Methods of Studying Cells and Cell Fractionation
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Questions and Answers

What is the first step in the process of cell fractionation?

  • Suspending the cells in a buffered solution
  • Blending the cells in a homogeniser (correct)
  • Spinning the tube in a centrifuge
  • Removing the supernatant
  • Which organelle is sedimented first during differential centrifugation?

  • Golgi apparatus
  • Nuclei (correct)
  • Rough endoplasmic reticulum
  • Mitochondria
  • What prevents organelles from bursting during the cell fractionation process?

  • Use of a strong acid solution
  • Using a hot, buffered solution
  • Adding an enzyme inhibitor
  • Placing the homogenate in a cold, buffered solution (correct)
  • Which part of the nucleus contains nuclear pores?

    <p>Nuclear envelope (A)</p> Signup and view all the answers

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

    <p>Protein folding and processing (D)</p> Signup and view all the answers

    Which structure is responsible for packaging and processing proteins and lipids?

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

    What is the role of the nucleolus within the nucleus?

    <p>Producing ribosomes (A)</p> Signup and view all the answers

    The smooth endoplasmic reticulum primarily produces what type of molecule?

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

    What is the primary function of mitochondria in a cell?

    <p>Energy production through respiration (A)</p> Signup and view all the answers

    What structure is primarily responsible for cell division and the formation of spindle fibers?

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

    Why is mitosis important for living organisms?

    <p>It produces genetically identical cells for growth. (A)</p> Signup and view all the answers

    What are ribosomes primarily involved in?

    <p>Protein production (A)</p> Signup and view all the answers

    What is the function of pili in prokaryotic cells?

    <p>To help the cell adhere to surfaces (B)</p> Signup and view all the answers

    During which stage of the cell cycle does the cell prepare for division?

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

    What do mesosomes do in prokaryotic cells?

    <p>Contain enzymes for respiration (A)</p> Signup and view all the answers

    What distinguishes viruses from living cells?

    <p>Inability to carry out metabolic processes (A)</p> Signup and view all the answers

    What process do single-celled organisms like yeast use to reproduce?

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

    In binary fission, where do the replicated DNA molecules attach within the prokaryotic cell?

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

    Which component of the cell membrane allows lipid-soluble molecules to pass through?

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

    What is the primary role of proteins integrated throughout the cell membrane?

    <p>To act as channels for substances (B)</p> Signup and view all the answers

    What is the fluid mosaic model's main characteristic?

    <p>Fluidity and flexibility of the membrane (D)</p> Signup and view all the answers

    What type of replication occurs in viruses after they inject their nucleic acids into a host cell?

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

    What type of proteins are located on the surface of the cell membrane?

    <p>Extrinsic proteins (A)</p> Signup and view all the answers

    Which type of molecule in the membrane acts as receptors for certain molecules?

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

    What role does cholesterol play in the cell membrane?

    <p>Makes the membrane more rigid (D)</p> Signup and view all the answers

    Which type of movement requires energy in the form of ATP?

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

    What describes facilitated diffusion?

    <p>Passive transport of polar or charged molecules through channel proteins (A)</p> Signup and view all the answers

    What is the primary function of glycoproteins in the cell membrane?

    <p>To act as cell surface receptors (B)</p> Signup and view all the answers

    During osmosis, water moves from

    <p>An area of high water potential to low water potential (A)</p> Signup and view all the answers

    What does co-transport primarily utilize for moving substances?

    <p>Ions to assist in moving substances (A)</p> Signup and view all the answers

    Which statement is true about active transport?

    <p>It requires energy to move substances against their concentration gradient (C)</p> Signup and view all the answers

    What happens during endocytosis?

    <p>Materials are transported into the cell enclosed in vesicles (A)</p> Signup and view all the answers

    What is a characteristic that distinguishes bacteria from viruses?

    <p>Bacteria are prokaryotic cells with a cell membrane. (B)</p> Signup and view all the answers

    How do glucose and amino acids enter the epithelial cells mentioned in the content?

    <p>By facilitated diffusion along with ions. (A)</p> Signup and view all the answers

    What is one factor that can increase the rate of gas exchange by diffusion?

