Origin of life Flashcards
(156 cards)
1
Q
What certain characteristics do all living organisms share?
A
Composed of cells, levels of organisation, use energy, respond to stimuli, grow, reproduce, adapt to environment, maintain homeostasis.
2
Q
What certain chemistry do all living organisms share?
A
Carbon-based, use energy, use oxidative gradients, contain proteins lipids carbs, use nucleic acids for heredity, use ATP, have same basic metabolic reactions.
3
Q
How old is the universe?
A
13,700,000,000 years old.
4
Q
What was the beginning of the solar system?
A
Explosion of star, formation of compounds, heavy metals, dust collapse, nebula, rotation round point.
5
Q
How were dust cloud Coalesces formed?
A
Gravity takes over, rotation round point, spinning flattens cloud into disc, collision between particles, planets form, sun compress ignites.
6
Q
How did planets form?
A
Inner planets form from mineral solids, outer planets form from gases, planetessimals.
7
Q
How were protoplanets formed?
A
Major collisions, gas giants form.
8
Q
What happened when the sun ignited?
A
Inner planets still chaotic and small, Jupiter supports asteroid belt.
9
Q
How was the moon formed?
A
Earth increases in size with protoplanet companion, collision.
10
Q
What happened during late heavy bombardment?
A
Sterilises earth, water falls to earth, meteorites fall.
11
Q
What were some implications of the early solar system?
A
Hydrogen abundant, high energy interior, magnetic field, atmosphere, meterorites, comets.
12
Q
Where did all the water come from?
A
Comets from late heavy bombardment, minerals dissolved in water, water covers planet.
13
Q
What happened during the hadean eon?
A
Earth spinning rapidly, smoggy toxic environment, dust/ash in atmosphere, anaerobic, surface water, violent tides, acidic, boiling sea.
14
Q
What is the panspermia theory?
A
Living organisms seeded by meteorites, identified from mars, mineral deposits, possible fossils.
15
Q
What have been detected on a non-terrestrial asteroid?
A
Nucleic acids uracil and nicotinic acid.
16
Q
What is the mineral clay theory for origin of life?
A
Water-bearing clays from concentration vessels for replication and patterning, source of mineral salts for catalysis of early processes, largely unsupported or supplanted.
17
Q
What is the primordial soup theory of origin of life?
A
Key elements react and form basic compounds for life - amino acids, nucleic acids, carbon based, spark of life from high energy source.
18
Q
What were the Miller-Urey experiments?
A
Replicated conditions of early earth based on predicted atmosphere of Jupiter, water, ammonia, methane, hydrogen, energy spark from lightening.
19
Q
What were the steps of the Muller-Urey experiments?
A
Mixture of liquid heated to gas, gases mix with spark, condenser, products collected and analysed.
20
Q
What was the outcome of the Muller-Urey experiments?
A
Amino acids were formed via Formaldehyde, conc of key components and energy from lightning could form building blocks of proteins.
21
Q
What are some major problems of the Muller-Urey experiments?
A
Analysis of early rocks shows atmosphere was CO2, N2, H2S, SO2, cant make AAs from these.
22
Q
What are some problems with primordial soup?
A
Unlikely to happen spontaneously, more complexity needed, energy source, concentration problem.
23
Q
What is all life based on?
A
Reactions of hydrogen and oxygen, free energy, reactions can be spontaneous.
24
Q
What is needed to drive reactions?
A
H+ gradients.
25
What is all life based on?
Reactions of hydrogen and oxygen, free energy, reactions can be spontaneous, need gradients.
26
What are proton gradients important for?
Producing reducing potential for chemical reactions.
27
What is the importance of deep sea vents?
Massive biodiversity, archaea, prokaryotes, animals.
28
What are black smokers?
Acidic, high pressure, iron pyrites, H2S released, +O2 — energy, flat eqm.
29
What is an alternative to the black smokers reactions due to little O2?
