Cell Biology: Cytoplasm and Cytoskeleton
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Questions and Answers

Which of the following organelles is responsible for the synthesis of lipids and steroids?

  • Lysosomes
  • Rough ER
  • Golgi Apparatus
  • Smooth ER (correct)

    • What is the primary function of ribosomes?

  • Break down waste products
  • Modify proteins
  • Produce ATP
  • Synthesize proteins (correct)

    • Which of the following is TRUE about the nucleus?

  • It is the site of lipid synthesis.
  • It is surrounded by a single membrane.
  • It is responsible for protein synthesis.
  • It contains the cell's genetic information. (correct)

    • What is the function of the nucleolus?

    <p>Produce ribosomes (D)</p> Signup and view all the answers

    Which of the following organelles is responsible for the modification and packaging of proteins?

    <p>Golgi Apparatus (C)</p> Signup and view all the answers

    Which of the following is a characteristic of mitochondria?

    <p>Contains its own DNA (D)</p> Signup and view all the answers

    What are the folds in the inner mitochondrial membrane called?

    <p>Cristae (D)</p> Signup and view all the answers

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

    <p>Cellular respiration (D)</p> Signup and view all the answers

    What is the difference between free ribosomes and bound ribosomes?

    <p>Free ribosomes produce proteins for internal use, while bound ribosomes produce proteins for export. (A)</p> Signup and view all the answers

    Which of the following is NOT a characteristic of eukaryotic ribosomes?

    <p>They are similar in size to prokaryotic ribosomes. (D)</p> Signup and view all the answers

    What is the role of the cytoskeleton in a cell?

    <p>Provides structural support and aids in movement. (C)</p> Signup and view all the answers

    Which of the following is NOT a state of the nucleus?

    <p>Cytoplasmic (B)</p> Signup and view all the answers

    Which of the following is associated with the synthesis of ribosomal RNA (rRNA)?

    <p>Nucleolar organizers (NOR) (B)</p> Signup and view all the answers

    What is the difference between heterochromatin and euchromatin?

    <p>Heterochromatin is tightly packed, while euchromatin is loosely packed. (A)</p> Signup and view all the answers

    Which of the following is a function of the nucleus?

    <p>Synthesis of RNA from DNA (A)</p> Signup and view all the answers

    Which type of cell typically has multiple nuclei?

    <p>Muscle cells (A)</p> Signup and view all the answers

    What is the primary composition of the dispersed phase in the cytoplasm?

    <p>1% minerals and 9% organic compounds (A)</p> Signup and view all the answers

    Which movement of the cytoplasm describes the flow around two vacuoles in opposite directions?

    <p>Fountaining movement (C)</p> Signup and view all the answers

    Which type of filament in the cytoskeleton provides mechanical support and is important for maintaining cell shape?

    <p>Intermediate filaments (D)</p> Signup and view all the answers

    What is the approximate diameter of microtubules in the cytoskeleton?

    <p>25 nm (B)</p> Signup and view all the answers

    What role does the cytoplasm primarily serve within the cell?

    <p>Environment for suspending organelles and metabolic reactions (C)</p> Signup and view all the answers

    What are the three functional regions of the Golgi apparatus?

    <p>Cis, medial, trans (B)</p> Signup and view all the answers

    What is the main function of lysosomes?

    <p>Intracellular digestion (C)</p> Signup and view all the answers

    Which type of plastid is primarily responsible for photosynthesis?

    <p>Chloroplast (D)</p> Signup and view all the answers

    Which of the following is NOT a type of lysosome?

    <p>Tertiary lysosome (A)</p> Signup and view all the answers

    What do autolysosomes do?

    <p>Remove damaged organelles (D)</p> Signup and view all the answers

    What happens to a centrosome before cell division?

    <p>It duplicates itself (C)</p> Signup and view all the answers

    Which of the following statements is true regarding hydrolytic enzymes in lysosomes?

    <p>They require acidic conditions to function (A)</p> Signup and view all the answers

    What type of plastids store proteins as aleurone grains?

    <p>Proteinoplasts (C)</p> Signup and view all the answers

    What do chromoplasts contribute to a plant cell?

    <p>Coloring of fruits and flowers (A)</p> Signup and view all the answers

    Which component of the Golgi apparatus processes vesicles from the endoplasmic reticulum?

    <p>Cis cisternae (B)</p> Signup and view all the answers

    Flashcards

    Cytoplasm

    Gel-like solution inside the cell, consisting of water and suspended particles.

