Lecture 1: origin of life

non-equilibrium

Does life prefer a state of equilibrium or non-equilibrium?

Life prefers non-equilibrium because it permits the flow of energy which allows molecules to be concentrated so reactions and life can occur.

Why does life prefer a state of non-equilibrium?

Equilibrium disperses everything and prevents complexity therefore prevents life. 

what does equilibrium do to life?

RNA, DNA, and amino acids

What are the essential building blocks of life?

They arose from simple chemistry on Earth through the concentration of chemicals on meteorites, and a tiny subset of all possible molecules was selected for life.

How did life’s building blocks come to be?

RNA world hypothesis

The idea that the RNA came first and is both a catalyst and a source of genetic information before DNA-protein systems evolved. 

Primordial soup theory

Life formed from simple molecules accumulating in ponds and oceans with energy inputs creating these complex chemicals that led to life

Panspermia theory

Organic molecules including amino acids may have arrived from space through meteorites (This is what he emphasized in class).

Earth

—- formed 4.6 billion years ago 

life

—- originated 3.9-3.5 billion years ago.

Meteorites contain diverse racemic mixtures of amino acids and other organic molecules such as PAHs that resemble the sugar-phosphate backbone of nucleic acids and were likely made from a concentration on meteorites.

What made meteorites good for the creation of life?

Only certain enantiomers are used 

Why is life’s chemistry so restricted?

Enantiomers

An ———- is one of a pair of molecules that share the same atomic connectivity but are mirror images of each other and cannot be superimposed.

Racemic mixture

A ——————— is a 50:50 mixture of the two enantiomers of a chiral molecule.

A polycyclic aromatic hydrocarbon (PAH) is a molecule made up of multiple fused aromatic (benzene-like) rings of carbon and hydrogen.

What is a PAH?

This experiment simulate early Earth’s atmosphere with methane, ammonia, and water vapor in it and it also had electrical sparks that made amino acids. It basically shows that simple molecules and energy made the building blocks of life.

What did the Miller-Urey experiment demonstrate?

D

—- can store information and catalyze reaction and is reactive and unstable for long term storage.

A. amino acids

B. Protein

C. DNA

D. RNA

C

— is more stable and better for storing information and acts as a genetic library.

A. amino acids

B. Protein

C. DNA

D. RNA

3

Life uses ——- base condons

Nullomers

short DNA sequences missing from genomes selected against because they cause problems or haven’t been useful

The hydroxyl (-OH) group on the 2nd carbon in the ribose sugar for RNA

4. What chemical property of RNA leads to its instability?

B

Which of the following best describes why life does not exist at equilibrium?

• A) All molecules are evenly distributed and unreactive at equilibrium

• B) Life requires energy flow and concentration gradients to sustain reactions

• C) Molecules at equilibrium form more complex structures

• D) None of the above

C

1. What experiment demonstrated that amino acids can form under prebiotic Earth conditions?

   • A) Griffith experiment

   • B) Hershey-Chase experiment

   • C) Miller-Urey experiment

   • D) Meselson-Stahl experiment

C

PAH molecules discovered in space resemble which major structure of life’s genetic material?

• A) Nitrogenous bases

• B) Amino acid side chains

• C) Sugar-phosphate backbone

• D) Ribosomes

False

1. True or False: Modern cellular life exclusively uses L-amino acids for protein synthesis.