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BIOC17 Lectures > Topic 2 > Flashcards

Topic 2 Flashcards

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1
Q

What is the current hypothesis on the origin of cells

A

The experiments that Spallanzani, Pasteur and others demonstrated is that: under the conditions that exist on your planet TODAY, living cells DO NOT arise from non-living matter. But the earth years ago looked different from what it is like today (4.6 billion years ago - 4 - 3.8 billion years where the first cells arised)

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2
Q

What are stromatolites

A

sedimentary rocks formed by cyanobacteria use dto date when the first organisms were

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3
Q

What is LUCA

A

The last universal common ancestor

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4
Q

What is the current hypothesis about the first cell type to evolve

A

Prokaryotes were the first cell type ot evolve.

For the first 2 billion years they were the only living inhabitants on this planet.

During this period, they extneisve shaped the conditions on the planet and in the atmosphere.
The diversity of cell types of present day evolved from prokaryotes.

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5
Q

Give a general overview on what happend originally on the earth

A

At the beginning, we were not in an oxygenated world.

LUCA formed at a period where we had no oxygen.

Prokaryotes like the purple and green bacteria did not use oxygen, used metals.

Oxygen produced by cyanobacteria began to appear in the atmosphere. -> allowed the slow transition to a world where we could support anaerobic respiration

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6
Q

What is anoxic

A

No free oxygen

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7
Q

What is cengenote

A

aka universal ancestor, a DNA based cell from which all other cell types on earth evolved -> believed to have evolved from RNA

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8
Q

A theory on how the first cengenote appeared

A

Self duplicating systems give rise to living cell like systems chemical , rather than biological.

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9
Q

explain prebiotic, abiogenic, abiotic

A
  • prebiotic: before life
  • abiogenic: not generated by biological system
  • abiotic: not involving biological systems
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10
Q

Explain how the first cengenote formed

A

Prebiotic syntheses:
+ random abiogenic (chemical reactions) produced mollecules similar to some cellular constituents like purines, amino acids…
+ abiogenic products accumulated in the absence of users
+ under anoxic conditions

Organic and inorganic substances are thought to have become sufficinetly concentrated to allow for frequent interactions

Reactants adhered to clay or other particles which catalyzed the reactions

interactions in hot sulfur rich microenvrionments -> give rise to RNA

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11
Q

Evolution of living cells from non-living material, the processes were:

A
  • not spontaneous
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12
Q

What are progenotes

A

early cell-like systems

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13
Q

When are DNA-based cell systems thought to have evolved

A

around the same time when bacteria evolved.

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14
Q

Whats the timeline for evolution for prebiotic evolution

A

Prebiotic chemistry
RNA

RNA and proteins (self replicating, enclosed in phosphomembernae)

DNA

LUCA

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15
Q
A
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16
Q

Give a proposed timeline of the evolution of eubacteria.achebacteria

A

chemicalevolution:
- probionts evolve, RNA based cell-like systems
- DNA based cell like systems -> evolved cenancestors
- prokayruotic, anerobic, heterotrophic

biocheical evoliton:
- split up of anerobic prokaryotes to give 2 cell lineages: archaebacteria and eubacteria
- anaerboibc photosynthetic (autotropic) eubacteria. supply nutrients to heterotropsh
- aerobic photosynthetic autotropic bacteria (similar to cyanobacteria)
- aerobic heterotosh

  • non-photosyntehtic aerobe autotropic eubacteria
  • free oxygen forms as a result of aerobic photosyntheiss -> lead to the oxygen revolution, ozone layer forms
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17
Q

Characteristics of the Universal ancestor (cenancestor)

A

The cenancestor cells is thought to have been:
- Prokaryotic: simple cell structure, no nuclear membrane
- heterotrophic: requires an organic carbon source for growht
- anaerobic: do not use oxygen in mteabosim

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18
Q

Many modern day bacteria are prokaryotic, heterotrophic and anerobic. Primarily are:

A

Eubacteria

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19
Q

current day prokaryotes. eubacteria

A
  • photosynthetic and non-photosynthetic
  • heterotropic and autotrophic
  • anaerobic and aerboic
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20
Q

Can anaerobic bacteria survive in oxygen

A

no

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21
Q

What is eubacteria is thought to have evolved directly from the cenancestor?

A

Non-photosynthetic, heterotropic, anaerobic eubacteria

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22
Q

How did archaebacteria evolve?

