Cell Biology Basics Quiz
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Questions and Answers

Who was the first to observe and name cells?

  • Robert Hooke (correct)
  • Matthias Schleiden
  • Theodor Schwann
  • Anton van Leeuwenhoek

    • Which principle of the cell theory states that cells are the smallest living things?

  • All organisms are composed of one or more cells
  • Cells arise only by division of existing cells
  • Cells are the basic units of all organisms (correct)
  • Cells can reproduce and repair

    • What is one characteristic that distinguishes prokaryotic cells from eukaryotic cells?

  • Eukaryotic cells reproduce only by binary fission.
  • Prokaryotic cells have a defined nucleus.
  • Prokaryotic cells do not have membrane-bounded organelles. (correct)
  • Eukaryotic cells are all unicellular.

    • What process is primarily responsible for cell division in prokaryotic cells?

    <p>Binary fission</p> Signup and view all the answers

    What term describes the genetic material in prokaryotic cells?

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

    Which of the following statements is true regarding eukaryotic cells?

    <p>Their genetic material is enclosed in a defined membrane.</p> Signup and view all the answers

    What does the term 'cellulae' refer to?

    <p>The small compartments seen by Hooke</p> Signup and view all the answers

    Which characteristic of cells supports their role as a unit of function?

    <p>Ability to absorb nutrients</p> Signup and view all the answers

    What is the main function of the nucleolus within the nucleus?

    <p>Synthesis of ribosome components</p> Signup and view all the answers

    Which structure is primarily responsible for maintaining the shape of the nucleus?

    <p>Nuclear lamina</p> Signup and view all the answers

    Which feature of the nuclear envelope controls the passage of proteins and RNA?

    <p>Nuclear pores</p> Signup and view all the answers

    What type of molecules can pass through the nuclear pore via passive diffusion?

    <p>Ions and small proteins</p> Signup and view all the answers

    What is the relationship between the outer membrane of the nuclear envelope and another organelle?

    <p>It is continuous with the endoplasmic reticulum</p> Signup and view all the answers

    How many rings are part of the nuclear pore complex structure?

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

    What role does the nuclear lamina play during cell division?

    <p>Deconstructing and reconstructing the nuclear envelope</p> Signup and view all the answers

    Which of the following is NOT a function of the nuclear pores?

    <p>Synthesizing DNA</p> Signup and view all the answers

    Which of the following best describes the structure of the plasma membrane in prokaryotic cells?

    <p>Double layer of phospholipids with embedded membrane proteins</p> Signup and view all the answers

    Which of the following statements about ribosomes in prokaryotic cells is true?

    <p>Ribosomes synthesize proteins</p> Signup and view all the answers

    What is found in the nucleoid region of prokaryotic cells?

    <p>A highly condensed double-stranded DNA</p> Signup and view all the answers

    Which feature is NOT a common characteristic of all cells?

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

    What is the role of plasmids in prokaryotic cells?

    <p>They contain genes that provide selective advantages</p> Signup and view all the answers

    What process occurs in the cytoplasm of prokaryotic cells?

    <p>Translation and transcription</p> Signup and view all the answers

    Which statement accurately describes prokaryotic cells?

    <p>They have a simpler organization than eukaryotic cells</p> Signup and view all the answers

    What is the primary function of peroxisomes in eukaryotic cells?

    <p>Detoxification of toxic substances</p> Signup and view all the answers

    Which of the following by-products is produced by peroxisomes during oxidative reactions?

    <p>Hydrogen peroxide</p> Signup and view all the answers

    How do mitochondria reproduce within eukaryotic cells?

    <p>Through binary fission</p> Signup and view all the answers

    Which structure within mitochondria is responsible for the majority of ATP production?

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

    Which component of mitochondria contains cytochrome c molecules important for apoptosis?

    <p>Intermembrane space</p> Signup and view all the answers

    What type of DNA do mitochondria contain?

    <p>Circular mitochondrial DNA</p> Signup and view all the answers

    What is the approximate protein composition of the outer membrane of mitochondria?

    <p>50-60%</p> Signup and view all the answers

    Which process occurs in the peroxisomes for detoxifying harmful substrates?

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

    Which of the following is NOT a characteristic of mitochondria?

    <p>They produce hydrogen peroxide</p> Signup and view all the answers

    What role do oxidase enzymes play in peroxisomes?

