Download Biosynthesis of a Secretory Protein

Biosynthesis of a Secretory Protein
The starred words are made of membranes. This
means that they are all composed of phospholipids
Ribosome*Rough Endoplasmic Reticulum
*Transport Vesicle
*Golgi Body
*Secretory Vesicle
*Plasma Membrane
Steps in the Synthesis, Modification
and Packaging of a Protein
1.
2.
3.
4.
5.
6.
Ribosome makes the polypeptide in the cytoplasm
Polypeptide goes through a protein import channel in the RER.
Within the RER, the polypeptide is cleaved, sugar added, and polypeptide
folds to take a specific shape.
Soluble proteins are transported in a transport vesicle to the Golgi Body
by exocytosis.
Transport vesicle with protein are moved from one area of the Golgi Body
to another by endocytosis and exocytosis.
Protein matures, modified, packaged and made ready for use in Golgi
Body and will either become
a) secretory vesicle
b) lysosome
released from cell
remain in cell
The next few slides illustrate the biosynthesis
pathway of a secretory protein or a lysosome.
Slide A shows the ribosome making the polypeptide and the
polypeptide moving into the RER.
Slide B shows the transport vesicle moving the protein through
the Golgi Body to be modified and packaged.
Slide C shows how the lysosome releases the digestive
enzymes into the food vacuole.
Secretory Protein Biosynthesis Animation
Slide A
Transport vesicle
buds off
4
Ribosome
Secretory
protein
inside transport vesicle
3
Sugar
chain
1
2 Glycoprotein
Polypeptide
Rough ER
Slide B
“Receiving” side of
Golgi apparatus
Golgi
apparatus
Transport
vesicle
from ER
New vesicle
forming
“Shipping” side
of Golgi apparatus
Transport
vesicle from
the Golgi
Golgi apparatus
Slide C
Lysosome
Digestion
Vesicle containing
damaged mitochondrion
Endomembrane System
• The organelles involved in the biosynthesis of a
protein are part of the endomembrane system.
• The ribosome is not because is not composed of a
plasma membrane.
• Watch the animation to see the nature of
membranes. They can fuse, break and reseal.
The Nature of Membranes
• The membrane is involved with endocytosis and
exocytosis which is how materials are moved within
the cell.
Don’t forget: Endocytosis and Exocytosis are two means by
which materials transported into or out of the cell. Below are
illustrations of these processes