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Biology > A2.1 Origin of Cells > Flashcards

A2.1 Origin of Cells Flashcards

1
Q

why was the Earth formed?

A

gravity caused dust and gas to come together

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2
Q

describe the pre-biotic atmosphere

A

only traces of oxygen because it reacted with other elements; methane concs higher bc of intense volcanic activity and meteorites; CO2 concs higher bc of volcanic emissions

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3
Q

why were temps higher than they are now?(4)

A

high concs of CO2 and CH4 which are heat-trapping greenhouse gases; comet and asteroid impacts; the ozone layer that now protects us wouldnt exist bc of lack of oxygen, without the layer more solar UV would have penetrated to earth’s surface; more lightening triggering other chemical processes

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4
Q

where would carbon compounds be formed?

A

specialized environments eg hot springs on land or hydrothermal vents in oceans

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5
Q

what would carbon compounds have formed?

A

droplets of water in the atmosphere, creating an ORGANIC AEROSOL HAZE which would have deposited into lakes/oceans creating a ‘soup’ of carbon compounds

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6
Q

what happened as organisms came about?

A

they increases oxy conc and decreased CO2 conc so ozone layer formed giving protection against UV + greenhouse effect was reduced

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7
Q

cells can be considered as…

A

the smallest units of self-sustaining life

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8
Q

what are the 3 components of cell theory?

A

all living organisms are composed of one or more cells; the cell is the most basic unit of life; all cells arise from pre-existing cells by division

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9
Q

what are the functions of life(Mr H Gren)

A

metabolism, response, homeostasis, growth, reproduction, excretion, nutrition

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10
Q

which developments are needed for the origin or cells?

A

catalysis, self-assembly(carbon compounds eg amino acids need to assemble to form polymers), compartmentalisation(membrane to enclose cell contents), self-replication

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11
Q

Miller-Urey experiment

A

passed steam through CH4, H, ammonia simulating earth’s atmo, used electricity to mimic lightening, found amino acids and carbon compounds could be formed, theorised these would then form polymers using energy from deep sea vents and trigger mechanisms for inheritance before becoming enclosed in a membrane to form a cell

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12
Q

strengths of miller-urey experiment

A

repeatable-similar experiments have shown a diversity of carbon compounds can form spontaneously in an atmosphere lacking oxygen

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13
Q

weaknesses of miller-urey experiment

A

miller and urey probs got some conditions wrong-pre-biotic Earth had more CO2 and N2 and less NH3 and CH4 and less lightning

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14
Q

what is a vesicle?

A

small droplets of fluid, enclosed in a membrane

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15
Q

what are exosomes?

A

extracellular vesicles which some cells produce

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16
Q

what does the membrane of vesicles consist of?

A

mainly phospholipids, experiments show that bilayers spontaneously form stable spherical structures

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17
Q

what would have happened if phospholipids were part of the ‘soup’ of carbon compounds?

A

they would have self-assembled into bilayers and vesicles would have likely formed but movement of pilar in and out would have been limited by hydrophobic membrane core so would have developed own internal chem(cell-like)

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18
Q

what can RNA do?

A

store info like DNA but is self-replicating and can act as a catalyst

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19
Q

what do some viruses use as genetic material?

A

RNA which supports theory that RNA could have been used before genes of DNA evolved

20
Q

LUCA

A

last universal common ancestor, the hypothetical organism from which all life on earth is believed to have descended

21
Q

what is convergent evolution?

A

when it’s possible for similar structures to evolve in organisms that don’t have a recent common ancestor

22
Q

conditions for luca?

A

would have used RNA to store genetic info and catalyse chemical reactions, would have been highly resistant to extreme environments

23
Q

evidence for luca?

A

universal genetic code in all cells, same building blocks for RNA and DNA in all cells, common molecular processes in all cells

24
Q

what is an emergent property?

