Protein Transport Mechanisms in Organelles
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Questions and Answers

Which mechanism is responsible for transporting proteins from the cytosol to the nucleus?

  • Transport across membrane
  • Bidirectional movement
  • Gated transport (correct)
  • Coated with ribosomes

    • What happens to proteins that lack sorting signals?

  • They are transported to mitochondria
  • They are transported to the nucleus
  • They stay in the cytosol (correct)
  • They diffuse freely through the membrane

    • Which organelle captures proteins from the cytosol during synthesis and is coated with ribosomes?

  • Nucleus
  • Mitochondria
  • Golgi apparatus
  • Endoplasmic reticulum (ER) (correct)

    • What type of transport is needed for molecules like DNA and RNA polymerases to move across nuclear pores?

    <p>Active transport</p> Signup and view all the answers

    In which mechanism does the transporter protein need to unfold for guidance across the hydrophobic interior of the membrane?

    <p>Protein translocation</p> Signup and view all the answers

    Which type of proteins are transported via nuclear pores guided by signal sequences with the help of soluble receptor proteins in the cytosol?

    <p>Proteins moving from cytosol to nucleus</p> Signup and view all the answers

    What directs proteins into different organelles based on their amino acid sequence?

    <p>Sorting signals</p> Signup and view all the answers

    What is the mechanism of transfer for soluble proteins from cytosol to ER?

    <p>Co-translational transport with SRP recognizing the signal sequence</p> Signup and view all the answers

    What initiates translocation and contains a signal sequence as well as a stop transfer sequence for transmembrane proteins?

    <p>N-terminal sequence</p> Signup and view all the answers

    What is responsible for shaping vesicles for transport and capturing molecules?

    <p>Clathrin and COP proteins</p> Signup and view all the answers

    Which proteins ensure specificity and docking of vesicles to target membranes, catalyzing membrane fusion?

    <p>Rab proteins and SNAREs</p> Signup and view all the answers

    What contributes to recognition and protection of proteins during secretion?

    <p>Glycosylation in the ER and Golgi</p> Signup and view all the answers

    Which mechanism involves ribosomes being brought down to the ER membrane by SRP?

    <p>Co-translational transport for soluble proteins</p> Signup and view all the answers

    What occurs for transmembrane proteins during transport?

    <p>They remain embedded in the membrane of vesicles and merge with the destination compartment membrane</p> Signup and view all the answers

    What is the main difference between constitutive and regulated secretion?

    <p>Regulated secretion requires signals, while constitutive secretion is continuous</p> Signup and view all the answers

    Soluble proteins and transmembrane proteins are transferred from cytosol to ER using the same mechanism

    <p>False</p> Signup and view all the answers

    Signal peptidases cleave off the signal sequence on the protein, and the N-terminal sequence initiates translocation

    <p>True</p> Signup and view all the answers

    Co-translational transport occurs for transmembrane proteins, with signal recognition particle (SRP) recognizing the signal sequence

    <p>False</p> Signup and view all the answers

    Vesicular transport relies on ATP and membrane budding, but not membrane fusion

    <p>False</p> Signup and view all the answers

    Each transport vesicle carries a mix of different proteins to its destination

    <p>False</p> Signup and view all the answers

    Soluble proteins and transmembrane proteins are both made in the ER and fully transported through its membrane, ending up in its lumen

    <p>False</p> Signup and view all the answers

    Transmembrane proteins partially transfer across the membrane, remain embedded in it, and go through the protein translocator

    <p>True</p> Signup and view all the answers

    Each transport vesicle carries only appropriate proteins to its destination

    <p>True</p> Signup and view all the answers

    Constitutive secretion occurs continuously, while regulated secretion requires signals to initiate

    <p>True</p> Signup and view all the answers

    Glycosylation protects proteins from degradation and aids in recognition during secretion

    <p>True</p> Signup and view all the answers

    Study Notes

    • Soluble proteins and transmembrane proteins are transferred from cytosol to ER with different mechanisms

    • Soluble proteins are made in ER, fully transported through its membrane, and end up in its lumen

    • Signal peptidases cleave off the signal sequence on the protein, and the N-terminal sequence initiates translocation

    • Transmembrane proteins partially transfer across the membrane, remain embedded in it, and go through the protein translocator

