Golgi Apparatus Structure and Function Quiz
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Questions and Answers

What is the primary structure of the Golgi apparatus?

  • A single-layer membrane
  • A rigid cell wall
  • A hollow sphere
  • A folded membrane (correct)

    • Which part of the Golgi apparatus faces the rough endoplasmic reticulum?

  • Trans Golgi
  • Cis Golgi (correct)
  • Golgi stack
  • Golgi lumen

    • What is the function of the rough endoplasmic reticulum in relation to the Golgi apparatus?

  • It stores vesicles before transport.
  • It modifies and synthesizes proteins. (correct)
  • It synthesizes lipids for the Golgi.
  • It performs cellular respiration.

    • What type of bilayer surrounds the Golgi apparatus?

    <p>Phospholipid bilayer</p> Signup and view all the answers

    What occurs when the rough endoplasmic reticulum has finished modifying proteins?

    <p>It buds off a vesicle containing modified proteins.</p> Signup and view all the answers

    Which organelle is located adjacent to the Golgi apparatus?

    <p>Rough endoplasmic reticulum</p> Signup and view all the answers

    What is a defining characteristic of the Golgi apparatus's structure?

    <p>Convoluted or coiled membranes</p> Signup and view all the answers

    What does the process of 'budding off a vesicle' refer to in the context of cellular transport?

    <p>The release of modified proteins for transport</p> Signup and view all the answers

    What is the function of COP1 in cellular transport?

    <p>To facilitate retrograde transport of vesicles</p> Signup and view all the answers

    Which transport process is regulated by COP2?

    <p>Movement of glycoproteins from the rough ER to the cis Golgi</p> Signup and view all the answers

    What happens to glycoproteins once they are released from vesicles in the Golgi?

    <p>They undergo various modifications</p> Signup and view all the answers

    Which type of modification can occur to N-linked glycosylation in the Golgi?

    <p>Trimming of sugar residues</p> Signup and view all the answers

    Which of the following describes the anterograde transport process facilitated by COP2?

    <p>Transporting vesicles to the cell membrane</p> Signup and view all the answers

    What is a primary role of the Golgi apparatus in protein processing?

    <p>Modification and packaging of proteins</p> Signup and view all the answers

    What specific direction does retrograde transport refer to?

    <p>From cis Golgi to rough ER</p> Signup and view all the answers

    What characterizes the endpoints of vesicle transport in cells?

    <p>They include the cell membrane and lysosomes</p> Signup and view all the answers

    What is the primary role of the Golgi apparatus in relation to proteins?

    <p>Modification and packaging of proteins</p> Signup and view all the answers

    Which cellular structure does the Golgi apparatus receive proteins from?

    <p>Rough endoplasmic reticulum</p> Signup and view all the answers

    How does a protein know to return to the rough ER after being modified by the Golgi?

    <p>It has a COP1 protein coat</p> Signup and view all the answers

    What happens to proteins that are identified with mannose 6-phosphate?

    <p>They are directed to become lysosomes</p> Signup and view all the answers

    What process is described when proteins are taken back into the cell for recycling?

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

    Which method does the Golgi use to modify proteins by adjusting the sugar residues?

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

    What role do clathrins play in the Golgi's function?

    <p>They coat proteins destined for the cell membrane or excretion</p> Signup and view all the answers

    In which part of the Golgi apparatus do proteins initially enter after being synthesized?

    <p>Cis Golgi</p> Signup and view all the answers

    What is the process of adding a sugar residue to the hydroxy group of an amino acid called?

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

    Which two amino acids can have a sugar residue added to their hydroxy groups?

    <p>Serine and Threonine</p> Signup and view all the answers

    What is the role of phosphorylation in protein modification?

    <p>To introduce a phosphate group to residues</p> Signup and view all the answers

    Which type of glycosylation involves trimming existing sugar residues?

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

    Which sugar is mentioned as potentially being phosphorylated in the context?

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

    Which of the following describes the consequence of adding a sugar to a protein?

    <p>It may activate the protein.</p> Signup and view all the answers

    What type of group is involved in N-linked glycosylation?