    <p>Increasing temperature. (B)</p> Signup and view all the answers

    What is the primary reason bacteria can survive independently while viruses cannot?

    <p>Bacteria can reproduce in isolation. (C)</p> Signup and view all the answers

    What is the first symptom of HIV infection?

    <p>Fever, tiredness, and headaches. (D)</p> Signup and view all the answers

    What structure do viruses lack compared to bacteria?

    <p>Cell membrane and organelles. (B)</p> Signup and view all the answers

    Tuberculosis (TB) is caused by which of the following?

    <p>Mycobacterium tuberculosis bacteria. (C)</p> Signup and view all the answers

    Which statement correctly describes the progression of HIV infection?

    <p>The immune system becomes weakened after initial exposure to HIV. (C)</p> Signup and view all the answers

    Which of the following symptoms is NOT associated with AIDS?

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

    What role do lysozymes play in the immune system?

    <p>They kill bacterial cells by damaging their cell walls. (A)</p> Signup and view all the answers

    Which of the following statements accurately describes an aspect of the specific immune response?

    <p>It produces responses specific to one type of pathogen. (B)</p> Signup and view all the answers

    What triggers inflammation during a non-specific immune response?

    <p>Histamines released by damaged tissues. (C)</p> Signup and view all the answers

    What characterizes phagocytosis in the immune response?

    <p>It is a process where white blood cells engulf pathogens. (B)</p> Signup and view all the answers

    Which cells are primarily responsible for the humoral immune response?

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

    What is the primary function of interferons in the immune response?

    <p>To prevent the spread of viruses to uninfected cells. (D)</p> Signup and view all the answers

    What is the role of memory cells in the immune system?

    <p>They replicate when exposed to the same antigen. (B)</p> Signup and view all the answers

    Flashcards

    Cell Fractionation

    The process of separating different components of a cell, such as organelles, for individual study.

    Ultracentrifugation

    A specialized type of centrifugation used to separate cell components based on their density and size, often used in cell fractionation.

    Homogenate

    A mixture of broken cells and their contents created by blending cells in a homogenizer.

    Differential Centrifugation

    A technique used in cell fractionation where a sample is spun at increasing speeds to sequentially separate organelles based on their density.

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    Pellet

    The dense material that settles at the bottom of a centrifuge tube during cell fractionation.

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    Supernatant

    The clear liquid that remains at the top of a centrifuge tube after sedimentation, containing lighter cell components.

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    Nucleus

    The control center of a eukaryotic cell, enclosed by a double membrane called the nuclear envelope.

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    Rough Endoplasmic Reticulum (RER)

    A network of interconnected, flattened membrane-bound sacs involved in protein synthesis and modification.

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    Mitochondria

    A double-membraned organelle responsible for cellular respiration, producing energy (ATP) for the cell.

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    Centrioles

    Small, cylindrical structures made of microtubules that play a vital role in cell division by forming spindle fibers that separate chromosomes.

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    Ribosomes

    Tiny organelles composed of two subunits (RNA and protein), responsible for protein synthesis.

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    Lysosomes

    Vesicles filled with digestive enzymes, breaking down cellular waste and worn-out organelles.

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    Interphase

    A stage in the cell cycle where the cell grows, prepares for division, and replicates its DNA.

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    Mitosis

    The process of cell division that produces two identical daughter cells, essential for growth and asexual reproduction.

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    Cytokinesis

    The division of the cytoplasm during cell division, resulting in the formation of two separate daughter cells.

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    Growth (related to mitosis)

    The ability to make new cells through mitosis, contributing to the development and growth of organisms.

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    Binary Fission

    The process by which prokaryotic cells divide into two identical daughter cells. It involves DNA replication, cell membrane growth and division of cytoplasm.

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    Circular DNA

    A circular molecule of DNA found in prokaryotic cells. It carries essential genetic information for the cell.

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    Plasmids

    Small, circular DNA molecules found in some bacteria and other prokaryotes. They replicate independently of the main DNA molecule.

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    Cell membrane

    A barrier that surrounds all cells and organelles. It's made of a phospholipid bilayer with proteins embedded in it.

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    Fluid mosaic model

    The arrangement of phospholipids and proteins in the cell membrane. It's called fluid because the components can move and mosaic because it's made of different molecules.