    <p>They remove free hydrogen atoms</p> Signup and view all the answers

    What is the primary function of the cytoskeleton in a eukaryotic cell?

    <p>Support the cell's shape and anchor organelles</p> Signup and view all the answers

    Which type of cytoskeletal fiber is primarily involved in muscle contraction?

    <p>Actin filaments (microfilaments)</p> Signup and view all the answers

    What characteristic differentiates microtubules from actin filaments?

    <p>Microtubules are formed from tubulin dimers, actin filaments from G-actin</p> Signup and view all the answers

    What role do microtubules play during cell division?

    <p>Movement of chromosomes</p> Signup and view all the answers

    How are microtubules described in terms of stability?

    <p>They are unstable and constantly polymerizing and depolymerizing.</p> Signup and view all the answers

    What structure is formed by a centriole?

    <p>9 groups of 3 microtubules</p> Signup and view all the answers

    What type of cytoskeletal fiber provides mechanical support to the cell?

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

    During which cellular process do actin microfilaments form the contractile ring?

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

    What is the diameter of actin filaments?

    <p>7 nm</p> Signup and view all the answers

    Where are microtubules typically nucleated in a cell?

    <p>At centrosomes near the center of the cell</p> Signup and view all the answers

    What type of RNA carries coding information from DNA to the protein synthesis machinery?

    <p>Messenger RNA (mRNA)</p> Signup and view all the answers

    Which type of chromatin is generally not active?

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

    During which part of the cell cycle is the nucleolus absent?

    <p>Mitosis</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

    What bond type joins the complementary strands of DNA in its secondary structure?

    <p>Hydrogen bonds</p> Signup and view all the answers

    Which molecule is primarily responsible for synthesizing proteins in the liver and glands?

    <p>Rough Endoplasmic Reticulum (RER)</p> Signup and view all the answers

    What is the structure of chromatin primarily composed of?

    <p>DNA and proteins</p> Signup and view all the answers

    What is the role of transfer RNA (tRNA) during translation?

    <p>Brings amino acids to the ribosome</p> Signup and view all the answers

    In eukaryotic cells, what distinguishes them from prokaryotic cells?

    <p>Presence of the endomembrane system</p> Signup and view all the answers

    What best describes the function of the Smooth Endoplasmic Reticulum (SER)?

    <p>Lipid and steroid hormone synthesis</p> Signup and view all the answers

    The process of transcription occurs in which part of the cell?

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

    Which nitrogenous base is NOT a part of DNA?

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

    What initiates the process of translation?

    <p>The start codon AUG</p> Signup and view all the answers

    Which part of the endomembrane system is most involved in modifying and packaging proteins?

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

    Study Notes

    Cytology and Histology

    • Cytology and histology are the study of cells and tissues, respectively.

    Cell Theory: History

    • Cells were not discovered until the invention of the microscope in the 17th century.
    • Robert Hooke (1665) observed cells and named them "cellulae" (Latin for "small rooms").
    • Anton van Leeuwenhoek (Dutch microscopist) observed living cells, calling them "animalcules".
    • Matthias Schleiden (1838) stated that all plants are composed of cells.
    • Theodor Schwann (1839) reported that all animal tissues are composed of cells.

    Cell Theory: Principles

    • All organisms are composed of one or more cells.
    • Cells are the basic units of organization of all organisms.
    • Cells arise only by division of a previously existing cell.

    Cell as a Living Being

    • Cells can absorb, process, and utilize food.
    • Cells can excrete waste.
    • Cells can secrete substances.
    • Cells can reproduce
    • Cells can repair themselves.

    Cell as a Unit

    • A structural unit: support for biological activities.
    • A reproduction unit: development or repairing of organs.
    • An information unit: contains hereditary information.
    • A unit of function: ensures the realization of the biological activities necessary for life.

    Prokaryotic vs. Eukaryotic Cells

    • Prokaryotic Cells (bacteria, archaebacteria):
      • Small (1 to 10 µm)
      • All unicellular
      • Genetic material (DNA) not enclosed in a membrane (nucleoid)
      • No internal membrane system
      • Cell division mainly by binary fission
    • Eukaryotic cells:
      • Larger (10 to 100 µm)
      • Uni or multi cellular
      • Genetic material (DNA) enclosed in a membrane (nucleus)
      • Contain numerous membrane-bounded organelles
      • Cell division by mitosis

    Prokaryotic Cell Division

    • Binary fission:
      • Replication of DNA
      • Segregation of DNA
      • Cell splitting into two identical daughter cells.

