eukaryotic cells
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Questions and Answers

What is the primary function of the Nucleus in eukaryotic cells?

  • Synthesis of proteins
  • Site of lipid synthesis
  • Control center of the cell containing DNA (correct)
  • Energy storage

    • Which of the following organelles is characterized by having a double membrane?

  • Lysosome
  • Golgi Apparatus
  • Mitochondrion (correct)
  • Ribosome

    • What are the main functions of Smooth Endoplasmic Reticulum (ER)?

  • DNA replication and RNA synthesis
  • Lipid synthesis, glycogen metabolism, and calcium storage (correct)
  • Ribosome production and energy generation
  • Protein synthesis and calcium storage

    • Which substructure is a non-membrane bound organelle?

    <p>Cytoskeleton elements</p> Signup and view all the answers

    What is the role of the Nuclear Pore Complex (NPC)?

    <p>Regulating transport between the nucleus and cytoplasm</p> Signup and view all the answers

    What is the primary function of intermediate filaments in a cell?

    <p>Providing structural support</p> Signup and view all the answers

    Which microscopy technique is particularly useful for viewing live cells and monitoring cell movement?

    <p>Phase contrast microscopy</p> Signup and view all the answers

    In the process of differential centrifugation, what is expected to be found in the sediment after the first centrifugation step at 600 g?

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

    What is the purpose of confocal microscopy?

    <p>To provide sharper images of a specimen</p> Signup and view all the answers

    What process involves grinding cells and then repeatedly centrifuging to separate cellular components?

    <p>Cell fractionation</p> Signup and view all the answers

    What is the primary function of the Rough Endoplasmic Reticulum?

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

    Which statement about ribosomes is true?

    <p>Ribosomes consist of rRNA and proteins.</p> Signup and view all the answers

    Where do proteins synthesized on bound ribosomes predominantly go?

    <p>Export outside the cell or into membranes</p> Signup and view all the answers

    What is the main function of the Golgi Apparatus?

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

    What occurs within lysosomes?

    <p>Digestion of materials and aged organelles</p> Signup and view all the answers

    What distinguishes the fates of proteins produced from free versus bound ribosomes?

    <p>Free ribosome proteins are only for use within the cell.</p> Signup and view all the answers

    What is the role of peroxisomes in the cell?

    <p>Degradation of fatty acids and toxic compounds</p> Signup and view all the answers

    Which of the following enzymes are found within lysosomes?

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

    What happens during peroxisomal biogenesis?

    <p>Peroxisomes replicate and assemble anew.</p> Signup and view all the answers

    What is the main function of the mitochondrion?

    <p>Site of aerobic cellular respiration</p> Signup and view all the answers

    Which cytoskeletal element is primarily involved in movement during cell division?

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

    What role do vesicles play in the cell?

    <p>Storage and transport</p> Signup and view all the answers

    What differentiates cilia from flagella?

    <p>Cilia are shorter and move in an oar-like motion</p> Signup and view all the answers

    Which of the following best describes the function of vacuoles in plant cells?

    <p>Store ions and nutrients, and create pressure</p> Signup and view all the answers

    What is the role of microfilaments in a cell?

    <p>Cell contraction</p> Signup and view all the answers

    Which statement accurately describes the structure of cilia and flagella?

    <p>Both have a 9+2 arrangement of microtubules</p> Signup and view all the answers

    Which of the following components is not part of the endomembrane system?

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

    Study Notes

    Substructures of Animal & Plant Cells

    • The plasma membrane, internal membranes, and organelles, and the cytoskeleton are the major components of eukaryotic cells.
    • The plasma membrane has a surface area of 700 µm2, while the internal membranes & organelles and cytoskeleton have surface areas of 7,000 µm2 and 94,000 µm2 respectively.

