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Questions and Answers
Which ion is essential for the process of Ca2+-dependent exocytosis?
Which ion is essential for the process of Ca2+-dependent exocytosis?
What is the primary role of exocytosis in neuronal communication?
What is the primary role of exocytosis in neuronal communication?
Which process involves the movement of vesicles to the site of release?
Which process involves the movement of vesicles to the site of release?
What characterizes the docking step in exocytosis?
What characterizes the docking step in exocytosis?
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Which cytoskeletal components facilitate vesicle trafficking in exocytosis?
Which cytoskeletal components facilitate vesicle trafficking in exocytosis?
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What is the correct sequence of steps in exocytosis?
What is the correct sequence of steps in exocytosis?
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Which of the following is NOT a step in the exocytosis process?
Which of the following is NOT a step in the exocytosis process?
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What is the end result of exocytosis?
What is the end result of exocytosis?
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Motor proteins involved in vesicle trafficking include which of the following?
Motor proteins involved in vesicle trafficking include which of the following?
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Which statement accurately reflects the priming step in exocytosis?
Which statement accurately reflects the priming step in exocytosis?
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What process involves the movement of materials out of the cell?
What process involves the movement of materials out of the cell?
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Which type of secretion occurs continuously and is not influenced by external signals?
Which type of secretion occurs continuously and is not influenced by external signals?
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In which process do cells engulf and internalize large particles or cells?
In which process do cells engulf and internalize large particles or cells?
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What is the primary difference between phagocytosis and pinocytosis?
What is the primary difference between phagocytosis and pinocytosis?
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What characterizes receptor-mediated endocytosis?
What characterizes receptor-mediated endocytosis?
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During which phase does the cell membrane increase in surface area due to the fused vesicle?
During which phase does the cell membrane increase in surface area due to the fused vesicle?
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What distinguishes calcium-dependent secretion from non-calcium-dependent secretion?
What distinguishes calcium-dependent secretion from non-calcium-dependent secretion?
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What stage is NOT involved in the formation of secretory vesicles?
What stage is NOT involved in the formation of secretory vesicles?
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What is primarily transported during pinocytosis?
What is primarily transported during pinocytosis?
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What is an example of a non-specific endocytosis process?
What is an example of a non-specific endocytosis process?
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Study Notes
Biological Membranes: Transport I (Macrotransfer)
- Class: Foundation Year
- Course: Fundamentals of Human Biology
- Code: FUNBIO.9
- Lecturer: Dr Irene Oglesby
- Date: 16th October 2024
Learning Outcomes
- ALO1: Recall the difference between macrotransfer and microtransfer processes.
- ALO2: Differentiate between exocytosis and endocytosis.
- ALO3: Explain the mechanism of both phagocytosis and pinocytosis.
- ALO4: Differentiate between receptor-mediated and fluid-phase pinocytosis.
- ALO5: Describe 4 stages in the secretory vesicle formation.
- ALO6: Differentiate between constitutive and regulated secretion.
Membrane Transport
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Macrotransfer: Transport of macromolecules and larger items into and out of the cell.
- Exocytosis: Movement out of the cell.
- Endocytosis: Movement into the cell.
Exocytosis
- Process of releasing large biomolecules through the plasma membrane.
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Tasks:
- Increase the surface area of the plasma membrane.
- Release substances from vesicles into the exterior.
- Integrate vesicle proteins into the plasma membrane.
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Two Types:
- Constitutive (Non-Ca2+-dependent): continuous release of newly synthesized proteins and lipids.
- Ca2+-dependent: release in response to a specific signal.
Vesicle Trafficking (Exocytosis): Distinct Steps
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- Vesicle trafficking: Movement of vesicles from the production site to the release site. Facilitated by cytoskeletons (actin and microtubules) and motor proteins (kinesin, dynein).
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- Tethering: A bridging complex forms at the tethering point.
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- Docking: The vesicle and the cell membranes attach. This brings the two membranes close together (<5-10 nm).
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- Priming: Molecular rearrangements, including ATP-dependent protein modifications and lipid rearrangements. Triggered by calcium influx (e.g. in the case of synaptic vesicles).
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- Fusion: The phospholipid bilayers of the vesicle and cell membrane merge. Driven by SNARE proteins.
Endocytosis
- Absorption of material from the outside by engulfing it with the cell membrane.
- Used by all body cells.
- Uptake of polar or large molecules that can't pass through the hydrophobic plasma membrane.
- Opposite of exocytosis.
Types of Endocytosis
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Phagocytosis:
- Ingestion of large particles like bacteria (to "eat").
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Pinocytosis:
- Ingestion of dissolved materials (to "drink").
- Receptor-mediated: involves specific receptors on the plasma membrane to bind to specific molecules for uptake.
- Fluid-phase: nonspecific uptake of dissolved substances.
Phagocytosis
- Plasma membrane extends around the material to be engulfed.
- Receptors on the plasma membrane may bind to antibodies on the surface of the foreign body.
- An intracellular vacuole (heterophagosome) is formed around the material.
- The vacuole fuses with a lysosome for digestion.
- This process is common in cells like monocytes, neutrophils, and macrophages.
Pinocytosis
- Receptor-mediated: molecules bind to receptors and are selectively adsorbed.
- Fluid-phase: no specific receptors.
Reading Material (Provided as links in lecture slides)
- Diffusion
- The Sodium-Potassium Pump
- Membrane Transport
- Synaptic Vesicle Trafficking
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Description
This quiz covers the fundamental concepts of macrotransfer processes in biological membranes, focusing on exocytosis and endocytosis. You will learn to differentiate between phagocytosis and pinocytosis and describe the stages of secretory vesicle formation. Ideal for students in the Foundation Year of Human Biology.