2H2S + Fe — FeS2 + 4H+ (not sufficient to fix CO2, more reactive CO works).
30
What are alkali vents?
Acid vents caused by moving plates, causes fusion or submergence, crust splits open and moves apart, exposes mantle, sea water in, meets magma, water and minerals + magma = serpentine rock.
31
What is serpentination for alkali vents?
Rocks mix with mantle, give up seawater, contaminations in water cause convection, forces magma to ridges, continuous activity driven.
32
What are the actions of alkali vents?
Releases energy as heat, reduces components of seawater, H2, S—H2S, N2 — NH3, CO2 — CH4 (components to produce AAs).
33
What are natural flow reactors made of?
Tynagh rock was hollow alkali vent chimneys are hollow, small cells some of them microscopic.
34
What is the purpose of natural flow reactors?
Appropriate compounds, concentrates compounds, provide Fe-S catalyst, thermochemical gradient, H2 gas for free energy.
35
What are porous cells?
Bioreactors.
36
What are some characteristics of the Hadean Eon?
Earth spinning rapidly, smoggy toxic environment, dust/ash in atmosphere, anaerobic.
37
How old is the Earth?
4.55 billion years old.
38
What are characteristics of the sea water during Hadean Eon?
Surface mostly water, violent tides, acidic, sea boils, some landed peaks above sea.
39
What are natural flow reactors?
Tynagh hollow rock, alkali vent chimneys hollow, small chambers.
40
What are the benefits of natural flow reactors?
Appropriate compounds, concentrates compounds, provide Fe-S catalyst, thermochemical gradient, H2 gas for free energy.
41
What does LUCA stand for?
Last Universal Common Ancestor.
42
Why can you predict what components of first life-forms were like by looking for commonalities?
All life-forms on the planet share certain characteristics.
43
What things do all life-forms on planet share commonalities in?
Membranes, ATP, nucleic acid, cells, genetic code, basic metabolism, DNA/RNA, protein.
44
What is LUCA?
Theoretical first organism that had all characteristics that life-forms on the planet share commonalities in.
45
What do you need to undertake metabolism?
Proteins.
46
What do you need to encode the proteins for metabolism?
Nucleic acids.
47
What do you need to replicate nucleic acids to encode proteins for metabolism?
More proteins!!
48
What has the ability to replicate or recur and to catalyse reactions?
RNA.
49
Why is RNA more suitable than DNA for early life creation?
DNA more stable, longer, easier to replicate, hereditary molecule in all life but no known catalysed activities and replication not conserved.
50
What is mean by DNA replication is not conserved?
Bacteria and Archaea have different enzymes so replication must have evolved after groups split so something else was there before.
51
How can RNA act as a catalyst?
RNA can bind to itself, can bind to others.
52
What is some evidence to show that there is a link between the activity of proteins and the RNA code?
Codon clusters tend to specify the same amino acids, 1st and 2nd base tend to be the same.
53
What is the significance of codon clusters specifying the same AAs?
You can synthesise amino acids from precursors using two nucleotides of RNA.
54
What has a strong correlation with the first bases of codons?
The biosynthetic pathways of the AAs they encode.
55
What has a strong correlation with the second bases of codons?
The nature of the amino acids.
56
How can you synthesis amino acids from precursors using two nucleotides of RNA?
1st specifies the precursor, 2nd determines product.
57
What can complex combinations form from?
An aggregation of RNA di-nucleotides.
58
What would happen if RNA was longer?
Amino acids transfer to more stable strand, dinucleotides acts as tRNA, produce 2-base code.
59
What concentration of RNA do you need for early life formation?
Need high concentrations for links to form spontaneously, low concs favour degradation.
60
Where did the RNA come from?
Vents, RNA polymerises spontaneously, convection and thermal currents split up vents with molecules, high concentrations, promote formation of polymers.
61
What are the origins of biological catalysts?
