Video clip ENDOMEMBRANE SYSTEM Definition of ENDOMEMBRANE SYSYTEM

Video clip

ENDOMEMBRANE SYSTEM Definition of ENDOMEMBRANE SYSYTEM:

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.

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.

Vesicle transport

Like a bubble Phospholipid bilayer MOSAIC Endomembrane System Membranes within the eukaryotic cell that work together to modify, process and ship molecules around and out of the cell. Semipermeable FLUID

Endomembrane System • • All made of phospholipid bilayer Includes: – – – – Nuclear envelope Rough ER Smooth ER Transport vesicles Golgi apparatus Lysosomes Secretory vesicles

The Endomembrane System nucleus nuclear pore cell membrane protein secreted rough ER ribosome vesicle proteins smooth ER transport vesicle cytoplasm Golgi apparatus

production of m. RNA from DNA in nucleus m. RNA out of nucleus through nuclear pore

Endoplasmic Reticulum • Function – processes proteins – manufactures membrane • Structure – membrane connected to nuclear envelope & extends throughout cell

Types of ER rough smooth

INSULIN being released by pancreas cells using exocytosis http: //fig. cox. miami. edu/~cmallery/255 ion/fig 14 x 26. jpg

Origin of Eukaryotic Cells

• Earth is 4. 6 byo • Life originated 3. 5– 4. 0 bya • Prokaryotes dominated earth for about 1 by

Cyanobacteria • A type of prokaryote with much infolding of the cell membrane • Capable of performing photosynthesis, which releases oxygen into the atmosphere Cyanobacterium heterocyst

Oxygen atmosphere • Oxygen begins to accumulate 2. 7 bya • evidence in banded iron in rocks (rusting) • makes aerobic respiration possible

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

Two processes are thought to have led to the origin of eukaryotes…. 1. Infoldings of the prokaryotic cell membrane 2. Endosymbiosis

Development of internal membranes • create internal micro-environments (“compartments”) • advantage = increase efficiency infolding of the plasma membrane ~2 bya endoplasmic reticulum (ER) nuclear envelope *note double membrane nucleus DNA cell wall Prokaryotic cell Prokaryotic ancestor of eukaryotic cells plasma membrane Eukaryotic cell

Membrane infolding Endosymbiotic theory

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)

Endosymbiotic Theory http: //en. wikipedia. org/wiki/Lynn_Margulis 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

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

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

Endosymbiosis • THEN e. Early eukaryotic cells engulfed Eukaryotic cell with mitochondrion photosynthetic bacteria but did not digest them • Led to origin of chloroplasts • mutually beneficial relationship chloroplast Endosymbiosis Eukaryotic cell with chloroplast & mitochondrion

A model of the origin of eukaryotes

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 70 s ribosomes

Genetic Evidence Both mitochondria & chloroplasts – have circular naked DNA – DNA shares common sequences with modern prokaryotes

Functional Evidence Both mitochondria & chloroplasts –move freely within the cell –reproduce independently from the cell through binary fission –are inhibited by antibiotics