Eukaryotic Cell Membranes Quiz
77 Questions
1 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary function of the Trans-Golgi Network?

  • Delivery of material to the endocytic pathway
  • Modification of the plasma membrane
  • Sorting of newly-made proteins (correct)
  • Packaging of secreted proteins

    • What is the role of actin in endocytosis?

  • It forms the primary structure of the endosome.
  • It provides pulling force for phagocytosis and micropinocytosis. (correct)
  • It regulates the pH gradient in the endocytic pathway.
  • It is directly involved in the fusion of vesicles with the target membrane.

    • What is the mechanism by which cells take up large particles, such as bacteria, during phagocytosis?

  • Actin-driven ruffles and engulfment (correct)
  • Macropinocytosis
  • Passive diffusion through the plasma membrane
  • Clathrin-mediated endocytosis

    • Which of the following statements about frustrated phagocytosis is TRUE?

    <p>It provides insights into the steps involved in the phagocytic process.</p> Signup and view all the answers

    What is the basis for the conclusion that membrane recycling occurs during phagocytosis?

    <p>There is no change in cell size despite a large amount of membrane being internalized.</p> Signup and view all the answers

    What is a key characteristic of macropinocytosis?

    <p>It allows cells to take up a large volume of extracellular material.</p> Signup and view all the answers

    What is the role of LDL receptors in clathrin-mediated endocytosis?

    <p>They capture LDL particles in circulation and facilitate their uptake.</p> Signup and view all the answers

    What is the function of dynamin in clathrin-mediated endocytosis?

    <p>It pinches off the clathrin-coated vesicle from the plasma membrane.</p> Signup and view all the answers

    How does the pH gradient contribute to the function of the endocytic pathway?

    <p>It facilitates the dissociation of cargo from receptors in the early endosome.</p> Signup and view all the answers

    What is the role of intraluminal vesicles (ILVs) in the late endosome?

    <p>They encapsulate cargo destined for degradation.</p> Signup and view all the answers

    What is the primary function of lysosomes?

    <p>Degrade cellular waste and foreign material.</p> Signup and view all the answers

    What is the origin of most mitochondrial and peroxisomal proteins?

    <p>They are encoded by the nuclear genome and imported into the organelles.</p> Signup and view all the answers

    What is the main function of the porins in the outer mitochondrial membrane?

    <p>Allow the entry of molecules up to 5,000 kDa.</p> Signup and view all the answers

    Where is the proton gradient generated for oxidative phosphorylation in mitochondria?

    <p>Across the inner mitochondrial membrane into the intermembrane space.</p> Signup and view all the answers

    Which of the following is NOT a characteristic of the inner mitochondrial membrane?

    <p>Permeable to large molecules like proteins.</p> Signup and view all the answers

    What is the significance of the circular mitochondrial genome?

    <p>It suggests a possible bacterial origin for mitochondria.</p> Signup and view all the answers

    What is the primary method by which proteins are imported into mitochondria?

    <p>Proteins are synthesized as unfolded polypeptide chains and then translocated</p> Signup and view all the answers

    What role do chaperone proteins play during the process of protein translocation into mitochondria?

    <p>They prevent proteins from folding prematurely during translocation</p> Signup and view all the answers

    How do peroxisomes differ from mitochondria in their structure?

    <p>Peroxisomes lack DNA and ribosomes while mitochondria contain their own DNA</p> Signup and view all the answers

    What is the function of the OXA complex in mitochondria?

    <p>Inserts and folds proteins that have previously entered the mitochondrial matrix</p> Signup and view all the answers

    What is a key characteristic of the TOM complex?

    <p>It creates a pore through which proteins are translocated into the mitochondrial matrix</p> Signup and view all the answers

    In what manner do proteins enter the peroxisome?

    <p>Through a process that requires ATP but doesn't necessitate unfolding</p> Signup and view all the answers

    Which of the following factors drives the translocation of the positively charged signal sequence through the inner mitochondrial membrane?

