a2.1 (origin of the cell)

Question 1

when was the formation of earth? how was it formed?

Answer 1

~ 4.5 billion years ago. when gravity pulled swirling gas and dust in to become the third planet from the sun, caused by gravity and high temps creating a hot molten mass

Question 2

when was water found?

Answer 2

~4.4 billion years ago

Question 3

where is water expected to have reached earth from?

Answer 3

acquired water from extra-planetary objects, meaning object from outside Earth’s orbit

Question 4

characteristics of pre-biotic earth x5

Answer 4

frequent volcanic eruptions

meteorites

lighting

high temperatures

high energy UV radiation would have penetrated the Earth’s surface

Question 5

the period from 4.5 to 4 billion years ago was called what? x2

Answer 5

hadean eon/pre-biotic earth

Question 6

how did earth’s first atmosphere likely start?

Answer 6

as a region of escaping hydrogen and helium, because these were the main gases in the dusty, gassy disk around the sun from which the planets formed

Question 7

how did earth’s second atmosphere start?

Answer 7

came from earth itself: it is generally thought that ammonia (NH3), methane (CH4), carbon dioxide (CO2) and water vapour (H2O) were present sometime after the crust cooled due to volcanic outgassing

Question 8

why was O2 not really found in the second atmosphere?

Answer 8

because it quickly reacted with other elements

Question 9

conditions of early earth (atmosphere, temp, UV, volcanic activity and asteroid activity)

Answer 9

atmosphere: “reducing atmosphere” with higher proportion of reactive gasses such as ammonia (NH3) and hydrogen (H2). very little oxygen (O2)

temp: significantly warmer than today due to heat from asteroid collisions and accretion (coming together, formation) of the planet

UV: no ozone (O3) layer to block radiation from the sun so intense UV radiation reached the surface

volcanic activity: volcanic eruptions released gasses (H2O and CO2) into the atmosphere

asteroid activity: constant bombardment by asteroids as the solar system was forming

Question 10

oparin and haldane independently proposed nearly identical hypotheses for the steps of how life could have originated on earth: x4

Answer 10

formation of simple organic molecules from inorganic compounds

assembly of carbon compounds into polymers

formation of a polymer that can self replicate (enabling inheritance and variation)

packaging of molecules into compartments with an internal chemistry different from the surroundings

Question 11

characteristics of inorganic molecules x3

Answer 11

do not have both carbon and hydrogen within the same molecule

usually have a small number of atoms

often associated with non-living matter

Question 12

characteristics of organic molecules x3

Answer 12

contain carbon and hydrogen

can be large molecules with many atoms

usually associated with living organism

Question 13

______ _______ _______ form from ________ precursors is the first step in oparin-haldane origin of life

Answer 13

simple organic molecules FORM FROM inorganic

Question 14

what did oparin and haldane hypothesize to how organic molecules form from inorganic precursors? (as today, most living things get the energy to synthesize molecules by oxidizing nutrients in cellular respiration or directly from the sun by photosynthesis)

Answer 14

oparin and haldane hypothesized that early earth provided the conditions necessary for the formation of carbon compounds. these conditions do not exist on earth today

Question 15

once formed, small _______ _______ may have been able to spontaneously form _______ on early Earth

Answer 15

organic molecules, polymers

Question 16

prebiotic formation of carbon compounds condensed into 3 stages

Answer 16

inorganic compounds → organic monomers → polymers

Question 17

examples of biological organic monomers x4

Answer 17

amino acids, nitrogenous bases, fatty acids and simple sugars

Question 18

when was chemical evidence of life?

Answer 18

~3.8 billion years ago

Question 19

when was fossil evidence of life?

Answer 19

~3.5 billion years ago

Question 20

when was photosynthesis believed to begin?

Answer 20

~3.2 billion years ago

Question 21

what was the period called the “great oxygenation event”?

Answer 21

a period in early photosynthesis where oxygen concentration in the atmosphere increased from 0% to around 20%

Question 22

when were the first animals?

Answer 22

635 million years ago

Question 23

when was the dinosaur extinction?

Answer 23

66 million years ago

Question 24

what does the cell theory suggest?

Answer 24

that all life is composed of one or more cells, it is the smallest structural unit that is capable of using energy to sustain itself in a highly ordered state

Question 25

are the sub-cellular components (golgi app, nucleus, etc) considered alive?

Answer 25

no

Question 26

reasons why viruses considered non-living x5

Answer 26

they are not made out of cells

they can not keep themselves in a stable state

they do not grow

they can not replicate themselves

they can not perform independent metabolism

Question 27

implications of cells being formed from preexisting cells x3

Answer 27

we can trace the origin of all the cells in our body back to the first cell; the zygote produced by the fertilization of a sperm and egg

all cells can be traced back through billions of years of evolution to “LUCA” the Last Universal Common Ancestor of all life on earth

if you keep going back in time, you must eventually reach the earliest cells to have existed. there must have been a first cell that arose from non-living material

Question 28

what is the final step of the Oparin-Haldane hypothesized process for the origin of life?

Answer 28

formation of protocells that carry out metabolic reactions within an enclosed system

Question 29

what did the Miller-Urey experiment test?

Answer 29

tested for the formation of simple organic molecules

Question 30

watch a video on pasteur’s expirement!!!!!!