    Organelles

    • Organelles are classified as either single-membrane, double-membrane, or non-membrane bound.
    • Double membrane-bound organelles include the nucleus, mitochondria, and chloroplast.
    • Single-membrane bound organelles include the smooth endoplasmic reticulum, rough endoplasmic reticulum, lysosomes, Golgi apparatus, peroxisomes, vacuoles, and vesicles.
    • Non-membrane bound organelles include ribosomes, proteasomes, cytoskeleton elements, cilia and flagella, centrioles, centrosomes, and basal bodies.

    Nucleus

    • Often the largest organelle in animal cells.
    • It is called the control center of the cell because it contains most of the cell's DNA.
    • The nucleus has a double-membrane structure which consists of an outer nuclear membrane, inter-membrane space, and inner nuclear membrane.
    • The inner material of the nucleus is called nucleoplasm.
    • The nucleolus is responsible for rRNA synthesis.
    • The nuclear lamina is the inner surface of the inner membrane.
    • Lamin proteins compose the nuclear lamina.
    • Nuclear pores are present within the nuclear envelop that regulate the transport of molecules into and out of the nucleus.

    Endoplasmic Reticulum (ER)

    • The ER is a single-membrane bound organelle that is an extensive network of closed, flattened membrane-bound sacs.
    • The ER membrane is continuous with the outer nuclear membrane and therefore the ER lumen is continuous with the inter-membrane space of the nucleus.
    • Rough ER has bound ribosomes whereas smooth ER lacks bound ribosomes.

    Smooth ER

    • It is continuous with rough ER.
    • Has 4 main functions:
      • Ca+2 storage
      • Glycogen metabolism
      • Lipid synthesis
      • Detoxification or modification of certain chemicals

    Rough ER

    • Located immediately adjacent to the nucleus.
    • Has ribosomes bound to its cytosolic surface.
    • Site for initial processing of newly synthesized proteins including those that will be exported from the cell, embedded in the plasma membrane, or found in the ER, Golgi apparatus and lysosomes.
    • The process of protein synthesis and initial processing takes place in the Rough ER lumen.

    Ribosomes

    • Sites of protein synthesis (translation).
    • Consist of rRNA and proteins.
    • Ribosomes may be either free in the cytosol or bound to the cytosolic surface of the rough ER.
    • A eukaryotic ribosome is composed of 2 subunits: a large subunit (60s) and a small subunit (40s).

    Fate of Proteins Synthesized on Bound or Free Ribosomes

    • Proteins made on bound ribosomes are meant for export from the cell, embedding into the plasma membrane, or targeting to the ER, Golgi or lysosomes.
    • Proteins made on free ribosomes are meant for use in the cytosol, nucleus, mitochondria, chloroplasts, peroxisomes.

    Golgi Apparatus

    • Series of flattened membrane-bound sacs (cisternae).
    • It is the post office of the cell and proteins from the rough ER arrive via transport vesicles.
    • Golgi shows polarity with cis and trans faces consisting of cis-Golgi, medial-Golgi and trans-Golgi.
    • Each part of the Golgi exhibits a range of differing luminal enzyme that modifies proteins.

    Secretory Pathway

    • Movement of proteins from bound ribosomes through the rough ER, via transport vesicles to the cis-Golgi, medial-Golgi, trans-Golgi, then to the cell membrane or lysosomes.

    Lysosome

    • The digestive system and garbage disposal system within an animal cell.
    • Contains hydrolytic enzymes that degrade polymers into monomeric subunits.
    • The optimal pH is around 4.8.
    • V-class proton pumps bring in H+ and Cl- channels bring Cl- into the lysosome.
    • Functions include digesting materials taken up by the cell, digesting damaged or aged organelles (autophagy), and playing a role in apoptosis.
    • Several human diseases are caused by defects in specific lysosomal enzymes and substrates accumulate in the lysosome.
    • Tay-Sachs disease is an example and it is caused by a deficiency in an enzyme that breaks down gangliosides, a type of glycolipid, which accumulate in nerve cells causing lysosomes to enlarge.

