Cell Membranes and Organelles-2
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What is the primary function of lysosomes within a cell?

  • Degradation of worn-out cellular components (correct)
  • Transport of nutrients
  • Synthesis of lipids
  • Storage of genetic material

    • In what way does autophagy function in relation to lysosomes?

  • It regulates cellular respiration
  • It synthesizes proteins
  • It degrades aged organelles (correct)
  • It promotes cell division

    • What is the result of a deficiency in lysosomal enzymes, such as in Tay-Sachs disease?

  • Increased nutrient absorption
  • Enlargement of nerve cells with swollen lipid-filled lysosomes (correct)
  • Enhanced breakdown of glycolipids
  • Reduced cell apoptosis rate

    • How do lysosomes contribute to cellular waste management?

    <p>By breaking down macromolecules and cellular debris</p> Signup and view all the answers

    Which characteristic differentiates vacuoles from lysosomes?

    <p>Vacuoles primarily store water and ions</p> Signup and view all the answers

    What is the role of turgor pressure generated by vacuoles in plant cells?

    <p>Promotes cell elongation during growth</p> Signup and view all the answers

    What process allows lysosomes to degrade materials taken into a cell?

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

    What is a typical feature of lysosomes found in a typical animal cell?

    <p>They vary greatly in size and shape</p> Signup and view all the answers

    What is the primary function of the cell wall?

    <p>Maintaining cell shape and rigidity</p> Signup and view all the answers

    Which of the following pathways is NOT involved in delivering materials to lysosomes?

    <p>Exocytic pathway</p> Signup and view all the answers

    How do endosomes function in the internalization of plasma-membrane proteins?

    <p>By sorting proteins for degradation</p> Signup and view all the answers

    Which molecule is specifically associated with the invagination of coated pits during the endocytic pathway?

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

    What type of materials are transported via the autophagic pathway to lysosomes?

    <p>Worn-out organelles and bulk cytoplasm</p> Signup and view all the answers

    What is the major distinction between cell walls and cell membranes?

    <p>Cell walls are much stronger than cell membranes.</p> Signup and view all the answers

    What role do hydrolytic enzymes play in lysosomes?

    <p>Degrading proteins, nucleic acids, and other large molecules</p> Signup and view all the answers

    Which of the following is a characteristic feature of the phagocytic pathway?

    <p>Moves whole cells and large insoluable particles to lysosomes</p> Signup and view all the answers

    What is the primary role of the N-terminal hydrophobic signal sequence in protein synthesis?

    <p>To ensure translation on the rough endoplasmic reticulum</p> Signup and view all the answers

    What happens to proteins synthesized on free ribosomes without a leader sequence?

    <p>They remain in the cytosol and lack specific tagging</p> Signup and view all the answers

    Which process is critical for directing enzymes to lysosomes?

    <p>Addition of mannose-6-phosphate in the Golgi complex</p> Signup and view all the answers

    How are secreted proteins released from the cell?

    <p>Via a controlled regulated manner or constitutive pathway</p> Signup and view all the answers

    What is the outcome for lysosomal proteins synthesized on bound ribosomes?

    <p>They move to the Golgi complex before acquiring a tagging modification</p> Signup and view all the answers

    What characterizes proteins synthesized on free ribosomes?

    <p>They remain free until they are tagged for specific organelles</p> Signup and view all the answers

    Which of the following statements is true regarding the ribosomes bound to the endoplasmic reticulum?

    <p>They synthesize proteins that are secreted or embedded in membranes</p> Signup and view all the answers

    Why do free ribosomes remain free during the protein synthesis process?

    <p>They synthesize only cytosolic proteins without specific tags</p> Signup and view all the answers

    What is the main function of SRP in the protein trafficking process?

    <p>To facilitate protein translocation into the ER</p> Signup and view all the answers

    How are lysosomal enzymes specifically modified during their processing?

    <p>By phosphorylating mannose residues</p> Signup and view all the answers

    What determines whether proteins synthesized on free ribosomes will remain in the cytosol?

    <p>Specific tags for organelle targeting</p> Signup and view all the answers

    What is the significance of the trans Golgi network in protein trafficking?

    <p>It modifies proteins for secretion or lysosomal delivery</p> Signup and view all the answers

    Which type of secretion mechanism involves the immediate release of proteins from the cell?

