Origins Of Life 2

Question 1

Why is LUCA useful to us when theorising about the origins of living organisms?

Answer 1

LUCA helps us understand the shared features of all life—such as genetic code, ATP use, and core metabolic pathways—allowing scientists to reverse-engineer the characteristics of the earliest forms of life by studying what is universally conserved.

Question 2

Why is RNA likely to have preceded Protein?

Answer 2

1. Can both store information (like DNA) and catalyse reactions (like proteins).
2. Shows enzymatic activity
3. Is capable of self-replication and forming complex structures.

Question 3

Why is RNA likely to have preceded DNA?

Answer 3

1. DNA replication enzymes differ between Bacteria and Archaea → implies DNA replication evolved after LUCA.
2. RNA can catalyse its own reactions, unlike DNA.
3. DNA is more stable but lacks RNA’s catalytic properties.
4. DNA likely evolved from RNA, gaining stability

Question 4

Where is the Krebs cycle backwards observed ?

Answer 4

In archaea in deep sea vents

Question 5

What enabled the descendants of LUCA to become free-living organisms?

Answer 5

A membrane
Development of a robust membrane would allow a “cell” to leave the mineral chamber and spread

Question 6

Why was LUCA unlikely to have been free-living?

Answer 6

LUCA likely existed in alkaline hydrothermal vent environments.
These vents provided:
1. Mineral compartments (concentration)
2. Redox gradients (energy)
3. Catalytic surfaces (e.g., Fe-S minerals)
LUCA was more like a “bioreactor” than an independent organism, reliant on environmental chemistry.

Question 7

How did the use of ATP evolve?

Answer 7

Early life likely used acetyl phosphate or thioesters as primitive energy carriers.
ATP provided a more efficient and universal energy currency.
The proton gradients in vents (H⁺) were harnessed to produce ATP, supporting the vent-origin theory of early metabolism.