    • The N-terminal sequence initiates translocation and contains a signal sequence as well as a stop transfer sequence

    • Co-translational transport occurs for soluble proteins, with signal recognition particle (SRP) recognizing the signal sequence

    • ER appears rough due to ribosomes being brought down to the membrane by SRP

    • Vesicular transport, an alternative method for protein transport, relies on ATP and membrane budding and fusion

    • Each transport vesicle only carries appropriate proteins to its destination

    • Transmembrane proteins stay in the membrane of the vesicle during transport and merge with the destination compartment membrane

    • ER and Golgi are involved in the secretory pathway

    • Constitutive and regulated secretion occur through different mechanisms, with regulated secretion requiring signals and constitutive secretion being continuous

    • Proteins undergo modifications during secretion, such as glycosylation in the ER and Golgi

    • Glycosylation protects proteins from degradation and aids in recognition

    • Clathrin and COP proteins coat vesicles and help shape them for transport and capture molecules

    • Rab proteins and SNAREs ensure specificity and docking of vesicles to target membranes, catalyzing membrane fusion.

    • Soluble proteins and transmembrane proteins are transferred from cytosol to ER with different mechanisms

    • Soluble proteins are made in ER, fully transported through its membrane, and end up in its lumen

    • Signal peptidases cleave off the signal sequence on the protein, and the N-terminal sequence initiates translocation

    • Transmembrane proteins partially transfer across the membrane, remain embedded in it, and go through the protein translocator

    • The N-terminal sequence initiates translocation and contains a signal sequence as well as a stop transfer sequence

    • Co-translational transport occurs for soluble proteins, with signal recognition particle (SRP) recognizing the signal sequence

    • ER appears rough due to ribosomes being brought down to the membrane by SRP

    • Vesicular transport, an alternative method for protein transport, relies on ATP and membrane budding and fusion

    • Each transport vesicle only carries appropriate proteins to its destination

    • Transmembrane proteins stay in the membrane of the vesicle during transport and merge with the destination compartment membrane

    • ER and Golgi are involved in the secretory pathway

    • Constitutive and regulated secretion occur through different mechanisms, with regulated secretion requiring signals and constitutive secretion being continuous

    • Proteins undergo modifications during secretion, such as glycosylation in the ER and Golgi

    • Glycosylation protects proteins from degradation and aids in recognition

    • Clathrin and COP proteins coat vesicles and help shape them for transport and capture molecules

    • Rab proteins and SNAREs ensure specificity and docking of vesicles to target membranes, catalyzing membrane fusion.

    • Soluble proteins and transmembrane proteins are transferred from cytosol to ER with different mechanisms

    • Soluble proteins are made in ER, fully transported through its membrane, and end up in its lumen

    • Signal peptidases cleave off the signal sequence on the protein, and the N-terminal sequence initiates translocation

    • Transmembrane proteins partially transfer across the membrane, remain embedded in it, and go through the protein translocator

    • The N-terminal sequence initiates translocation and contains a signal sequence as well as a stop transfer sequence

    • Co-translational transport occurs for soluble proteins, with signal recognition particle (SRP) recognizing the signal sequence

    • ER appears rough due to ribosomes being brought down to the membrane by SRP

    • Vesicular transport, an alternative method for protein transport, relies on ATP and membrane budding and fusion

    • Each transport vesicle only carries appropriate proteins to its destination

    • Transmembrane proteins stay in the membrane of the vesicle during transport and merge with the destination compartment membrane

    • ER and Golgi are involved in the secretory pathway

    • Constitutive and regulated secretion occur through different mechanisms, with regulated secretion requiring signals and constitutive secretion being continuous

    • Proteins undergo modifications during secretion, such as glycosylation in the ER and Golgi

    • Glycosylation protects proteins from degradation and aids in recognition

    • Clathrin and COP proteins coat vesicles and help shape them for transport and capture molecules

    • Rab proteins and SNAREs ensure specificity and docking of vesicles to target membranes, catalyzing membrane fusion.

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    Cell sorting, endocytosis and exocytosis 17-10-23.docx

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    Test your knowledge about the mechanisms of transporting proteins into organelles, including the role of sorting signals and the synthesis process. Understand how proteins are directed to specific organelles and the consequences of lacking sorting signals.

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