Podcast
Questions and Answers
What is a key role of the dynamin protein in vesicle transport?
What is a key role of the dynamin protein in vesicle transport?
Which type of vesicle is involved in retrograde transport from the Golgi back to the ER?
Which type of vesicle is involved in retrograde transport from the Golgi back to the ER?
What purpose do retromer-coated vesicles serve in cellular transport?
What purpose do retromer-coated vesicles serve in cellular transport?
How do lysosomes maintain their acidic internal pH?
How do lysosomes maintain their acidic internal pH?
Signup and view all the answers
What is a distinctive characteristic of clathrin-coated vesicles?
What is a distinctive characteristic of clathrin-coated vesicles?
Signup and view all the answers
Which mechanism allows vesicles to recognize the correct acceptor membrane?
Which mechanism allows vesicles to recognize the correct acceptor membrane?
Signup and view all the answers
Which of the following statements about COPII-coated vesicles is true?
Which of the following statements about COPII-coated vesicles is true?
Signup and view all the answers
What type of cells are mostly affected by peroxisomal disorders?
What type of cells are mostly affected by peroxisomal disorders?
Signup and view all the answers
Which feature distinguishes late endosomes from early endosomes?
Which feature distinguishes late endosomes from early endosomes?
Signup and view all the answers
What is a common feature of lysosomal storage disorders?
What is a common feature of lysosomal storage disorders?
Signup and view all the answers
What is the primary function of regulated secretory vesicles?
What is the primary function of regulated secretory vesicles?
Signup and view all the answers
Which proteins are carried to the plasma membrane by the constitutive secretory pathway?
Which proteins are carried to the plasma membrane by the constitutive secretory pathway?
Signup and view all the answers
What characterizes the transport of proteins in polarized cells?
What characterizes the transport of proteins in polarized cells?
Signup and view all the answers
What is NOT a function of the Golgi complex?
What is NOT a function of the Golgi complex?
Signup and view all the answers
Which statement about coats on transport vesicles is incorrect?
Which statement about coats on transport vesicles is incorrect?
Signup and view all the answers
How are proteins targeted specifically to lysosomes?
How are proteins targeted specifically to lysosomes?
Signup and view all the answers
What differentiates regulated secretory vesicles from other transport vesicles?
What differentiates regulated secretory vesicles from other transport vesicles?
Signup and view all the answers
What is required for the incorporation of new proteins and lipids into the plasma membrane?
What is required for the incorporation of new proteins and lipids into the plasma membrane?
Signup and view all the answers
What is a characteristic of proteins retained within the Golgi complex?
What is a characteristic of proteins retained within the Golgi complex?
Signup and view all the answers
What does the unauthorized use of the contents of these slides lead to?
What does the unauthorized use of the contents of these slides lead to?
Signup and view all the answers
Study Notes
Copyright Information
- Slides are the exclusive property of the instructor and/or third parties.
- Reproduction, even partial, by any means (analog or digital) without consent is forbidden.
- Unauthorized use is the full responsibility of the user.
- Use for private study is permitted, but not for profit or commercial purposes.
Cellular Biology I
- Lorena Di Pietro is the instructor.
- [email protected] is the instructor's email address.
The Endomembrane System
- This is a topic of study, likely a slide title.
- Images/illustrations of cells are included (likely microscopy images).
Golgi Complex - Functions (Protein Sorting)
- Proteins are carried to the plasma membrane by a constitutive secretory pathway.
- This pathway involves incorporating new proteins and lipids, and continuous secretion from the cell.
- Other proteins are transported to the cell surface through a distinct pathway of regulated secretion, or may be targeted to other intracellular destinations (like lysosomes).
Golgi Complex - Functions (Protein Sorting): Regulated Secretion
- Regulated secretory vesicles are larger than other transport vesicles.
- They store their contents, releasing them only with specific signals directing fusion with the plasma membrane.
Golgi Complex - Functions (Protein Sorting): Proteins Within the Golgi
- Proteins that function within the Golgi complex must be retained within that organelle.
- These retained proteins are associated with the Golgi membrane rather than being soluble proteins within the lumen.
Type of Transport Vesicles (Coated Vesicle Budding)
- Transport vesicles have protein coatings that form to guide them.
- Coats form through GTP-binding proteins, v-SNARE proteins, Membrane cargo proteins, Membrane cargo receptor proteins, and coat proteins.
- Vesicles choose their specific cargo and dock at appropriate target membranes.
- Many steps in vesicle transport rely on various GTP-binding proteins.
Type of Transport Vesicles (General Characteristics)
- Vesicles budding from intracellular membranes have a distinct two-layered protein "cage" coating their cytosolic surface.
- Coating proteins are discarded before vesicles fuse with their target membrane to allow membrane interaction and fusion.
Type of Transport Vesicles (Functions of Protein Coats)
- Protein coats act as mechanical devices to curve membranes, causing vesicle budding (outer layer).
- Specific components can be selected for transport (inner layer).
- Coats mediate recognition and targeting to the correct acceptor membrane.
Type of Transport Vesicles (Different Types Explained)
- COPII-coated vesicles mediate anterograde transport (forward direction) from the ER through ERGIC to cis-Golgi.
- COPI-coated vesicles mediate retrograde transport (backward direction) from ERGIC and Golgi back to ER and from trans-Golgi to cis-Golgi
- Clathrin-coated vesicles move from TGN, endosome, and plasma membrane
- Retromer-coated vesicles facilitate retrieval transport from endosome to Golgi apparatus
Type of Transport Vesicles (Clathrin-Coated Vesicles)
- Clathrin forms a structural scaffold (the outer layer) of the coating.