A

either 1) spilt off from non-photosynthetic heterotrophic anaerboic eubacteria
2) directly from cenancestor

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23
Q

Cyanobacteria is thought o have evolved from

A

Photosynthetic eubacteria but carry out a type of photosyntehsis simialr to that of higher plants, rather than photosyntehtic bacteria

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24
Q

Staining abnormalities

Study These Flashcards
A

Stain percipitate: common in acid fast stain
crsytal violet crystals

25
Chemolithotrophs?
aerobic non photosyntehtic autotrophs nitrifying
26
Difference between heterotrophic prokaryotes and autodtropic prokaryotes
heterotrophic: contain few intracellular membrane-bound or membrane structures. Autotrophic prokaryotes: contain extensivd membrnae structures
27
Common features of modern prokayrotes (in general)
In general, with the exception of the membranes of autotrophs, bacteria contain few sub-celluar structures in the cytoplasm except: - filled with ribosomes: - no nuclear membrane - bacterial chromosome and plasmid DNA - inclusion bodies only seen under specific metabolic conditions (polyhydroxybutyrate, sulfur, polyphosphate)
28
Common features of modern prokaryotes (genome)
- DNA replication transcription and translation all take place in the same ceullar compartment, in the cytoplasm - the genome: DNA and most genes are hapolid (there maybe some additional copies of 1 or 2 bacterial genes on plasmids within the cells) - most genes lack introns - Eubacteria and cyanobacteria, but not archebacteria contain only 1 major DNA dependent RNA polymerase (repsonsible for transcription of mRNA, tRNA and rRNA - All ctonain 1 minor DNA dependent RNA polymerase (primase) involved in DNA replication
29
Special features of modern Archaebacteria (genome, replication, morphology)
- they have several DNA-dependent RNA polymerase and in addition to primase (the RNA polymerase is similar to eukaryotic RNA polymerase) - some have multiple origins of replication - they have unusal cell walls and membrane lipids, not found in any other of organisms, prokayrotic, eukaryotic - morphologically and physiologically diverse with morphologies similar to eubacteria (rod, cocci, spiral) - some archaebacteria are as different from eubacteria as they are from eukaryoties
30
Special features of modern Archaebacteria (habitats)
- some archaebacteria and eubacteria can live in extreme environments like: + thermoacidophiles + hyperthermophiles (deep sea hydrothermal vents, sulfur rich envrionments) + halophiles (salted environemtns) + alkophiles + psychrophiles (ice)
31
Speical features of modern cyanobacteria When light is available? No light O2 available. Special membranes Fix n2
- evolved from photosyntehtic anaerobic eubacteria. - When sufficient light is available: photosynthetic and autotrophic - When insufficient light is available: heterotropic - When oxygen is present: carry out photosynthesis similar to that seen in higher plants (eukaryotes), but is different from photosyntehsis in anerboic photosynthetic bacteria - Many speices can fix nitrogen gas N2 into NH3 (ammonia) - All have extensive intracellular membrane systems called thylakoids: electron transport chain of some photosynthesis is located - some product a range of toxins- harmful, potential for phamracoligica
32
What are the 3 characteristics of the earliest cell types
- Prokaryotic - Heterotrophic - anaerobic
33
What is anaerobe? Obligate? Facultative? Aerotolerant?
- Grow in absence of oxigen - Obligate anerobe: cannot grow in. the prescence of oxygen (oxygen is lethal) - facultative anaerobe (can do both but prefers oxygen cause more eneryg is produced) - aerotolerant: grow equally well in the prescne or abscence of oxygen
34
What is aerobic
Utlize and requires oxygen in metabolism
35
What is microaerophilic:
require oxygen lelvesl 2-10% which is below the level of atmospheric oxygen (20%)
36
When are anaerobes and microaerophiles thought to have evovled?
before aerobes, when the earth was just starting to change from anoxic to aerobic
37
Why can't anaerobes and microaerophiles live in an oxygenated envrionment?
Because they lack all or some of the enzymes that allow cells to process it (SOD, catalase)
38
Question on the experiment of different tubes of oxic/anoxic regions
39
What are heterotrophs? Photoheterotrophs Chemoheterotrophs? examples
- Require carbon in some organic form: glucose or some organic carbon molecule. -> to build carbon skeleton to build cell constituents - Heterotrophs cannot use Co2 as a major carbon source - all organisms except autotrophs are heterotropsh Photoheterotrophs: use sunlight as energy source: like purple nonsulfur bacteria and green nonsulphur bacteria Chemoheterotrophs: use organic compounds as energy source (most bacteria, all fungi, animal)
40
All bacteria except cynaobacteria are
anaerobic photosynthesizing autotrophs
