C5.2: Membrane-bound organelles Flashcards
Golgi apparatus is named after ___, an Italian biologist who discovered the organelle
Camillo Golgi
a membrane-bound packaging organelle of eukaryotic cells found in the cytoplasm and is made up of approximately four to eight flattened, stacked pouches called cisternae
Golgi apparatus
organelles that is -situated in between the endoplasmic reticulum and the cell membrane
Golgi
the whole golgi apparatus is supported by
cytoplasmic microtubules
long, flattened and sac-like structures that are arranged parallelly in bundles
cisternae
Held together by matrix proteins exists primarily as fiber-like bridges
cisternae
GRASP:
Golgi Reassembly Stacking Protein
The volume enclosed by the membranes of any citerna or subcompartment of the Golgi apparatus, including the cis- and trans- Golgi networks
lumen
Help move the proteins from the ER and transport these proteins to the Golgi apparatus for further sorting and refining
Transport vesicles
Form from trans Golgi network and store their contents until specific signals direct them to fuse with the plasma membrane through the process of exocytosis
Secretory vesicles
Three Primary Compartments of Golgi
Cis face
medial-golgi network
trans face
- cisternae nearest the endoplasmic reticulum; entry face
Cis face
- central layers of cisternae • Pertain to the golgi sacs in between the cis- Golgi network and the trans- Golgi network
medial-golgi network
- cisternae farthest from the endoplasmic reticulum; exit face
Trans face
associated with the movement of molecules from
the endoplasmic reticulum to their final destination and the modification of certain products along the way.
Golgi apparatus
two models of golgi
Vesicular Transport Model
Cisternal Maturation Model
Vesicular Transport Model originally developed and advocated by ___ and ___
George Palade, Marilyn Farquhar
This model claims that Golgi cisternae are stable compartments that house certain protein modification enzymes that function to add or remove sugars, add sulfate groups and perform other modifications. The vital element of this model is that the cisternae themselves are stationary.
Vesicular Transport Model
This model depicts the Golgi apparatus as a far dynamic organelles as it indicates that the cis cisternae move forward and mature into trans cisternae. This occurs when a new cis cisterna is formed by the fusion of vesicles at the cis face.
Cisternal Maturation Model
Refers to the pathway in which the newly synthesized proteins and lipids from the ER are transported to the Golgi complex to the plasma membrane or other target site
Anterograde transport
The transport of proteins and lipids in the reverse direction; use as a quality control
Retrograde transport
This happens when Golgi proteins are retrieved to be recycled to the earlier compartments or when proteins/ lipids need further modifications and when they are brought in the wrong Golgi compartment.
Retrograde
The step- by- step process that a protein undergoes from the ER to the Golgi and finally to the target site
protein cargo
step-by-step process in protein cargo (5)
- Budding
- Transportation
- Fusion
- Modification
- Sorting and Tagging
The ER sends the “protein cargo” via a transport vesicle budding off from the ER exit sites.
Location:
Budding;
ER
The transport vesicle travel along the microtubule toward the cis- Golgi network/ face (entry face)
Location:
Transportation ;
Cytoplasmic microtubule
Markers and membrane proteins in the transport vesicle interact with the receptors in the cis- Golgi network and fuses with the membrane of the Golgi apparatus then releases the proteins into the Golgi lumen.
Location:
Fusion;
Cis-golgi
Golgi apparatus ensures that the products are in their ideal state, hence, in this step, protein undergoes post- translational modification
Location:
Modification;
various regions of Golgi
post- translational modification of Golgi (4)
Phosphorylation-
Acetylation-
Methylation-
Lipid modifications
the process of adding phosphate groups to proteins essential for
proteins necessary for signaling pathways and cellular processes
Phosphorylation-
the addition of acetyl groups to the protein necessary for protein- protein
interactions, protein stability and gene expression regulation
Acetylation-
the addition of methyl groups to proteins essential for protein- protein interactions, protein localization and stability
Methylation-
Golgi apparatus is the site for modifying lipids such as the addition
of lipid anchors.
Lipid modifications
The Golgi sorts the modified protein cargo based on sorting signals added to the protein molecule to ensure that the proteins destined for the plasma membrane undergo glycosylation-
Sorting and Tagging
a process involving the addition of sugar molecules that will determine their final destinations.
