EE Lecture 14: What is Life?

Question 1

what does life need to happen

Answer 1

an external source of energy

Question 2

what is the 2nd Law of thermodynamics

Answer 2

2nd Law of thermodynamics: entropy of closed system increases over time

Question 3

what is lifeq

Answer 3

a highly ordered state of matter, which expends energy from enviro to maintain order and information, counteracting second law of thermodynamics

Question 4

which law of thermodynamics does life defy

Answer 4

second law

Question 5

how does life defy 2nd law of thermodynamics

Answer 5

because it restores entropy as opposed to increasing it

Question 6

how does order arrive in molecules

Answer 6

self replication - autocatalysis
sequences vary in fitness - formation rate
supply of energy rich monomers
imperfect replication - mutation
competition

Question 7

what is current life based on (chemically)

Answer 7

nucleic acids - info storage&replication

proteins - function but not info

Question 8

what is Eigen’s paradoz

Answer 8

need info for function to occur, but info meaningless without function

Question 9

what is an RNA world

Answer 9

can artificially select RNA with catalytic properties eg. polymerase

Question 10

what is a metabolism world

Answer 10

interacting protein networks with some heritability, self copying

Question 11

what are main theories of how life originated on earth

Answer 11

1. prebiotic soup
2. primordial pizza
3. fat or water drops
4. hydrothermal vents

Question 12

discuss prebiotic soup as a theory of how life originated on earth

Answer 12

concentrated mixture of precursor molecules in ancient seas zapped by lightning
did reconstructions in lab experiments

Question 13

discuss primordial pizza as a theory of how life originated on earth

Answer 13

life originated on a surface, catalyst and favours cooperation - clay or iron pyrites

Question 14

what is cooperation

Answer 14

spontaneous cooperation between nucleic acids and proteins on surface

Question 15

discuss fat/water drop theory of how life originated on earth

Answer 15

fat or water drops were compartments protecting cooperating molecules from cheats

Question 16

discuss hydrothermal vents as a theory of how life originated on earth

Answer 16

provided alternative energy sources - these could reflect ancient condns

Question 17

what do ideas on how life evolved depend on

Answer 17

basic requirements for life to evolve and reconstructions of what earth was like

Question 18

when did life originate

Answer 18

use meteorites

earliest rocks interpreted as fossils 3.5BILLION YRS AGO

Question 19

what evidence was used to suggest that life originated 3.5bn yrs ago

Answer 19

microfossils
stromatolites
C12/C13 ratios in ancient rocks

Question 20

what are the problems associated with using fossils/rocks to determine when life originated

Answer 20

contamination of old rocks with newer material

interpretation of “structures” dont know if life or not

Question 21

is there a LUCA

Answer 21

all life descends from one origin
universal genetic code
arbitrary language or optimal design?