Biology: Introduction to Cells and Life
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Questions and Answers

What are the two characteristics of the bilayer of phospholipids/phosphoglycerides?

  • Amphipathic (correct)
  • Asymmetrical (correct)
  • Non-fluid
  • Symmetrical

    • Integral proteins in the cell membrane cannot be extracted without breaking the membrane.

    True

    What is the function of peripheral membrane proteins in the cell membrane?

    Enzymes

    Bulk transport of fluid matter and substances dissolved in it occurs through ________.

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

    What are the functions of the cell wall?

    <p>Prevents rupturing of cells, maintains shape of the cell, acts as a point of anchorage for flagella, contributes to pathogenicity/Virulence.</p> Signup and view all the answers

    What is the composition of the cell membrane?

    <p>Lipids (20%-79%), proteins (20-70%), carbohydrates (1-5%).</p> Signup and view all the answers

    Which organelles are absent in the cytoplasm? (Select all that apply)

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

    The __________ is a circular cytoplasmic structure formed by the invagination of the cell membrane.

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

    Match the inclusion body with its description:

    <p>Glycogen granule = Storage polymer in prokaryotes Carboxysomes = Contain RUBISCO Sulphur granule = Accumulated by bacteria in a sulphur rich environment Gas vacuoles = Formed from gas vesicles for buoyancy</p> Signup and view all the answers

    What is biology?

    <p>The study of life and living organisms</p> Signup and view all the answers

    Which scientist stated that no body can live if its constituent parts are not formed of cells in 1809?

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

    What is the fundamental structural and functional basis of life?

    <p>A cell</p> Signup and view all the answers

    Match the scientist with their contribution: (a) Matthias Schleiden, (b) Theodor Schwann, (c) Robert Hooke, (d) Anton Von Leeuwenhoek

    <p>Matthias Schleiden = Concluded that plants are made up of one or another kind of cell Theodor Schwann = Concluded that animals are made up of one or another kind of cell Robert Hooke = Observed honeycomb-like compartments in cork under a microscope and named them cells Anton Von Leeuwenhoek = Observed living organisms, called 'Animalcules', and is considered the Father of microbiology</p> Signup and view all the answers

    All organisms, according to cell theory, are composed of cells and their products.

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

    Cell theory was formulated by Theodor Schwann and Matthias Schleiden in ______.

    <p>1838-1839</p> Signup and view all the answers

    What is the modern cell theory?

    <p>Cells arise from pre-existing cells, and all organisms' activities are outcomes of interactions between constituent cells.</p> Signup and view all the answers

    Study Notes

    What is Biology?

    • The study of life and living organisms
    • Involves the study of the structure, function, growth, evolution, and distribution of all living organisms

    Characteristics of Living Organisms

    • Made up of cells
    • Respond to stimuli
    • Grow and develop
    • Reproduce
    • Metabolize
    • Evolve

    Cell Biology

    • Cell is the fundamental structural and functional unit of life
    • All organisms are composed of one or more cells
    • Cells are the basic units of life

    Why is Cell considered a Structural Unit of Life?

    • All organisms are composed of cells
    • Cells are the building blocks of body
    • Cells are organized to form tissues, organs, and systems
    • Division of labor increases efficiency

    Why is Cell considered a Functional Unit of Life?

    • The activity of an organism is the sum total of all activities of its cells
    • All cells possess the same genetic material, though mature cells may become specialized for certain functions
    • Organelles perform different functions and control the activity of the cell

    Discovery of Cell

    • Zachris Janssen built the first microscope in 1590
    • Galileo modified the microscope in 1610
    • Robert Hooke observed honeycomb-like structures in cork and coined the term "cell" in 1665
    • Anton Van Leeuwenhoek discovered bacteria, protozoans, and sperm cells in 1673

    Cell Theory

    • Proposed by Matthias Schleiden and Theodor Schwann in 1838-1839
    • States that all organisms are composed of cells and their products
    • Cells are the structural and functional units of all organisms
    • Limitations: did not explain how new cells were formed

    Modern Cell Theory

    • Formulated by Rudolf Virchow in 1855
    • States that all cells arise from pre-existing cells
    • All organisms are composed of cells and their products
    • Activities of an organism are the outcomes of the sum total of activities of its constituent cells

    Cell Size and Shape

    • Cells vary in size and shape
    • Mycoplasma is the smallest cell, while ostrich egg cells are the largest
    • Human neuron cells are the longest, and human RBCs are the smallest

    Prokaryotic Cell

    • General characteristics: small size, kingdom Monera, and bacteria are common members
    • Structures: cell envelope, cell wall, cell membrane, and cytoplasm
    • Functions: protection, support, and selective transport

    Cell Wall

    • Below glycocalyx and above cell membrane
    • Rigid covering provides strength and support
    • Made up of peptidoglycan or murein

    Gram Staining

    • Differentiates between Gram-positive and Gram-negative bacteria
    • Gram-positive bacteria retain blue color, while Gram-negative bacteria do not

    Cell Membrane

    • Innermost to cell envelope
    • Composed of phospholipid bilayer and proteins
    • Functions: protective covering, selective transport, and formation of cytoplasmic structures

    Cytoplasm

    • Crystallo-colloidal complex
    • High content of water
    • Forms protoplast (CM + cytoplasm)
    • Granular due to ribosomes

    Cytoplasmic Structures

    • Mesosomes
    • Chromatophores
    • Ribosomes
    • Nucleoid
    • Plasmid
    • Inclusion bodies

    Eukaryotic Cell

    • Cell wall (non-living)
    • Protoplasm (living)
    • Cytoplasm
    • Nucleus
    • Cell membrane

    Differences between Plant and Animal Cells

    • Size: plant cells are larger

    • Cell wall: present in plant cells, absent in animal cells

    • Shape: plant cells have a definite shape, while animal cells often change shape

    • Vacuole: large central vacuole in plant cells, smaller vacuoles in animal cells

    • Nucleus: peripheral nucleus in plant cells, central nucleus in animal cells

    • Plastid: present in plant cells, absent in animal cells### Cell Membrane Characteristics

    • Also known as Plasma membrane, Biomembrane, or Plasmalemma

    • Discovered by Schwann in 1838

    • Tripartite/Trilaminar structure: 3 layered with outer dark, middle transparent, and inner dark layers

    • Size/Thickness: Average 75 Å, ranging from 50 Å to 100 Å

    • Dynamic, quasi-fluid, film-like, and semi-permeable

    Composition

    • Lipids (20%-79%), proteins (20%-70%), and carbohydrates (1%-5%)
    • Lipid and protein composition can vary, e.g., human RBC: 52% protein and 40% lipids, myelinated neuron: 20% protein and 80% lipids

    Fluid Mosaic Model

    • Proposed by Singer and Nicholson in 1972
    • Cell membrane shows a quasi-fluid structure with a mosaic pattern
    • Protein "icebergs" in a sea of lipids

    Protein Types

    • Intrinsic (integral) proteins: 70% of the membrane, cannot be extracted without breaking the membrane
    • Extrinsic (peripheral) proteins: 30% of the membrane, superficially placed and removable with a slight change in pH

    Functions of Cell Membrane

    • Compartmentalization
    • Formation of intercellular junctions
    • Secretion
    • Semi-permeability
    • Transport (passive and active)

    Transport

    • Passive transport: without energy, along the gradient, e.g., neutral solutes
    • Active transport: with energy, against the gradient, e.g., Na+/K+ pump
    • Carrier proteins are required for transport of polar solutes, large molecules, charged ions, and amino acids

    Bulk Transport

    • Enclosure of material in vesicles of membrane
    • Carrier vesicles formed by membrane invagination
    • Types: Pinocytosis (cell drinking) and Phagocytosis (cell eating)

    Membrane Fluidity

    • Ability of membrane components to move
    • Movements: rotational, lateral diffusion, and flip-flop
    • Degree of fluidity: should be optimized, as excessive or low fluidity is detrimental
    • Regulation of fluidity: cholesterol acts as a fluidity buffer

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