GLYCOSYLATION:
Formation of Glycoprotein
PROTEIN GLYCOSYLATION:
process by which the carbohydrate is covalently attached to the protein molecule is called ___. In this process, ___ is formed.
protein glycosylation; glycoprotein
Oligosaccharides may be attached to proteins via three specific amino acids:
Asparagine,
Serine, and Threonine.
Two types of bonds between a sugar and a protein
N- glycosidic bond/ linkage
O- glycosidic bond/ linkage
formed between the nitrogen of the Asparagine and a sugar; begins in the ER;
N- glycosidic bond/ linkage
For sugar to attach on Asn, the sequence must be: -
Asn- arbitrary protein (excluding Pro)- Thr/ Ser
bond formed between the oxygen on the Serine or Threonine and a corresponding sugar
molecule
O- glycosidic bond/ linkage
where the process is complete exclusively in the Golgi apparatus
O- glycosidic bond/ linkage
The protein is packaged into transport vesicles with distinct membrane proteins or markers that will specifically interact with the membrane receptors of their target destination
packaging
Lipids are transported through a specialized transport vesicles called ER- to- Golgi
transport vesicles also referred to as ___ as the budding vesicle is coated with ____ proteins.
COPII vesicles; Coat Protein Complex II (COPII)
Upon a signal, the vesicle fuses to the plasma membrane to release the proteins outside the cell in the process called __ which only occurs as a response to a particular stimulus.
regulated secretion
This process ensures a steady supply of essential molecules from the cell to the extracellular environment.
CONSTITUTIVE AND REGULATED SECRETION
Lysosomal proteins that are synthesized in the ER will be transported in the Golgi for modifications via transport vesicles. The Golgi will modify these proteins by the addition of _______ When these tags are recognized by the M6P receptors, proteins will be sorted and become transport vesicles.
mannose-6- phosphate (M6P) tags.;
process by which proteins are distributed throughout the cell and released to the extracellular matrix.
MEMBRANE TRAFFICKING
a key process for maintaining the sustainability of the cell by transporting these proteins and other nutrients to all the parts of the cellular system
MEMBRANE TRAFFICKING
membrane trafficking pathways are classified into two major categories
exocytosis
endocytosis
the secretory pathway that transports newly synthesized proteins from the endoplasmic reticulum (ER) to the plasma membrane (PM) and/or the extracellular space
exocytosis
a pathway in which the process starts from the plasma membrane to the cell interior
endocytosis
Types of Transport Proteins (2)
Facilitated Diffusion
Active Transport
- a transport protein simply creates an opening for a substance to diffuse down its concentration gradient
Facilitated Diffusion
- the cell expends energy in order to move a substance against its concentration gradient
Active Transport
Other Types of Transport Proteins (2)
Carrier Proteins
Channel/pore Protein
have to change shape in order to pass the molecule across the plasma membrane
Carrier Proteins
serves as a tunnel across the membrane into the cell via passive transport, a process called facilitated diffusion
Channel Protein
responsible for bringing in ions and other small molecules into the cell
Channel Protein
proteins open holes in the membrane of a cell. These proteins are characterized by being open to both the intracellular and extracellular space at the same time
Channel/Pore Protein
typically designed so that only one specific substance can pass through
Channel/Pore Protein
use charged amino acids, spaced at precise distances, to attract their desired ion while repelling all others. The desired ion can then flow through the channel while other substances cannot.
voltage-gated ions channels
are only open to one side of the membrane at once because they transport substances against their concentration gradient
Carrier Proteins
typically use energy to change shape
Carrier Proteins
example of carrier proteins (2)
Sodium-potassium pump
Sodium-glucose transport protein
used the energy of ATP to change its shape from being open to the intracellular solution to being open to the extracellular solution (allows it to collect ions inside the cell and release them outside of it, and then vice versa.)
Sodium-potassium pump
uses the concentration gradient of sodium, to move glucose against its concentration gradient, without using ATP directly
Sodium-glucose transport protein
Examples of Transport Proteins (3)
Sodium-Potassium Pump
Sodium-Glucose Transport Prot
Gated Ion Channels
