Cell Biology: Smooth Endoplasmic Reticulum
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Questions and Answers

What is the primary function of the Smooth Endoplasmic Reticulum?

  • Protein synthesis
  • Studded with ribosomes
  • Storing intracellular calcium
  • Transport vesicle synthesis (correct)

    • The Rough Endoplasmic Reticulum is studded with ribosomes on its outer surface.

    True

    What term describes the process of importing proteins into the Rough Endoplasmic Reticulum?

    Co-translational process

    The Smooth ER can also be referred to as ______.

    <p>transitional ER</p> Signup and view all the answers

    Match the following parts of the Endoplasmic Reticulum with their functions:

    <p>Smooth ER = Transport vesicle synthesis Rough ER = Protein synthesis Both = Lipid synthesis None = Contains ribosomes</p> Signup and view all the answers

    Which component forms a continuous structure with the Rough Endoplasmic Reticulum?

    <p>Nuclear envelope</p> Signup and view all the answers

    The internal compartment of the Endoplasmic Reticulum is referred to as the ______.

    <p>ER lumen</p> Signup and view all the answers

    Proteins are imported into the ER only after their translation is completed.

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

    What is the primary function of the trans Golgi network (TGN)?

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

    The Golgi apparatus is primarily responsible for the synthesis of proteins.

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

    What are the two types of glycosylation mentioned?

    <p>N-linked and O-linked</p> Signup and view all the answers

    The Golgi apparatus consists of stacks of membranes called __________.

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

    Match the following components of the Golgi apparatus with their descriptions:

    <p>Cis-face = Faces the endoplasmic reticulum Trans-face = Faces the cell membrane Medial cisterna = Middle sacs in the Golgi stack CGN = Cis Golgi network</p> Signup and view all the answers

    Which process within the Golgi apparatus is responsible for adding carbohydrate chains to proteins?

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

    O-linked sugars are added in groups of about 14 sugars within the Golgi.

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

    Name one function of the Golgi apparatus.

    <p>Protein modification or packaging</p> Signup and view all the answers

    What is the primary function of the signal recognition particle (SRP)?

    <p>To bind the ER signal sequence and dock the ribosome</p> Signup and view all the answers

    The stop-transfer sequence allows a polypeptide to be cleaved off completely from the translocon.

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

    What happens to a polypeptide after it is fed into the ER lumen?

    <p>The signal sequence is cleaved off, producing a soluble protein.</p> Signup and view all the answers

    The process of proteins being transported from the ribosome into the ER is called __________.

    <p>co-translational translocation</p> Signup and view all the answers

    Match the following processes with their descriptions:

    <p>Folding = Spontaneous process that helps proteins achieve their functional shape Disulfide bond formation = Stabilizes tertiary and quaternary protein structures Proteolytic cleavage = Breaks specific peptide bonds within proteins Multimeric protein assembly = Combines more than one polypeptide chain into a functional unit</p> Signup and view all the answers

    What amino acid sequence is typically found at the N-terminal of proteins destined for the Golgi, PM, or secretion?

    <p>A signal sequence of 16-30 amino acids</p> Signup and view all the answers

    Only properly folded proteins are transported to the Golgi for further processing.

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

    What role does the translocon play in protein synthesis?

    <p>It guides the translating polypeptide into the ER lumen.</p> Signup and view all the answers

    What happens to peptides produced by the release of ubiquitin molecules?

    <p>They may be further broken down to amino acids.</p> Signup and view all the answers

    Failure of proteasomes can lead to the accumulation of protein aggregates in cells.

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

    Name one neurological disorder caused by protein aggregates.

    <p>Alzheimer's disease</p> Signup and view all the answers

    The inner mitochondrial membrane contains proteins that create an electrochemical ______.

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

    Match the following components of the mitochondria with their characteristics:

    <p>Outer membrane = Contains pores for material transport Inner membrane = Folded into cristae Mitochondrial matrix = Location for the Krebs cycle Cristae = Increases surface area for enzymes</p> Signup and view all the answers

    Which of the following statements about the cellular respiration process is true?

    <p>The transition phase occurs after glycolysis and before the citric acid cycle.</p> Signup and view all the answers

    The ______ of the mitochondria contains ribosomes.

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

    What is the primary function of cristae in mitochondria?

