2023-12-25T23:24:17+03:00[Europe/Moscow] en true <p>What is the structure of the ER (Endoplasmic Reticulum)? </p>, <p>What are the functions of the ER? (RER) (3)</p>, <p>What are the functions of the ER? (SER) (3)</p>, <p>What are the differences between the RER and the SER?</p>, <p>Where are newly synthesised lipids targeted to?</p>, <p>What are signal sequences?</p>, <p>Picture demonstrating protein synthesis and modification in both the ribosomes free in the cytosol and membrane bound ribosomes</p>, <p>What are the four ways that proteins can be modified inside the RER?</p>, <p>What is proteolysis? (process and purpose)</p>, <p>What is Disulfide bond formation? (process and purpose)</p>, <p>What is glycosylation? (process and purpose)</p>, <p>What is deglycosylation? (process and purpose)</p>, <p>What happens to proteins that fail any quality check?</p>, <p>What does ERAD stand for?</p>, <p>What is the Structure of the Golgi apparatus?</p>, <p>What is the function of the Golgi apparatus? (5)</p>, <p>Picture of table outlining the functions of the Golgi apparatus:</p>, <p>Vesicles transport proteins to and from...?(3)</p>, <p>How is bud formation facilitated?</p>, <p>What are the COPI and COPII proteins?</p>, <p>What do v-SNARES and t-SNARES do in the target membrane?</p>, <p>A summary:</p> flashcards

The Endoplasmic Reticulum and Secretory Pathway (The Living Cell)

By the end of this lecture, students should be able to: · Identify endoplasmic reticulum (ER) and Golgi apparatus in electron micrographs. · Describe the structure and function of the endoplasmic reticulum and Golgi apparatus. · Explain the ER-mediated protein synthesis pathway. · Understand the main post-translational modifications to which proteins are subject during their transport through the ER and Golgi complex.

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  • What is the structure of the ER (Endoplasmic Reticulum)?

    - Single-membrane compartment -continuous network of tubular and flat vesicular structures in the cytoplasm (“little net”).- Space inside is connected with the space between the two membrane surfaces of the nuclear membrane-continuous with the nuclear envelope.- Two parts with different functions: granular/rough ER (ribosomes attached for the translation and folding of new proteins) and agranular/smooth ER (synthesis of lipids and detoxification of certain drugs and toxins by cytochrome P450 enzymes)

    - Single-membrane compartment -continuous network of tubular and flat vesicular structures in the cytoplasm (“little net”).- Space inside is connected with the space between the two membrane surfaces of the nuclear membrane-continuous with the nuclear envelope.- Two parts with different functions: granular/rough ER (ribosomes attached for the translation and folding of new proteins) and agranular/smooth ER (synthesis of lipids and detoxification of certain drugs and toxins by cytochrome P450 enzymes)

  • What are the functions of the ER? (RER) (3)

    - Protein synthesis- Glycosylation,

    - Folding and assembly to form multi-protein complexes.

  • What are the functions of the ER? (SER) (3)

    - Lipid synthesis (cholesterol, phospholipids). - Ca2+ sequestration (isolating something from its usual environment)- Detoxification by cytochrome P450 enzymes.

  • What are the differences between the RER and the SER?

  • Where are newly synthesised lipids targeted to?

    The ER, nucleus, mitochondria or peroxisomes

    The ER, nucleus, mitochondria or peroxisomes

  • What are signal sequences?

    Amino acids at the N-terminal end of the protein that are recognisedby enzyme systems within the cell that transport the protein to the correct destination.

  • Picture demonstrating protein synthesis and modification in both the ribosomes free in the cytosol and membrane bound ribosomes

  • What are the four ways that proteins can be modified inside the RER?

    -Proteolysis (Signal Peptide)-Disulfide bond formation)-Glycosylation-Deglycosylation

    -Proteolysis (Signal Peptide)

    -Disulfide bond formation)

    -Glycosylation

    -Deglycosylation

  • What is proteolysis? (process and purpose)

    Proteolysis (Signal Peptide):

    Process:

    Removal of the signal peptide, a specific sequence at the N-terminal end of a polypeptide.

    Typically occurs during or after translocation into the endoplasmic reticulum.

    Purpose:

    Signal peptide guides the protein to the ER; removal is necessary for the mature protein.

  • What is Disulfide bond formation? (process and purpose)

    Disulfide Bond Formation:

    Process:

    Formation of covalent bonds (disulfide bonds) between cysteine residues in the polypeptide chain.