    <p>Amine group</p> Signup and view all the answers

    How does the addition of a sugar residue potentially affect a protein’s activity?

    <p>By inducing a conformational change</p> Signup and view all the answers

    What type of proteins are critical for directing vesicles to the Golgi apparatus?

    <p>COP2 proteins</p> Signup and view all the answers

    Which side of the Golgi faces the rough endoplasmic reticulum?

    <p>Cis Golgi</p> Signup and view all the answers

    What occurs after proteins are modified in the Golgi apparatus?

    <p>They bud off to the cell membrane or become lysosomes</p> Signup and view all the answers

    What shape describes the Cis Golgi?

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

    Which side of the Golgi apparatus faces towards the cell membrane?

    <p>Trans Golgi</p> Signup and view all the answers

    Which of the following best describes the role of the Golgi apparatus?

    <p>Modifies, sorts, and packages proteins</p> Signup and view all the answers

    What is the internal area of the Golgi apparatus referred to as?

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

    After proteins are sorted in the Golgi, what might happen to them?

    <p>They can be either secreted or directed to lysosomes</p> Signup and view all the answers

    What is the primary function of the cristae found in the inner mitochondrial membrane?

    <p>To increase the surface area for metabolic reactions</p> Signup and view all the answers

    Which of the following statements about the outer mitochondrial membrane is correct?

    <p>It is highly permeable.</p> Signup and view all the answers

    What are TOM and TIM in the context of mitochondrial function?

    <p>Channels for protein transport through the outer and inner membranes, respectively</p> Signup and view all the answers

    Which metabolic reaction occurs in the mitochondrial matrix?

    <p>Krebs cycle</p> Signup and view all the answers

    What is a side effect of the electron transport chain in mitochondria?

    <p>Formation of reactive oxygen species</p> Signup and view all the answers

    Which type of acid is generated during fatty acid oxidation in the mitochondrial matrix?

    <p>Acetyl-CoA</p> Signup and view all the answers

    What notable feature does mitochondrial DNA have compared to nuclear DNA?

    <p>It is inherited maternally</p> Signup and view all the answers

    Which of the following components is essential for the process of oxidative phosphorylation?

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

    Which process occurs in the mitochondrial matrix and produces high-energy molecules?

    <p>Krebs cycle</p> Signup and view all the answers

    What type of ribosomes are found in mitochondria?

    <p>70S ribosomes</p> Signup and view all the answers

    During which process is acetyl-CoA generated from fatty acids in the mitochondrial matrix?

    <p>Beta oxidation</p> Signup and view all the answers

    Which cycle converts toxic ammonia into less toxic urea?

    <p>Urea cycle</p> Signup and view all the answers

    What role does the mitochondria play in apoptosis?

    <p>It releases cytochrome c.</p> Signup and view all the answers

    Which statement correctly describes mitochondrial DNA (mtDNA)?

    <p>It is circular and replicates independently.</p> Signup and view all the answers

    Which process can amino acids and odd-chain fatty acids undergo in the mitochondrial matrix?

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

    What theory explains the origin of mitochondria as once independent cells?

    <p>Endosymbiotic theory</p> Signup and view all the answers

    Which metabolic process is involved in converting pyruvate into acetyl-CoA?

    <p>Pyruvate conversion</p> Signup and view all the answers

    What is the primary purpose of the Krebs cycle?

    <p>To generate electron carriers like NADH and FADH2</p> Signup and view all the answers

    What occurs during beta-oxidation in the mitochondrial matrix?

    <p>Conversion of fatty acids to acetyl-CoA</p> Signup and view all the answers

    How does mitochondrial DNA (mtDNA) replicate?

    <p>Through a process called fission</p> Signup and view all the answers

    Which of the following is a function of mitochondrial ribosomes?

    <p>Translate RNA molecules for mitochondrial functions</p> Signup and view all the answers

    Which statement about the endosymbiotic theory is accurate?

    <p>Mitochondria originated from engulfed bacteria.</p> Signup and view all the answers

    What is the role of cytochrome c in mitochondria?

    <p>Facilitate apoptosis by activating caspases</p> Signup and view all the answers

    Which cycle occurs partially in the mitochondrial matrix and is involved in detoxifying ammonia?

