Cell Biology: Chromatin and Filaments
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Cell Biology: Chromatin and Filaments

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Questions and Answers

What is the primary function of euchromatin?

  • It stores proteins for future use.
  • It tightly compacts genetic material.
  • It acts as a reserve of DNA.
  • It facilitates the expression of DNA. (correct)

    • What are the building blocks of chromatin?

  • Proteins and RNA
  • DNA and nucleosomes
  • DNA and histones (correct)
  • DNA and ribosomes

    • What role do dynein and kinesin proteins play in cellular processes?

  • They synthesize proteins.
  • They move along microtubules in opposite directions. (correct)
  • They facilitate DNA replication.
  • They regulate cell adhesion.

    • Who discovered lysosomes and coined the term?

    <p>Christian de Duve</p> Signup and view all the answers

    What type of RNA is responsible for carrying the genetic information from DNA to the ribosomes?

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

    Which of the following enzymes is NOT typically found in lysosomes?

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

    What is the function of the Rough Endoplasmic Reticulum?

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

    What function do peroxisomes primarily serve?

    <p>Protecting the cell from hydrogen peroxide</p> Signup and view all the answers

    What is cytoplasm described as?

    <p>The liquid portion outside the nucleus</p> Signup and view all the answers

    During which phase does DNA duplication occur before cell division?

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

    What is the role of lysosomes in the cell?

    <p>Digestion of cellular waste</p> Signup and view all the answers

    What is the main role of catalase in peroxisomes?

    <p>Forming water and oxygen from hydrogen peroxide</p> Signup and view all the answers

    What do vacuoles primarily do in plant cells?

    <p>Store waste and maintain turgor pressure</p> Signup and view all the answers

    What best describes heterochromatin?

    <p>It is tightly packed and serves as a reserve.</p> Signup and view all the answers

    What distinguishes autophagy from autolysis?

    <p>Autophagy involves the breakdown of organelles, while autolysis leads to whole cell destruction.</p> Signup and view all the answers

    Who first described vacuoles during microscopic studies?

    <p>Anton van Leeuwenhoek</p> Signup and view all the answers

    What is the primary role of chloroplasts identified by Julius von Sachs?

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

    What is facilitated diffusion?

    <p>Net movement of particles from high to low concentration</p> Signup and view all the answers

    Which solution has a lower concentration of solutes than the cell?

    <p>Hypotonic solution</p> Signup and view all the answers

    What type of pressure is involved in osmosis?

    <p>Osmotic pressure</p> Signup and view all the answers

    What defines an isotonic solution in relation to a cell?

    <p>Equal concentration of solutes inside and outside the cell</p> Signup and view all the answers

    Which pigment is primarily involved in photosynthesis?

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

    What describes passive transport?

    <p>Transport without energy usage</p> Signup and view all the answers

    Which of the following results from a hypertonic solution?

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

    What is the primary characteristic of a hypotonic solution?

    <p>Higher solute concentration inside the cell</p> Signup and view all the answers

    Which process describes the movement of substances from low concentration to high concentration?

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

    What is phagocytosis commonly referred to as?

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

    How does endosmosis affect a cell placed in a hypotonic solution?

    <p>The cell swells and may undergo turgidity</p> Signup and view all the answers

    What term describes the maximum pressure that stops osmosis?

    <p>Osmotic pressure</p> Signup and view all the answers

    Which of the following processes is crucial for maintaining turgidity in plant cells?

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

    What is a significant role of osmosis in living organisms?

    <p>Transporting nutrients and releasing waste</p> Signup and view all the answers

    What happens to animal cells in a hypertonic solution?

    <p>They become flaccid and undergo plasmolysis</p> Signup and view all the answers

    What is primarily associated with lipid metabolism in the smooth endoplasmic reticulum?

    <p>Breakdown of fatty acids</p> Signup and view all the answers

    Which mechanism is specific to N-type glycosylation?

    <p>Addition of sugar to asparagine</p> Signup and view all the answers

    What is the primary function of the rough endoplasmic reticulum (RER)?

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

    Which type of enzyme is specifically involved in the detoxification process within the liver?

    <p>CYP 450</p> Signup and view all the answers

    Which of the following is NOT a function of the smooth endoplasmic reticulum?

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

    Which of the following statements correctly describes the ribosomes?

    <p>They synthesize proteins from mRNA.</p> Signup and view all the answers

    What characterizes the smooth endoplasmic reticulum (SER)?

    <p>Functions in lipid metabolism</p> Signup and view all the answers

    What type of proteins are synthesized in the endoplasmic reticulum destined for?

    <p>Cytoplasm and extracellular secretion</p> Signup and view all the answers

    Study Notes

    Chromatin

    • DNA and histone proteins form the nucleosome, a fundamental unit of chromatin structure.
    • Euchromatin is a loosely packed form of chromatin, associated with active gene expression, where DNA is transcribed into mRNA.
    • Heterochromatin is a tightly packed form of chromatin, typically associated with inactive or silenced genes.
    • Chromatin is thread-like, while a chromatid is a condensed form of chromatin.
    • DNA is transcribed into mRNA, which is then translated into proteins.

    Intermediate Filaments

    • These filaments regulate cell adhesion to the extracellular membrane and matrix.
    • Involved in cell-to-cell (intracellular) and cell-to-organelle interactions.
    • They help maintain cell shape and integrity.

    Microtubules

    • Composed of α-tubulin and β-tubulin subunits.
    • Function as a "railroad system" for intracellular transport, facilitated by motor proteins like dynein and kinesin.
    • Play a crucial role in cell division, forming spindle fibers that separate chromosomes.

