Cell Theory and Types of Cells
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Questions and Answers

Which of the following statements accurately describes the function of ribosomes within eukaryotic cells?

  • Ribosomes regulate the passage of molecules in and out of the nucleus.
  • Ribosomes synthesize DNA for cell replication.
  • Ribosomes primarily produce energy for cellular functions.
  • Ribosomes are responsible for synthesizing proteins. (correct)

    • What is the primary distinguishing feature between prokaryotic and eukaryotic cells?

  • Eukaryotic cells contain ribosomes, while prokaryotic cells do not.
  • Eukaryotic cells possess a nuclear envelope surrounding their DNA. (correct)
  • Prokaryotic cells contain membrane-bound organelles distinct from eukaryotic cells.
  • Prokaryotic cells have a membrane-bound nucleus, whereas eukaryotic cells do not.

    • Which structure within a eukaryotic cell is primarily involved in gene expression and regulation?

  • Nucleus (correct)
  • Ribosomes
  • Nuclear lamina
  • Nucleolus

    • What role do nuclear pores play in the functioning of eukaryotic cells?

    <p>They regulate the transport of molecules between the nucleus and the cytoplasm.</p> Signup and view all the answers

    How are chromatin and chromosomes related to each other during cell division?

    <p>Chromatin tightly wraps into chromosomes, allowing for easier segregation during cell division.</p> Signup and view all the answers

    Which of the following correctly describes the endomembrane system in eukaryotic cells?

    <p>It includes various membranes that differ in structure and function to support different cellular jobs.</p> Signup and view all the answers

    What is the main function of the nucleolus found within the nucleus of eukaryotic cells?

    <p>To produce ribosomal RNA (rRNA).</p> Signup and view all the answers

    How does the structure of the nuclear envelope contribute to its function?

    <p>It consists of a double membrane, enhancing genetic material protection and molecule regulation.</p> Signup and view all the answers

    What is the primary function of the rough endoplasmic reticulum?

    <p>Synthesize and transport secretory proteins</p> Signup and view all the answers

    Which component of the endomembrane system is directly involved in the sorting and shipping of proteins?

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

    What distinguishes the smooth endoplasmic reticulum from the rough endoplasmic reticulum?

    <p>Absence of ribosomes</p> Signup and view all the answers

    In the context of the endomembrane system, what role do transport vesicles play?

    <p>Transfer membrane and contents between compartments</p> Signup and view all the answers

    What is a notable feature of the Golgi apparatus that aids in the sorting of products?

    <p>The addition of molecular ID tags such as phosphate groups</p> Signup and view all the answers

    Which option correctly describes the relationship between the nuclear envelope and the endoplasmic reticulum?

    <p>The nuclear envelope is confluent with the rough endoplasmic reticulum.</p> Signup and view all the answers

    What specific function does the smooth endoplasmic reticulum perform in liver cells?

    <p>Break down toxins and drugs</p> Signup and view all the answers

    Where does the Golgi apparatus receive materials from?

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

    What is the structure of the Golgi apparatus commonly described as?

    <p>Stacked pancakes</p> Signup and view all the answers

    What is the primary function of the cell wall in plant cells?

    <p>To protect and support the plant cell</p> Signup and view all the answers

    Which component is found between the primary cell wall and the plasma membrane in mature plant cells?

    <p>Secondary cell wall</p> Signup and view all the answers

    What role do plasmodesmata play in plant cells?

    <p>Facilitate communication and transport between adjacent cells</p> Signup and view all the answers

    What is the characteristic structure of the primary cell wall during the early stages of plant growth?

    <p>Thin and flexible</p> Signup and view all the answers

    Which polysaccharide is primarily found in the middle lamella of plant cells?

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

    What happens to the primary cell wall as the plant cell matures?

    <p>It hardens as stronger materials are added</p> Signup and view all the answers

    Which of the following correctly describes the relationship between the primary and secondary cell walls?

    <p>The secondary wall is added to the interior of the primary wall</p> Signup and view all the answers

    Which function is NOT associated with peroxisomes?

    <p>Breaking down carbohydrates for energy</p> Signup and view all the answers

    What is the primary role of microtubules in the cytoskeleton?