    <p>The electrochemical H+ gradient established by electron transport</p> Signup and view all the answers

    What happens to the signal sequence of precursor proteins after translocation into the mitochondrial matrix?

    <p>It is cleaved off by mitochondrial enzymes</p> Signup and view all the answers

    What is a common function performed by peroxisomes in liver cells?

    <p>Detoxification processes, including alcohol metabolism</p> Signup and view all the answers

    What occurs during the mitochondrial life cycle process of fission?

    <p>Mitochondria split into separate entities, one containing debris</p> Signup and view all the answers

    What is the primary effect of cholesterol on biological membranes?

    <p>Makes membranes less permeable to small molecules</p> Signup and view all the answers

    What distinguishes integral membrane proteins from peripheral membrane proteins?

    <p>Integral proteins are embedded by a hydrophobic domain</p> Signup and view all the answers

    What role do tight junctions play in epithelial cells?

    <p>Maintain different phospholipid compositions in membranes</p> Signup and view all the answers

    How does the cytoskeleton contribute to red blood cell shape?

    <p>Through spectrin's network that allows flexibility</p> Signup and view all the answers

    What is the significance of membrane asymmetry in blood coagulation?

    <p>Facilitates nucleation site for coagulation cascade</p> Signup and view all the answers

    What is a characteristic feature of membrane transport proteins?

    <p>They predominantly transport specific solutes like sugars and ions</p> Signup and view all the answers

    Which type of transport requires energy to move solutes?

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

    What is the role of lipid rafts in cellular signaling?

    <p>Cluster signaling molecules for enhanced signaling efficiency</p> Signup and view all the answers

    How does the phospholipid bilayer impact the passage of polar molecules?

    <p>The bilayer acts as a barrier to polar molecules and ions</p> Signup and view all the answers

    What determines an individual's blood group in the ABO system?

    <p>Structure of oligosaccharides attached to membrane proteins</p> Signup and view all the answers

    What happens to red blood cells when placed in a hypotonic solution?

    <p>They can potentially burst due to fluid influx</p> Signup and view all the answers

    What is necessary for the activity of small G proteins in relation to membranes?

    <p>Fatty acid modifications that allow cycling on and off membranes</p> Signup and view all the answers

    What contributes to the non-uniform lipid composition in biological membranes?

    <p>The formation of microdomains or rafts</p> Signup and view all the answers

    What defines the electrochemical gradient affecting solute transport across membranes?

    <p>Membrane potential combined with the concentration gradient</p> Signup and view all the answers

    How does the transport speed of channel proteins compare to that of carrier proteins?

    <p>Channel proteins can transport ions significantly faster than carrier proteins</p> Signup and view all the answers

    What is a key role of ion channels in cells?

    <p>To form selective pathways for rapid ion movement</p> Signup and view all the answers

    What occurs during the transcellular transport of glucose in epithelial cells?

    <p>A combination of several carriers is involved in glucose uptake</p> Signup and view all the answers

    What is the state of DNA in non-dividing cells?

    <p>Loosely packed into a structure known as chromatin</p> Signup and view all the answers

    What role does heterochromatin play in transcriptional activity?

    <p>Heterochromatin is primarily composed of DNA that is less transcriptionally active</p> Signup and view all the answers

    What hypothesis suggests the origin of the nucleus in eukaryotic cells?

    <p>Endosymbiosis and membrane invagination hypothesis</p> Signup and view all the answers

    What is not a feature of carrier proteins in the context of solute transport?

    <p>They can transport ions faster than channels</p> Signup and view all the answers

    What characterizes euchromatin in relation to gene transcription?

    <p>It contains most of the actively transcribed genes</p> Signup and view all the answers

    What best describes the role of membrane potential in solute transport?

    <p>It contributes to the establishment of the electrochemical gradient</p> Signup and view all the answers

    What best describes the nuclei of eukaryotic cells?