    Dispersive phase

    The part of cytoplasm primarily made up of water, about 90% of total cytoplasm.

    Cytoskeleton

    A network of protein filaments providing structural support to the cell.

    Microtubules

    Tubules with a diameter of about 25 nm, involved in cell processes like transport and division.

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    Actin filaments

    Thin filaments (about 7 nm) providing mechanical support and maintaining cell shape.

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    Mitochondria division

    Mitochondria divide similarly to bacteria, showing evolutionary links.

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    Golgi apparatus

    Organelles with cisternae for processing and packaging cellular products.

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    Cisternae

    Flattened membrane-bound structures in the Golgi apparatus.

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    Post-translational modification

    Changes made to proteins after synthesis for functionality.

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    Lysosomes

    Membrane-bound vesicles for intracellular digestion, containing hydrolytic enzymes.

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    Hydrolytic enzymes

    Acidic enzymes in lysosomes that digest cellular waste.

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    Primary lysosomes

    Lysosomes formed in the ER and Golgi containing inactive enzymes.

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    Chloroplasts

    Plastids containing chlorophyll for photosynthesis in plant cells.

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    Centrosome

    Structure containing two centrioles that organize cell division.

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    Plastids

    Organelles in plant cells that perform various functions like storage and pigmentation.

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    Cytoplasm movement

    The movement of cytoplasm and organelles within a cell.

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    Organelles types

    Organelles can be double membrane bound, single membrane bound, or non-membrane bound.

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    Double membrane organelles

    Organelle types like nucleus, mitochondria, and chloroplasts with two membranes.

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    Single membrane organelles

    Organelle types like Golgi apparatus and lysosomes surrounded by one membrane.

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    Non-membrane bound organelles

    Structures like ribosomes and cytoskeleton that lack surrounding membranes.

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    Nucleus functions

    The nucleus synthesizes DNA, RNA, and ribosomes.

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    Endoplasmic Reticulum (ER)

    Network of membranes involved in protein and lipid synthesis.

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    Ribosomes types

    Ribosomes can be free in cytoplasm or bound to the ER.

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    Mitochondria

    Organelles for ATP production through respiration, with a double membrane.

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    Mitochondrial structure

    Mitochondria have an outer smooth membrane and inner folded membrane (cristae).

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    Nucleolus

    Part of the nucleus responsible for ribosomal RNA synthesis.

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    Chromatin types

    DNA in the nucleus can be either condensed (heterochromatin) or dispersed (euchromatin).

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    Vacuoles

    Storage sacs in cells, functioning as waste and water balance areas.

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    Study Notes

    Cytoplasm

    • Cytoplasm is a gel-like solution within cells.
    • It contains particles too small to settle and too large to dissolve in water.
    • Composed of:
      • Dispersive phase (mostly water: 90%)
      • Dispersed phase (particles in water):
        • 9% organic compounds (proteins, sugars)
        • 1% minerals (salts)
    • Functions:
      • Fills cell, gives shape
      • Suspends organelles
      • Site of metabolic reactions
      • Transports materials via cytoplasmic movement (rotation, circulation, pulsation, fountaining)
    • Exists in two forms:
      • Sol (semi-liquid, more fluid)
      • Gel (semi-solid, thicker)
    • Cytoplasmic flexibility and thickness due to high protein content.

    Cytoskeleton

    • The cytoskeleton is the internal cellular "skeleton."
    • A system of filaments with three types:
      • Intermediate filaments:
        • 8-10 nm diameter
        • Tissue-specific proteins (e.g., keratin)
        • Provide mechanical strength, maintain cell shape, and form the nuclear lamina.
      • Microtubules:
        • ~25 nm diameter
        • Composed of tubulin
        • Form centrioles, mitotic spindle, transport pathways within cells, and cilia/flagella.
        • In non-dividing cells, microtubules cluster in the centrosome.
      • Actin filaments:
        • ~7 nm diameter
        • Composed of actin
        • Support cells and organelles, drive cytoplasmic and organelle movement , and facilitate cell shape changes and muscle contraction.

    Membrane-bound Organelles

    • Categorized by membrane count:
      • Double membrane:
        • Nucleus: Contains genetic material.
        • Mitochondria: Site of cellular respiration.
        • Chloroplasts: Found in plant cells.
      • Single membrane:
        • Golgi apparatus: Modifies and sorts proteins.
        • Lysosomes: Contain digestive enzymes.
        • Peroxisomes: Break down peroxides.
        • Endoplasmic reticulum (ER): Network of channels, site of protein synthesis (rough ER) and lipid synthesis (smooth ER)
        • Vacuoles:
          • Animal cells: Waste storage
          • Plant cells: Water balance and waste disposal.