    Facilitated by enzymes in the ER that catalyse the oxidation of cysteine residues.

    Purpose:

    Contributes to the stabilization and proper folding of the protein structure.

  • What is glycosylation? (process and purpose)

    Glycosylation:

    Process:

    Addition of carbohydrate (sugar) groups to specific amino acid residues, often serine or threonine.

    Enzymatic process involving the attachment of sugar moieties (refers to a functional group or a distinctive part of a molecule) to the protein.

    Purpose:

    Aids in protein folding, stability, and recognition.

    Essential for proper targeting and function of glycoproteins.

  • What is deglycosylation? (process and purpose)

    Deglycosylation:

    Process:

    Removal of previously added carbohydrate groups from glycoproteins.

    Mediated by enzymes that cleave the glycosidic bonds between sugars and amino acids.

    Purpose:

    Regulatory process that can modulate protein function.

    Necessary for recycling or degradation of certain glycoproteins.

  • What happens to proteins that fail any quality check?

    Will not be exported from the ER and are degraded by ubiquitination and the proteasome

  • What does ERAD stand for?

    Endoplasmic-Reticulum-Associated protein degradation

    Endoplasmic-Reticulum-Associated protein degradation

  • What is the Structure of the Golgi apparatus?

    Structure of Golgi Apparatus:Single-membrane compartment.Consists of 4 to 8 stacked layers of thin, flat, enclosed vesicles called cisternae.Cisternae lie near one side of the nucleus.Compartments within Golgi Apparatus:Three networks or compartments:Cis Compartment:First cisternae structure.Located closer to the nucleus.Medial Compartment:Intermediate structures between cis and trans compartments.Trans Compartment:Final structure.Located closer to the cell membrane.

    Structure of Golgi Apparatus:

    Single-membrane compartment.

    Consists of 4 to 8 stacked layers of thin, flat, enclosed vesicles called cisternae.

    Cisternae lie near one side of the nucleus.

    Compartments within Golgi Apparatus:

    Three networks or compartments:

    Cis Compartment:

    First cisternae structure.

    Located closer to the nucleus.

    Medial Compartment:

    Intermediate structures between cis and trans compartments.

    Trans Compartment:

    Final structure.

    Located closer to the cell membrane.

  • What is the function of the Golgi apparatus? (5)

    Protein Modification:

    Addition or modification of carbohydrate moieties (refers to a functional group or a distinctive part of a molecule) to proteins.

    Lipid Synthesis:

    Synthesis of lipids, including sphingomyelin and glucosylceramide.

    Protein and Lipid Sorting:

    Directs proteins and lipids to specific cellular destinations.

    Transport:

    Vesicles transport proteins from one cisternae to another in the Golgi apparatus (cis to trans direction).

    Maturation of Proteins:

    Processes proteins received from the endoplasmic reticulum, modifying them into their mature forms

  • Picture of table outlining the functions of the Golgi apparatus:

  • Vesicles transport proteins to and from...?(3)

    • From the Golgi apparatus to lysosomes, the plasma membrane or theexterior.• From the plasma membrane to lysosomes.• From endosomes to the plasma membrane.

  • How is bud formation facilitated?

    By the binding of different coat proteins (e.g. COPS).

    By the binding of different coat proteins (e.g. COPS).

  • What are the COPI and COPII proteins?

    Are coat proteins that help packaged proteins bud off from RER

    Are coat proteins that help packaged proteins bud off from RER

  • What do v-SNARES and t-SNARES do in the target membrane?

    -V-SNARE binds to t-SNARE (target) in the target membrane-The transport vesicle fuses to the target membrane and the cargo delivered.

    -V-SNARE binds to t-SNARE (target) in the target membrane

    -The transport vesicle fuses to the target membrane and the cargo delivered.

  • A summary:

    -Endoplasmic reticulum is a single-membrane compartment consisting of two differentiated parts-rough and smooth, which carry out different functions.- The synthesis, modification, folding and transport of the proteins takes place in the rough endoplasmic reticulum (and GA).- Proteins move to the Golgi apparatus-single membrane compartment- in vesicles.- As proteins move through the Golgi apparatus, glycosylation is modified.- Signal sequences direct proteins to ER (remember SRP cycle).- From the Golgi apparatus, proteins are directed in vesicles to the lysosomes or to the cell membrane, or they are secreted