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ENDOMEMBRANE SYSTEM Definition of ENDOMEMBRANE SYSYTEM:
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Vesicle fuses with the Golgi and protein is modified as it passes through.
Protein is packaged into transport vesicles and travels to the Golgi along the cytoskeleton “track” Using RNA code, a protein is synthesized on a ribosome and transported in channels of the ER.
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Completed protein is packaged into secretory vesicles for release from the cell or stored in vesicle or lysosome if used inside the cell. Vesicle fuses with the Golgi and protein is modified as it passes through. Protein is packaged into transport vesicles and travels to the Golgi along the cytoskeleton “track” Using RNA code, a protein is synthesized on a ribosome and transported in channels of the ER.
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Vesicle transport
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Endomembrane System Phospholipid bilayer Like a bubble MOSAIC
Membranes within the eukaryotic cell that work together to modify, process and ship molecules around and out of the cell. Semipermeable FLUID
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Endomembrane System All made of phospholipid bilayer Includes:
Nuclear envelope Rough ER Smooth ER Transport vesicles Golgi apparatus Lysosomes Secretory vesicles
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The Endomembrane System
proteins transport vesicle Golgi apparatus smooth ER rough ER nuclear pore nucleus ribosome cell membrane protein secreted cytoplasm
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production of mRNA from DNA in nucleus mRNA out of nucleus
nuclear membrane mRNA nuclear pore production of mRNA from DNA in nucleus mRNA out of nucleus through nuclear pore
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Endoplasmic Reticulum
Function processes proteins manufactures membrane Structure membrane connected to nuclear envelope & extends throughout cell accounts for 50% membranes in eukaryotic cell
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Types of ER rough smooth
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INSULIN being released by pancreas cells using exocytosis
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Origin of Eukaryotic Cells
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Prokaryotes dominated earth for about 1by
Earth is 4.6 byo Life originated 3.5–4.0 bya Prokaryotes dominated earth for about 1by 21
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Cyanobacteria Cyanobacterium heterocyst A type of prokaryote with much infolding of the cell membrane Capable of performing photosynthesis, which releases oxygen into the atmosphere 22
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Oxygen atmosphere Oxygen begins to accumulate 2.7 bya
evidence in banded iron in rocks (rusting) makes aerobic respiration possible 23
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Eukaryotes nearly all are aerobic,
they depend on free oxygen to carry out their metabolic processes Accordingly, they could not have evolved before at least some free oxygen was present in the atmosphere
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Two processes are thought to have led to the origin of eukaryotes….
Infoldings of the prokaryotic cell membrane Endosymbiosis
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Development of internal membranes
create internal micro-environments (“compartments”) advantage = increase efficiency ~2 bya nuclear envelope *note double membrane endoplasmic reticulum (ER) plasma membrane infolding of the plasma membrane nucleus DNA cell wall plasma membrane Prokaryotic cell Prokaryotic ancestor of eukaryotic cells Eukaryotic cell
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Membrane infolding Endosymbiotic theory
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Given what you know about in folding and the cell membrane as a phospholipid bilayer:
Why is the nuclear membrane a DOUBLE membrane (two layers of bilayer)
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Bozeman Originally proposed in early 1900’s
Endosymbiotic Theory Bozeman Originally proposed in early 1900’s Idea reintroduced in 1963 by Lynn Margulis Suggests that engulfed prokaryotes shared symbiotic relationship with host cell Advantages for both: ~ one supplies energy ~ other raw materials & protection
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Endosymbiosis In this relationship one cell lived within the other, which is a special type of symbiosis called endosymbiosis in some cases of a symbiotic relationship, one symbiont cannot live independently of the other This may have been the case early symbiotic prokaryotes that became increasingly interdependent until the unit could exist only as a whole
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Endosymbiosis FIRST early eukaryotic cells engulfed aerobic bacteria
but did not digest them Led to the origin of mitochondria Mutually beneficial relationship internal membrane system aerobic bacterium mitochondrion Endosymbiosis Ancestral eukaryotic cell Eukaryotic cell with mitochondrion
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Endosymbiosis photosynthetic bacteria but did not digest them
Eukaryotic cell with mitochondrion THEN eEarly eukaryotic cells engulfed photosynthetic bacteria but did not digest them Led to origin of chloroplasts mutually beneficial relationship chloroplast mitochondrion Endosymbiosis Eukaryotic cell with chloroplast & mitochondrion
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A model of the origin of eukaryotes
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Resemble bacterial structure
Structural Evidence Both mitochondria & chloroplasts Resemble bacterial structure Are found in membranous envelopes (like a cell membrane) are the same approximate size as prokaryotes have 70s ribosomes
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have circular naked DNA
Genetic Evidence Both mitochondria & chloroplasts have circular naked DNA DNA shares common sequences with modern prokaryotes
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move freely within the cell
Functional Evidence Both mitochondria & chloroplasts move freely within the cell reproduce independently from the cell through binary fission are inhibited by antibiotics
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Where Did Organelles Come From ?
Membranous infoldings Nucleus ER Golgi Lysosomes Vesicles Endosymbiosis Mitochondria Chloroplasts
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Theory of Endosymbiosis
Lynn Margulis How is the word “theory” in science different than the use of the word theory in every day language?
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