    <p>Constitutive secretion</p> Signup and view all the answers

    What role do transport vesicles play in protein trafficking?

    <p>To transport proteins between the ER and Golgi complex</p> Signup and view all the answers

    Which of the following is NOT a destination for proteins synthesized on free ribosomes?

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

    What marks the transition from free ribosome synthesis to bound ribosome synthesis for proteins?

    <p>Formation of a signal peptide</p> Signup and view all the answers

    Which statement regarding the nucleus is accurate?

    <p>Nuclear pores allow for selective transport between the nucleus and cytosol.</p> Signup and view all the answers

    What is the primary function of the nucleolus?

    <p>Synthesis of rRNA.</p> Signup and view all the answers

    How does the mitochondria contribute to cellular respiration?

    <p>It generates ATP through the oxidation of carbohydrates and proteins.</p> Signup and view all the answers

    Which of the following statements about the nuclear envelope is true?

    <p>It has multiple nuclear pores that facilitate transport.</p> Signup and view all the answers

    Where is chromatin predominantly found within the nucleus?

    <p>In regions of heterochromatin.</p> Signup and view all the answers

    What is a characteristic feature of mitochondria?

    <p>They can comprise up to 25 percent of cytoplasmic volume.</p> Signup and view all the answers

    Which of the following best describes chromatin?

    <p>DNA and proteins that package genetic material.</p> Signup and view all the answers

    Which function does the outer nuclear membrane serve?

    <p>It merges with the rough ER.</p> Signup and view all the answers

    What is the primary function of the inner mitochondrial membrane?

    <p>To host enzymes for ATP synthesis during sugar and lipid oxidation</p> Signup and view all the answers

    What structural feature of the inner mitochondrial membrane increases its surface area?

    <p>Folds known as cristae</p> Signup and view all the answers

    How do mitochondria replicate?

    <p>Through binary fission, similar to bacteria</p> Signup and view all the answers

    What initiates the process of apoptosis involving mitochondria?

    <p>The formation of pores in the mitochondrial membrane by proapoptotic proteins</p> Signup and view all the answers

    What is the main cause of diseases associated with mitochondria?

    <p>Errors in the 37 mitochondrial genes</p> Signup and view all the answers

    Which of the following statements about mitochondrial DNA (mtDNA) is accurate?

    <p>mtDNA is exclusively inherited from the mother in most multicellular organisms</p> Signup and view all the answers

    What is one of the primary components of the outer mitochondrial membrane?

    <p>Half lipid and half protein composition</p> Signup and view all the answers

    What role does acetyl coenzyme A (acetyl-CoA) play in metabolism?

    <p>It delivers the acetyl group to the citric acid cycle for oxidation</p> Signup and view all the answers

    Study Notes

    Cell Membranes and Organelles-2

    • Cells are constantly changing, exhibiting various movements like chromosome and vesicle translocation, and shape changes from crawling to swimming.

    • Eukaryotic cells contain a nucleus and many other organelles.

    • Different organelles have their unique membranes.

    • Unique proteins within each organelle determine its function.

    • Nucleus, mitochondria, and chloroplasts have two bilayer membranes.

    • Other organelles are surrounded by a single membrane.

    • Plant and fungal cells lack lysosomes but contain a large central vacuole performing lysosome functions.

    • Plant cell walls are primarily cellulose, providing shape and rigidity.

    • Animal cells lack cell walls and have an extracellular matrix made of collagen, glycoproteins, and other components, providing support and structure.

    Internal Organisation of the Cell

    • Materials move to lysosomes through three pathways: endocytic, phagocytic, and autophagic.

    • The endocytic pathway transports soluble molecules into the cell.

    • The phagocytic pathway moves whole cells or large insoluble particles.

    • The autophagic pathway moves worn-out organelles and cytoplasm.

    • Hydrolytic enzymes within lysosomes break down proteins, nucleic acids, and other large molecules in the acidic lysosomal lumen.

    Endosomes

    • Endosomes sort and return plasma membrane proteins and soluble materials from the extracellular medium.

    • They sort materials back to the membranes or to lysosomes for degradation.

    • Endocytic pathway involves invagination of a plasma membrane section into a coated pit, lined by proteins like clathrin.

    Lysosomes

    • Lysosomes are digestive sacs with an acidic lumen, breaking down materials internalized by the cell and worn-out parts.

    • Vary in size and shape and are numerous in animal cells.