RNA replicate faster, catalyses reactions, gradually longer, structural and catalytic, structural elements to proteins, riboproteins evolve.
62
What does an acid-base gradient provide?
REDOX potential to facilitate amino-carboxy fusion.
63
What are the origins of DNA?
DNA and RNA very similar, derive deoxyribose from ribose, derive thiamine from uracil, evolved from RNA, permanent and stable.
64
What does the story of the origins of life so far tell us?
Early life like a bioreactor, concentrated space, replication and increasing complexity.
65
How do you synthesis Carbon based compounds from scratch?
TCA cycle, carbon fuel in, H+ out, CO2 out, used for making, energy ATP.
66
What is the Martin-Russel Theory?
Vents have H2 and CO2, catalysed by enzymes in Archaea, enzymes use S, Fe, Fe-S, Ni co factors, relatively inert, high energy, ATP, ATP too complex for early life.
67
What do acetyl thioesters provide?
Reducing power.
68
What is formed when CO2 and acetyl thioester react and whats the significance?
Pyruvic acid - entry point of TCA cycle.
69
What is formed when PO3 and acetyl thioester react and whats the significance?
Acetyl phosphate - ATP alternative.
70
What is a better way of providing energy for metabolism than redox gradients of alkali vents?
ATP - production allows for using small increments to produce larger whole.
71
What was holding everything together in early earth life?
Mineral cells in vents.
72
Why did LUCA need something to hold it together?
Would not have been free-living.
73
What can mineral cells provide?
Concentration, stable environment, redox potential, catalysts, concs of nucleic acids, sub structure for chemical reactants.
74
What do you need to exist outside of mineral cells?
A covering to maintain integrity, conc and gradient differences.
75
What must have developed to allow existence outside of mineral cells?
Membranes.
76
What kind of membranes must all modern organisms have had?
Lipid membrane.
77
What would development of a robust membrane allow?
A cell to leave the mineral chamber and spread.
78
What were membranes unlikely to have been originally?
Lipids.
79
How could membranes have originated?
From of Fe-S bubbles around alkaline vents, simple organic molecules from Fe-S catalysed reactions, compounds diffuse and collide, results in precipitated peptides coat inside surface of bubbles.
80
How did membranes evolve?
Gained complexity, turned into lipid membranes and cell walls, internal linings then external coverings.
81
What suggests that there was a change in membranes occurring late?
Differences in membrane structures between bacteria and archaea.
82
What are the differences between acetogens and methanogens?
Acetogens produce acetic acid, methanogens produce methane.
83
What happened post LUCA?
Two divergences, eukaryotes split off c.1.8 bya.
84
When did eukaryotes split off?
c.1.8 bya.
85
What organelles are present in Euk cells?
Nucleus, ER, Golgi, lysosome/vacuole, endosomes, mitochondria, chloroplasts, peroxisomes, ribosomes, plasma membrane.
86
What compartments of Euk cells are termed semi autonomous?
Mitochondria and chloroplasts.
87
What five things defines a semi-autonomous organelle?
Specific function, genome, transcription/ translation machinery, distinct biogenesis, self-replicating by binary fission.
88
What are semi-autonomous organelles genomes like?
Circular DNA genome with unique organelles genes, numerous copies, associated with membrane.
89
What are specific transcription and translation machinery found in semi-autonomous organelles?
RNA polymerase, tRNA and ribosomes.
90
Where are organelle genes contained?
In both the organelle DNA and nuclear DNA.
91
Where are proteins synthesised?
Some in the cytoplasm and imported into organelles and some synthesised in the organelle.
92
How does binary fission happen?
Constrict at centre and pull apart, creates two equal halves with same components.
93
Can organelle fusion occur?
Yes.
94
What is the endosymbiosis theory?
That semi-autonomous organelles were originally prokaryotes.
95
What is an overview of how the endosymbiosis theory would work?