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    Intrinsic protein

    A type of protein that spans the cell membrane, helping specific substances to cross.

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    Extrinsic protein

    Proteins found on the surface of the cell membrane, often involved in cell signaling or attachment.

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    Glycolipid

    A type of lipid found on the cell surface containing a carbohydrate molecule. They act as receptors for molecules and help cells recognize each other.

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    Diffusion

    The movement of molecules from an area of high concentration to an area of low concentration, requiring no energy.

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    Facilitated Diffusion

    The movement of molecules across a membrane from an area of high concentration to an area of low concentration, requiring no energy, but using transport proteins.

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    Diffusion Gradient

    A difference in the concentration of a substance between two areas. The steeper the gradient, the faster the rate of diffusion.

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    What causes Tuberculosis?

    Tuberculosis (TB) is caused by the bacterium Mycobacterium tuberculosis. The bacteria infect phagocytes in the lungs and lie dormant inside tubercles, forming hard nodules.

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    Initial TB infection

    The initial infection with Mycobacterium tuberculosis often goes unnoticed as the bacteria are contained within tubercles.

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    Progression of TB

    When the immune system weakens, the bacteria in the tubercles become active and can damage lung tissue, leading to coughing, weight loss, and breathing difficulties.

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    What is HIV?

    HIV (Human Immunodeficiency Virus) is a virus that attacks and weakens the immune system.

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    What is AIDS?

    AIDS (Acquired Immunodeficiency Syndrome) is the final stage of HIV infection, where the immune system is severely compromised, leaving the body vulnerable to infections.

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    Simple Diffusion

    Small, non-polar, lipid-soluble molecules like oxygen and carbon dioxide move through the cell membrane from an area of high concentration to an area of low concentration.

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    Osmosis

    Water molecules move from an area of high water potential to an area of low water potential through a selectively permeable membrane.

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    Active Transport

    This active transport process requires energy to move molecules against their concentration gradient, from an area of low to high concentration.

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    Endocytosis

    Large particles are enclosed in vesicles made from the cell membrane and transported into the cell.

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    Exocytosis

    Vesicles containing large particles fuse with the cell membrane and release their contents outside the cell.

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    Co-Transport

    Ions are used to move other substances across the cell membrane. This is common in the ileum, where sodium and potassium ions are actively pumped out of epithelial cells.

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    Channel Protein

    A type of protein in the cell membrane that helps polar and charged molecules cross the membrane.

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    Skin

    The outer layer of skin, made of keratin, providing a physical barrier against infection.

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    Stomach acid (Hydrochloric acid)

    A strong acid in the stomach that kills bacteria, preventing infections.

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    Gut and skin flora

    Beneficial bacteria that live on the skin and in the gut, competing with pathogens for resources.

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    Antigens

    Molecules found on the surface of cells that identify them as self or non-self.

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    Inflammation

    A complex response to injury or infection, characterized by redness, swelling, heat, and pain.

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    Lysozyme action

    Enzymes present in bodily fluids like tears and mucus, capable of killing bacteria by damaging their cell wall.

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    Interferon

    Proteins released by infected cells to prevent viruses from spreading to uninfected cells.

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    Phagocytosis

    A process by which white blood cells engulf and destroy pathogens.

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    Study Notes

    Methods of Studying Cells

    • Light microscopes use convex glass lenses to resolve images 0.2µm apart. Resolution is limited by the wavelength of light.
    • Magnification is calculated as image size divided by real object size.
    • Resolution is the smallest distance between two objects that can be distinguished as separate.
    • Electron microscopes have higher resolution (0.1nm) than light microscopes, enabling the study of smaller structures.
    • Transmission electron microscopes (TEM) use a beam of electrons passing through a thin section of a specimen. Darker areas indicate areas that absorb electrons.
    • Scanning electron microscopes (SEM) use a beam of electrons that scan the surface of a specimen, creating a 3D image based on the scattering pattern.
    • Electron microscopes require a vacuum environment to prevent electron deflection.