    <p>Urea cycle</p> Signup and view all the answers

    What is the primary purpose of the cristae in the inner mitochondrial membrane?

    <p>To increase surface area for metabolic reactions</p> Signup and view all the answers

    Which molecules are transported by the mitochondrial membrane for metabolic reactions?

    <p>Carbohydrates, fatty acids, and amino acids</p> Signup and view all the answers

    What crucial role does the mitochondrial matrix play in energy production?

    <p>It conducts the Krebs Cycle and processes pyruvate.</p> Signup and view all the answers

    What is the effect of the electron transport chain on protons?

    <p>It generates a concentration gradient by moving them to the intermembrane space.</p> Signup and view all the answers

    Which process is not associated with the functions of the mitochondrial matrix?

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

    Which component of the mitochondrial membrane is responsible for the electron transport chain?

    <p>Inner membrane</p> Signup and view all the answers

    What substance is formed as a byproduct of the electron transport chain?

    <p>Reactive oxygen species (ROS)</p> Signup and view all the answers

    Which of the following statements about the outer mitochondrial membrane is correct?

    <p>It contains channels that facilitate selective transport.</p> Signup and view all the answers

    Study Notes

    Golgi Apparatus Structure and Function

    • The Golgi apparatus is composed of stacked, flattened, membrane-bound sacs called cisternae.
    • The cis Golgi network (CGN) faces the rough endoplasmic reticulum (RER).
    • The RER synthesizes proteins and modifies them before sending them to the Golgi apparatus.
    • The Golgi apparatus is surrounded by a phospholipid bilayer.
    • After modifications are complete in the RER, proteins are packaged into transport vesicles and sent to the Golgi apparatus.
    • The Golgi apparatus is located near the endoplasmic reticulum.
    • A defining characteristic of the Golgi apparatus is its stacked structure, consisting of multiple cisternae.
    • Budding off a vesicle refers to the process of creating a small, membrane-bound sac that pinches off from the Golgi apparatus to transport molecules.
    • COP1 proteins regulate retrograde transport, which moves molecules back to the ER.
    • COP2 regulates anterograde transport, which moves molecules forward from the ER to the Golgi and eventually to the trans Golgi network (TGN).
    • Glycoproteins are modified and sorted in the Golgi and then transported to other organelles or secreted from the cell.
    • The Golgi can further modify N-linked glycosylation by trimming or adding sugar residues.
    • Anterograde transport facilitated by COP2 moves cargo from the RER to the Golgi to the plasma membrane.
    • The Golgi apparatus plays a crucial role in protein processing, including modifications and sorting.
    • Retrograde transport refers to the movement of molecules from the Golgi back to the ER.
    • Vesicle transport ends in the Golgi, lysosome, or plasma membrane.
    • The Golgi apparatus modifies, sorts, and packages proteins for transport to other organelles or for secretion from the cell.
    • The Golgi apparatus receives proteins from the endoplasmic reticulum via transport vesicles.
    • Proteins that have a signal sequence indicating they need to return to the ER are recognized and bundled within the lumen of the Golgi transport vesicles.
    • Proteins identified with mannose 6-phosphate are destined for lysosomes, where they will be used for degradation of cellular debris.
    • Endocytosis is the process of taking back proteins into the cell for recycling.
    • The Golgi modifies proteins by adjusting the sugar residues through glycosylation.
    • Clathrin proteins form a cage-like structure around vesicles that transport specific proteins from the Golgi to other destinations.
    • Proteins initially enter the cis Golgi network after being synthesized.
    • Adding a sugar residue to the hydroxy group of an amino acid is called glycosylation.
    • Serine and threonine are amino acids that can have a sugar residue added to their hydroxy groups.
    • Phosphorylation plays a role in protein modification by adding a phosphate group to a protein.
    • N-linked glycosylation involves trimming existing sugar residues from the protein.
    • Mannose is a sugar that can undergo phosphorylation.
    • Adding a sugar to a protein can influence its structure, function, and stability.
    • N-linked glycosylation involves the attachment of a sugar residue to a nitrogen atom in the side chain of an asparagine amino acid.
    • Adding a sugar residue can potentially affect a protein's activity by changing its shape or its ability to interact with other molecules.
    • SNARE proteins are essential for directing vesicles to the correct target membrane, such as the Golgi apparatus.
    • The cis Golgi network faces the rough endoplasmic reticulum (RER).
    • After proteins are modified in the Golgi apparatus, they are sorted and packaged into vesicles for transport to their final destination.
    • The cis Golgi is typically shaped like a cup.
    • The trans Golgi network faces the cell membrane.
    • The Golgi apparatus is involved in modifying, sorting, and packaging proteins and lipids for delivery to other organelles or secretion from the cell.
    • The internal area of the Golgi apparatus is called the lumen.
    • After proteins are sorted in the Golgi, they may be packaged into vesicles for transport to other organelles, secreted from the cell, or retained within the Golgi for further processing.