    <p>Nuclei are dynamic structures that can change based on transcriptional status</p> Signup and view all the answers

    Which of the following accurately describes the function of the sodium/potassium pump?

    <p>It maintains the electrochemical gradients by pumping Na+ out and K+ into the cell</p> Signup and view all the answers

    In the context of electrochemical transport, what are coupled carriers?

    <p>Proteins that transport two different solutes simultaneously, often against gradients</p> Signup and view all the answers

    What distinguishes the open confirmation of ion channels?

    <p>Channels allow rapid movement of ions down their gradients</p> Signup and view all the answers

    Which of the following accurately describes the difference between the plasma membrane and organelle membranes?

    <p>The plasma membrane serves as the outer boundary of the cell, while organelle membranes divide the cytoplasm into compartments.</p> Signup and view all the answers

    What is the significance of the phospholipid structure in biological membranes?

    <p>Their amphipathic nature allows them to form a bilayer, separating the internal cell environment from the external environment.</p> Signup and view all the answers

    Which of the following correctly describes the 'flip-flop' movement of phospholipids in a membrane?

    <p>Phospholipids can move between the inner and outer leaflets, a rare event.</p> Signup and view all the answers

    What is the relationship between the saturation of fatty acid chains and membrane fluidity?

    <p>Unsaturated chains with more double bonds lead to increased fluidity because they are less tightly packed.</p> Signup and view all the answers

    How do organisms living in cold temperatures adapt their membranes to maintain fluidity?

    <p>They increase the proportion of unsaturated fatty acids, introducing more double bonds and increasing fluidity.</p> Signup and view all the answers

    What is the significance of the negatively charged nature of phosphatidyl serine in biological membranes?

    <p>It plays a role in apoptosis and other cellular processes.</p> Signup and view all the answers

    Based on the information provided, why are all biological membranes considered fluid?

    <p>The lateral movement of phospholipids within the membrane bilayer.</p> Signup and view all the answers

    Which of the following accurately describes the role of cholesterol in biological membranes?

    <p>Cholesterol is an amphipathic molecule that modulates membrane fluidity.</p> Signup and view all the answers

    Which of the following is NOT a function of the nucleolus?

    <p>Processing of mRNA</p> Signup and view all the answers

    What is the function of the nuclear lamina?

    <p>To provide structural support for the nucleus</p> Signup and view all the answers

    What is the role of the scramblase in maintaining membrane asymmetry?

    <p>It catalyzes the exchange of phospholipids between the two leaflets of the membrane</p> Signup and view all the answers

    Which of the following is TRUE about the endoplasmic reticulum (ER)?

    <p>The ER is connected to the nuclear envelope.</p> Signup and view all the answers

    Which of the following statements about the movement of molecules through nuclear pores is TRUE?

    <p>Large molecules can only enter the nucleus by active transport.</p> Signup and view all the answers

    What is the primary function of the Golgi apparatus?

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

    Which of the following is NOT a type of vesicle coat?

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

    What is the role of SNARE proteins in vesicular transport?

    <p>They help to ensure that vesicles fuse with the correct target membrane</p> Signup and view all the answers

    Which of the following is a characteristic of the smooth endoplasmic reticulum (SER)?

    <p>It is involved in the synthesis of steroid hormones</p> Signup and view all the answers

    Which of the following molecules would be most likely to enter the nucleus by diffusion?

    <p>A small lipid molecule</p> Signup and view all the answers

    Which of the following organelles is NOT part of the secretory pathway?

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

    What is the difference between a v-SNARE and a t-SNARE?

    <p>v-SNAREs are found in the vesicle membrane, while t-SNAREs are found in the target membrane</p> Signup and view all the answers

    What is the role of chaperone proteins in the ER?

    <p>They help to fold newly synthesized proteins into their correct three-dimensional structures</p> Signup and view all the answers

    Which of the following is NOT true about the nuclear envelope?

