Evolution of membrane complexity, lipid structures and membrane proteins
Learning objectives:
1. Understand the likely evolutionary pathways to the development of internal membrane systems in eukaryotic cells
2. Know basic structure of membrane lipids
3. Understand the different ways in which protein are attached to membranes and the characteristic structures of
membrane-integral proteins.
Evolution of membrane complexity
Scheme for evolution of the internal membranes of eukaryotic cells
There are no definite answer about evolution due to no fossil records.
Assume precursor cell has a membrane
There are 2 possible routes to acquire extra membrane to produce a cell with many internal membrane organelles:
- Route 1: invagination of the plasma membrane to increase the surface area
- Route 2: generate more membrane inside the cell by capturing cells
Mitochondria have 2 membrane (OMM & IMM)
Mitochondria started out as a bacteria
- How do we know? Sequence mitochondria DNA to get phylogeny, which revealed what sort of bacterium the
mitochondria was.
Mitochondria has own genome distinct from nucleus DNA
Mitochondria went through symbiosis with proeukaryote to produce a cell with mitochondria
- The same occurred with plant and algae cells with chloroplast
- Chloroplast has own DNA, which can be sequence to find type of bacterium
- Chloroplast has 3 membranes
Outer membrane
Inner membrane
Thylakoid membrane
Cyanobacterium is the precursor of chloroplast
Where did the OMM and Outer chloroplast membrane originate form?
- Some text book mention that the OMM started out as another invagination of the plasma membrane
, Step 1
- Invagination of prokaryote cell swallowed mitochondria
- Mitochondria started as a gram-negative bacterium (2
membrane; outer membrane & plasma membrane).
- Phylogenetic tree reveals that mitochondria came from a
gram negative bacteria
- Outer membrane of a gram negative bacteria contains a
class of proteins called porins.
- Outer membrane of mitochondria contains proteins
build in a similar way to porins but are not porins.
Mutated descends of porins with function
change
TOM = trasnslocon of the outer mitochondrial
membrane.
TOM function = import proteins encoded in the
nucleus and synthesised in the cytoplasm
- Mitochondrial matrix = cytoplasm of mitochondrial
that was once bacteria.
- Inner mitochondrial membrane = plasma membrane
of ancestral bacteria
Learning objectives:
1. Understand the likely evolutionary pathways to the development of internal membrane systems in eukaryotic cells
2. Know basic structure of membrane lipids
3. Understand the different ways in which protein are attached to membranes and the characteristic structures of
membrane-integral proteins.
Evolution of membrane complexity
Scheme for evolution of the internal membranes of eukaryotic cells
There are no definite answer about evolution due to no fossil records.
Assume precursor cell has a membrane
There are 2 possible routes to acquire extra membrane to produce a cell with many internal membrane organelles:
- Route 1: invagination of the plasma membrane to increase the surface area
- Route 2: generate more membrane inside the cell by capturing cells
Mitochondria have 2 membrane (OMM & IMM)
Mitochondria started out as a bacteria
- How do we know? Sequence mitochondria DNA to get phylogeny, which revealed what sort of bacterium the
mitochondria was.
Mitochondria has own genome distinct from nucleus DNA
Mitochondria went through symbiosis with proeukaryote to produce a cell with mitochondria
- The same occurred with plant and algae cells with chloroplast
- Chloroplast has own DNA, which can be sequence to find type of bacterium
- Chloroplast has 3 membranes
Outer membrane
Inner membrane
Thylakoid membrane
Cyanobacterium is the precursor of chloroplast
Where did the OMM and Outer chloroplast membrane originate form?
- Some text book mention that the OMM started out as another invagination of the plasma membrane
, Step 1
- Invagination of prokaryote cell swallowed mitochondria
- Mitochondria started as a gram-negative bacterium (2
membrane; outer membrane & plasma membrane).
- Phylogenetic tree reveals that mitochondria came from a
gram negative bacteria
- Outer membrane of a gram negative bacteria contains a
class of proteins called porins.
- Outer membrane of mitochondria contains proteins
build in a similar way to porins but are not porins.
Mutated descends of porins with function
change
TOM = trasnslocon of the outer mitochondrial
membrane.
TOM function = import proteins encoded in the
nucleus and synthesised in the cytoplasm
- Mitochondrial matrix = cytoplasm of mitochondrial
that was once bacteria.
- Inner mitochondrial membrane = plasma membrane
of ancestral bacteria