    Mitochondrial Structure

    • Sausage-shaped organelle found in both animal and plant cells
    • Double-layered membrane: outer membrane and inner membrane
    • Outer membrane is highly permeable
    • Inner membrane is less permeable and has selective proteins for transport
    • Intermembrane space lies between outer and inner membranes, rich in proton ions
    • Inner membrane folds into cristae, increasing surface area for metabolic reactions
    • Space enclosed by inner membrane is called the mitochondrial matrix, contains mitochondrial DNA and ribosomes

    Mitochondrial Functions

    • Mitochondrial protein transport is essential
    • Unfolded proteins, synthesized in the cytoplasm by ribosomes, are transported through channels called TOM and TIM
    • TOM is on the outer membrane and TIM is on the inner membrane
    • Once inside the mitochondrial matrix, proteins are folded properly
    • Miscellaneous transport includes movement of nutrients, ions, and molecules like carbohydrates, fatty acids, and amino acids for metabolic reactions
    • Electron transport chain occurs primarily on the inner membrane
    • High-energy electrons from NADH and FADH2, formed during metabolic reactions like the Krebs cycle, are transferred to protein complexes
    • Electrons are passed down the chain, pumping protons into the intermembrane space
    • This proton gradient drives ATP production via oxidative phosphorylation
    • A side effect of the electron transport chain is the formation of reactive oxygen species (ROS) such as hydrogen peroxide and superoxide radicals

    Mitochondrial Matrix Functions

    • The mitochondrial matrix is the site of several metabolic reactions:
      • Krebs cycle: A series of reactions where acetyl-CoA (produced from pyruvate) is oxidized, generating ATP, NADH, and FADH2
      • Fatty acid oxidation (beta-oxidation): The breakdown of fatty acids into acetyl-CoA
      • Gluconeogenesis: The synthesis of glucose from non-carbohydrate sources
      • Urea cycle: A metabolic pathway that removes ammonia from the body
    • Mitochondrial DNA:
      • Maternal DNA
      • Encodes for some, but not all, of the proteins needed for mitochondrial function
    • Mitochondrial Ribosomes:
      • The mitochondrial matrix contains ribosomes, which are responsible for translating mitochondrial mRNA into proteins

    Mitochondrial Functions

    • Mitochondrial Matrix: The mitochondrial matrix is the space enclosed by the inner membrane of the mitochondria. It contains a variety of enzymes, including those involved in the Krebs cycle, beta oxidation, and urea cycle.
    • Krebs cycle: This cycle occurs in the mitochondrial matrix and produces NADH and FADH2, high-energy molecules that carry electrons to the electron transport chain.
    • Beta oxidation: Fatty acids are broken down into acetyl-CoA through beta oxidation, which also occurs within the mitochondrial matrix.
    • Urea cycle: This cycle occurs partially in the mitochondrial matrix and partially in the cytoplasm. It converts toxic ammonia into less toxic urea, which can be excreted.
    • Gluconeogenesis: Amino acids and odd-chain fatty acids can be converted back into glucose through gluconeogenesis, which partially occurs in the mitochondrial matrix and partially in the cytoplasm.
    • Heme synthesis: This process occurs in both the mitochondrial matrix and cytoplasm and uses Krebs cycle intermediates to produce heme.
    • Ketogenesis: Acetyl-CoA can be shunted into the synthesis of ketones within the mitochondrial matrix.
    • Apoptosis: The mitochondria plays a role in programmed cell death (apoptosis) by releasing cytochrome c, a protein that activates caspases, enzymes that damage cell membranes and organelles.
    • Mitochondrial DNA (mtDNA): The mitochondria has its own circular DNA molecule that replicates to produce more mitochondria through fission.
    • Mitochondrial Ribosomes: Mitochondria contains 70S ribosomes, which are different from the 80S ribosomes found in the cytoplasm of eukaryotic cells. These ribosomes translate mtDNA into proteins, which account for 15% of the mitochondria's total protein content.
    • Endosymbiotic Theory: The theory that mitochondria were once independent bacterial cells that were engulfed by early eukaryotic cells.

