1.22 The Synthesis and Transport of Proteins Flashcards
Due to their size, eukaryotes have a relatively small ___ ___ to ___ ratio.
As a result, the ___ ___ is too small to carry out all the vital ___ it is responsible for.
surface area to volume ratio.
plasma membrane (Aka cell membrane), functions
How do eukaryotic cells combat their small surface area?
They have a system of internal membranes
The ___ ___ forms a network of membrane tubules that is continuous with the ___ membrane.
Endoplasmic Reticulum (ER), nuclear
What is the difference between the RER and the SER?
RER has ribosomes on its cytosolic face
The ER is where ___ and some ___ are synthesized.
lipids, proteins
Lipids are synthesized in the ___, and are subsequently inserted into its ___.
SER, membrane
The synthesis of all proteins begins in ___ in the ___.
ribosomes, cytoplasm
Cytosolic proteins are ___ in the cytoplasm, where they ___.
completed, remain
Transmembrane proteins however are finished being translated in ___ attached to the ___.
ribosomes, RER
What do transmembrane proteins contain that allows them to be translated in the cytoplasm AND the RER?
they contain a signal sequence which halts translation in the cytoplasm and directs the ribosome to doc with the RER.
What is a signal sequence?
A short sequence of amino acids that determines a proteins eventual location within a cell, and can instruct ribosomes to stop translation, move to the RER, and then resume translation
What happens once the ribosome synthesizing the transmembrane protein has docked with the RER?
it resumes translation and once complete, the protein is inserted into the membrane of the ER.
Once the proteins are inside the ER, they are ___ by vesicles.
transported
vesicles = vehicles
What are vesicles?
Vesicles are tiny sacs that transport molecules between membrane compartments
Vesicles then carry proteins to the ___ ___, which they ___ to.
Golgi Apparatus, fuse
What is the Golgi Apparatus?
A series of flattened membrane disks that is the site of post-translational modification
What is the major modification that happens to proteins in the Golgi Apparatus?
The addition of carbohydrate groups
Describe how carbohydrates are added to proteins in the golgi apparatus.
Enzymes catalyse the addition of several sugars to the protein, to form carbohydrates.
How do molecules move through the Golgi Apparatus?
inside vesicles, which move through by fusing to one disk, budding off and fusing to the next one in the stack
Vesicles that leave the Golgi Apparatus can take proteins to the ___ ___ and to ___.
plasma membrane and lysosomes
What are lysosomes?
Membrane bound organelles that contain a variety of hydrolases, for digesting proteins, lipids, nucleic acids and carbohydrates
When vesicles travel to other membranes, they move along ___.
microtubles
(= to roads)
What is a lumen?
the inside space of a tubular structure
What are secreted proteins?
proteins that are released/secreted out of the cell
Secreted proteins are translated in ribosomes attached to the ___ and enter its ___.
RER, lumen
Rearrange the steps that follow the translation of a secretion protein.
1. Released out of the cell
2. Travel through the ER’s lumen
3. Packaged into secretory vesicles
4. Travel through the Golgi Apparatus
5. Proteolytic cleavage
2, 4, 5, 3, 1.
Travel through ER,
Golgi Apparatus,
Proteolytic Cleavage,
Secretory Vesicle,
Released out of cell
Many secretory proteins require p___ c___ to become ___.
This is because they are created to be ___.
Proteolytic cleavage, active.
dormant/inactive
What is Proteolytic cleavage an example of?
What does it do?
post-translational modification.
activates dormant/inactive proteins
What is an example of a secretion protein?
digestive enzymes, peptide hormones
Vesicles travel along ___.
microtubules (eg secretory vesicles travel along microtubules when moving to cell membrane to release secretory protein out of cell)
