Topic 1

Question 1

Why are RNA able to do well at genetic stage AND catalysis

Answer 1

• RNA can catalyze reactions just like proteins.

• RNA can base pair, form double-stranded structures just like
DNA (can also store genetic information)

Question 2

Some evolutionary forces start to kick in for the development of RNA

Answer 2

• Improved replication
• Simple functions (stability, binding other molecules)
• More complex functions (enzymes)

Question 3

Eventually, RNA was able to

Answer 3

• Self-replicating RNA (RNA replicase ribozyme)
• Binding amino acids/oligopeptides (stabilize RNA structures/functions) – protein building blocks become more important
• Simple ribosomes that make useful peptides
• More complex proteins
• Introduction of DNA (similar to RNA, more stable.Better long-term genetic storage) o
• “Cell” compartmentalization. RNA/proteins that facilitate these structures

Question 4

RNA can form intricate, stable structures that can:

Answer 4

• Carry out a wide range of chemical reactions

- Specifically bind many molecules

Question 5

Proteins are still made today using RNA components

Answer 5

• tRNA

- The active component of ribosomes is a catalytic RNA (proteins = accessory factors, RNA = core of ribosome).

Question 6

Many apparent “relics” from RNA world

Answer 6

• Common biological molecules with ribonucleotide components (see next slide)
• Various ribozymes (RNA enzymes), riboswitches (mRNA“receptors” that bind ligands – regulate gene expression),
  the ribosome itself!

Question 7

Wheredid the first microbe evolve?

Answer 7

• Precursors to life emerged ~4 bya 
• We do not know where, but one
hypothesis is hydrothermal systems
on ocean flood 
• Stable environment, low UV light,
compartments (“cells”), energy,
organic molecules (incl. RNA
nucleotides)

Question 8

Last Universal Common Ancestor (LUCA)

Answer 8

• DNA replication, transcription, translation, cell division
• ATP served as energy intermediate
• Lipid bilayer membrane.
• Anaerobic metabolism (no oxygen!) – likely used H2 as energy source, CO2 as carbon source

Question 9

Chemotroph:

Answer 9

Derive energy from releasing bond energy from chemical compounds

Question 10

Phototroph:

Answer 10

Absorbs light, transforms it into chemical energy

Question 11

Chemoorganotrophs

Answer 11

Consume organic chemical for energy

Question 12

Chemolithotrophs

Answer 12

Consumes inorganic chemicals for energy

Question 13

The rise of oxygen on earth

Answer 13

• For the first ~ 2 billion years on
earth, the atmosphere was devoid of
oxygen (“anoxic”)

• Oxygen in atmosphere made ideal
electron acceptor – gave rise to
aerobic organisms • Also ozone (O3) layer – protects vs.UV (lethal to cells, damages DNA)

Question 14

Rise of photosynthetic bacteria that
use sunlight as energy, producing
oxygen as a waste product

Answer 14

(cyanobacteria) - oxygenic

photosynthesis

Question 15

The endosymbiotic theory

Answer 15

• It is widely agreed that Eukaryotes emerged when an archaea-like ancestor engulfed a bacterium that became an endosymbiont (organism living within another organism in symbiotic relationship)
• Eventually this bacterium became the mitochondria (and transferred many bacterial genes into host organism)
• Plants emerged in a second event when an engulfed photosynthetic bacterium became basis for chloroplast

Question 16

The serial endosymbiosis theory

Answer 16

• Eukaryotes: Nucleus-bearing line that split from Archaea
• Mitochondria: Stable engulfing of an aerobic respiring bacterium from phylum Alphaproteobacteria into early eukaryotic cell cytoplasm.
• Chloroplasts: Stable engulfing of a photosynthetic cyanobacterium-like cell (phylum Cyanobacteria) into cytoplasm of a eukaryotic cell.

Question 17

Symbiogenisis hypothesis

Answer 17

Mitochondria engulfed during the arches stage and then the nucleus formed while the eukaryotic cells developed

Question 18

Evidence of endosymbiotic theory

Answer 18

• DNA replication, transcription, translation machinery of eukaryotes more similar to archaea than bacteria

Mitochondria and chloroplasts:
• Have their own genomes, ribosomes, tRNA
• This machinery is bacterial
• Mitochondria related to Proteobacteria, chloroplasts related to Cyanobacteria