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Green Fluorescent Protein (GFP)

  • Defined as GFP or green fluorescent protein.

  • Originates from a jellyfish living deep in the ocean.

  • Gene can be taken and expressed in a mouse, resulting in the mouse turning green due to genetic code conservation.

  • Genetic code is the same in jellyfish as it is in mice.

Conservation of Proteins

  • Many proteins are highly conserved across species.

    • Examples include:

    • Glycolytic enzymes

    • Ribosomal proteins

    • ATP synthase

  • Implication of protein conservation:

    • Suggests strong evidence for a universal common ancestor for all life on Earth.

Universal Common Ancestor

  • Significant clue that life shares a lot of similarities, suggesting life arose from a single ancestor rather than multiple origins.

  • Common understanding emphasizes thorough examination of life forms showing their similarities.

Eukaryotic Organelles

  • Eukaryotes are more complex than prokaryotes with organelles that are membrane-bound.

    • Examples of organelles include:

    • Nucleus:

      • Contains DNA.

      • Has a double membrane structure.

      • Nuclear pores present to facilitate mRNA export to the cytosol.

    • Mitochondria:

      • Site of respiration; nearly all eukaryotic cells have mitochondria.

      • Those that lack mitochondria evolved into alternate forms.

    • Chloroplasts:

      • Found in plants, algae, and some protists; sites of photosynthesis.

      • Distinction from bacteria which can perform photosynthesis but don't possess chloroplasts.

    • Mitochondria and chloroplasts are similar in that they:

    • Have their own DNA and ribosomes.

    • Replicate independently, rooted from bacterial origins (endosymbiotic theory).

Endomembrane System

  • Involves components like:

    • Endoplasmic Reticulum (ER) which includes:

    • Smooth ER

    • Rough ER

    • Golgi apparatus.

    • Vesicles for transport between organelles.

  • Unique to eukaryotes and essential for cellular function.

Cytoskeleton

  • Composed of:

    • Microtubules

    • Actin filaments

  • Important for cellular structure and motility.

  • Images can be used to visualize the cytoskeleton through fluorescent microscopy.

Key Features of Eukaryotes

  • Double membrane nucleus

  • Presence of mitochondria

  • Endomembrane system

  • Cytoskeleton

  • Chloroplasts are present in a subset of eukaryotes.

Phylogenetic Relationships

  • Prefix meanings:

    • "Pro" means "before" (referring to prokaryotes).

    • "Eu" means "true" (referring to eukaryotes).

  • Discussions on the evolutionary relationships which emphasize the importance of understanding endosymbiotic theory.

Endosymbiotic Theory

  • Provides explanation for origins of mitochondria and chloroplasts in eukaryotes.

Archaea are more similar to eukaryotes than to bacteria.

Evolution of Eukaryotic Life

  • The acquisition of mitochondria through endosymbiosis marked the beginning of eukaryotic life.

  • Endosymbiotic process:

    • An aerobic bacterium formed a symbiotic relationship with an archaea, leading to the evolution of eukaryotic cells.

    • This partnership is why mitochondria have double membranes, similarly to bacteria.

Evidence Supporting Endosymbiotic Theory

  • Mitochondrial DNA is closely related to bacterial DNA.

  • Chloroplast DNA is closely related to cyanobacteria.

  • Both organisms possess:

    • Their own RNA polymerases and ribosomes.

    • Similarities in protein synthesis to bacteria.

    • Division processes akin to bacterial division.

Theories for Mitochondrial Evolution

  • Early respiration likely did not utilize oxygen; the electron transport chain may have adapted for oxygen tolerance.

  • Multiple hypotheses about the evolution of mitochondrial functions:

    • Hydrogen Hypothesis proposes a host cell dependent on hydrogen, with an endosymbion producing hydrogen as a byproduct.

    • This concept has gained traction as it aligns with the functions of mitochondria today.

Evolution of Chloroplasts

  • Derived from a secondary endosymbiotic event with cyanobacteria.

  • Occurred in organisms that had already acquired mitochondria, leading to the evolution of chloroplasts around 1-2 billion years ago.

  • This crucial step led to the emergence of plants.

Membrane Structures

  • Mitochondria and chloroplasts each possess double membranes.

  • Doubt remains about whether the nucleus evolved through endosymbiosis, likely originating from membrane bending proteins (COP or COP1 proteins).

Summary of Endosymbiotic Theory

  • Consolidation of previously discussed concepts regarding endosymbiosis and its implications for understanding eukaryotic cell evolution.