Origin Of Cells Flashcards
Unit 1, Cell Biology
What was the conditions of pre-biotic Earth like?
Water vapour, Methane, Carbon dioxide, Nitrogen, Hydrogen & Ammonia
Lots of lightning and volcanic eruptions. Also very high temperature and UV radiations.
When was the Earth formed and when do we think that first life was created?
4.6 Billion and 3.8 Billion years ago
What is the cell theory?
- all cells come from pre existing cells
- All living things are made of cells
- Cell is the smallest unit of life
Exceptions to the characteristics of life?
Mature red blood cell doesn’t have a DNA.
Mules cannot reproduce
Key differences between living vs non living cells?
- living things use energy to keep them in a highly ordered state
- living things pass on the ability to maintain a highly ordered state
Why are viruses non living?
They can’t replicate themselves
Can’t grow
Can’t perform individual metabolism
Can’t keep themselves in a stable state
What is spontaneous generation / abiogenesis?
A theory that living things can be formed from non living things
Who is Louis Pasteur?
He and other biologists proved evidence that spontaneous generation theory is false.
What is LUCA?
The Last Universal Common Ancestor of life on Earth
Why is it difficult of directly test the hypotheses related to the origin of cells?
- conditions on Earth were very different
- it’s not possible to exactly replicate with certainty the conditions that would have existed on early Earth
- well preserved fossils are rare
- methods used to estimate dates of the first living cells have ranges of uncertainty.
J. B. S. Haldane?
Described Earth as a “hot dilute soup,” said that the early earth contained water vapour, CO2 and ammonia
What 4 process has to occur to form the first cells?
- The abiotic synthesis of small organic molecules such as amino acids, sugars, and nucleotides.
- The joining of these small molecules (monomers) into polymers, including proteins and nucleic acids.
- The origin of self-replicating molecules that eventually made inheritance possible.
- The packaging of these molecules into protobionts (protocell), droplets with membranes that maintained an internal chemistry different from that of their surroundings.
Miller-Urey experiment?
Attempt to recreate conditions in prebiotic earth that lead to synthesis of organic compounds.
Carbon containing organic molecules formed. They organized into carbohydrates, nucleic acids, lipids and proteins.
Difference between inorganic molecules and organic molecules
- Do not have both carbon and hydrogen within the same molecule; contains carbon and hydrogen
- Usually have a small number of atoms; can be large molecules with many atoms.
- Often associated with non-living matter; usually associated with living organisms
What is polymerization?
It is a process which relatively small molecules, called monomers, combine chemically to produce a large chain like molecule, called polymer.
It is an anabolic reaction, in which complex molecules form from simpler molecules by condensation reactions.
What is anabolic reactions?
Reactions that absorb energy and build bigger molecules.
What is condensation reactions?
A reaction in which two molecules join to form a single molecule, water is removed.
What is protobionts?
They are aggregates of abiotically produced molecules surrounded by a membrane or membrane like structure.
What is a RNA?
It is a polymer formed by condensation of nucleotide monomers (composed of sugar, phosphate and nitrogen base) similar to DNA.
Under certain conditions it can replicate itself without the use of enzymes which makes it the more likely candidate for the first genetic material.
RNA World hypothesis?
Idea before any gene/protein cycle ever existed, chains of a chemical called RNA were forming naturally. Some RNA chains were able to function as enzymes and were even able to evolve by making copies of themselves. With slight modifications
What is Ribozymes function?
- The ribozyme binds to a specific molecule
- The ribozyme catalyzes a reaction that changes the substrate by breaking or building chemical bonds
- The ribozyme releases the product and is ready to work on another molecule of substrate
Evidence for LUCA?
The genetic code could have been easily been different but this specific genetic code has been found to be universal in all organisms.
What are various approaches used to estimate the dates of the major events in the evolution of life on Earth?
- chemical evidence
- biomarkers
- fossil evidence
- genetic evidence
Chemical evidence used to estimate dates of the first living cells and the lasts universal common ancestor?
Found in rocks containing fossil like structures with isotopes suggesting they may be the remains of living organisms. They contained organic compounds with a carbon isotopic signature that could result from biological processes.
Evidence of microscopic life can be trapped in the rocks and analyzed using ratios of chemical isotopes.
Biomarkers used to estimate dates of the first living cells and the lasts universal common ancestor?
They are the molecular fossils of lipids (preserved better than DNA and protein) and other organic compounds. Encased in sedimentary rocks, these molecules can remain intact over hundreds of millions if year and help with estimates of the living organisms age
Fossil evidence used to estimate dates of the first living cells and the lasts universal common ancestor?
Stromatolites firm when mats of Cyanobacteria living in shallow water secrete calcium slowly building rock mounds
Evidence from ancient seafloor hydrothermal vents that life may been present at these locations about 3.8 billion years ago
Genetic evidence used to estimate dates of the first living cells and the lasts universal common ancestor?
Using a molecular clock to compare the geneses of modern organisms, traces back to LUCA
What those genes of LUCA indicate about LUCA?
It indicates that LUCA was an obligate anaerobe (did not use oxygen), lived in an environment high in hydrogen, carbon dioxide and iron and was able to live in extreme heat. It also indicates that it was a chemoautotroph, obtaining energy from hydrogen and converting energy from CO2 and nitrogen into essential organic compounds
This conditions can be found in deep sea hydrothermal vents.
What does endosymbiosis mean?
Endosymbiosis (endosymbiont) means when one organism lives inside another (host)
What is the advantage of differenciation?
They have advantage of having cells that can perform different functions (called differentiation), only features needed for the function developing
What are advantages of being multicellular?
It has longer life spans, generally larger so can exploit niches (unicellular organisms can’t) and its complex due to differentiation.
