A2.1 Origin of Cells

Question 1

endosymbiotic theory

Answer 1

• a prokaryote ancestor ingests a smaller prokaryote
  the smaller prokaryote evolves a way to avoid being ingested = lives inside its new host

Question 2

endosymbiosis

Answer 2

• small photosynthesizing prokaryote evolve into chloroplast = pay host w/glucose
• smaller respiring prok. evolve into mitochondria = glucose to energy
• both host & symbiont benefit
  ex: chorella tiny gren cells inside amoeba

Question 2

Evidence for endosymbiosis

Answer 2

based on mitochondria & chloroplasts
* reproduce binary fission
* own circular, non membrane DNA
* both transcribe mRNA from DNA
* both 70s Ribosomes
* both double membrane
* similar bacteria size

Question 2

compartmentalisation

Answer 2

The orginisation of different functions and processes within specific subcellular structures seperated by plasma membranes

Question 3

pre-biotic earth

Answer 3

period on earth before life existed

Question 3

pre biotic earth conditions

Answer 3

• little O2
• reducing gases
• high temp.
• large bodies of water
• lightning
• no ozone layer

Lack of electromagnetic field
-> earth heated up & cooled = generating sun protective

Question 3

spontaneous origin of cells

Answer 3

1. simple organic molecules
2. chemical recations
3. larger molecules asmbled (CO2, Phospholipid)
4. RNA containing molecules self replicated
5. formation of membrane bound compartments

Question 4

Miller-Urgy Experiment

Answer 4

simulated pre biotic earth conditions to show spontaneous formation
* water, gas inlet (NH3, H2, Ch4)
* electrical sparks
1. water vapourized = run through electrical sparks & gases
2. cooled & condensed
3. droplets collect = premordial soup (basic AA)

Question 4

Autotrophic

Answer 4

An organism that can produce its own chemical energy using light, inorganic compounds or other

Question 5

LUCA

Answer 5

Last Universal Common Ancestor
=> single celled autotrophic microbic & RNA genome

Question 6

Evidence for LUCA

Answer 6

• universal genetic code, conserved => used to find differnece in genome
• before 3 domains of life = now 2
• scientists found out genes can be horizontally transferred without reproduction
• 355 genes in LUCA which are same

Question 7

stromatolites

Answer 7

rocks in which fossils of microorganism can be found

Question 8

Discovery of LUCA

Answer 8

• existed 2.5-3-5 Mil. years ago
• existed deep in alkaline hydrothermal
• H2, minerals & high temp

Question 9

how to date fossils

Answer 9

contain radioactive isotopes => half life calculations
Absolute= graph
relative= use layers in earth

Question 10

spontaneous coalescene of fatty acids into bilayers

Answer 10

• spherical bilayer = physical seperation
• interior of vesicle has chemical environment

Question 11

RNA as first genetic material

Answer 11

1. RNA formed form inorganic catalyst
2. rna replicate w/ribozymes
3. membrane compartmentalisation
4. inside cell = RNA produce protein & DNA
5. DNA took over
6. proteins took over enzymes

Question 11

benefits of compartmentalisation

Answer 11

• internal conditions can be differentiated (e.g. pH)
• isolation of toxic/damaging substances
• flexibility of changing number & position of organelles

Question 12

premordial soup

Answer 12

A hypothetical mixture of organic compounds formed in the conditions present on pre-biotic earth