Origin of Cells A2.1

Question 1

What was oxygen like during pre-biotic Earth? What caused it?

Answer 1

concentrations very low because it reacted with methane and locked away in the Earth’s core

Question 2

What was methane like during pre-biotic Earth? What caused it?

Answer 2

concentrations very high because of volcanic activity and meteorite bombardment

Question 3

What was carbon like during pre-biotic Earth? What caused it?

Answer 3

concentrations very high because of emissions from volcanoes

Question 4

What was ozone like during pre-biotic Earth? What caused it?

Answer 4

barely existed because of lack of O2, therefore UV radiation would have been higher

Question 5

How would carbon compounds form during pre-biotic Earth?

Answer 5

• in specialized environments
• in droplets of water in the atmosphere
• deposited by rainfall into pools, lakes, seas. creating a “soup” of carbon compounds

Question 6

What are some examples of carbon compounds that might have formed during pre-biotic Earth?

Answer 6

• carboxylic acid
• aldehydes
• amino acids
• nitrogenous bases

Question 7

What does MRHGREN stand for and what does it do?

Answer 7

metabolism
response
homeostasis
growth
reproduction
excretion
nutrition
- characteristics of life, used to describe what is required to maintain life, not life itself.

Question 8

How come viruses are not considered living?

Answer 8

viruses depend on a host for a living and therefore cannot maintain life on its own.
- cant make energy
- cant maintain stability
- cant grow, etc

Question 9

What are the two theories for how life formed?

Answer 9

• abiogenesis
• biogenesis

Question 10

What is abiogenesis?

Answer 10

life developed independently from non-living or inanimate substances. (spontaneous generation)

Question 11

What is biogenesis?

Answer 11

complex life only arise from pre-existing living things through reproduction. (non-spontaneous gen)

Question 12

What are necessary requirements for the evolution of first cells?

Answer 12

• catalysis
• self-assembly
• compartmentalization
• self-replication of molecules

Question 13

What is catalysis?

Answer 13

to give control over which chemical reactions occur

Question 14

What is self-assembly?

Answer 14

carbon compounds such as amino acids must assemble to form polymers

Question 15

What is compartmentalization?

Answer 15

a membrane must be developed to enclose cell contents

Question 16

What is self-replication of molecules?

Answer 16

as a basis for inheritance and the persistence of successful variants

Question 17

What are some reasons cells could have arisen from non-living things?

Answer 17

• non-living synthesis of simple organic molecules
• simple organic molecules became assembled into more complex polymers
• these polymers became packaged into vesicles of diff internal chemistry
• certain polymers formed capacity to self-replicate (therefore inheritance)

Question 18

What was the Miller-Urey experiment?

Answer 18

• evidence of carbon compounds origin
• simulated the atmosphere at early Earth
• created amino acid and carbon from a mixture of methane, ammonia, and hydrogen

Question 19

Explain in steps what the Miller-Urey experiment did

Answer 19

• water boiled to reflect high temp in prebiotic Earth
• vapor mixed w/ gases (CH4, H2, NH3) to create a reducing atmosphere (no O2)
• electrical discharge (lightning) as energy source, led to reactions
• after cooling, a week later, traces of organic molecules are found

Question 20

What are vesicles?

Answer 20

small droplets of fluid, enclosed in a membrane
- cell like but not yet proper cells

Question 21

What are the membrane of vesicles composed of?

Answer 21

phospholipids

Question 22

What happens when phospholipids mixed with water?

Answer 22

the phospholipid naturally self-assembles into bilayers, creating the basis for vesicles.

Question 23

Why is the internal chemistry of vesicles different from its surroundings?

Answer 23

movement of polar molecules is limited

Question 24

Why is RNA the presumed first genetic material?

Answer 24

• RNA can store info in the same way as dNA but is both self-replicating AND act as enzyme
• Replication needs enzyme actions
• enzymes need genes to be made
• can form complex 3D structures of polypeptides

Question 25

What is LUCA?

Answer 25

the last universal common ancestor, the evolutionary link between the abiotic phase of Earth’s history and the biotic phase

Question 26

How do we know share ancestory?

Answer 26

• using info from DNA alignment studies
• all living things use the same four letter code which translates onto codon specific same amino acids

Question 27

How come LUCA is the ONE common ancestor?

Answer 27

other life forms evolved but likely extinct from competition with LUCA, AKA natural selection

Question 28

What are some evidence for LUCA near hydrothermal vents?

Answer 28

• genes found in LUCA is similar to bacteria that need anaerobic metabolism and carbon dioxide fixation, conditions preferably around hydrothermal vents
• 355 genes identified for protein families among bacteria and archaea bacteria.
  explanation:
  Genes proposed to belong to LUCA are involved in the use of molecular hydrogen as an energy source (hydrothermal vents are rich in hydrogen)
  LUCA is also thought to have possessed a gene that is currently found in extremophiles existing in high temperature environments (like hydrothermal vents)

Question 29

Where are hydrothermal vents found?

Answer 29

tissues in the oceanic crust, gushing hot water.

Question 30

What does the water in hydrothermal vents carry and what does it do?

Answer 30

• reduced inorganic chemicals
• these chemicals used as source of energy for assembly of simple carbon compounds into polymers

Question 31

What does fossilization do for LUCA?

Answer 31

extremely rare but contribute to the understanding of the history of life.