29 Questions
What is the main process described in the text involving the fusion of vesicle membrane with the cell membrane?
Exocytosis
What is the main purpose of phagocytosis?
To internalize large structures or whole cells
Which of the following statements about pinocytosis is FALSE?
It requires a microfilament network for vesicle formation
How is the movement of secretory vesicles facilitated in exocytosis?
By interaction with motor proteins on microtubules
What type of exocytosis involves continuous secretion of vesicle contents once they are formed?
Constitutive exocytosis
What distinguishes receptor-mediated endocytosis from the other types of endocytosis?
Specific receptors make the process more concentrated
Which of the following molecules can be secreted through exocytosis?
Proteins like components of the cell membrane
Which cellular structure is crucial during the formation of phagosomes?
Microfilament network
To maintain a relatively constant plasma membrane surface area, what should be the relationship between membrane fusion and loss of membrane segments?
Membrane fusion should be equal to loss of membrane segments
During which process is the cell membrane under tremendous strain?
Phagocytosis
What is the purpose of the interaction between secretory vesicles and motor proteins during exocytosis?
To move vesicles along microtubules towards cell membrane
What role does RME play in endocytosis?
It makes the process more specific and concentrated
What needs to occur before secretion in regulated exocytosis?
Stimulation by a signal or stimulus
In muscle contraction, which neurotransmitter is contained in vesicles in the motor neuron?
Acetylcholine
What initiates the release of acetylcholine into the synapse in muscle contraction?
Action potential reaching the axon terminus
How are endocytic vesicles formed?
Membrane pinching off from cell membrane
What is one fate of endocytosed material after being released into the cell?
Fusing with lysosomes for digestion
How do vesicles move inward toward the interior of the cell?
Motor proteins along microtubules
What is the main difference between exocytosis and endocytosis?
Exocytosis involves internalizing macromolecules, while endocytosis involves secretion.
Which of the following statements correctly describes exocytosis?
It involves the fusion of membranes to release vesicles from the cell.
In endocytosis, what is the initial step that occurs involving membrane adherence?
Membranes come in apposition with each other.
Which of the following is a characteristic of exocytosis?
It involves the release of molecules out of the cell.
What distinguishes endocytosis from exocytosis?
Endocytosis internalizes molecules, while exocytosis releases molecules.
Which statement accurately describes the role of vesicles in transport across the cell membrane?
Vesicles are involved in both exocytosis and endocytosis processes.
What happens when the pH shifts from 7 to acidic in the presence of apotransferrin?
Iron will be released and apotransferrin will be retained.
Where is the iron released to be utilized by the cell after it dissociates from apotransferrin?
Cytosol
What process transports apotransferrin back to the cell membrane after it has released iron?
Exocytosis
How does exposing apotransferrin and its receptor to pH 7 affect their binding affinity?
Decreases their binding affinity
What is the process of continuous endocytosis and exocytosis between cell surface membranes called?
Transcytosis
Study Notes
Cell Membrane Dynamics
- Vesicles have their own lipid bilayer and membrane, and can fuse with the plasma membrane through membrane fusion, resulting in a loss of segment from the plasma membrane and the gain of more membrane materials.
- For a cell to maintain a relatively constant plasma membrane surface area, the rate of vesicle fusion and membrane fusion should be equal.
Exocytosis
- Exocytosis is the process of secretion, where a secretory vesicle formed in the Golgi apparatus ruptures to release its contents outside the cell.
- Vesicles are carried by motor proteins on microtubules and adhere to the cell membrane, then fuse with the plasma membrane, releasing their contents.
- Secretory vesicles move a distance to reach the cell surface, enabled by interaction with motor proteins, which move along microtubules.
- Different materials can be secreted, including components of the cell membrane, cell wall, or cell coat, extracellular matrix components, hormones, and other substances.
Types of Exocytosis
- Constitutive exocytosis: continuous secretion, where a secretory vesicle is formed and fuses with the plasma membrane, releasing its contents.
- Regulated exocytosis: secretion that requires a signal or stimulus before releasing contents, such as in muscle contraction, where vesicles release acetylcholine into the synapse.
Endocytosis
- Endocytosis is the process of internalizing macromolecules from the extracellular fluid, involving the invagination of the cell membrane and membrane fusion.
- Fates of endocytosed material include digestion, processing, and passage through the cell.
Types of Endocytosis
- Phagocytosis: cell eating, where a cell engulfs another whole cell or large structure, forming a phagosome.
- Pinocytosis: cell drinking, where a cell engulfs extracellular fluid containing dissolved substances, forming a vesicle.
- Receptor-mediated endocytosis (RME): involves receptors that recognize and bind specific substrates, making the process more specific and concentrated.
Transcytosis
- Transcytosis is the continuous process of endocytosis and exocytosis, starting from one cell surface membrane to another, such as the absorption of immunoglobulins by infants from mother's breast milk.
Test your knowledge on the transport of small molecules and macromolecules across the cell membrane in Cell Biology. Learn to differentiate passive from active transport and understand the different types of membrane flow.
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