    <p>Separating chromosomes during cell division</p> Signup and view all the answers

    Which characteristic distinguishes intermediate filaments from microfilaments and microtubules?

    <p>They provide a more permanent framework within the cell.</p> Signup and view all the answers

    What distinguishes eukaryotic cilia and flagella from each other?

    <p>Cilia move in a whip-like manner, while flagella move in a wave-like motion.</p> Signup and view all the answers

    Which statement accurately describes the composition of microfilaments?

    <p>They consist of actin protein in a double twisted chain.</p> Signup and view all the answers

    What is the main function of the cytoskeleton?

    <p>To provide mechanical support and maintain cell shape.</p> Signup and view all the answers

    How do peroxisomes differ from mitochondria?

    <p>Peroxisomes detoxify harmful substances while mitochondria primarily generate energy.</p> Signup and view all the answers

    Which structure anchors eukaryotic cilia and flagella to the cell?

    <p>Basal body</p> Signup and view all the answers

    The stroma is primarily associated with which cellular structure?

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

    What role does catalase play in peroxisomes?

    <p>It converts hydrogen peroxide into water and oxygen.</p> Signup and view all the answers

    What is the primary function of lysosomes in animal cells?

    <p>Hydrolyze food and damaged cell parts</p> Signup and view all the answers

    Which statement about mitochondria is accurate?

    <p>Mitochondria generate ATP through cellular respiration</p> Signup and view all the answers

    What is autophagy in the context of lysosomes?

    <p>The massive rupture of lysosomes leading to cell self-digestion</p> Signup and view all the answers

    What is the role of the contractile vacuoles in freshwater protists?

    <p>Pump excess water out of the cell</p> Signup and view all the answers

    How does the internal structure of chloroplasts facilitate photosynthesis?

    <p>The stroma provides a site for sugar synthesis, while granum contains pigments</p> Signup and view all the answers

    What is a significant consequence of lysosome rupture in a cell?

    <p>It triggers apoptosis or controlled cell death</p> Signup and view all the answers

    What indicates that lysosomal enzymes operate optimally at a specific pH level?

    <p>They are inactive at neutral pH</p> Signup and view all the answers

    Which cellular structure is involved in both energy production and growth?

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

    What feature differentiates vacuoles from lysosomes?

    <p>Vacuoles store nutrients, whereas lysosomes digest them</p> Signup and view all the answers

    What is a key characteristic of mitochondria?

    <p>They have their own DNA and ribosomes</p> Signup and view all the answers

    Study Notes

    Cell Theory

    • Cells are the fundamental units of structure and function in living things.
    • All living things are composed of cells.
    • Cells arise from pre-existing cells.

    All Cells

    • Surrounded by a plasma (cell) membrane.
    • Contain cytosol (a semi-fluid substance within the membrane).
    • Contain organelles (structures with specific functions).
    • Contain DNA (deoxyribonucleic acid).
    • Contain ribosomes (responsible for protein synthesis).

    Prokaryotic Cells (Bacteria)

    • Lack a nucleus.
    • Lack membrane-bound organelles.
    • Have DNA in the nucleoid region.

    Eukaryotic Cells (Plants, Animals, Fungi, Protists)

    • Have a nucleus enclosed by a nuclear envelope.
    • Contain membrane-bound organelles.
    • DNA is contained within the nucleus.

    Nucleus and Nuclear Envelope

    • Contains genes, including additional genes in mitochondria and chloroplasts.
    • Surrounded by a double membrane (separated by 20-40 nm space).
    • Contains nuclear pores lined by proteins (the nuclear pore complex), regulating the passage of molecules.
    • The nuclear side of the envelope is lined with a network of protein filaments (nuclear lamina) maintaining its shape.
    • Contains chromatin (DNA and histone proteins).
    • Chromatin condenses to form chromosomes during cell division.
    • The nucleolus is a densely stained, ribosome-producing region within the nucleus.

    Ribosomes

    • Synthesize proteins.
    • Composed of proteins and RNA (rRNA).
    • Can be free in the cytosol or bound to the rough endoplasmic reticulum (ER) or nuclear envelope.
    • Free ribosomes make proteins for the cytosol.
    • Bound ribosomes make proteins for cell membranes or export.