A

characteristics of an organism not evident on a cellular level created by interactions between cells

25
Q

eg of minerals found in alkaline hydrothermal vents that act as catalysts to build organic molecules

A

iron and sulfur

26
Q

what is a micelle

A

an aggragate created through self-assembly of amphipathic molecules;hydrophobic ends face in and hydrophilic ends fce out

27
Q

what is a protocell

A

structures formed from the aggregation of abiotic components but has some similarities to living cells

28
Q

bc Earths early atmosphere was absent of O2 this suggests luca was…

A

anaerobic

29
Q

bc of earths hot thermal vents underwater it suggests luca was…

A

thermophilic bc thermal vents are v hot and autotrophic bc no organisms to take nutrition from and wouldnt use light as an energy source bc deep ocean is v dark

30
Q

fossils for the 3rd part of the timeline for early life

A

rocks in australia contain fossilized stromatolites which are rocky mounds formed by mats of cyanobacteria in shallow seawater which trap sediments and secrete CaCO3

31
Q

isotope ratios in rocks for the 2nd part of the timeline for early life

A

carbon originating from living organisms has a low 13C/12C ratio, banded iron rock dating from 3.8 Gya shows this, suggesting life had evolved by then

32
Q

genomic info for the 1st part of the timeline for early life

A

the no. of differences between the genomes of 2 species is proportional to the time since they diverged from a common ancestor. LUCA and the first living cells existed 4.5 Gya

33
Q

what kind of environment was it likely that LUCA lived in?

A

high concs of H, CO2 and iron and these conditions are found in and around hydrothermal vents in oceans

34
Q

which conditions do hydrothermal vents have that are needed for the 1st cells to form?

A

alkaline, white smoke that comes out is fluid at temps of 60 to 90 and contains high concs of H, methane, ammonia and sulfides. These chemicals could have been used to generate energy anaerobically which protocells could have used to assemble carbon compounds into polymers. CO2 needed by evolving protocells would have been abundant in the pre-biotic ocean water

35
Q

how did pasteur disprove spontaneous generation?

A

showed air was full of microorganisms, heated some broth in a flask to kill the microorganisms and left open to air through a swan-neck flask and nothing formed, broke the swan neck flask and saw microorganisms developed

36
Q

what are the 3 atypical cells and why are they atypical?

A

skeletal muscle bc they’re multinucleated; aseptate fungi bc they contain hyphae(cells) but no septa(cell walls); acetabularia bc they’re large single cells

37
Q

what happens as cells increase in size?

A

SA:V ratio decreases; reduces speed at which substances enter and exit the cell; reduces rate of both energy and heat transfer limiting rate of metabolism; this restricts the size of the cell which is why most cells are small

38
Q

define differentiation

A

development of cells in different ways to carry out specific functions; involves the expression of certain genes in a cell’s genome and enables emergent properties

39
Q

pluripotent

A

stem cell can differentiate to form any cell in an organism

40
Q

multipotent

A

stem cell can differentiate to form many different cells in an organism

41
Q

where can stem cells be found in humans?

A

embryonic(contained within embryo, pluripotent); cord blood stem cells(found in umbilical cord, multipotent); adult stem cells(found in bone marrow, multipotent)

42
Q

how can stargardt’s disease be treated with stem cells?

A

blindness in children due to a dysfunction of retinal cells in the eye, stem cells injected into the eye and differentiate into healthy retinal cells curing the blindness

43
Q

how can stem cells be used to treat leukaemia?

A

production of abnormal WBCs; stem cells extracted from bone marrow and chemotherapy kills the remaining cells; stem cells reintroduced and differentiate to form new healthy WBCs

44
Q

what does endosymbiotic theory provide evidence for?

A

provides evidence for the origin of eukaryotes

45
Q

which experiment disproved spontaneous generation?

A

Louis Pasteur

46
Q

what is the endosymbiotic theory?

A

states that larger prokaryotes engulfed smaller prokaryotes; have their og membrane and the membrane of larger prokaryotes

47
Q

what characteristic of a steroid shows it is a lipid?

A

it has a very low proportion for oxygen to carbon

Biology (12 decks)

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