    Cell Fractionation and Ultracentrifugation

    • Cell fractionation separates cellular components to study them in detail.
    • Differential centrifugation is a common method.
    • Homogenization is the initial blending of cells to form a homogenate.
    • The homogenate is spun in a centrifuge at increasing speeds, separating organelles by density. Heavier organelles settle first.
    • Each step results in a pellet (sedimented material) and a supernatant (liquid).
    • Organelles are separated based on their density.
    • The process is carried out in cold, buffered solutions to prevent damage.

    Cell Structure

    • Eukaryotic cells have a nucleus and membrane-bound organelles.
    • The nucleus encloses DNA, with nuclear pores for molecule exchange. It has a nucleolus involved in ribosome production.
    • The rough endoplasmic reticulum (RER) folds and modifies proteins with ribosomes attached.
    • The smooth endoplasmic reticulum (SER) synthesises and processes lipids.
    • The Golgi apparatus modifies, sorts, and packages proteins and lipids.
    • Mitochondria are responsible for respiration, containing cristae for increased surface area.
    • Lysosomes contain digestive enzymes.
    • Centrioles are involved in cell division.

    Prokaryotic Cells

    • Prokaryotic cells (bacteria) lack organelles and have a single circular DNA.
    • Cell wall, capsule, plasmids, flagellum, pili, are examples of prokaryotic cell structures.
    • Mesosomes are infoldings of the cell membrane, involved in respiration (and other functions).

    Cell Division - Mitosis

    • Mitosis produces genetically identical daughter cells for growth and repair.
    • Mitosis involves four stages: prophase, metaphase, anaphase, telophase.
    • Interphase is the phase of cell growth and DNA replication before mitosis.
    • Cytokinesis is the division of the cytoplasm to form two daughter cells.
    • Binary fission is the cell division method in prokaryotes, differing from mitosis in the stages.

    Biological Membranes

    • Cell membranes are fluid mosaics.
    • The membrane is comprised of a phospholipid bilayer.
    • Hydrophilic heads face outward, hydrophobic tails inward, this structure controls permeability.
    • Proteins, cholesterol, glycolipids are embedded in the membrane, performing various functions.
    • Proteins include integral (transmembrane) and peripheral proteins.
    • Cholesterol regulates membrane fluidity.
    • Glycolipids and glycoproteins act as cell recognition markers.

    Cell Transport

    • Passive transport (diffusion, osmosis, facilitated diffusion) moves substances down a concentration gradient.
    • Active transport moves substances against the concentration gradient, requiring energy (ATP).
    • Exocytosis and endocytosis transport large substances.
    • Co-transport couples movement of one substance with another.

    Bacteria and Viruses

    • Bacteria are prokaryotic; viruses are non-living.
    • Cell wall structures and organelles are features of bacteria, absent in viruses.
    • Genetic material (DNA/RNA) is a key component of both, but structurally different.

    Immune Response

    • Physical barriers include skin and stomach acid.
    • Non-specific responses include inflammation, lysozyme action, and phagocytosis.
    • Specific responses involve lymphocytes (B cells and T cells);
    • B cells produce antibodies (humoral response),
    • T cells have cell-mediated response.
    • Memory cells speed up subsequent immune response.
    • Vaccination uses antigens to stimulate immunity.

    Antibodies

    • Antibodies are proteins that bind to specific antigens (foreign substances).
    • They form an antigen-antibody complex which can trigger various immune responses, like phagocytosis and clumping.

    Ethical Considerations

    • Ethical concerns exist around vaccine development, testing, and usage.
    • Considerations include animal use, safety for humans, and compulsory vaccination.

    Monoclonal Antibodies

    • Monoclonal antibodies are identical antibodies produced in labs.
    • They are used therapeutically (directly targeting cancerous cells), diagnostically (measuring specific components), and for pregnancy testing.

    HIV

    • HIV is a virus responsible for AIDS.
    • Its structure includes a lipid envelope, capsid, RNA genetic material, and reverse transcriptase.
    • ELISA is a diagnostic test for HIV.

    Antibiotics

    • Antibiotics are largely ineffective against viruses.

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    Description

    Explore the techniques of studying cells, including light and electron microscopy. Learn about the principles of resolution, magnification, and cell fractionation, which are essential for understanding cellular components. This quiz covers the essential methodologies used in modern cell biology.

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