    <p>It is permeable to all molecules</p> Signup and view all the answers

    What is the function of the 'flippase' in maintaining membrane asymmetry?

    <p>It moves phospholipids from the extracellular leaflet to the cytosolic leaflet</p> Signup and view all the answers

    Which of the following statements about the structure of the nuclear pore is TRUE?

    <p>The nuclear pore is asymmetrical</p> Signup and view all the answers

    Study Notes

    Eukaryotic Cell Membranes

    • Biological membranes vary in appearance by location and function.
      • Plasma membrane: Forms the cell boundary and regulates passage of materials.
      • Organelle membranes: Divide the cytoplasm into compartments for optimal function.
    • Fundamental membrane properties:
      • Barrier: Prevents random molecule movement
      • Flexible: Adapts to cell shape changes
      • Self-repairing: Recovers from damage
      • Continuous: forms a closed compartment
      • Selectively permeable: Controls movement of specific molecules
    • Membrane composition:
      • Lipids, proteins, and carbohydrates form all membranes (prokaryotic and eukaryotic, plasma, and intracellular).
      • Oligosaccharide chains (sugars) are attached to lipids and proteins, frequently branched
      • Phospholipids: key component; move laterally in the bilayer.
        • Slower movement between leaflets (flip-flop).
        • Each phospholipid layer is a leaflet.
      • Fluidity depends on fatty acid chain saturation:
        • More double bonds (unsaturated) = more fluidity, less tight packing
        • Warm-blooded animals have less unsaturated chains than cold-blooded animals to maintain fluidity
    • Major membrane phospholipids:
      • Four main classes
      • Phosphatidylserine: Only negatively charged phospholipid, critical for apoptosis and other processes.
      • Cholesterol: Amphipathic; packs between phospholipids, reducing membrane permeability and rigidity.
        • Local effect, doesn't make membrane overall rigid.
    • Bacterial cell membranes: Single phospholipid layer.

    Lipid Bilayer Structure

    • Phospholipids are amphipathic.
      • Hydrophilic polar headgroup
      • Hydrophobic non-polar tails
    • Lipids form micelles or bilayers in aqueous solutions.
    • Bilayers prefer sealed compartments due to energy reasons.

    Membrane Proteins

    • Membrane proteins embedded in specific orientations for specific functions (e.g., receptor proteins).
    • Protein mobility varies, reflecting functions and attachments.
    • Integral proteins: Directly inserted into the membrane by hydrophobic regions.
    • Peripheral proteins:
      • Associate with integral proteins or directly bind lipids
      • Some are covalently bound to lipids which insert into membrane.
    • Small G proteins: Cycle between membranes and cytosol via fatty acid modifications.
    • Membrane lipids are not homogenous, form clusters (microdomains)
    • Cholesterol and sphingolipids form microdomains (rafts), increasing membrane thickness.
    • Tight junctions: Prevent movement between apical and basolateral membranes, maintaining different membrane compositions in these domains.

    Membrane Asymmetry and Interactions

    • Membranes are asymmetric: different lipid compositions in each leaflet.
    • Protein orientation consistent across the membrane
    • Blood groups (ABO): Determined by oligosaccharide chains on plasma membrane proteins and lipids.
    • O is universal donor, AB is universal acceptor.
    • Membrane asymmetry (e.g., phosphatidylserine localization) is crucial for:
      • Coagulation
      • Cell recognition and clearance
    • Membrane transport proteins.

    Membrane Transport

    • Phospholipid bilayer acts as a barrier to most solutes (especially polar molecules and ions).
    • Hydrophobic molecules can cross easily.
    • Active vs. Passive Transport:
      • Passive: Solutes move down concentration gradient.
      • Active: Solutes move against gradient, requiring energy.
    • Carriers, Channels:
      • Channels transport solutes faster (up to 100 million ions/sec).
      • Channels are significantly faster than carriers.
      • Channels are highly selective based on ion size and charge
      • Ion channels: Form channels, open and close rapidly, regulated by various factors, critical for neuronal signaling, and diverse in function
      • Carriers: Undergo conformational changes to transport solutes.
    • Electrochemical gradients:
      • Combination of membrane potential and concentration gradient that influences direction of solute movement
    • Coupled carriers: Movement of one solute drives other(s).
    • Transport driven by gradients of other ions (Na+, H+) in different organisms.

