A2.1 Origin of cells

Question 1

what were the conditions on Early Earth

Answer 1

molten rock surface
as it cools down, released gases form atmospher( high amounts of carbon dioxide)
greenhouse gases lead to higher temperatures
lack of oxygen and ozone = high amounts of UV radiation
UV radiation = damages DNA/ causes mutation
lower levels of UV allowed life to exist

Question 2

what would the conditions on Early Earth lead to

Answer 2

it may have led to carbon compounds being formed spontaneously

Question 3

what would high levels of UV radiation may have led to

Answer 3

bases of nucleotides are highly efficient at reducing the harmful effects of UV, meaning RNA has more of a chance to form chains
possible that UV was a selection factor that drove processes forward

Question 4

what are the three principles that define life

Answer 4

evolution through natural selection(ability to reproduce and vary genetically)
life forms are contained and separate from, but in communication with their environment
chemical and physical machines that receive/respond to info

Question 5

what would happen if life were to evolve with different liquids

Answer 5

they would be fundamentally different

Question 6

what is the flaw with only having knowledge of earth life

Answer 6

unable to distinguish which properties of life on earth are unique and which are needed to qualify as life

Question 7

why is it hard to classify viruses

Answer 7

they exhibit some features of life when present on a host cell but otherwise, do not respond to stimuli

Question 8

what are the common features of cells

Answer 8

stable, partially permeable membrane that surrounds cell compounds
genetic material that can be passed onto newly formed cells, and control functions of cells
metabolic processes that allow energy generation, enabling growth, maintenance and reproduction

Question 9

what would the formation of living cells have required

Answer 9

synthesis of simple organic molecules
assembly of these molecules into polymers
development of self replicating molecules
retention of these molecules within membraneous sacs

Question 10

what are the three theories for the origin of life

Answer 10

protocell first
gene first
metabolism first

Question 11

explain the theory of life that states protocell came first

Answer 11

a cell like compartment that had basic metabolism but lacked developed genetic systems
divided into daughter cells that eventually evolved until acquiring a genetic system

Question 12

explain the theory of life that states gene first

Answer 12

RNA or DNA arose spontaneously and were capable of replication
they evolved throuhg natural selection, formation variants with cell membranes leading to metabolism

Question 13

explain the theory of life that states metabolism first

Answer 13

self sustaining system of simple reactions, capable of feeding on nutrients and energy arose spontaneously, perhaps on mineral surface. eventually evolved cells and genetic systems
theory is favored because functions of life require high amounts of energy

Question 14

what is the evidence for the origin of carbon compounds

Answer 14

found that amino acids were formed naturally with other compounds
shows us that organic molecules can be synthesized outside cells, in the absence of oxygen

Question 15

what is polymerization

Answer 15

when monomers combine chemically to produce a larger molecule

Question 16

what is required for polymerization to take place in the absence of cells and enzymes

Answer 16

concentration of biologically important molecules such as monosaccharides, amino acids and fatty acids
clay also show to promote polymerisation

Question 17

where could polymerisation have taken place

Answer 17

may have happened in water close to volcanoes where its hot, pressure is high and gases being vented are rich in sulfur etc.

Question 18

why are fatty acids likely to have formed the components of cell membranes

Answer 18

they are amphipathic( polar and non polar ends)
meaning they form monolayers on water

Question 19

why are the formation of microspheres/vesicles important

Answer 19

systems were able to develop a chemical environment different from their surrounding

Question 20

what is required for the evolution of life from a mixture of polymers and their monomers

Answer 20

a self replication system
an ability to catalyse chemical change

Question 21

what is the other possible function of RNA other than an information molecules

Answer 21

possible it functioned as an enzyme

Question 22

what is the RNA world Hypothesis

Answer 22

the earliest life forms used RNA as genetic material and enzymes
only after evolution, did DNA take over as the genetic material

Question 23

What are ribozymes

Answer 23

RNA molecules that have catalytic properties

Question 24

Why is RNA though to play a central role in the origin of life

Answer 24

Due to its unique potential as a carrier of genetic info and as catalysts

Question 25

How can DNA be used as evidence for similarities and differences between species

Answer 25

the more similar the genes the more closely related two species are

Question 26

What is LUCA

Answer 26

the last universal common ancestor
an organism that existed 4 billion years ago which we all evolved from

Question 27

Why may other organisms that lived as the same time as LUCA may have gone extinct

Answer 27

due to competition for resources

Question 28

How can the age of LUCA and other such organisms be predicted

Answer 28

through genomic analysis, where the average time for mutations to take place is estimated

Question 29

what characteristics is LUCA assumed to have

Answer 29

anaerobic
CO2 fixing
H2 dependent
N2 fixing
thermophilic

Question 30

Where are the fossils of first life most likely to be

Answer 30

in rocks near deep sea, hydrothermal vents