A2.1 Origin of Cells

Question 1

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

Answer 1

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

Question 2

what hypothesized conditions allowed organic compounds to be formed?

Answer 2

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

Question 3

when and how was earth formed?

Answer 3

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

Question 4

what are the principles of the cell theory?

Answer 4

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

Question 5

how did the cell theory come to be?

Answer 5

• 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

Question 6

what are the characteristics of living things?

Answer 6

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

Question 7

define paradigm shift

Answer 7

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

Question 8

how was the first cell theorized to have developed?

Answer 8

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

Question 9

who conducted the miller-urey experiment and when?

Answer 9

stanley miller and harold urey in 1953

Question 10

what was the purpose of the miller-urey experiment?

Answer 10

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

Question 11

what is a reducing environment?

Answer 11

lacking oxidizing gases, mostly reducing gases like H, H2S

Question 12

describe the procedure used in the miller-urey experiment

Answer 12

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

Question 13

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

Answer 13

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

Question 14

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

Answer 14

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

Question 15

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

Answer 15

• 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

Question 16

what are other theories about the origins of life?

Answer 16

asteroids/comets, volcanoes, hydrothermal vents

Question 17

how could life have come from volcanoes?

Answer 17

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

Question 18

what is a non-reducing environment?

Answer 18

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

Question 19

what is a hydrothermal vent?

Answer 19

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

Question 20

when were hydrothermal vents first observed?

Answer 20

1977

Question 21

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

Answer 21

• 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

Question 22

how are vesicles formed?

Answer 22

when fatty acids placed in water, form themselves into vesicles

Question 23

what is another name for a vesicle?

Answer 23

liposome

Question 24

what are some functions of vesicles?

Answer 24

engulf other molecules, grow, replicate

Question 25

what is the difference between a protocell membrane and a modern cell membrane?

Answer 25

protocell membranes only had fatty acids; modern membranes have proteins, etc. embedded

Question 26

define compartmentalization

Answer 26

development of vesicle

Question 27

what is the evidence for RNA being the first genetic material?

Answer 27

• assembles spontaneously from nucleotides
• self-replication; genetic material
• enzymatic

Question 28

what is an example of an enzymatic RNA molecule?

Answer 28

ribozyme; catalyzes things like peptide bond formation

Question 29

why could DNA not have been the first genetic material?

Answer 29

needs proteins and other molecules to replicate/grow/survive; RNA is the molecule that delivers and replicates code

Question 30

what is the evidence of a LUCA?

Answer 30

• universal genetic code using nucleotides
• 300 genes in every animals’ cells
• common molecular processes and transport mechanisms

Question 31

was the LUCA the only life form that existed during its time?

Answer 31

other life forms evolved but couldn’t compete

Question 32

what traces of life get fossilized?

Answer 32

shell, bone, footprints, impressions of soft body parts

Question 33

when did the LUCA form and what type of organism was it?

Answer 33

cyanobacteria 3.5 billion years ago

Question 34

which two types of cells did the LUCA branch into?

Answer 34

simple (bacteria/archaea) and complex cells (plants/animals)

Question 35

define half-life

Answer 35

time it takes for half of radioactive isotope to become stable element

Question 36

what is absolute/radioactive dating?

Answer 36

organisms accumulate isotopes at constant rates, which start decaying after death; using half-lives and amount of isotope left in fossil, can find age

Question 37

what is relative dating?

Answer 37

sediment strata layer from oldest at the bottom to youngest at the top; age of fossil approximated from age of strata

Question 38

why is relative dating less accurate than absolute dating?

Answer 38

approximate, geological procceses could disturb layers

Question 39

what is an index fossil?

Answer 39

similarly aged fossils found in different places, means strata are same age

Question 40

what is genomic/genetic analysis?

Answer 40

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

Question 41

why is genomic/genetic analysis sometimes unfavourable?

Answer 41

hard to find DNA in older fossils