Free living pro organisms engulfed by a Euk cells, host cell retained engulfed cell, mutual benefit, compartmentalisation of function, shared genetic info, system of protein/metabolite import/export.
96
How many semi-autonomous organelles are there?
Two.
97
What kind of cells have mitochondria and chloroplasts?
Plants and algae.
98
What cells only contain mitochondria?
Mitochondria.
99
From what we know about where we find mitochondria and chloroplasts, was was the original endosymbiosis event of?
Mitochondria (in all cell types).
100
What are three simple steps to describe how endosymbiosis happened?
Engulfing a cell, metabolic integration, swapping of genetic info.
101
Does endosymbiosis and transfer of genes need to happen in one event?
No could have been multiple, each transferred little bits, final conditions support full endosymbiosis.
102
What gives circumstantial evidence for the endosymbiosis theory?
Approx size, number of membranes, circular genome, pro enzymes and complexes and codon usage, componentes of membranes, multiple endosymbiosis examples.
103
What membranes do chloroplasts and mitochondria have?
Outer and inner membranes.
104
What are the TOC and TIC - TOM and TIM components of outer/inner membranes?
Complex protein import systems.
105
What is TOC?
Prokaryotic export channel, reinserts into organelles as an export channel.
106
What is an example of multiple endosymbiosis?
Numerous membranes per subcellular organelle.
107
What are examples of molecular evidence of endosymbiosis?
Ox-Phos complexes similar to in pros, photosynthetic mechanisms in chloroplast identical to Cyanobacteria, nuclear genes that affect organelles are homologous to others, division proteins and mechanisms.
108
What can E.coli FitsZ genes be used for and who did this?
Search for homologue in plants, used by Osteryoung and Vierling 1996.
109
What is used to form a division furrow in the middle of a bacterium to analyse FtsZ?
Filamenting temperature sensitive.
110
What happens when you knock out the FtsZ gene?
Stops the chloroplasts from dividing.
111
What does the FtsZ experiment conclude?
There is a nuclear genes that affects chloroplasts that is homologous to Cyanobacterial equivalent but doesn’t affect the plant in any other way.
112
What can prokaryotic like genes similar to FtsZ affect?
Mitochondrial division.
113
What happened to transfer genes to the nucleus?
Loss of most prokaryotic division genes, transfer to nucleus, duplication of FtsZ, duplication/mutation of Dynamin for use with organelle, loss of proteins for mitochondria.
114
What other organelles was the command centre the possible endosymbiotic origin for?
Golgi, ER, peroxisomes, nucleus.
115
What is Macro symbioses?
Mutual benefit and support, nutrition, colony members interact and become inter reliant, leads to multicellular organisms.
116
Overview of other endosymbioses?
First stage - seperate metabolisms, then mathanogenic bacterium feeds proto mitochondrion, proto feed methanogenic, host feeds itself, compartmentalisation, gene transfer.
117
Second stage of other endosymbiosis?
Loss of independence, specific metabolic roles, methanogen becomes nucleus, mitochondrion provides energy, compartments specialised membrane systems, DNA in nucleus.
118
Where did all the oxygen come from?
Has always existed on earth, much lower levels, oxygen produced by chemical reaction photolysis.
119
120
What is Mars environment like?
Has sedimentary rock and evidence of rivers and oceans, now barren and dry (expect polar caps).
121
Why is Mars now dry?
Lost its water via photolysis as no ozone layer, UV spilts water into hydrogen and oxygen.
122
What happens to hydrogen from photolysis on Mars and why?
Hydrogen is less dense and so is lost into space.
123
What happens to oxygen on Mars and why?
Oxygen heavier and remains but is incorporated by reacting with elements in the air or crust (CO2 or iron oxides).
124
What other planet do we think is similar to Mars and why is it hard to tell?
Venus, but impossible to survey.
125
Why was the rate of water loss on earth affected by rate of O2 formation?
Rate of O2 formation > rate of O2 incorporation therefore accumulation in atmosphere.