Answer 30

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Question 31

hypothesized processes needed for the spontaneous origin of cells on earth. x4

Answer 31

the synthesis of simple organic molecules from inorganic compounds.

the assembly of these organic molecules into polymers.

the formation of a polymer that can self replicate (enabling inheritance).

packaging of molecules into membranes with an internal chemistry different from the surroundings.

Question 32

watch a video on the Miller-Urey expirement!!!!!!

Answer 32

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Question 33

what is another sign on the precense of organic compounds

Answer 33

in 1969 a meteorite (estimated to be 4.6 billion years old (older than earth)) landed in the town of Murchison, Australia. the meteorite contains many organic molecules, including amino acids, ribose and nitrogenous bases

other extraplanetary objects have also been found to contain organic molecules used by life on earth. these results demonstrate that the molecules of life on earth were present in the early solar system and are not unique to earth.

Question 34

3 ways membranes can exist as

Answer 34

vesicles, micelles, bilayer

Question 35

early cell membranes may have formed from what?

Answer 35

fatty acids

Question 36

composition of a fatty acid x2

Answer 36

hydrocarbon chain/tail (hydrophobic)

carboxyl (COOH) group attached to one end. (very soluble in water)

Question 37

____ ____ in a watery solution will be attracted to each other and will spontaneously form spherical structures called _____

Answer 37

fatty acids, micelles

Question 38

RNA is a polymer formed by what?

Answer 38

the condensation of nucleotide monomers

Question 39

why do we assume that RNA is the first molecule to pass on genetic info between generations?

Answer 39

RNA molecules can act as catalysts for their own replication (can form copies of their own sequence without the use of enzymes)

Question 40

define polymerization

Answer 40

the process in which relatively small molecules, called monomers, combine chemically to produce a large chainlike molecule, called a polymer

Question 41

how do ribozymes function similarly to protein enzymes? x3 steps

Answer 41

the ribozyme binds to a specific molecule (the substrate)

the ribozyme catalyzes a reaction that changes the substrate by breaking or building chemical bonds

the ribozyme releases the product and is ready to work on another molecule of substrate.

Question 42

watch video on RNA as a catalyst!!

Answer 42

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Question 43

main piece of evidence that RNA arose before DNA in evolution

Answer 43

ribose is readily produced in laboratory experiments that attempt to simulate conditions on the primitive earth. deoxyribose is harder to make, and in present-day cells it is produced from ribose in a reaction catalyzed by a protein enzyme, suggesting that ribose predates deoxyribose in cells

Question 44

evidence that DNA replaced RNA as a more stable repository of genetic information x3

Answer 44

the deoxyribose in the DNA sugar-phosphate backbone makes DNA chemically more stable than chains of RNA, so that much greater lengths of DNA can be maintained without breakage

the hydrogen bonds holding together the double-helical structure of DNA add additional stability

the use of thymine rather than uracil further enhances DNA stability. thymine is much less susceptible to mutation than uracil and those that do occur are easier to repair

Question 45

what does LUCA stand for?

Answer 45

last universal common ancestor (of life on earth)

Question 46

is LUCA the first form of life? why?

Answer 46

no, extinct lineages exist that do not link to LUCA as an ancestor

Question 47

what type of cell would LUCA be?

Answer 47

a small, single-celled prokaryotic cell

Question 48

evidence collected by dr madeline weiss (finding 355/6.1 million common genes between bacteria and archea) shows what about LUCA?

Answer 48

was an obligate anaerobe (did not use oxygen)

was a chemoautotroph, obtaining energy from hydrogen and converting carbon dioxide and nitrogen into essential organic compound

was able to live in extreme heat

Question 49

what location would LUCA likely have lived in

Answer 49

the conditions are found in deep hydrothermal sea vents, the gassy, metal-laden, intensely hot plumes caused by seawater interacting with magma erupting through the ocean floor

Question 50

how do hydrothermal vents occur?

Answer 50

are the result of seawater percolating down through fissures in the ocean crust in the vicinity of spreading centers or subduction zones (places on Earth where two tectonic plates move away or towards one another)

The cold seawater is heated by hot magma and reemerges to form the vents, where seawater in hydrothermal vents may reach temperatures of over 700° Fahrenheit

Question 51

why doesnt seawater boil in hydrothermal vents?

Answer 51

because of the extreme pressure at the depths where the vents are formed

Question 52

how can evidence of microscopic life can be trapped in the rocks and analyzed using ratios of chemical isotopes?

Answer 52

life generally prefers ¹²C, so higher proportions of it suggest that the fossil is one of a living organism

Question 53

define biomarker

Answer 53

the molecular fossils of lipids and other organic compounds, encased in sedimentary rocks, these molecules can remain intact over hundreds of millions of years

Question 54

______ generally preserve better in sediments over long periods of time than molecules like DNA and proteins

Answer 54

lipids

Question 55

define stromatolites

Answer 55

structures created by photosynthetic bacteria that live in shallow water

Question 56

how does bacteria in stromatolites aid in fossilization?

Answer 56

as they become covered in clay and particles, the bacteria move upwards toward the light they require. this movement traps and bind sediments into layers. minerals precipitate inside the layers, creating fossilized stromatolites even as the microbes die off.

Question 57

how does the molecular clock approach work?

Answer 57

uses differences in the genomes of species to tell how much time has passed since they shared a common ancestor (the number of differences in the genomes of two species is proportional to the time since they diverged from a common ancestor)