood of necessary reactions occurring.
What is a significant problem with the primordial soup regarding RNA?
Presence of other sugars questioning why only ribose was used
Fill in the blank: Nucleotides have _______ instead of monophosphates.
triphosphates
What conditions are necessary for spontaneous metabolism?
- High temperature
- High pressure
- Presence of redox metals (Fe or Ni)
What do alkaline smokers form that is crucial for proto-metabolism?
Minerals rich in redox metals through serpentinization.
This reaction also releases H2 gas, OH ions are also present
These conditions facilitate chemical reactions necessary for early life.
How did methanogens conduct metabolism?
Use CO2 and H2 to form organic compounds through a proton gradient maintained by conditions around alkaline smokers.
What role could formic acid have played in proto metabolism?
Formed self-assembling membranes that disrupt essential metals for proto-metabolism
Outline the evolution of catalysts at alkaline smokers.
- Minerals and free metals formed crystals in a membrane (e.g. FeS)
- Crystals reacted with each other and grew
- Some ruptured membranes others bound to hydrophobic amino acids, stopping their growth and allowing them to partition the membrane to contact conditions necessary for proto-metabolism (e.g. utilise the geological proton gradient to reduce CO2)
- This enabled fatty acid and amino acid formation, the former would have enlarged the membrane until it split in two (abiotic cell division)
- Cells inherited different configurations of catalysts depending on fission
What are membranes made from?
Amphiphile molecules such as phospholipids
What is the structure of a phospholipid? Could it have formed prebiotically?
- Hydrophilic head (phosphate and glycerol)
- Hydrophobic tail (two fatty acids)
- Too complex to have formed prebiotically, however other amphiphiles could have formed micelles and vesicles, their size determined by their type and local conditions
What experimental evidence supports the formation of proto cells?
Heating and concentrating nucleotides and lipids causes micelles to fuse and form multilamellar films with nucleotides encapsulated within.
What happens after several hydration/dehydration cycles in proto cell experiments?
- RNA-like molecules contained a number of repeating units, up to 100
- At the end, the molecules were encapsulated in vesicles that self assembled following rehydration
True or False: RNA molecules are encapsulated in vesicles that self-assemble after rehydration.
True
