Topic 1 Flashcards

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1
Q

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

A

• RNA can catalyze reactions just like proteins.

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

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2
Q

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

A
  • Improved replication
  • Simple functions (stability, binding other molecules)
  • More complex functions (enzymes)
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3
Q

Eventually, RNA was able to

A
  • 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
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4
Q

RNA can form intricate, stable structures that can:

A
  • Carry out a wide range of chemical reactions

- Specifically bind many molecules

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5
Q

Proteins are still made today using RNA components

A
  • tRNA

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

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6
Q

Many apparent “relics” from RNA world

A
  • 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!
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7
Q

Wheredid the first microbe evolve?

A
• 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)
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8
Q

Last Universal Common Ancestor (LUCA)

A
  • 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
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9
Q

Chemotroph:

A

Derive energy from releasing bond energy from chemical compounds

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10
Q

Phototroph:

A

Absorbs light, transforms it into chemical energy

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11
Q

Chemoorganotrophs

A

Consume organic chemical for energy

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12
Q

Chemolithotrophs

A

Consumes inorganic chemicals for energy

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13
Q

The rise of oxygen on earth

A

• 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)

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14
Q

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

A

(cyanobacteria) - oxygenic

photosynthesis

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15
Q

The endosymbiotic theory

A
  • 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
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16
Q

The serial endosymbiosis theory

A
  • 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.
17
Q

Symbiogenisis hypothesis

A

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

18
Q

Evidence of endosymbiotic theory

A

• 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