    Endomembrane System

    • Many membranes in eukaryotic cells are part of the endomembrane system.
    • Components of this system include the nuclear envelope, endoplasmic reticulum (ER), Golgi apparatus, lysosomes, vacuoles, and the plasma membrane.
    • These components are directly continuous or connected via transfer of membrane sacs (vesicles).

    Endoplasmic Reticulum (ER)

    • Membranous tubules forming internal fluid-filled spaces (cisternae).
    • Continuous with nuclear envelope.
    • Rough ER (with ribosomes): Synthesizes proteins, modifies proteins, and inserts proteins into membranes.
    • Smooth ER (lacks ribosomes): Synthesizes lipids, metabolizes carbohydrates, detoxifies poisons, and stores calcium ions.

    Golgi Apparatus

    • Flattened membranous sacs (cisternae).
    • Has cis (receiving) and trans (shipping) faces.
    • Modifies, sorts, packages, and ships proteins.

    Lysosomes

    • Membrane-bound sacs containing hydrolytic (digestive) enzymes.
    • Breakdown of food, cellular debris, and damaged cell parts.
    • Maintain a low internal pH; preventing accidental "self destruction" if a lysosome ruptures.
    • Involved in autophagy (recycling of cell's organelles and macromolecules)

    Vacuoles

    • Membrane-bound sacs with varied functions.
    • Food vacuoles (formed by phagocytosis).
    • Contractile vacuoles (in protists, pump excess water).
    • Large central vacuole (in plant cells): Stockpile proteins or inorganic ions; dispose of metabolic byproducts; storing defensive compounds.

    Mitochondria

    • Not part of the endomembrane system.
    • Double membrane (outer and inner).
    • Inner membrane folds (cristae) increase surface area for chemical reactions.
    • Fluid-filled space inside inner membrane (matrix).
    • Contains DNA, ribosomes, enzymes for cellular respiration (breaks down sugars, fats, and other fuels in the presence of oxygen).
    • Site of cellular respiration, generates ATP (adenosine triphosphate).

    Chloroplasts

    • Not part of the endomembrane system; found in plants and algae.
    • Site of photosynthesis.
    • Convert solar energy to chemical energy and synthesize sugars from CO2 and H2O.
    • Double membrane (outer and inner).
    • Contains thylakoid sacs in stacks (grana), surrounded by stroma.
    • Site of photosynthesis for plants.

    Peroxisomes

    • Single membrane; built from proteins and lipids in cytosol.
    • Involved in metabolism (e.g., breakdown of fatty acids, detoxification).
    • Contain enzymes that transfer hydrogen to oxygen, producing hydrogen peroxide (H2O2), and contain the enzyme catalase which converts H2O2 to H2O and O2.

    Cytoskeleton

    • Network of fibers extending throughout the cytoplasm.
    • Provides mechanical support and maintains cell shape.
    • Anchors organelles.
    • Dynamic; structure changes over time.
    • Three main types: microtubules, microfilaments, and intermediate filaments.

    Microtubules

    • Hollow tubes made of tubulin protein subunits.
    • Support, motility (cilia, flagella), and chromosome movements.
    • Movement inside cell of organelles and vesicles.

    Microfilaments

    • Two intertwined actin strands.
    • Cell shape maintenance and cell motility (e.g., muscle contraction, ameboid movement).

    Intermediate Filaments

    • Fibrous proteins.
    • Cell shape maintenance and anchors nucleus and organelles.

    Animal Cell Extracellular Matrix (ECM)

    • Outside cell membrane; composed of glycoproteins (mostly collagen).
    • Strengthen tissues and serve as channels for transmitting external stimuli.
    • Three types of intercellular links: tight junctions, desmosomes, and gap junctions.

    Plant Cell Walls

    • Found in plants, fungi, and some prokaryotes.
    • Made of cellulose and other polysaccharides.
    • Protects, supports, and maintains shape.
    • Primary cell wall is thin, flexible, and formed in young plants.
    • Middle lamella is a layer between cell walls of adjacent cells/pectins(thick polysaccharide).
    • Secondary cell wall may be formed in older plants and placed between the primary wall and plasma membrane. (several laminated layers).
    • Plasmodesmata (channels through walls) allows cytosol to pass between adjacent plant cells.

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