    Transcellular Transport of Glucose

    • Glucose uptake driven by Na+ electrochemical gradient.
    • Involves apical Na+/glucose symporter, basal Na+/K+ pump, and basal glucose uniporter.

    Nucleus

    • Defining eukaryotic feature; separates transcription and translation for greater flexibility of gene expression.
    • DNA is packaged into chromosomes using histone proteins.
    • Chromatin: DNA is loosely packed in non-dividing cells.
    • Chromosomes are visible prior to cell division.

    Nucleus Structure and Function

    • Heterochromatin: Densely stained, less transcribed DNA regions.
    • Euchromatin: Less densely stained, active transcription areas.
    • Nucleolus: rRNA processing; ribosome synthesis.
    • Nuclear pores: Control size-dependent entry of molecules into the nucleus.

    Secretory Pathway

    • Lipids are synthesized in the ER.
    • Scramblases equilibrate lipids, allowing fluidity but not asymmetry.
    • Flippase maintains lipid asymmetry.
    • ER is continuous with nuclear envelope, forming a network of tubes and flattened sacs called cisternae.

    Vesicular Transport

    • Transport between ER and Golgi (and other compartments) occurs via vesicles.
    • Vesicle coats aid in formation and target recognition.
    • SNARE proteins mediate vesicle fusion.

    Golgi Apparatus

    • Processes, sorts, and packages secreted proteins and cell membrane components.
    • Modification reactions take place in Golgi cisternae.
    • Trans-Golgi Network (TGN): Major sorting station for proteins.

    Endocytosis

    • Multiple endocytic pathways exist for taking up various materials (e.g. nutrients, large molecules).
    • Examples of pathways include phagocytosis, pinocytosis, and receptor-mediated endocytosis.
    • Phagocytosis: Internalizing large particles.
    • Pinocytosis: Internalizing small liquids or molecules.
    • Receptor-mediated endocytosis: Clathrin-mediated uptake of specific molecules.

    Mitochondria and Peroxisomes

    • Mitochondria have double membrane, outer and inner.
    • Mitochondrial cristae maximize inner membrane surface area.
    • Mitochondria contain their own DNA.
    • Mitochondrial DNA inherited maternally.
    • Mitochondria undergo fusion, fission, mitophagy.
    • Proteins imported using signal sequences and membrane translocators (TOM, TIM, etc.).
    • Peroxisomes: single-membrane organelles for oxidative reactions (e.g., fatty acid metabolism, detoxification).
    • Proteins use signal sequences and translocators to enter peroxisomes.

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Description

    Test your knowledge on the structure and function of eukaryotic cell membranes. This quiz covers various aspects such as plasma membranes, organelle membranes, and their fundamental properties. Dive into the details of membrane composition and fluidity to understand how cells maintain their integrity.

    More Like This

    Mastering Biological Membranes
    10 questions

    Mastering Biological Membranes

    PrettyMoose avatar
    PrettyMoose
    Membrane Biologiche e Eucariotiche
    43 questions

    Membrane Biologiche e Eucariotiche

    VivaciousPlumTree avatar
    VivaciousPlumTree
    Biología Celular: Membrana y Citoplasma
    40 questions

    Biología Celular: Membrana y Citoplasma

    FruitfulWaterfall1764 avatar
    FruitfulWaterfall1764
    Biología Celular: Estructuras y Funciones
    48 questions

    Biología Celular: Estructuras y Funciones

    InsightfulAnemone avatar
    InsightfulAnemone
    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser