Biology Chapter: Cell Structures and Functions
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Questions and Answers

Which of the following is NOT a characteristic of prokaryotic cells?

  • They contain organelles with specialized functions (correct)
  • They can be free-living single cells
  • DNA is not enclosed within a membrane
  • They are often part of multicellular organisms

    • Which of the following components is most abundant in a cell?

  • Proteins
  • Lipids
  • Nucleic acids
  • Water (correct)

    • What is the primary role of transport proteins in the cell membrane?

  • To facilitate energy processing within the cell
  • To provide structural support to the cell
  • To serve as a barrier that prevents all molecules from entering
  • To allow selective passage of specific molecules (correct)

    • During evolution, what two processes are involved in natural selection?

    <p>Random variation and selective propagation</p> Signup and view all the answers

    Which element is NOT one of the six elements that compose cells?

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

    Which of the following statements about eukaryotic cells is true?

    <p>Their DNA is partitioned in a membrane-bound nucleus</p> Signup and view all the answers

    Which of the following is a function of the cell membrane?

    <p>Separate the internal environment from the external environment</p> Signup and view all the answers

    Which type of microorganism is characterized as having no cellular structure?

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

    What role do mitochondria and chloroplasts play in cells?

    <p>They produce energy for the cell</p> Signup and view all the answers

    Which of the following is a method by which cells reproduce?

    <p>By division into two daughter cells</p> Signup and view all the answers

    Which of the following statements correctly describes the flow of genetic material?

    <p>Polynucleotide → DNA → Polypeptide.</p> Signup and view all the answers

    What component is NOT a fundamental building block of all cell membranes?

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

    Which structure is unique to bacterial cells compared to eukaryotic cells?

    <p>Cell wall made of peptidoglycan</p> Signup and view all the answers

    Which of the following components of eukaryotic cells is correctly described?

    <p>Cilia are appendages in eukaryotic cells.</p> Signup and view all the answers

    What is a key feature of RNA among self-replicating molecules?

    <p>RNA can catalyze biochemical reactions.</p> Signup and view all the answers

    Which statement accurately describes the bacterial cell size compared to eukaryotic cells?

    <p>Bacterial cells have a diameter ranging from 0.1-5.0 µm.</p> Signup and view all the answers

    Who is credited with the discovery of the cellular world through the use of microscopes?

    <p>Robert Hooke</p> Signup and view all the answers

    Which statement regarding prokaryotic cell structures is correct?

    <p>Prokaryotic cells have a nucleoid instead of a nucleus.</p> Signup and view all the answers

    Which of the following is NOT one of the three domains of life?

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

    What type of organism thrives in high salinity environments?

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

    Which type of virus is known to specifically attack bacterial cells?

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

    What is the primary energy source for phototrophs?

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

    Which type of stem cells can differentiate into all types of cells?

    <p>Totipotent stem cells</p> Signup and view all the answers

    What is the role of the protein coat in viruses?

    <p>Providing protection and aiding entry into host cells</p> Signup and view all the answers

    Which statement best describes the concept of reductionism in biology?

    <p>Breaking down complex processes into simpler components for analysis</p> Signup and view all the answers

    What is the primary difference between organotrophs and autotrophs?

    <p>Organotrophs rely on organic materials, while autotrophs utilize inorganic materials.</p> Signup and view all the answers

    At what stage of development is a zygote in humans?

    <p>After fertilization and before cell division</p> Signup and view all the answers

    What is a characteristic of thermacidophiles?

    <p>They prefer sulfur-rich, high-temperature environments.</p> Signup and view all the answers

    Which of the following terms describes the flow of energy through an ecosystem?

    <p>Energy transformation</p> Signup and view all the answers

    Which statement accurately describes the structure of proteins?

    <p>Proteins consist of 20 different amino acids that form their unique structure.</p> Signup and view all the answers

    What role do nucleic acids play in cells?

    <p>They store hereditary information and carry coding for protein synthesis.</p> Signup and view all the answers

    Which of the following describes the composition and function of lipids?

    <p>Lipids serve as important energy sources and make up cell membranes.</p> Signup and view all the answers

    What is the correct sequence for the organization of genetic material in cells?

    <p>Nucleotide &gt; Nucleosome &gt; Chromatin &gt; Chromosome &gt; Genome.</p> Signup and view all the answers

    Which of the following functions is associated with the cytoskeleton?

    <p>Changing shape and enabling movement of the cell.</p> Signup and view all the answers

    What is one potential outcome of a genetic mutation?

    <p>Mutations in the genome can be beneficial, neutral, or harmful.</p> Signup and view all the answers

    Which of the following substances is primarily used to store glucose for energy in plants?

    <p>Starch.</p> Signup and view all the answers

    What process allows cells to reproduce their genetic information?

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

    Which structural level of protein organization is characterized by the folding of polypeptide chains into specific shapes?

    <p>Tertiary structure.</p> Signup and view all the answers

    What is the role of ATP in a cell?

    <p>Provides the energy necessary for various cellular processes.</p> Signup and view all the answers

    Study Notes

    Order of Cells

    • Cells are the simplest form of life and reproduce by dividing in two.
    • Higher organisms are cellular cities where groups of cells perform specialized functions.
    • Cells carry out a number of complex tasks including:
      • Order: They exhibit a high degree of order and complexity.
      • Evolutionary Adaptations: They evolve over time to adapt to their environment.
      • Regulation: They regulate their internal environment to maintain homeostasis.
      • Response to Homeostasis: They respond to changes in their environment.
      • Energy Processing: They obtain and use energy.
      • Reproduction: They reproduce to create new cells.
      • Growth and Development: They grow and develop over time.

    Cells

    • Cells are small membrane-bounded compartments filled with concentrated aqueous solutions of chemicals.
    • Lipids are fatty acids composed of carbon, hydrogen, and oxygen.
    • Proteins are composed of amino acids and provide structural support.

    Modern Cell Theory

    • Cells are the fundamental unit of life.
    • Cells arise from pre-existing cells through division.
    • Cells contain DNA that is passed from cell to cell during division.
    • Cells are composed of six elements: carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur.
    • Energy flow in living organisms occurs at the cellular level.
    • The plasma membrane is selectively permeable, allowing specific molecules to pass in and out.
    • Transport proteins in the cell membrane facilitate the selective passage of molecules.
    • Each transport protein is specific to a particular molecule.

    Major Components of a Cell

    • Water is the most abundant molecule in cells.
    • Nucleic acids (DNA and RNA) store and transmit genetic information.
    • Other important components include proteins, carbohydrates, lipids, and organelles.

    Organelles

    • Organelles are orderly arrangements of molecules that perform specific functions.
    • Mitochondria produce energy in animal cells.
    • Chloroplasts produce energy in plant cells.

    Different Types of Cells

    • Prokaryotic Cells:

      • DNA is not separated from the cytoplasm.
      • Bacteria and archaea are examples of prokaryotes.
      • Some prokaryotes are free-living, while others are part of multicellular organisms.

    • Eukaryotic Cells:

      • DNA is enclosed within a membrane-bound nucleus.
      • Plants, animals, fungi, and protists are examples of eukaryotes.

    • Similarities between Prokaryotic and Eukaryotic Cells:

      • Contain chromosomes
      • Use DNA as genetic material
      • Have ribosomes
      • Contain cytoplasm
      • Have a plasma membrane
      • Possess vacuoles

    Types of Microorganisms

    • Bacteria
    • Fungi
    • Viruses
    • Prions
    • Parasites
    • Protozoans

    The Evolution of the Cell

    • Natural selection involves two processes:
      • Random variations in genetic information are passed from one generation to the next.
      • Variations that are beneficial for survival and reproduction are selected for.

    From Molecules to the First Cells

    • Organic molecules found in cells include amino acids, sugars, purines, and pyrimidines.
    • DNA, RNA, and proteins are composed of hydrogen, carbon, nitrogen, oxygen, sulfur, and phosphorus.
    • Amino acids and nucleotides associate to form polymers.
    • Polynucleotides are self-replicating molecules and can undergo natural selection.
    • RNA can catalyze biochemical reactions.
    • The flow of genetic material is from polynucleotide to DNA to polypeptide.
    • DNA is the hereditary material.
    • Friedrich Wohler synthesized urea in the 1800s.
    • There are twenty different types of amino acids.
    • Phospholipids are the fundamental building blocks of all cell membranes.
    • They have a hydrophilic head and a hydrophobic tail.
    • Proteins are polypeptides, DNA and RNA are polynucleotides, and carbohydrates are polysaccharides.
    • The nucleus is enclosed by an outer and inner nuclear membrane and is surrounded by cytoplasm.

    How are cells studied?

    • Microscopes are used to study cells.
    • Electron microscopes provide higher magnification, resolution, and detail compared to light microscopes.
    • Robert Hooke discovered cells using a microscope.

    Classifications of Living Things: Domains of Life

    • There are three domains of life:
      • Bacteria: Domain and Kingdom
      • Eukaryota: Kingdoms: Fungi, Plants, Animals, Protists
      • Archaea: Domain and Kingdom

    Prokaryotic Cell Structure

    • Appendages:

      • Pili
      • Flagella
      • Axial Filaments

    • Cell Envelope:

      • Capsule (glycocalyx)
      • Outer membrane (bilayer with phospholipids and lipopolysaccharides)
      • Inner layer: phospholipids
      • Outer layer: lipopolysaccharides

    • Cell Wall:

      • Peptidoglycan

    • Periplasm:

      • Space between the cell membrane and the peptidoglycan cell wall

    • Plasma/Cell Membrane:

      • Encloses the cytoplasm
      • Composed of membrane lipids and proteins
      • Contains cholesterol

    • DNA in Nucleoid:

      • Not enclosed in a membrane

    • Cytoplasm:

      • The intracellular fluid

    • Size:

      • Bacteria cells are much smaller than eukaryotic cells (0.1-5.0 μm diameter).
      • E.coli weighs approximately 25 × 109.
      • The total weight of bacteria in the human body is estimated to be 1-1.5 kg.
      • There are approximately 5 × 1030 bacteria on Earth, weighing around 102 kg.

    Eukaryotic Cell Structure

    • Appendages:

      • Cilia
      • Flagella

    • Cell Walls:

      • Composed of cellulose or chitin (only in plants)
      • Animal cells do not have cell walls

    • Plasma/Cell Membrane:

      • Encloses the cytoplasm
      • Composed of membrane lipids and proteins
      • Contains cholesterol

    • Glycocalyx:

      • A carbohydrate-rich layer on the cell surface

    • Cytoplasm:

      • The intracellular fluid

    • Nucleus:

      • Contains the DNA

    • Ribosomes:

      • Involved in protein synthesis

    • Membrane-bound organelles:

      • Specialized structures within the cell

    • Size:

      • Eukaryotic cells are much larger than bacteria (10-100 μm).

    Archaea vs. Bacteria

    • Halophiles:

      • "Salt-loving" archaea that require high salt concentrations for survival.
      • Chemoheterotrophic (consume organic compounds for energy).

    • Thermacidophiles:

      • "Heat and acid-loving" archaea that thrive in hot, acidic environments.
      • Example: Sulfur-producing archaea at 80°C and pH < 2.

    • Methanogens:

      • "Methane-producing" archaea that live in oxygen-free environments.
      • Autotrophic (produce their own food).

    Single-celled Organisms Reproduction

    • Sexual Reproduction:

      • Meiosis, a process that produces gametes (sex cells).

    • Asexual Reproduction:

      • Budding, a process of cell division that results in a daughter cell.
      • Mitosis, a process of cell division that produces two identical cells.

    Viruses

    • Ultimate parasites:

      • Viruses require a host cell to grow and reproduce.
      • They transport their genetic material by infecting a host cell.

    • Size:

      • Viruses are much smaller than cells (100 nm).

    • Composition:

      • A protein coat encloses the genetic material.

    • Functions of the protein coat:

      • Protects the virus from the environment.
      • Allows the virus to enter the host cell.

    • Example:

      • Bacteriophage: A virus that attacks bacteria.

