Flashcards in Intracellular Compartments and Protein Sorting: Part 2 Deck (40):
What are the two different ways a single pass transmembrane protein can be oriented in the ER membrane?
1. with the carboxy end in the ER lumen
2. with the amino end in the ER lumen
What are the two sites of a translocator protein? Which way does the translocator open?
1. hydrophobic stop-transfer binding site
2. hydrophobic start-transfer binding site
The path of a transmembrane protein from translation to the PM goes from ______ --> ______ --> _______ --> ______
cytosol --> ER --> Golgi --> PM
What process occurs in the Golgi?
-glycosylation of lipids and proteins
What is the definition of the Golgi apparatus?
-receives proteins and lipids from ER, modifies them, and then dispatches them to other destinations in the cell
Where does protein glycosylation actually start? Which process occurs in the Golgi and is required for mature proteins?
2. complex oligosaccharide processing
Golgi has different enzymes in each _____
What does the process of membrane insertion result in?
-membrane protein asymmetry (each protein is inserted into the membrane in the ER in a specific manner)
How is protein asymmetry maintained?
through vesicular transport
What is an endosome?
-membrane-bound organelle that carries materials newly ingested by endocytosis and passes them to lysosomes for degredation
What is a lysosome?
-small sac of digestive enzymes that functions in degrading worn-out organelles, as well as macromolecules and particles taken into the cell by endocytosis
Where is endocytosed material found?
-in the early endosome
Lysosome proteins are delivered to _____ directly from the _____ in ______
Where are lysosome proteins found? What are the three compartments called?
-in heterogenous looking compartments
-late endosome, endolysosome, lysosome
Why do mature lysosomes fuse with endosomes?
-to recycle lysosomal proteins
Lysosomes are the main site of ______ _____ which contain approx. 40 types of _____ _____
What type of environment do enzymes in lysosomes require? (high or low pH?) Why?
acidic environment/low pH; protects the contents of the cytosol from digestion
How are lysosomes acidified?
by a proton pump (V-type ATPase)
Lysosomal membrane proteins are _______ to protect them from proteases in the _______
What are some products of digestion that are transferred out of the lysosome to the cytosol?
AA, sugars, nucleotides
What are classical lysosomes?
-when the majority of endocytosed material has been digested
True or False.
Lysosomal proteins from the ER and Golgi are always incorporated into endosomes at the same stage.
Where are lysosomal hydrolases found?
early and late endosomes
How much of the cell volume do plant vacuoles occupy?
List five processes/functions involving plant vacuoles.
2. nutrient storage
3. waste storage
4. increasing cell size
5. turgor pressure
What is turgor pressure?
-when vacuoles get much larger and push the cytoplasm gets against the membrane
The volume of a plant cell increases without increasing the volume of the ______
What is the function of peroxisomes?
use molecular oxygen to oxidize organic molecules
What do oxidative reactions produce?
Where do peroxisomes function?
in the breakdown of long fatty acid chains
What kind of proteins are found in peroxisomes?
-proteins inserted into the ER
-proteins imported from the cytosol
Describe the movement of proteins (3 ways)
1. within cell, between different compartments
2. out of cell
3. into cell
Where is protein synthesis initiated?
Describe the post-translational process. Which components are unfolded and which are folded?
-proteins are fully synthesized in the cytosol before sorting
-unfolded: mitochondria, plastids
-folded: nucleus, peroxisomes
How does a nuclear protein get into the nucleus? This process can be regulated by _______ _______
-gated transport; occurs through NPC
A protein with a normal nuclear import signal is found in the _____.
A protein with a mutated or deleted signal is found in the ______.
What are three additional factors required for transcription initiation?
2. enhancer site
3. DNA loop
What is the estrogen receptor?
-a ligand-modulated regulator of transcription
What happens when estradiol is NOT present?
estrogen receptor remains in the cytosol