Cell Structure and Organelles
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Questions and Answers

What are the primary functions of the mitochondria in a cell?

  • Digestion of cellular waste
  • Lipid synthesis
  • Energy production in the form of ATP (correct)
  • Protein synthesis

    • What component of the cytoplasm is known as the fluid portion?

  • Nucleus
  • Cytosol (correct)
  • Organelles
  • Extracellular fluid

    • Which of the following correctly describes the role of the Golgi complex?

  • Protein maturation and targeting (correct)
  • Energy production
  • Regulating cell membrane permeability
  • Site for lipid synthesis

    • What is the role of lysosomes within a cell?

    <p>Digestive organelle</p> Signup and view all the answers

    Which structure serves as the cell's depot for chromosomal DNA?

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

    What is one primary function of the plasma membrane in a cell?

    <p>Structural support</p> Signup and view all the answers

    Which property of phospholipids contributes to the formation of the lipid bilayer in the plasma membrane?

    <p>Amphipathic nature</p> Signup and view all the answers

    What role does the plasma membrane play in cellular communication?

    <p>Establishing communication with the external environment</p> Signup and view all the answers

    Which model is used to describe the structure of the plasma membrane?

    <p>Fluid mosaic model</p> Signup and view all the answers

    What is the primary characteristic of the plasma membrane that allows it to regulate the flow of materials?

    <p>Selective permeability</p> Signup and view all the answers

    Which of the following components predominantly make up the plasma membrane?

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

    What separates the internal contents of a cell from the external environment?

    <p>Plasma membrane</p> Signup and view all the answers

    Which of the following is NOT a function of the plasma membrane?

    <p>Storing nutrients</p> Signup and view all the answers

    What characteristic distinguishes the head region of a phospholipid in the plasma membrane?

    <p>It is hydrophilic due to phosphate.</p> Signup and view all the answers

    What does the term 'like seeks like' refer to in the context of the plasma membrane?

    <p>Hydrophobic regions interact with other hydrophobic regions.</p> Signup and view all the answers

    What distinguishes integral membrane proteins from peripheral membrane proteins?

    <p>Integral proteins are covalently bonded to lipids.</p> Signup and view all the answers

    Which section of the phospholipid bilayer is hydrophobic?

    <p>The fatty acid tails.</p> Signup and view all the answers

    Which of the following statements about membrane proteins is true?

    <p>Metabolically active membranes contain more proteins.</p> Signup and view all the answers

    What is the role of lipid-anchored proteins in the membrane?

    <p>They are tightly integrated into the lipid bilayer.</p> Signup and view all the answers

    What type of protein crosses the lipid bilayer seven times?

    <p>Transmembrane proteins.</p> Signup and view all the answers

    What happens to peripheral proteins when removed from the membrane?

    <p>They can be removed without disrupting the membrane's integrity.</p> Signup and view all the answers

    What characterizes active transport?

    <p>It moves substances against their concentration gradient using ATP.</p> Signup and view all the answers

    Cotransport (symport) is defined by what specific feature?

    <p>Simultaneous movement of two or more solutes in the same direction using energy.</p> Signup and view all the answers

    Which of the following best describes diffusion?

    <p>It is a passive process that occurs until dynamic equilibrium is reached.</p> Signup and view all the answers

    Which statement about countertransport (antiport) is accurate?

    <p>It transports molecules in opposite directions through carrier proteins.</p> Signup and view all the answers

    What is the primary requirement for bulk flow transport?

    <p>Pressure gradient.</p> Signup and view all the answers

    What do phospholipid heads face in the plasma membrane?

    <p>The aqueous extracellular fluid</p> Signup and view all the answers

    Which type of membrane protein serves as a cellular recognition site?

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

    What is the primary function of ion channels within the plasma membrane?

    <p>Form pores for specific ions to pass through</p> Signup and view all the answers

    Which of the following correctly describes osmosis?

    <p>Movement of solvent by concentration gradient</p> Signup and view all the answers

    Which transport mechanism requires the assistance of carrier proteins?

    <p>Facilitated diffusion</p> Signup and view all the answers

    What role do cholesterol molecules play in the plasma membrane?

    <p>Insert into the lipid layer to enhance fluidity</p> Signup and view all the answers

    Which mechanism allows for the movement of water through the plasma membrane?

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

    What is the function of cell-identity markers in the plasma membrane?

    <p>To identify whether a cell is self or foreign</p> Signup and view all the answers

    Study Notes

    Cell Structure

    • Microtubules are the largest cytoskeleton fiber.
    • Intermediate filaments include myosin and keratin.
    • The main parts of a cell are the plasma membrane, cytoplasm, and nucleus.

