A2.1 Flashcards
Origins of Cells
Evolution of Cells
What is Homeostasis?
- Maintaining of a consistent internal environment even whene xternal change
- can be essential requirement of living organisms to maintain constant
- organisms differ in terms of how many things they keep constant: endotherms maintain internal temp while ectotherms (reptiles) don’t
Evolution of Cells
What is Primordial soup
- origin of living compounds began as a water-based sea of simple monomers (amino acids, carbon and hdyrogen chain)
- solution was supported by MILLER UREY experiment
Evolution of Cells
What are Vesicles?
- Term for any small ‘bubble’ of fluid surrounded by a phospholipid bilayer
- Forms automatically when phospholipids are in water and this is thought to be a model of how cells originate
- They also form by established membrances (like cell membrane/ golgi apparatus) breaking off.
Evolution of Cells
What is compartmentalisation?
- The separation of functions into specific regions of the cell (specific organelles), which allows multiple distinct metabolic functions to occur at the same time.
- Occurs to a small degree in prokaryotes/ bacteria and to a much larger extent in eukaryotic cells.
Evolution of Cells
What is Coalescence?
- Regarding vesicle or membrane formation.
- NATURAL coming together of things – (in this context) refers to fatty acids/ phospolipids naturally arranging themselves away from water, thus them coming together and automatically forming a ring like structure with water both inside and outside the ring.
Evolution of Cells
Abiotic Conditions of Early Earth vs Present
- Abiotic conditions found on early earth were different —-> may have allowed for SPONTANEOUS formation of compounds
Differences include:
- GASES: methane, ammonia, and hydrogen sulfide and little O2 and ozone.
- PENETRATION OF UV LIGHT: due to no ozone, leading to high temperatures.
- Regular Lightning
Evolution of Cells
Requirements for Life
For any organisms to be considered ALIVE must be able to perform:
- Metabolism
- Growth
- Reproduction
- Respond in some way to their environment (stimulis)
- Maintain homeostasis
- Use food for energy/ nutrition
Evolution of Cells
Three Principles of Cell Theory
- All organisms are composed of one (unicellular) or more cells. (multicellular)
- Cells are the smallest unit of life.
- All cells come from pre-existing cells.
Evolution of Cells
Requirements for cells to evolve
1) Catalysis - some sort of enzyme that can speed up slow chemical reactions.
2) Self replication of molecules needed.
3) Self assembly of those molecules into larger polymers and structures/ organelles.
4) Compartmentalisation – functions being assigned to organelles.
Evolution of Cells
Organic vs Inorganic compounds.
ORGANIC:
- Generally complex carbon (and hydrogen) based compound that is made in living organisms
- play a crucial role in living processes.
- Include carbs, lipids, proteins, and nucleic acid.
INORGANIC:
- Do not have to contain carbon (most do not)
- Often found outside of living organisms as well as inside them.
- Simpler.
Evolution of Cells
The Miller-Urey Experiment
Wanted to test the hypothesis that inorganic gases could react (with conditions similar to early Earth including heat and electrical activity) to create organic compounds.
- Found evidence of long C and H chain and amino acids –> this fluid containing simple monomers –> first step in evolution of life —> PRIMORDIAL SOUP.
Evolution of Cells
Fatty Acids and Vesicle Formation
Requirement to make a cell –> a boundary (CELL MEMBRANE).
- Phospholipids in an aqueous solution naturally form a barrier to create a vesicle (fluid surrounded by membrane.)
- Fatty acids were present in the ‘primordial soup’ then this same process could have created the cell membranes of early cells.
RNA World Hypothesis and LUCA
What are ribozymes?
A special type of RNA that can act as a catalyst.
- Play a role in protein synthesis.
- Also evidence that RNA could have actually been the first catalyst (needed for cells to develop) and evolved prior to protein based enzymes.
RNA World Hypothesis and LUCA
What are protocells?
A general term for any unit contained by a membrane that is completing cellular reactions.
- Likely the ancestors of modern cells that contained polymers inside a membrane.
- More compartmentalisation and self replication would develop for a true cell to exist.
RNA World Hypothesis and LUCA
What are radioactive isotopes?
An isotope is an unstable form of an element and a radioactive isotope emits radiation which means they are able to be measuremed effectively.
- Radioisotopes are used to date fossils —> fossils contain them as do living organisms.
- Isotopes are taken up at a consistent rate.
- When comparing how much of an isotope remains compared to how much initially would have been, fossils can be dated.