    Rough Endoplasmic Reticulum (RER)

    • Studded with ribosomes, making it the site of protein synthesis.
    • Proteins synthesized on the RER are destined for:
      • Lysosomes (digestive enzymes)
      • Plasma membrane (membrane proteins)
      • Excretion out of the cell
    • RER also participates in protein folding and N-type glycosylation, adding sugar residues to proteins.

    Smooth Endoplasmic Reticulum (SER)

    • Lacks ribosomes.
    • Involved in lipid metabolism, breaking down lipids into fatty acids, phospholipids, and cholesterol, including steroid hormones like estrogen and testosterone.
    • Plays a role in biotransformation, detoxifying xenobiotics through enzymes like CYP450 (important for liver function).

    Golgi Apparatus

    • Composed of flattened membrane-bound sacs called cisternae.
    • Has a trans face (exit side) and a cis face (entry side).
    • Functions:
      • Receives materials from SER and RER.
      • Modifies proteins, including O-type glycosylation (adding sugar residues to serine and threonine).
      • Packages large molecules for transport to:
        • Plasma membrane
        • Lysosomes
        • Excretion out of the cell

    Ribosomes

    • Sites of protein synthesis.
    • Composed of ribosomal RNA (rRNA) and proteins.
    • Found free in the cytoplasm or bound to the RER.
    • Function: Translate mRNA into amino acid chains to produce proteins.

    Lysosomes

    • Discovered by Christian de Duve in 1955.
    • Known as "suicide bags" or "recycling bodies."
    • Contain hydrolytic enzymes (hydrolases) for breaking down large molecules, including:
      • Nucleases
      • Lipases
      • Proteases
      • Glucosidases
    • Involved in:
      • Autophagy: Breakdown of non-functional organelles.
      • Autolysis: Self-destruction of damaged cells, releasing enzymes for reuse.

    Peroxisomes

    • Protect cells from the harmful effects of hydrogen peroxide production.
    • Contain an oxidation enzyme, catalase, which breaks down hydrogen peroxide into oxygen and water.
    • Involved in:
      • Neutralizing free radicals.
      • Oxidative reactions, where oxygen is added.

    Cytoplasm

    • The jelly-like substance inside the cell membrane, containing the nucleus, organelles, and other cellular components.
    • Supports and suspends organelles, facilitates the movement of materials within the cell.
    • Two components:
      • Cytosol: The liquid portion surrounding the organelles.
      • Organelles: Membrane-bound structures with specific functions.

    Nucleus

    • Contains the cell's genetic material (DNA) in the form of chromatin.
    • Surrounded by a nuclear envelope with pores for the passage of molecules.
    • Contains nucleoplasm/karyoplasm, a fluid similar to cytoplasm, within the nucleus.

    Vacuoles

    • Large, membrane-bound sacs filled with fluid, primarily water.
    • More prominent in plant cells.
    • Functions:
      • Storage of nutrients and waste products.
      • Maintenance of turgor pressure in plant cells.

    Chloroplasts (Plants)

    • Sites of photosynthesis.
    • Contain chlorophyll, the green pigment that captures light energy.
    • Have a system of membranes, including thylakoids (flattened sacs containing chlorophyll) and grana (stacks of thylakoids).

    Transport of Materials Across Membrane

    Passive Transport

    • Does not require energy, moving molecules down their concentration gradient (from high to low concentration).
    • Types:
      • Simple diffusion: Movement of non-polar molecules across the membrane.
      • Facilitated diffusion: Movement of polar molecules with the help of transport proteins.

    Active Transport

    • Requires energy (ATP) to move molecules against their concentration gradient (from low to high concentration).
    • Examples:
      • Sodium-potassium pump.

    Bulk Transport

    • Movement of large molecules or particles across the membrane.
    • Types:
      • Exocytosis: Movement of materials out of the cell.
      • Endocytosis: Movement of materials into the cell, enclosed in a membrane vesicle.
        • Phagocytosis: "Cell eating" of large particles.
        • Pinocytosis: "Cell drinking" of fluids and small molecules.

    Diffusion

    • The spontaneous movement of particles from a region of higher concentration to a region of lower concentration.

    Osmosis

    • The movement of water or solvents across a semi-permeable membrane from a region of lower concentration to a region of higher concentration, in response to the concentration gradient of solutes.
    • Types:
      • Endosmosis: Movement of water into the cell, causing it to swell or become turgid.
      • Exosmosis: Movement of water out of the cell, causing it to shrink or become flaccid.
    • Osmotic solutions:
      • Isotonic: Same solute concentration inside and outside the cell.
      • Hypertonic: Higher solute concentration outside the cell, causing water to move out of the cell.
      • Hypotonic: Higher solute concentration inside the cell, causing water to move into the cell.

    Osmotic Pressure

    • The minimum pressure required to stop the movement of water across a semi-permeable membrane.
    • In a hypertonic solution, the osmotic pressure is higher than the pressure inside the cell, forcing water out. In hypotonic, the pressure is lower, drawing water in.
    • Examples:
      • Feeling thirsty after salty food (hypertonic solution).
      • Swelling of resins and seeds when soaked in water (hypotonic solution).
      • Dialysis of the kidney (regulation of water and solute levels in the blood).
      • Water and mineral movement in plants.

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    Description

    This quiz covers essential concepts in cell biology, focusing on chromatin structure, intermediate filaments, and microtubules. You'll learn about the roles of euchromatin and heterochromatin, the significance of intermediate filaments in cell adhesion, and the function of microtubules in intracellular transport and cell division.

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