    Cytoplasm

    • Consists of all of the cellular content inside the cell.
    • Located between the plasma membrane.
    • Excludes the cell nucleus.
    • Contains two main components: cytosol and organelles.

    Cytosol

    • The fluid portion of the cytoplasm.
    • Also known as intracellular fluid.
    • Contains water, dissolved solutes (electrolytes), and suspended particles such as proteins and nucleic acids.

    Organelles

    • Structures enclosed within discrete intracellular membranes with varying shapes, sizes, and functions.
    • Major structures include mitochondria, endoplasmic reticulum, Golgi complex, and lysosomes.

    Mitochondria

    • Responsible for energy production in the form of adenosine triphosphate (ATP).

    Endoplasmic Reticulum (ER)

    • Has two forms: smooth and rough.
    • Smooth ER is the site for synthesis of lipids, phospholipids, and steroids.
    • Rough ER contains ribosomes, the sites for protein synthesis.

    Golgi complex

    • Functions as a processing station.
    • Participates in protein maturation.
    • Targets newly synthesized proteins to their appropriate subcellular destinations.

    Lysosome

    • The cell’s digestive organelle.

    Nucleus

    • Associated with gene expression and cell division.
    • The cell’s depot for its complement of chromosomal DNA.
    • Stores genetic information.
    • The control center of a cell.
    • The uniqueness in a cell’s architectural features and its associated function is regulated by gene expression.

    Plasma Membrane Functions

    • Provides structural support through a network of cytoskeleton.
    • Physically isolates internal contents (intracellular) from the external environment (extracellular).
    • Regulates the exchange of materials into and out of the cell.
    • Establishes communication between cells and its external environment.

    Plasma Membrane Structure

    • The basic structural framework of the plasma membrane is the lipid bilayer.
    • The plasma membrane is mostly composed of phospholipids.
    • Phospholipids are amphipathic molecules.
    • Polar heads are hydrophilic (water-loving).
    • Nonpolar tails are hydrophobic (water-fearing).
    • The head region faces the watery fluids on either side of the plasma membrane - cytosol (intracellular) and extracellular.
    • Hydrophobic fatty acid tails form the nonpolar region in the membrane’s interior.

    Membranes Proteins

    • The more metabolically active a membrane is, the more proteins it contains.
    • Two main categories of membrane proteins: integral and peripheral.

    Integral Membrane Proteins

    • Tightly attached to the membrane.
    • Classified into transmembrane proteins and lipid-anchored proteins.
    • Transmembrane proteins cross the lipid bilayer.
    • Lipid-anchored proteins insert themselves into either side of the cell membrane.

    Peripheral Membrane Proteins

    • Loosely attached to the membrane.
    • Can be removed without disrupting the integrity of the membrane.

    General Function of Membrane Proteins

    • Ion channels form pores that allow a specific ion to pass through.
    • Receptors serve as cellular recognition sites, binding specific molecules.
    • Carriers or transporters selectively move molecules or ions across the membrane.
    • Enzymes catalyze specific biological reactions inside or outside the cell.
    • Linkers anchor plasma membranes of neighboring cells to one another.
    • Cell-identity markers identify a cell whether it is one of its own or foreign.

    Six Basic Transport Mechanisms

    • Diffusion: movement of solute within a medium and membrane in biological systems, due to a concentration gradient.
    • Osmosis: movement of solvent through a membrane down its concentration gradient. Requires water channels (aquaporins).
    • Facilitated diffusion: carrier-mediated transport; from higher to lower concentration; for transporting large or electrically charged molecules.
    • Active transport: move against concentration gradient; requires energy from ATP.
    • Cotransport (symport): carrier-mediated simultaneous movement of two or more solutes in the same direction.
    • Countertransport (antiport): similar to cotransport but the transported molecules are moving in opposite directions.

    Four Main Categories of Transport Processes

    Bulk Flow

    • Movement due to pressure gradient.
    • Flow from high pressure to low.
    • Examples include blood flow in a vessel and air moving in and out of lungs.

    Diffusion

    • Movement due to a concentration gradient such as chemical, electrical, or both.
    • Flow from high concentration to low.
    • Can occur in an open system or through a plasma membrane.
    • Passive process requiring no energy input.
    • Ends when dynamic equilibrium is established.

    Protein-Mediated Transport

    • Facilitated diffusion.
    • Active Transport.
    • Cotransport.
    • Countertransport.

    Vesicular Transport

    • Movement of molecules within membrane-bound vesicles.
    • Requires energy.
    • Exocytosis: Vesicles move from inside the cell to outside the plasma membrane.
    • Endocytosis: Vesicles move from outside to the inside of the cell.

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