    Non-membrane bound organelles

    • Cell wall: Outer covering of non-animal cells
    • Cytoskeleton: Provides cell structure
    • Ribosomes: Site of protein synthesis
    • Centrosome/Microtubule Organizing Center: Contains centrioles and microtubules important in cell division
    • Centrioles: Cylindrical organelles involved in spindle fiber formation

    Nucleus

    • Structure:
      • Usually one per cell (monokaryocytes)
      • Some cells have two or more nuclei (di/polykaryocytes)
      • Some cells (like red blood cells) lack a nucleus
      • Shape, size depends on cell type and activity
      • Typically centrally located, but can vary
      • Makes up about 10% of cell volume.
    • Functional states:
      • Interphase: Resting state, before cell division
      • Mitotic: During cell division
      • Metabolic: Directs metabolic processes in non-dividing cells.
    • Internal Components and Functions:
      • Nuclear envelope, membrane protecting nucleus
      • Nucleoplasm/Nuclear matrix, fluid inside
      • Nucleolus site of ribosome production (made of ribosomal RNA subunits from fragments of 5 chromosomes)
      • Chromatin: DNA & proteins, exists in two forms:
        • Heterochromatin (condensed, less active)
        • Euchromatin (dispersed, active RNA production)
      • Nuclear function:
        • DNA replication
        • RNA synthesis (transcription)
        • Ribosome formation

    Endoplasmic Reticulum (ER)

    • Network of interconnected membranes (cisternae, channels, vesicles)
    • Increases internal surface area for cellular processes.

    • Facilitates transport and compartmentalization within the cell

    • Smooth ER: Lipid synthesis, detoxification

    • Rough ER: Protein synthesis, modification, and connection to other organelles.


    Ribosomes

    • Small structures composed of rRNA & proteins.

    • Two types in eukaryotic cells:
      • Free ribosomes (synthesize proteins for the cytosol)

      • Bound ribosomes (attached to ER, synthesize proteins for secretion or modification).

    • Ribosomes in mitochondria and chloroplasts are smaller (70S) than those in the cytoplasm (80S)


    Mitochondria

    • Vary in number, size and shape dependent on cell function
    • Two membrane structure (outer and inner) with inner membrane folds (cristae)
    • Contain mtDNA, 70S ribosomes, enzymes for ATP production
    • Site of aerobic respiration, ATP production (Krebs cycle, electron transport chain)
    • Function in cellular energy production and movement within cells.


    Golgi Apparatus

    • Flattened sacs (cisternae); with vesicles
    • Three functional regions: cis, medial, and trans
    • Processes proteins and lipids for export
    • Adds carbohydrates to molecules (e.g., proteins, lipids)
    • Modifies substances received from ER, cell membrane, and endosomes
    • Involved in maturation of precursor proteins like proalbumin and preproinsulin.

    Lysosomes

    • Membrane-bound vesicles for intracellular digestion

    • Contain hydrolytic enzymes (acid hydrolases)
    • Function in acidic conditions (pH 5)

    • Two types:
      • Primary lysosomes (contain inactive enzymes)
      • Secondary lysosomes (contain endocytosed materials and autophagosomes), divided into:
        • Autolysosomes(autolysis & autophagy)
        • Heterolysosomes(formed by fusing with digested material)

    • Break down cellular components, recycling their materials

    Centrosome

    • Structure found near the cell nucleus.
    • Composed of centrioles.
    • Duplicates during cell division to help organize spindle fibers in cell division.

    Plant Cells

    • Contain additional components:

      • Plastids (oval-shaped organelles with their DNA and ribosomes)
      • Cell wall: Provides rigidity and protection
      • Vacuoles: Storage of water.



    Plastids

    • Three types:
      • Chloroplasts (photosynthesis, contain chlorophyll)

      • Chromoplasts (pigments, color)
      • Leucoplasts (storage, store protein, starch, and fats).

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    Description

    This quiz covers the essential components of the cytoplasm and cytoskeleton within cells. Learn about the composition, functions, and types of cytoplasmic solutions, as well as the structural importance of the cytoskeleton in maintaining cell shape and strength.

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