    Mitochondria Structure

    • Sausage-shaped organelle within the cell
    • Contains two membranes: an outer membrane and an inner membrane.
    • The outer membrane is highly permeable.
    • The inner membrane is less permeable and contains highly regulated transporters to control what moves in and out.
    • The intermembrane space is located between the outer membrane and inner membrane.
    • The intermembrane space is rich in proton ions, which play an important role in the electron transport chain.
    • The inner membrane folds inward to create structures called cristae, which increase the surface area for metabolic reactions.
    • Enclosed within the inner membrane is the mitochondrial matrix.
    • The mitochondrial matrix contains mitochondrial DNA and ribosomes, allowing the mitochondria to produce some of its own proteins.

    Mitochondria Function

    • The mitochondrial membrane plays a crucial role in protein transport.
    • Unfolded proteins, generated from the nucleus, are transported into the mitochondria through channels called TOMs and TIMS.
    • The mitochondrial membrane transports a variety of molecules, including carbohydrates, fatty acids, and amino acids, which are necessary for metabolic reactions.
    • The inner mitochondrial membrane is responsible for the electron transport chain.
    • Proteins embedded in the inner membrane, including Complexes I–IV, are involved in electron transport.
    • NADH and FADH2, produced during metabolic processes, deliver high-energy electrons to the electron transport chain.
    • The electron transport chain pumps protons from the mitochondrial matrix to the intermembrane space.
    • The resulting gradient of protons powers ATP synthase, which uses the energy to produce ATP through the process of oxidative phosphorylation.
    • One of the negative side effects of the electron transport chain is the production of reactive oxygen species (ROS).

    Mitochondrial Matrix Function

    • The mitochondrial matrix serves as a site for a variety of metabolic reactions.
    • Pyruvate, a product of glycolysis, enters the mitochondria and is converted to acetyl-CoA.
    • Acetyl-CoA undergoes a series of reactions called the Krebs Cycle, which generates NADH and FADH2 molecules, critical to energy production.
    • The mitochondrial matrix also plays a role in processes such as gluconeogenesis, the urea cycle, and fatty acid oxidation.

    Mitochondrial DNA and Ribosomes

    • Mitochondria possess their own DNA (mtDNA), distinct from nuclear DNA.
    • mtDNA replicates to allow for the division of mitochondria through a process called fission.
    • mtDNA undergoes transcription, generating RNA molecules.
    • These RNA molecules are translated by mitochondrial ribosomes (70S ribosomes), which are distinct from the 80S ribosomes found in the cytoplasm.
    • Mitochondrial ribosomes synthesize proteins, primarily for the mitochondria's own functions.

    Other Mitochondrial Functions

    • Mitochondria play a crucial role in protein transport, both across their outer and inner membranes.
    • They utilize the electron transport chain, located in the inner mitochondrial membrane, for ATP production through oxidative phosphorylation.
    • They are involved in miscellaneous transport processes, moving molecules across their membranes.
    • Mitochondria participate in apoptosis, programmed cell death, by releasing cytochrome c from the matrix, which activates caspases, leading to cellular breakdown.

    Endosymbiotic Theory

    • The endosymbiotic theory suggests that mitochondria originated from ancient bacteria that were engulfed by eukaryotic cells.
    • This theory is supported by the presence of mtDNA and 70S ribosomes in mitochondria, similar to those found in bacteria.

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