origin and evolution of cells Flashcards
what does the primitive atmosphere consist of and what can you tell me about it?
- devoid of molecular oxygen (O2) which allowed interaction of Carbon and hydrogen between themselves and with other atoms => formation of organic molecules (prebiotic and abiogenic synthesis of Organic Compounds)
- Chemical reactions become more diverse => organic soup formed
- RNA- only biopolymer, able to influence reactions in the environment, biochemical reactions and their own replication (at ‘RNA world’)
- RNA started to catalyze protein synthesis
What was the Miller-Urey experiment? What year?
- Stanley Miller & Harold Urey made an experiment that simulated the conditions in early earth (1953 )
what can you tell me about the first type of transport system?
There was a membrane around RNA and proteins; lipids self-organized into bi-layers (fairly permeable)- allows import and export of substance without today’s transport system
what was used to store genetic information in early earth?
later, more stable DNA was used to store genetic information
who was LUCA?
- Last Universal Common Ancestor (LUCA)
- LUCA lived almost 4 billion years ago
- It was an anaerobic chemoautotroph
- used energy from anaerobic oxidation of H2 and fixed O2 by chemosynthesis
- regard to its structure, it was a prokaryote
draw a prokaryote
list the characteristics of prokaryotes
- small, mostly unicellar (1-10μm)
- surrounded by a lipid cell membrane
- genetic information stored in cytoplasm with ribosomes
- circular DNA molecule in the nucleoid and plasmids
- cell wall (above membrane) has appendages (w/attachment function) called pili or fimbriae
- no nucleus , no membrane bound organelles
- Gram-negative bacteria have 2nd outer lipid membrane for protection
- Some bacteria more by flagella
- Some bacteria (under extreme conditions) turn into metabolically inactive, highly resistant form called spore
what are cyanobacteria and give me an example?
- Cyanobacteria are photoautotrophes & have pigment-containing membranes (They are exceptions of prokaryotes)
- Escherichia coli
what can you tell me about Escherichia coli
- Escherichia coli Iives in our intestine without harm
- bacterial conjugation- transfer of plasmid or part of chromosome via protein “tunnel” formed by long pilus (F pilus) to another cell (asexual process)
- Cell division: by binary fission, 2 bacterial chromosomes are segregated to the opposite poles and new wall is formed in the middle
- Digestion: Polymers cannot pass through the cell membrane, enzymes are secreted to hydrolyse polymers to monomers
- Respiration: As O2 accumulated many prokaryotes become aerobic
- electron transport chains and ATP synthase are in cell membrane
what are the two groups of prokaryotes?
bacteria (eubacteria) & archaea (archaebacteia)
what are some characteristics between the two groups of prokaryotes?
bacteria (eubacteria)
* numerous and prosperous
* e.gbacteria, cyanobacteria
archea (archaebacteria)
* live in hot springs & extreme habitats
* include ancestor of eukaryotes
* e.g. Halophiles , Thermophils
draw a eukaryote
what are some charactersistics of a eukaryote
- developed at least 2.7 billion years ago
- large (typicaIly 10-100μm)
- Nucleus with linear Chromosomes
- intracellular membranes encloses compartments
- Mitochondria
- Flagella (different from prokaryotic ones)
- mostly aerobic heterotroph
- Some are photoautotraphs with chloroplasts
- Division by mitosis
- Sexual processes
- cytoskeleton network of filament (microtubules, microfilament, intermediate filaments)
- most important groups : Plants, Fungi, Animals, Humans
what is the endosymbiotic theory
Endosymbiotic theory was proposed in 1920s by Ivan Wallin
Origin of mitochondria
* had it’s own DNA and ribosomes (of prokaryotic type)
* precursor: alpha-proteobacteria
Origin of chloroplasts
* Own DNA and ribosomes (of prokaryotic type)
* eukaryotes became photoautotrophs by ingesting cyanobacteria turning them into chloroplasts
