Comprehension - L08-L09 Flashcards
What 5 things are a part of the endo-membrane system?
ER
Golgi Complex
Endosomes
Lysosomes
Vacuoles
What are the 3 steps of the endomembrane system?
- Transport materials from donor to recipient compartment
- Transport materials out of the cell (secretory)
- Transport materials into the cell (endosytic)
During the transport of materials from the donor compartment the recipient compartment, what happens to the proteins?
Proteins (secreted proteins, lysosomal enzymes, membrane proteins) are directed to the correct destination with sorting signals
During the transport of materials from the donor compartment to the recipient compartment, what are the sorting signals and what do they do?
- Amino acid sequences
- Attached oligosaccharides
Signals are recognized by receptors in the membranes of budding vesicles
In the Secretory Pathway, what are the types of biomolecules synthesized in the ER?
- Lipids
- Steroid hormones
- Secreted proteins
- Integral membrane proteins
- Glycosolyation of proteins
Modifications occur where?
The Golgi complex
What happens in constitutive secretion?
- Materials are continually transported in secretory vesicles from their site of synthesis and secreted
- Contributes to the formation of the plasma membrane
What happens in the regulated secretion?
Materials are stored in membrane bound compartments and only are released due to stimuli
What happens in the endocytic pathway?
Materials move from the outer surface of the cell to compartments within the cell (endoscopes and lysosomes)
In the endocytic pathway, what do endosomes do?
Materials are taken up and are transported to early endoscopes for sorting
Late endosomes are more acidic
Fuse with lysosomes to deliver cargo for degradation
In the endocytic pathway, what do lysosomes do?
Hydrolytic (digestive) enzymes and acidic pH
Roles in breakdown of material and organelle turnover
What is autoradiography?
Following the location of radioactively labeled materials in a cell
Pulse chase experiment
What is the Pulse step of Pulse Chase?
Radio-labelled amino acids are incorporated in the digestive enzymes being synthesized
Exposed to the radio labelled aa for only a short time
What is the Chase step of the Pulse Chase?
- Transfer cells to media with only unlabelled aa
- Enzymes synthesized during this time will not be radio labeled
What are the characteristics of the Rough ER?
- Ribosomes bound on cytosolic surface
- Network of cistern
- Continuous with the outer membrane of nuclear envelope
What are the characteristics of the Smooth ER?
- Lacks ribos
- Interconnected curved, tubular membranes
- Continuous with Rough ER
What are the functions of the smooth ER?
- Synthesis of steroid hormones
- Synthesis of membrane lipids
- Detox of liver compounds
- Sequester Ca2+ ions in muscle
What are some functions of the Rough ER?
- Protein synthesis
- Addition of sugars is initiated
What happens in the RER ribosomes?
1/3 of proteins are made
Cotranslational translocation where peptides move into the lumen of the ER as it is being synthesized by the ribo
What happens in the Free ribosomes?
2/3 of proteins are synthesized
proteins released into cytosol
What is cotranslational translocation?
Synthesis of secreted proteins and soluble proteins that reside in endomembrane
All protein synthesis begins on what?
A free ribosome
Which end does cotranslational translocation synthesize first?
N-Terminal end gets synthesized first
In cotranslational translocation, what does SRP Stand for and what does it do?
Signal Recognition Particle binds to the signal sequence and the ribosome
Polypeptide synthesis is halted temporarily
The amino acids that flank the cytosolic end of the transmembrane domain are (Positive/Negative)
Positively charged amino acids
What are the positively charged amino acids?
Arginine (R, Arg)
Lysine (K, Lys)
Histidine (H, His)
What does PE do?
What does PS do?
What does PI do?
PE: Promotes curvature
PS: -ve charge interacts with transmembrane protein
PI: Roles in signal transduction
What happens in cotranslational translocation if the positive charges are on the N terminal side of the transmembrane domain?
The translocon will reorient the transmembrane domain