    • Contain hydrolytic enzymes (lysosomal enzymes) for breaking down macromolecules.

    • Digest worn-out cellular membranes and organelles.

    • Recycle membrane proteins back to the plasma membrane.

    Autophagy

    • Autophagy (eating oneself) is a process where an aged organelle is degraded within a lysosome.

    • Materials taken in by endocytosis or phagocytosis can also be broken down in lysosomes.

    • In phagocytosis, bacteria and other large insoluble particles are engulfed and internalized.

    Deficiency in Lysosomal Enzymes

    • Tay-Sachs disease is caused by a defect in an enzyme that breaks down certain glycolipids (gangliosides).

    • These glycolipids are abundant in nerve cells. The condition results in a buildup of harmful substances.

    Vacuoles and Vesicles

    • Vacuoles store water, ions, and nutrients.

    • They break down macromolecules and help with cell elongation.

    • In plant cells, vacuoles are large, and the osmotic flow of water generates turgor pressure.

    Peroxisomes

    • Peroxisomes detoxify molecules and break down fatty acids to produce acetyl groups for biosynthesis.

    • Found in most animal cells and some plant cells (except erythrocytes).

    • Contain oxidases that use molecular oxygen to break down organic substances and form hydrogen peroxide (H₂O₂).

    • Also contain catalase, which breaks down hydrogen peroxide.

    Oxidation of Very Long Fatty Acids (VLFAs)

    • Peroxisomes are involved in the oxidation of very long fatty acids (VLFAs).

    • Mitochondria are responsible for oxidizing short, medium, and long-chain fatty acids.

    Endoplasmic Reticulum (ER)

    • Smooth ER synthesizes lipids, detoxifies hydrophobic compounds, and stores calcium.

    • Rough ER synthesizes, processes, and sorts proteins (secreted, lysosomal, or membrane-bound proteins). It is especially important in cells secreting proteins.

    Ribosomes

    • Ribosomes are the site of protein synthesis.

    • They are found free in the cytoplasm or attached to the rough ER.

    • Ribosomes translate mRNA into proteins. Proteins are critical to a cell's function.

    Protein Targeting. Signal Sequences

    • Proteins' final destination depends upon their signal sequences.

    • N-terminal hydrophobic signal sequences direct proteins to the rough ER.

    • Lysosomal enzymes are tagged with mannose-6-phosphate in the Golgi complex.

    Trafficking of Proteins synthesized on Bound/Free Ribosomes

    • Proteins destined for various destinations are transported appropriately using different methods.

    • Proteins destined for secretion or lysosomes will have initial targeting to organelles followed by modification.

    • Proteins that have no targeting or initiating sequence remain in the cytoplasm.

    The Nucleus

    • The nucleus houses a cell's genetic material (DNA).

    • The nuclear envelope has pores allowing exchange with the cytosol.

    • The nucleolus is a region within the nucleus that produces rRNA.

    Mitochondria

    • Mitochondria are critical for energy production (ATP).

    • They have two membranes, an outer and inner.

    • They contain their own DNA independently from the nuclear DNA.

    • The inner membrane folds extensively (cristae) to increase surface area.

    Chloroplasts

    • Chloroplasts are found only in plant cells.

    • Essential in photosynthesis, converting carbon dioxide, water, and sunlight into glucose, providing the plant and other organisms with energy and food.

    • Surrounded by two membranes including grana, thylakoids membranes, and stroma.

    Cytoskeleton

    • Provides structural support and aids in cell movement and division (mitosis).

    • Includes intermediate filaments, microtubules, and microfilaments.

    Golgi Apparatus and Vesicles

    • Processes and sorts proteins secreted by the rough ER including lysosomal proteins and membrane proteins.

    • Packages proteins into vesicles which move to other cell locations.

    • Also modifies proteins before they are transported.

    Cell Membranes and Organelles - Review Questions

    • Questions regarding the major organelles, their functions, protein type, and location within cells are addressed.

    • These questions focus on the roles of ribosomes, protein trafficking, types of secretions, targeting, phosphorylation of lysosomal proteins, and examples of diseases related to these processes.

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    Cell Membranes And Organelles-2 PDF

    Description

    Explore the complex structures and functions of eukaryotic cells in this quiz. Learn about organelles, their membranes, and the unique roles of proteins within these cellular components. Understand how these features contribute to cellular organization and function.

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