    We Develop From A Single Cell: The Zygote

    • Zygote:

      • Formed by the union of an egg and sperm.
      • Contains the instructions for building the human body.
      • Approximately 200 micrometers in diameter.
      • A zygote contains approximately 60-100 trillion (1012) cells.

    • Embryonic Stem Cells (ES):

      • Cells with the potential to develop into all cell types in the body.

    • Totipotent Stem Cells:

      • Can differentiate into all cell types.

    • Pluripotent Stem Cells:

      • Can differentiate into many cell types.

    • Organization of Cells:

      • Cells are organized from simple to complex:
        • Atoms
        • Simple molecules
        • Chain molecules
        • Molecular structures
        • Cells
        • Organs
        • Organisms
        • Population
        • Ecosystem

    • Reductionism:

      • Studying the parts of a system to understand the system as a whole.

    • Ecosystem Dynamics:

      • Cycling of nutrients
      • Flow of energy

    Energy Conversion

    • Work requires a source of energy.
    • Energy can be stored in different forms: light, chemical, kinetic, and thermal.
    • Energy exchange involves energy transformations.
    • Energy flows through an ecosystem, entering as light and exiting as heat.
    • Calorie: The amount of heat needed to raise the temperature of 1 gram of water by 1°C.
    • Joule: The amount of energy required to apply a one-newton force over a distance of one meter.

    Primary Sources of Energy in Organisms

    • Organotrophs:

      • Feed on other living things or organic chemicals.
      • Examples: animals, fungi, gut bacteria (consumers).

    • Inorganotrophs:

      • Feed on non-living things.
      • Examples: autotrophs (producers).
        • Phototrophs: Use sunlight as their energy source. (plants, algae)
        • Chemoautotrophs: Use energy from chemicals in rocks (lithotrophic).

    • Decomposers:

      • Break down dead organisms.

    • Metabolic fuels:

      • Organisms obtain energy from food sources like sugars, proteins, lipids, vitamins, and minerals.

    • Mitochondria:

      • The "power plants" of cells.

    Small Molecules of the Cell and Their Functions

    • Water:

      • Interacts with water and biomolecules.
      • Most abundant biological medium.
      • Small and fast molecule.
      • Polar and dipolar, allowing the formation of hydrogen bonds.
      • Cohesive, resulting in surface tension.
      • Moderates temperature.
      • Expands when frozen.
      • Versatile solvent.

    • Small molecules:

      • Carry energy (ATP).
      • Transmit signals (hormones and neurotransmitters).
      • Link into macromolecules (covalently).

    • Macromolecules:

      • Large molecules with the same bonds (IVOT lipids).

    • Proteins:

      • Provide cell structure and perform most cellular tasks.
      • Composed of twenty different amino acids.

    • Carbohydrates:

      • Used as fuel, strengthen plant cell walls, and store glucose for energy.
      • Composed of monosaccharides (e.g., glucose).

    • Lipids:

      • Important energy source and components of cell membranes.
      • Composed of long fatty chains.

    • Nucleic acids (DNA/RNA):

      • Store hereditary information and carry protein coding from DNA to protein synthesizing machinery.
      • Composed of a sugar and a phosphate group joined by covalent and non-covalent bonds.

    • The Genome:

      • The complete set of DNA packaged into chromosomes.
      • Replicated during cell division (linear).
      • Mutations can be beneficial or harmful.
      • Nucleotide > nucleosome > chromatin > chromosome > genome

    • Monomers and Polymers:

      • Monomers (small molecules) join together to form polymers through repeated chemical linkage reactions.
      • Cells produce three main types of macromolecules: polysaccharides, proteins, and nucleic acids.
      • Proteins and nucleic acids exhibit greater information complexity.

    • Protein Structure:

      • Primary, secondary, tertiary, and quaternary structures.

    What Cells Can Do

    • Separated from the external environment by the plasma/cell membrane.
    • Produce energy (ATP).
    • Produce their own external environment (extracellular matrix proteins, gap junctions).
    • Change shape and move (cytoskeleton filaments).
    • Send and sense information (external and internal signals transmitted, receptors).
    • Grow and divide (mitosis and meiosis).
    • Die (apoptosis - programmed death).

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