a2.1 origin of cells (hl only)

Question 1

conditions of early earth

Answer 1

• no free oxygen
• no ozone as a result
• high co2 conc
  high methane conc

Question 2

why did early earth lack free oxygen

Answer 2

no cyanobacteria that created oxygen

Question 3

result of the conditions of early earth

Answer 3

temperature was high because of greenhouse effect
- uv can simply penetrate

Question 4

outline the Miler-urey experiment

Answer 4

• five-litre flask: mixed methane, hydrogen and ammonia (stimulate pre-biotic atmosphere) + water vapour + electrical charges (lightning)
• produced a variety of carbon compounds
• showed that it was possible for carbon compounds to form spontaneously on earth before life had evolved

Question 5

assumptions of the Miler-urey experiment

Answer 5

the conditions stimulated pre-biotic conditions accurately enough

Question 6

what would happen if carbon-based compounds were able to form

Answer 6

1. rna was formed
2. phospholipids form vesicles on their own

Question 7

why is rna formation significant

Answer 7

• can self replicate and has a high error rate to promote mutations
• can act as a catalyst
  dna may be evolved to introduce genetic stability after sufficient functions were accumulated

Question 8

why is phospholipid formation important

Answer 8

was maybe our first cell membrane

Question 9

what did pasteur’s experiment disprove

Answer 9

spontaneous generation

Question 10

remak theory

Answer 10

one cell turns into two cells

Question 11

evidence for a last universal common ancestor [2]

Answer 11

1. universal genetic code
2. existence of shared genes across all species

Question 12

biggest assumption about LUCA

Answer 12

LUCA had the same genes as us

Question 13

what do the gene have in common [3]

Answer 13

related to
1. anaerobic respiration
2. carbon fixation
3. nitrogen fixation

Question 14

where might LUCA have come from

Answer 14

hydrothermal vents