A2.1 Origin of Cells Flashcards

early earth, cell theory, miller-urey, RNA, LUCA, hydrothermal vents

1
Q

what was the atmosphere of early earth first theorized to be like and by who?

A

oparin and haldane suggested had N, CO2, H2S, water vapour, NH3, and traces of methane and H; no O2/O3

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2
Q

what hypothesized conditions allowed organic compounds to be formed?

A

first O2 from photosynthesis, high levels UV light from lack of ozone, high temperatures from high concentrations CO2, combined with lightning and volcanic activity

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3
Q

when and how was earth formed?

A

4.5 billion years ago from smaller particles colliding to form big particles, which attracted more particles

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4
Q

what are the principles of the cell theory?

A
  1. cells are the basic unit of life
  2. all organisms are made of one or more cells
  3. all cells come from pre-existing cells
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5
Q

how did the cell theory come to be?

A
  • 1665: Robert Hooke sees 1st cells in cork
  • few years later, Antonie van Leeuwenhoek saw 1st living cells, coined “animalcules”
  • 1838: Matthias Schleiden said plants made of “separate beings” called cells; same with animals 1839
  • 1880s: Louis Pasteur boiled chicken broth, sterilizing it, and confirmed life couldn’t appear without pre-existing cells
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6
Q

what are the characteristics of living things?

A

made of cells, metabolism, homeostasis, response to stimuli, growth, DNA, reproduction, excretion, need for nutrition

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7
Q

define paradigm shift

A

when theories are completely abandoned due to conflicting evidence (radical change in orthodox beliefs)

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8
Q

how was the first cell theorized to have developed?

A
  1. synthesis of small carbon compounds from abiotic matter
  2. compounds form polymers through condensation reactions catalyzed by hot sand/clay/rock
  3. membranes contain polymers
  4. create self-replicating molecules so inheritance and control occurs
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9
Q

who conducted the miller-urey experiment and when?

A

stanley miller and harold urey in 1953

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10
Q

what was the purpose of the miller-urey experiment?

A

to determine whether the hypothesized reducing environment of pre-biotic earth could have formed organic compounds

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11
Q

what is a reducing environment?

A

lacking oxidizing gases, mostly reducing gases like H, H2S

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12
Q

describe the procedure used in the miller-urey experiment

A
  1. upper apparatus with NH3, CH4, H2, representing reducing environment
  2. lower chamber of water, heated to form vapour that travels to apparatus
  3. 2 electrodes produce 7500 V at 30 A, simulating lightning in apparatus
  4. water continues to condenser to allow gas compounds to condense
  5. sample collected to see molecules in it after 1 week, when water is brown-black
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13
Q

what was discovered/concluded through the miller-urey experiment?

A

organic molecules like fatty and amino acids were identified; suggests life originated from primordial soup

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14
Q

what were the strengths of the miller-urey experiment and primordial soup theory?

A
  • modelled pre-biotic earth
  • demonstrated spontaneous generation of organic molecules
  • could be replicated
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15
Q

what were the weaknesses of the miller-urey experiment and primordial soup theory?

A
  • debate of actual pre-biotic atmosphere
  • didn’t produce all molecules needed for life
  • proteins dissolve in water, so amino acids could not have combined to form polypeptides
  • couldn’t account for all conditions
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16
Q

what are other theories about the origins of life?

A

asteroids/comets, volcanoes, hydrothermal vents

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17
Q

how could life have come from volcanoes?

A

inorganic gases produced by volcanoes (water vapour, CO2, SO2, traces of CO and H2S) would result in non-reducing environment

18
Q

what is a non-reducing environment?

A

lacking reducing gases, mostly oxidizing gases; wouldn’t form carbon compounds because lacking H for H bonds

19
Q

what is a hydrothermal vent?

A

crack beneath ocean floor that water heated by magma-heated rocks rises out of, picks up lots of dark minerals and appears black

20
Q

when were hydrothermal vents first observed?

21
Q

what is the evidence for hydrothermal vents being the origin of life?

A
  • oldest fossils/precipitates found nearby
  • commonality of genetic sequences in organisms nearby
  • mineral-rich, acidic and basic fluids necessary for reactions
  • H and C form reducing environment
22
Q

how are vesicles formed?

A

when fatty acids placed in water, form themselves into vesicles

23
Q

what is another name for a vesicle?

24
Q

what are some functions of vesicles?

A

engulf other molecules, grow, replicate

25
what is the difference between a protocell membrane and a modern cell membrane?
protocell membranes only had fatty acids; modern membranes have proteins, etc. embedded
26
define compartmentalization
development of vesicle
27
what is the evidence for RNA being the first genetic material?
* assembles spontaneously from nucleotides * self-replication; genetic material * enzymatic
28
what is an example of an enzymatic RNA molecule?
ribozyme; catalyzes things like peptide bond formation
29
why could DNA not have been the first genetic material?
needs proteins and other molecules to replicate/grow/survive; RNA is the molecule that delivers and replicates code
30
what is the evidence of a LUCA?
* universal genetic code using nucleotides * 300 genes in every animals' cells * common molecular processes and transport mechanisms
31
was the LUCA the only life form that existed during its time?
other life forms evolved but couldn't compete
32
what traces of life get fossilized?
shell, bone, footprints, impressions of soft body parts
33
when did the LUCA form and what type of organism was it?
cyanobacteria 3.5 billion years ago
34
which two types of cells did the LUCA branch into?
simple (bacteria/archaea) and complex cells (plants/animals)
35
define half-life
time it takes for half of radioactive isotope to become stable element
36
what is absolute/radioactive dating?
organisms accumulate isotopes at constant rates, which start decaying after death; using half-lives and amount of isotope left in fossil, can find age
37
what is relative dating?
sediment strata layer from oldest at the bottom to youngest at the top; age of fossil approximated from age of strata
38
why is relative dating less accurate than absolute dating?
approximate, geological procceses could disturb layers
39
what is an index fossil?
similarly aged fossils found in different places, means strata are same age
40
what is genomic/genetic analysis?
compares amount of genetic difference, based on rates of genetic mutation (number of mutations between species tells when they diverged); used to estimate the LUCA's age
41
why is genomic/genetic analysis sometimes unfavourable?
hard to find DNA in older fossils