1.5 The Origin of Cells Flashcards
Explain the following quote: “There is therefore a continuity of life from its origins on Earth to the cells in our bodies today.”
An individuals’ cells can be traced back to their zygote and from their to their parents ad infinitum to the very first cell (specifically through maternal mitochondrial DNA)
What are three reasons (other than Pasteur’s experiments) that biologists generally accept that cells can only come from other cells?
- A cell is highly complex and no natural mechanism has been suggested for producing cells from simple subunits.
- No example is known of increases in the number of cells in a population, organism, or tissue without cellular division.
- Viruses are produced from simpler subunits but they do not consist of cells
Describe Pasteur’s experiments.
Pasteur found that microorganisms were in the air, not appearing spontaneously. The swan-necked flasks prevented those bacteria from entering. When they couldn’t enter, no microorganisms were present. The broken flask showed it was the swan-necked flask which prevented microorganisms from growing.
How did the Miller & Urey experiment show that organic molecules could be formed by simulating early Earth conditions?
Simulated early Earth conditions by passing steam through methane, hydrogen, and ammonia and by using electrodes as lightning. This produced amino acids and other carbon compounds necessary for life.
What is it about deep-sea vents that make it a possible site for polymerization?
Deep-sea vents are characterized by gushing hot water carrying reduced inorganic materials, a possible energy source for the assembly of carbon compounds into polymers.
What happens to amphipathic molecules in a water based environment?
They readily form vesicles resembling the plasma membrane of a small cell, allowing different internal chemistry from that of its surroundings to develop.
Why is RNA considered to be a good candidate for the first inherited genetic material?
- Can store information in the same way as DNA
- Both self-replicating and can act as a catalyst
Explain endosymbiotic theory.
Mitochondria: larger eukaryote used anaerobic respiration and consumed a eukaryote using aerobic respiration/photosynthesis which was much more efficient. The larger cell would supply food to the smaller one and the smaller one would provide energy.
What evidence is there that both mitochondria and chloroplasts were once independently living prokaryotic cells?
- Have their own genes, on a circular DNA molecule similar to those of prokaryotes
- Have their own 70S ribosomes like prokaryotes
- Transcribe their DNA and use the mRNA to synthesize their own proteins
- Can only be produced by division of pre-existing mitochondria and chloroplasts by binary fission, like prokaryotes