- Different inner adaptors connect to different cargo receptors to select transported components.
- Dynamin is a GTPase protein that pinches off clathrin-coated vesicles.
Type of Transport Vesicles (Clathrin Triskelion structure)
- Each clathrin subunit is composed of three heavy chains and three light chains forming a three-legged structure (triskelion).
- Assembled clathrin triskelions create a basket-like network of hexagons and pentagons forming coated pits.
Type of Transport Vesicles (COPII-Coated Vesicles)
- COPII vesicles mediate the initial step of the ER-ERGIC-CGN path (forward transport).
- Vesicle budding happens in specialized ER regions lacking bound ribosomes.
- ER export signals on ER membrane proteins interact with COPII proteins to facilitate transport.
Type of Transport Vesicles (COPI-Coated Vesicles)
- Retrograde path for enzymes: Proteins residing in the ER have a retrieval signal (Lys-Asp-Glu-Leu).
- This signal binds to the COPI coat, facilitating the proteins' return to the ER.
- Transport components (inner & outer layers) are pre-assembled.
Type of Transport Vesicles (Targeting to Specific Compartments - General Concepts)
- Recognition for specific compartments is based on protein-protein interactions.
- Specificity lies in the repertoire of proteins expressed on both membranes involved.
- Interaction among membrane proteins facilitates docking and enables membrane fusion.
Type of Transport Vesicles (Targeting to Specific Compartments - Tethering)
- Vesicles tether to the target membrane through interactions among tethering proteins.
- GTP-Rab proteins interact with the membrane through a lipid anchor.
Type of Transport Vesicles (Targeting to Specific Compartments - Docking)
- Vesicles dock to the target membrane through v-SNARE and t-SNARE protein interactions within the membrane proteins.
Type of Transport Vesicles (Targeting to Specific Compartments - Docking - Fusion Pore Formation)
- Membrane fusion (between vesicle and target) arises from v-SNARE and t-SNARE interaction.
- Contact between membranes creates a fusion pore for fusion.
Retromer Vesicles
- Retromer is a distinct coat protein class, with no close sequence/structural resemblance to other coated vesicle proteins.
- It's involved in cellular trafficking from endosomes to the TGN and plasma membrane.
- Crucial for proper lysosome function, establishing Wnt gradients, maintaining metabolite homeostasis, and other cellular processes.
- Defects in functions are tied to various human diseases.
Cranio-lenticulo-sutural dysplasia (CLSD)
- Autosomal recessive syndrome
- Characterized by late-closing fontanels, sutural cataracts, facial dysmorphisms, and skeletal defects.
- Due to mutations in the SEC23A gene, encoding a COPII protein.
- Electron microscopy reveals dilated ER in fibroblasts and impaired vesicle budding.
Lysosomes
- Digestive organelles with diverse shapes and sizes.
- Contain around 50 hydrolytic enzymes (acidic hydrolases), with a pH of 4.6.
Lysosomes (Main Functions)
- Digest material taken up from outside the cell.
- Digest obsolete components of the cell itself (for reuse of materials or expulsion).
Lysosomes (Material Digestion)
- Lysosomes digest material from endocytosis, phagocytosis, and autophagy.
Lysosomes - Endosomes
- Lysosomes form by fusion of transport vesicles from the trans-Golgi network with endosomes.
- Endosomes act as distribution centers in the endocytic pathway.
- Endosomal lumen fluid is acidified by H+-ATPase in the membrane.
Lysosomes - Endosomes (Early and Late)
- Early endosomes are near the cell periphery and function as sorting stations.
- Late endosomes are closer to the nucleus, receive newly synthesized lysosomal enzymes from the TGN, and exchange content with lysosomes.
- Early endosomes mature into late endosomes.
Autophagy
- Degradation of organelles by enclosure in vesicles from ER that fuse with lysosomes.
- This process involves identification and collection of cellular components for degradation.
Lysosomal Storage Disorders
- A group of inherited metabolic disorders linked to lysosomal dysfunction.
- Prevalence around 1/8000 live births, with symptoms varying.
- Disorders result from deficiencies in activators, enzymes, or transporters that lead to accumulation of waste products in lysosomes, often forming large vacuoles.
Peroxisomes
- Small, membrane-enclosed organelles.
- Contain enzymes for diverse metabolic reactions, including energy metabolism.
- Major sites of oxygen utilization, like mitochondria.
Peroxisomes (Role in Oxidation & Hydrogen Peroxide)
- Involved in oxidation reactions, generating hydrogen peroxide.
- Contain catalase to break down hydrogen peroxide to water or use it to oxidize organic compounds (formic acid, formaldehyde, alcohol).
Peroxisomes (Biosynthesis & Myelin)
- Essential for animal peroxisome function in catalyzing the first reaction in plasmalogen synthesis (a major class of phospholipids in myelin).
- Myelin is formed through extensive and modified plasma membrane wrappings around nerve axons.
Peroxisomes (Protein Import & Replication)
- Several distinct peroxins (Pex genes) participate in peroxisome protein import, a process powered by ATP hydrolysis.
- Like mitochondria and plastids, peroxisomes can replicate themselves.
Peroxisomal Disorders
- Originate from defects in peroxisome functions.
- Classified into peroxisome biogenesis disorders and single enzyme deficiencies.
- Often feature profound abnormalities in the nervous system due to myelination problems, usually showing the most severe defects in the brain, liver, and kidney.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
Explore the complexities of the endomembrane system in cellular biology, focusing on the Golgi complex and its role in protein sorting. This quiz will assess your understanding of the pathways involved in protein and lipid transport within the cell.
