Lec 4: What is Life?

Question 1

What are the 4 factors included in most theories of life?

Answer 1

1) Must be able to maintain internal homeostasis
2) Must respond to external stimuli
3) Consume and produce energy
4) Reproduce and have a form of heredity

Question 2

How do organisms maintain internal homeostasis? What do they regulate?

Answer 2

• regulate through cell membranes and transport across membranes
• regulate temp, pH, and [proteins] and [solutes]

Question 3

Responses to external stimuli can be … or …

Answer 3

physical or chemical

Question 4

How is ATP generated?

Answer 4

Through chemiosmosis. electrochemical potential energy (gradient)

Question 5

Describe the 2 types of reproduction.

Answer 5

1) Asexual: single organism clones itself

2) Sexual: cells from parents unite to form first cell of new organism. offspring different from parent.

Question 6

When did life first evolve on Earth?

Answer 6

During the Archean, 3.5 Ga ago.

Question 7

How does life produce macromolecules?

Answer 7

Through the activity of enzymes. Enzymes are proteins that act as catalysts to increase the rate of metabolic processes.

Question 8

What is LUCA? What are lines of evidence for LUCA?

Answer 8

the last universal common ancestor

Evidence for LUCA is based on the fact that ALL forms of life:

• are carbon based
• have similar enzymes from one species to another
• pass information through DNA or RNA
• only have left-handed amino acids and right-handed nucleic acids

Question 9

Explain the Primordial Soup Theory.

Answer 9

• proposed by Darwin in 1871

- based on idea that early Earth had high concentrations of elements abundant in life (C, H, H2O vapor, ammonium)

Question 10

What are the 4 steps of the primordial soup theory?

Answer 10

1) Early Earth –> chemically reducing atmosphere
- not a lot of oxygen in atmosphere, mostly reducing gases

2) when exposed to energy (from lighting or sun), this atmosphere produced monomers
3) compounds accumulated in a soup
4) their high concentration in certain areas eventually led to formation of polymers

• -> life emerged from these polymers
• -> early cells broke down organic compounds to generate ATP, creating heterotrophy

Question 11

Describe the RNA World Theory

Answer 11

• 1962
• RNA formed first
• eventually led to protein and DNA formation

Question 12

Describe the Deep Sea Hydrothermal Vent Theory.

Answer 12

• 2010
• hydrothermal vents found in mid-ocean ridges, resulting from divergent plate boundaries
• alkaline water from vents meets acidic water from ocean, creating a natural proton gradient
• all life forms are driven by proton concentration differences across cells’ membranes, suggesting that earliest living cells harvested energy in a similar way