    Peroxisomes

    • Degrade fatty acids and toxic compounds.
    • Contain oxidases: hydrolytic enzymes that use O2 to oxidize organic substances.
    • They contain catalase that breaks down H2O2 (2H2O2  2H2O + O2).
    • Peroxisomes are self-assembling structures that only last a day.
    • Their reproduction is called peroxisomal biogenesis.

    Endomembrane System

    • A group of membranes and organelles in eukaryotic cells that works together to modify, package, and transport lipids and proteins. It is composed of the nuclear envelope, membranes of endoplasmic reticulum, Golgi apparatus, vesicles, and lysosomes.

    Mitochondrion

    • It is a double-membrane-bound organelle that has an outer membrane, intermembrane space.
    • The inner membrane forms cristae that are infoldings with a lumen termed matrix.
    • It contains circular mtDNA, granules, and mitoribosomes.
    • It is the site of aerobic cellular respiration and is often referred to as the powerhouse of the cell.

    Vesicles & Vacuoles

    • They are single-membrane bound sacs that serve a number of roles including storage, transport, endocytosis, and exocytosis.
    • Vacuoles act as storage sites for ions and nutrients in plant cells.
    • The uptake of water by osmosis creates pressure that pushes the membrane up against the cell wall.

    Cytoskeleton Elements

    • Responsible for maintaining and changing cell shape, internal transport, anchoring internal and external components, movement of the cell, movement of chromosomes during cell division, and scaffolding of the cell.
    • Three types:
      • Microtubules: polymers of α and β tubulin.
      • Microfilaments: polymers of actin.
      • Intermediate filaments: various proteins.

    Functions of Microtubules

    • Movement of chromosomes during cell division.
    • Component of centrioles, basal bodies, and centrosomes.
    • Serve as tracks for the movement of vesicles and vacuoles.
    • Internal scaffolding of eukaryotic cilia and flagella.

    Cilia & Flagella

    • Cytoplasmic extensions that act as locomotor structures.
    • Cilia are shorter and move in an oar-like motion.
    • Flagella are longer and move in a whip-like motion.
    • Cilia and flagella are structurally similar and share a 9+2 microtubule arrangement.

    Functions of Microfilaments

    • Cell contraction, e.g., cleavage furrow formation during cytokinesis.
    • Act as anchors for extracellular elements.
    • Cytoplasmic streaming.

    Functions of Intermediate Filaments

    • Scaffold for the cell.
    • Internal lining of the inner nuclear membrane.

    Microscopy

    • The basic microscope is a bright-field microscope.
    • Phase contrast and differential interference contrast microscopy can view details of live cells and monitor cell movement.
    • Fluorescence microscopy views proteins tagged with fluorescent proteins.
    • Confocal microscopy allows for sharper images of a specimen.

    Preparing Tissues for Microscopy

    • Tissues are fixed, embedded, and cut into sections.
    • Deconvolution fluorescence microscopy reduces blurring and produces sharper images.

    Differential Centrifugation

    • This technique separates cells and organelles based on size and density.
    • Cells are ground and then centrifuged at different speeds to separate different components.
    • The first centrifugation step at 600 g sediments the nuclei.
    • The second centrifugation step at 15,000 g sediments mitochondria, lysosomes, and ER.
    • The third centrifugation step at 100,000 g sediments ribosomes.
    • The final, soluble portion of the cytoplasm with no sediment is collected.

    Equilibrium Density-Gradient Centrifugation

    • This technique further separates organelles based on density using sucrose banding.
    • The organelle pellets are further separated by density using sucrose density gradients through centrifugation.

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    Eukaryotic Cells: An Overview

    Description

    Explore the essential components of animal and plant cells in this quiz. From the plasma membrane to various organelles like the nucleus and mitochondria, test your knowledge of cell structure and function. Understand the classifications of organelles and their unique characteristics.

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