    Mitosis

    • A type of cell division that results in two identical daughter cells in eukaryotic cells.

    Cellular Features Shared by All Cells

    • Nucleoid/Nucleus: Contains DNA, the genetic material.
    • Cytoplasm: Semifluid matrix containing sugars, amino acids, and proteins.
    • Ribosomes: Synthesize proteins.
    • Plasma Membrane: Encloses the cell and separates its contents from the surroundings, a phospholipid bilayer with embedded proteins.

    Prokaryotic Cells: Simple Organization

    • Prokaryotes lack a nucleus and membrane-bounded organelles.
    • They have a nucleoid region containing a single, circular DNA molecule.
    • Many have plasmids, small, extrachromosomal DNA molecules.
    • Exhibit three basic shapes: cocci (spherical), bacilli (rod-shaped), and spirilla (spiral-shaped).

    Prokaryotic Cell Walls: Peptidoglycan

    • Peptidoglycan is a unique polymer found in bacterial cell walls determining their shape.
    • Cell walls protect the cell, maintain its shape, and prevent excessive water uptake or loss.
    • Antibiotics target the peptidoglycan synthesis in bacteria for treatment of bacterial infections.

    Gram-positive vs. Gram-negative Bacteria

    • Gram-positive bacteria: Thicker peptidoglycan layer, stains purple with Gram stain.
    • Gram-negative bacteria: Thinner peptidoglycan layer, stains pink with Gram stain, usually located outside the cell wall (outer membrane).
    • Outer membrane resistant to antibiotics.

    S-layer, Capsule, Flagella, and Pili

    • S-layer: Additional glycoprotein layer outside peptidoglycan, providing protection or adhesion.
    • Capsule: Gelatinous layer surrounding the cell wall, found in many pathogenic bacteria enhance adhesion and protect the cell
    • Flagella: Long, whip-like appendages for motility.
    • Pili: Short, hair-like appendages for attachment or genetic exchange (conjunction).

    Bacterial Conjugation

    • Process where bacteria exchange genetic material through pili.

    Cell Division: Binary Fission

    • Asexual reproduction mode in bacteria.
    • Duplication of DNA.
    • The cell wall constricts, creating two new cells.

    Archaea

    • Archaea have unusual membrane lipids and their DNA structure and the cell wall is differently composed compared to bacteria.
    • Peptidoglycan is absent.

    Eukaryotic Cells

    • More complex than prokaryotic cells.
    • Cells have compartmentalization (organelles) and a membrane system.

    Eukaryotic Cell Organization

    • Cells are organized into two main parts:
      1. Nucleus: the control center of the cell.
      2. Cytoplasm: the region outside the nucleus, where most cellular processes occur

    The Nucleus

    • Spherical shape.
    • Located in the central region of the cell.
    • Contains DNA (genetic material) that synthesizes nearly all the proteins of eukaryotic cells.
    • Nucleus exhibits nucleolus, which plays a role in ribosome components synthesis
    • Nuclear envelope: Double membrane surrounding the nucleus, perforated with pores allowing substances to move in and out of the nucleus.
    • The network of fibers within the nuclear envelope is called the nuclear lamina.

    The Nuclear Envelope

    • Double phospholipid bilayer membrane.
    • Perforated with pores.
    • Controls the passage of proteins and RNA-protein complexes which transport materials between the nucleus and the cytoplasm.
    • Continuous with the endoplasmic reticulum.
    • Nucleus shape is due to the nuclear lamina, involved in deconstruction/reconstruction during cell division.
    • Nuclear pores are complex structures (orthogonal radial symmetry), consisting of multiple proteins which helps control the passage of substances.
    • Exchange in both directions between the cytoplasm and the nucleoplasm using active or passive transport.

    Nucleolus

    • Dark-staining region in the nucleus.
    • Where ribosome subunits are assembled.

    Chromatin: DNA Packaging

    • DNA is packaged with proteins (histones) forming chromatin.
    • Two forms: Heterochromatin (generally not active) and Euchromatin (active).
    • In non-dividing cells: DNA is a thin network of threads called chromatin.
    • When cell prepares to divide, Chromatin forms distinct structures called chromosomes.