41
What are autortophs? photoautotrophs, chemoautotrophs and exampes?
Autrophs: can use CO2 as major (but not direct carbon source) co2 is fixed into carbohydrates -> source of carbon skeletons. Autotrophs cna be photosyntehtic, non photosyntehtic, aerobic, non-aerobic Photoautotrophs use sunlight as energy source (cyanobacteria, purple sulture, green sulfur bacteria) Chemoautotrophs (chemolithotrophs): use inorganic compound source as energy source (non-photosyntehtic)
42
Chemoheterotrophs are mostly associated with:
humans
43
How is photosyntehtic bacteria different from cyanobacteria
Use H2, H2S as electron donor vs H2O by cyanobacteira
44
What are chemolithotrophs
- Only found in prokaryotes, widely distributed in eubacteria and archae - Energy from inroganic compounds, indiviudal cell types usually specialize in the type of inorganic material (H2, H2S,..) - Thought to have evolved from cyano bacteria (lost the ability for photosynthesis after the world became aerobic) - Lives in inhospitalable environments such as sulfur hot springs, rich in reduced inorganic compounds => most are archaea - modern day examples: can derive eneryg from the metabolism of organic substances but also from the oxidation of inorganic substants -> play important role in biogeochemical cycling of elements
45
How did heterotrophs give rise to autotrophs>
primordial soup rich in organic nutreints accumulated by abiogenic syntehsis over millions of yer heterotrophs evolve rapidly utilize nutrients made by abiogenic processes rate of nutrient utilization is much greater than the rate of abiogenic syntehicis essential nutrients become limiitng -> provide selective pressure Cells with pahways able to synthesize a misisng essential nutrient -> selective advantage cells which could synthesize precursors -> took over. eventually those that could syntheisze from co2 would predominate
46
How does heterotrophs depend on autotrophs for survival
autotrophs restore organic substances to the biosphre. -> organic substances would be available for use by heterotrpsh, permitting the coexistence of heterotrophs and autotrophs
47
Modern day example of autotrophs
algae green plants cyanobacteria
48
Remember that all bacteria, except cyanobacteria
carry out anaerobic photosyntheis
49
How did aerobes evolve from anaerobes?
First autotrophic pathway was likley anaerobic: example: photosynthesis in eubacteria (anaerobic, autotrophic pathway) Bacterial photosynthesis: uses chlorophyls but is an anaerobic porcess uses sulfur to reduce (fix) Co2 uses H2 from H2S to reduce Co2 into carbohydrates, releasing free elemental sulfur or other sulfur compounds. CO2 + H2S -> CHO + S
50
The process of cyanobacterial photosyntheiss
The evolution of cyanobacteria occured when there was little or no free oxygen on the planet aerobic photosynthesis, involves using chlorphhul, and uses H2O to reduce/fix Co2. Co2 + H2o -> CHO + O2 first carried out by cyanobacteria -> subsequently evolved eukaryotic alage
51
How did the atmosphere change from an...atophore to a ....
from a reducing atmophore to an oxidizing atmosphree. previously reduced substances were oxidized
52
green/purple bacteria would use?
H2S not H2O
53
What is endosymbiosis?
It is a symbiotic association between different cell types (symbionts). One or more endosymbionts form a stable association within another partner in the association (like rizobium)
54
What is giardia
unicellellular, present day example of a eukaryote that has a nucleus but no mitochondria. it is a parasite that causes giardiasis. major cause of gastrointestinal disease
55
Explain the endosymbiont pathway. Origin of eukaryotic cells and their mitochondria
Archael cell acauires eukaryotic features, gets a double membrane -> become ancestral ANAEROBIC eukaryote. Eykaryiote injects AEROBIC bacterium (after oxuugenation of the planet) -> becomes aerobic eukaryote. this symbiotnat system can carry out aerobic metabolism. ome of the bacterial genes move to the nucleus -> endosymbiontns become mitochondria. =====> hence, becomes a heterotrophic organism the aerobic eukaryote can injest a cynaonbacteairia . => becomes a symbiont, new cell can make ATP using energy from sunlight. cyanobacteria moves geens into the nuclus -> beocme chloropasts
56
is the chloropast/mitochondira self sustianing
can still divide, but not self sustaining since need host for mRNA, proteins
57
Explain the hydrogen hypostheiss
symbiotic association based on h2 and co2 fule for methane producing archaea . endosymbiosis, gene transfer, increased host-endosymbiotnat dependence. the archael cell evolves eukayrotic feastures, protein import system evolves, endosymbiont becomes an organelle.
58
No mitochondira: close to the root of eukrya?
its not bc they evolved w.out mitochondria, they just lost the mitochondria
59

BIOC17 Lectures (13 decks)

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