    <p>To increase the surface area for oxidative phosphorylation enzymes.</p> Signup and view all the answers

    What is the primary function of peroxisomes?

    <p>Oxidation of long chain fatty acids</p> Signup and view all the answers

    Peroxisomes are only found in liver and kidney cells.

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

    What enzyme do peroxisomes contain to break down hydrogen peroxide?

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

    In animal cells, ____ can also perform beta-oxidation similar to peroxisomes.

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

    Match the conditions with their corresponding characteristics or functions:

    <p>Adrenoleukodystrophy = X-linked disorder affecting ABCD1 gene Beta-oxidation = Breakdown of long chain fatty acids Catalase = Enzyme that converts H2O2 to water and oxygen Oxidases = Enzymes that oxidize substances using oxygen</p> Signup and view all the answers

    What by-product is generated during the oxidation process in peroxisomes?

    <p>Hydrogen peroxide</p> Signup and view all the answers

    Peroxisomes perform the synthesis of bile acids.

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

    What condition can occur due to a lack of an essential enzyme in peroxisomes in Adrenoleukodystrophy?

    <p>Build up of long-chain saturated fatty acids</p> Signup and view all the answers

    Study Notes

    Endoplasmic Reticulum (ER)

    • The ER is a network of membranous tubules and sacs known as cisternae, with a luminal cavity separate from the cytosol.
    • Composed of two types: Smooth ER (lacks ribosomes) and Rough ER (studded with ribosomes).
    • Rough ER is involved in protein and phospholipid synthesis and processes proteins destined for various locations.
    • Smooth ER functions in the synthesis of transport vesicles and lipid metabolism.

    Functions of the Endoplasmic Reticulum

    • Synthesis of phospholipids, lipids, and proteins.
    • Storage of intracellular calcium ions.
    • Production of transport vesicles for protein transport to other organelles.

    Protein Import into Rough ER

    • Co-translational process where proteins are entered into the ER while being synthesized.
    • Involves translocating proteins with a specific ER signal sequence (16-30 amino acids).
    • Signal Recognition Particle (SRP) binds to the signal sequence and facilitates docking of the ribosome to the ER membrane via the translocon.

    Modifications in Rough ER

    • Protein folding is spontaneous, with chaperones helping ensure correct folding.
    • Disulfide bonds stabilize protein structures.
    • Proteolytic cleavage breaks specific peptide bonds.
    • Assembly into multimeric proteins occurs in the ER.

    Golgi Apparatus

    • Comprises stacks of membranes called cisternae, with distinct cis (entry) and trans (exit) faces.
    • Functions in final protein modification, sorting, and packaging.
    • Involved in glycosylation, phosphorylation, protein trimming, and sugar production.

    Glycosylation

    • Process begins in the ER and continues in the Golgi, creating glycoproteins and proteoglycans.
    • N-linked sugars are added as a group in the ER, while O-linked sugars are added one at a time in the Golgi.
    • Glycosylation is essential for protein targeting and ensuring proper cell interactions.

    Mitochondria

    • Enclosed by a dual membrane; the inner membrane forms folds (cristae) to increase surface area for oxidative phosphorylation.
    • Mitochondrial matrix contains enzymes for glucose breakdown.
    • Key site for ATP production through cellular respiration processes: glycolysis, transition phase, citric acid cycle, and electron transport chain.

    Peroxisomes

    • Abundant in liver and kidney cells; characterized by their ability to perform oxidation of long-chain fatty acids (beta-oxidation).
    • Generate hydrogen peroxide as a by-product, which is broken down by catalase.
    • Contain antioxidant enzymes to mitigate oxidative stress within cells.

    Adrenoleukodystrophy (ALD)

    • An X-linked disorder caused by a defect in the ABCD1 gene, affecting peroxisomal function.
    • Resulting enzyme deficiency leads to the accumulation of long-chain fatty acids, affecting myelin sheath integrity.
    • Symptoms include lethargy, skin changes, reduced blood sugar, and potential paralysis.
    • "Lorenzo's Oil," a mixture of unsaturated fatty acids, may slow disease progression.

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    Description

    Explore the structure and function of the Smooth Endoplasmic Reticulum (ER) in this quiz. Learn how this biosynthetic factory plays a crucial role in cellular processes by creating a network of membranous tubules and sacs. Discover the relationship between the ER membrane and the nuclear envelope in cell biology.

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