    Primary Structure of DNA

    • A nucleotide polymer.
    • Composed of a phosphate group, deoxyribose sugar, and nitrogenous bases (A, T, C, G).

    Secondary Structure of DNA

    • Double helix.
    • Two complementary strands held together by hydrogen bonds.
    • A–T (2 hydrogen bonds); C–G (3 hydrogen bonds).
    • Antiparallel.

    Structure of Chromatin

    • Composed of DNA wrapped around histones (proteins).
    • Two forms: hetero- and euchromatin.
    • Levels of chromatin condensation.

    Ribosomes

    • Complex molecular assemblies.
    • Composed of rRNA and proteins.
    • The cell's protein synthesis machinery.
    • Found free in cytoplasm or attached to endoplasmic reticulum.

    Ribosomes: Protein Synthesis

    • Synthesize proteins for the cytoplasm, nucleus, mitochondria, other organelles, to endomembrane system, etc.
    • Need mRNA and tRNA to function effectively.
    • Ribosome subunits join to make a functional ribosome (when actively synthesizing proteins).

    mRNA

    • The genetic information from DNA is transferred to the cytoplasm to the protein synthesis machinery in the form of mRNA.
    • mRNA is a matrix on which amino acids for a specific protein are polymerized.

    Transcription

    • Takes place in the nucleus.
    • One DNA strand acts as a template.
    • Uses RNA polymerase.
    • Synthesizes an RNA strand following the complement rule.

    Translation

    • mRNA migrates into cytoplasm and attaches to a ribosome.
    • mRNA is read codon by codon.
    • Codons correspond to amino acids.
    • tRNA carries specific amino acids to the ribosome.
    • Amino acids are linked to create a protein molecule.

    Expression of Genetic Information

    • DNA triplets (codons) correspond to mRNA codons.
    • mRNA codons correspond to specific anti-codons on tRNA.
    • Anti-codons correspond to specific amino acids.

    The Endomembrane System

    • Internal membranes in eukaryotic cells that divide the cell into compartments.
    • Includes nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, and vacuoles.
    • Channels for molecular passage.
    • Surfaces for lipid and protein synthesis

    Endoplasmic Reticulum (ER)

    • Largest internal membrane in eukaryotic cells.
    • Two types:
      • Rough ER (RER): Studded with ribosomes, synthesizes and modifies proteins, and plays a role in protein folding and quality control.
      • Smooth ER (SER): Synthesizes lipids, metabolizes carbohydrates, stores calcium ions, and plays a role in detoxification.

    Golgi Apparatus

    • Stacked, membranous sacs (cisternae) in eukaryotic cells.
    • Processes, packages, and distributes molecules (proteins and lipids) synthesized in the ER.
    • 3 zones: Cis, medial, and Trans face.

    Lysosomes

    • Membrane-bound vesicles in eukaryotic cells.
    • Contain enzymes that break down macromolecules (proteins, nucleic acids, carbohydrates, lipids).
    • Involved in recycling of cellular components and destroying harmful substances.

    Peroxisomes

    • Membrane-bound organelles in eukaryotic cells.
    • Contain enzymes that carry out oxidation reactions.
    • Involved in several biological functions, including detoxification of harmful substances and breakdown of fatty acids.

    Mitochondria

    • Sausage-shaped organelles involved in cellular respiration.
    • Produce ATP (adenosine triphosphate), the cell's energy currency.
    • Contain their own DNA and ribosomes, but depend on the nucleus for many of their proteins.

    The Cytoskeleton

    • Network of protein fibers throughout the cytoplasm of eukaryotic cells, maintaining cell shape and movement/transport of intracellular components.
    • Three types of fibers:
      • Actin filaments (microfilaments) for mobility, maintaining and changing cell shape during cell division.
      • Microtubules for structure/organization and mobility.
      • Intermediate filaments for cell strength.

    Centrosomes and Centrioles

    • Centrosome is the microtubule organizing center (MTOC).
    • Centrioles occur in pairs, near the nucleus, involved in cell division.

    Intermediate Filaments

    • Tough, stable fibers that maintain cell morphology and shape.
    • More durable than actin filaments or microtubules.
    • Constituted by proteins (e.g., vimentin, keratin)

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