126
Why did the accumulation of O2 in the earths atmosphere lead to oceans remaining?
In sufficient quantities photolysis reverses to replenish water.
127
What makes the earths atmosphere and environment so different?
Photosynthetic life.
128
What gases change in concentration over time?
CO2, CH4, O2.
129
What happens when CH4 drops?
O2 increases.
130
What was the great oxygenation event (GOE)?
Massive increase in O2 levels, small rise 2.7bya, large rise 2.2bya.
131
What is the evidence of the GOE?
Rock isotope composition - mass independent fractionation of sulfur isotopes and great rusting event - increase in iron oxides.
132
Explain the first cause of GOE - late appearance of the oxygen producing life forms.
2.5bya, sharp drop in mantle melting activity, changes in chemical makeup of surface rocks, diminished melting in crust, reduced production of reactive iron oxide based volcanic gases.
133
Explain the second cause of the GOE - reduction in reactive gases.
2.5bya, sharp drop in mantle melting activity, changes in chemical makeup of surface rocks, diminished melting in crust, reduced production of reactive, iron oxide based volcanic gases.
134
Explain the third cause of the GOE - oxygen from photosynthesis.
Cyanobacteria first fossils 2.7bya, stromatolites found from 3.5bya, formed from biofilms of microorganisms trapping and cementing sedimentary particles.
135
What is the extinction of anaerobes theory?
Increase in oxygen levels toxic to anaerobic prokaryotes therefore catastrophic extinction.
136
What is the ice age snowball earth theory?
2.45-2.2bya, global temps plummet, major ice ages, glaciations, ice covering, followed by period of tectonic instability.
137
What could have caused the sudden global temperature drop?
O2 increases in atm, reacts with CH4 — CO2, CH4 potent greenhouse gas, CO2 weaker.
138
What are benefits of photosynthesis?
Free carbon source, free living, protection.
139
What is photosynthesis?
Fixation of CO2 into carbs, CO2 stable from of carbon, need reducing power, energy, catalyst, precursor to add CO2.
140
What are the carbon reactions?
Take CO2, add to precursor, uses RuBISCO, energy and reducing power.
141
What are the light reactions?
Use energy from sunlight to drive redox change, produce highly reduced compound, use H+ gradient to make ATP.
142
How do the light reactions use energy from sunlight to excite electrons?
Light energy excites electrons, oxidises donor compound, reduces higher redox potential compound, does it twice.
143
How does the light reaction find a replacement electron?
Uses light to split water, uses oxygen evolving centre or manganese cluster.
144
What do all photosynthetic organisms have in common?
Photosystems, pigments, RuBISCO, Mn cluster, ATP synthase.
145
What do all current photosynthetic organisms use?
Equivalent of P1 and P2 or both.
146
When do two photosystems have different roles?
When used in isolation by bacteria.
147
What do both photo systems essentially do?
Use pigments to capture light energy.
148
What is the role of P1?
Uses light energy to drive the production of a strong reducing agent.
149
What is the role of P2?
Uses light energy to drive the import of H+ ions to make redox gradient to drive ATP production.
150
What are the two common features of electron transport?
Absorb light, allow for protons to move.
151
What are the same conformations of all photosynthetic organisms?
PS1, PS2 or both, cores the same, protein structures the same, evolved early.
152
How did photosynthesis evolve in pros?
Can trace through pro lineages, start as independent photosystems then combine Cyanobacteria for modern photosynthesis.
153
Why is there variation in photosystems?
Selective loss - structures were removed and selective fusion - structures were combined.
154
Why photosynthesise?
Good for allowing electrons and protons to set up gradients, need to do processes yourself if leave vents, utilise UV light.
155
What can Manganese do and what is this good for?
Can exist in number of valency states, absorb high energy electrons, very reactive, good at providing direction and preventing UV damage.
156
What Manganese structures are found in deep-sea vents?
Crystal structures.
