Cell Structure and Function Quiz
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What is the primary difference between prokaryotic and eukaryotic cells?

  • The presence or absence of mitochondria
  • The presence or absence of a nucleus (correct)
  • The presence or absence of a cell wall
  • The presence or absence of ribosomes

    • What is the minimum size of an object that can be observed using a light microscope?

  • 1000 nm
  • 100 nm
  • 500 nm
  • 200 nm (correct)

    • What is the name of the darkened region in the central part of a prokaryotic cell where the DNA is found?

  • Nucleus
  • Nucleoid (correct)
  • Cytoplasm
  • Mitochondria

    • What is the function of organelles in eukaryotic cells?

    <p>To perform specialized functions</p> Signup and view all the answers

    What is the term for the study of the structure and function of cells?

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

    What is the primary function of ribosomes in cells?

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

    What is the name of the living part of the cell?

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

    What is the main component of the cytosol?

    <p>Water (70-80%)</p> Signup and view all the answers

    What is the resolution of an electron microscope?

    <p>0.2 nm</p> Signup and view all the answers

    What is the function of the nuclear pores in the nuclear envelope?

    <p>To control the passage of ions, molecules, and RNA</p> Signup and view all the answers

    What is the composition of protoplasm?

    <p>Water, proteins, lipids, carbohydrates, and electrolytes</p> Signup and view all the answers

    What is the combination of DNA and proteins in the nucleus called?

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

    Where are attached ribosomes typically found?

    <p>On the membrane of the endoplasmic reticulum</p> Signup and view all the answers

    What is the function of the nucleolus in the nucleus?

    <p>To produce ribosomes</p> Signup and view all the answers

    What is the primary difference between free and attached ribosomes?

    <p>Their location</p> Signup and view all the answers

    What is the percentage of water in the cytosol?

    <p>70-80%</p> Signup and view all the answers

    What is the primary function of the plasma membrane in terms of the cell's external environment?

    <p>To isolate the interior of the cell from the external environment</p> Signup and view all the answers

    What is the role of aquaporins in the plasma membrane?

    <p>To allow the free passage of water molecules across the membrane</p> Signup and view all the answers

    What is the composition of the phospholipid bilayer in the plasma membrane?

    <p>Two layers of phospholipids with hydrophilic heads and hydrophobic tails</p> Signup and view all the answers

    What is the function of carbohydrates in the plasma membrane?

    <p>To allow cells to recognize each other</p> Signup and view all the answers

    What type of molecules can pass through the plasma membrane easily?

    <p>Small lipid-soluble molecules, such as oxygen and carbon dioxide</p> Signup and view all the answers

    What is the term used to describe the plasma membrane's ability to allow certain molecules and ions to enter and exit the cytoplasm freely?

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

    What is the main component of the fluid present in the cell and surrounded by the cell membrane?

    <p>Water and organelles</p> Signup and view all the answers

    What is the location of the nucleus within the cytoplasm?

    <p>May or may not be centrally located</p> Signup and view all the answers

    What is the primary function of the Golgi complex?

    <p>To package and address proteins to their proper destinations</p> Signup and view all the answers

    Which organelle is responsible for breaking down and recycling cellular waste?

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

    What is the term for the process by which a lysosome breaks down and recycles parts of a cell?

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

    What is the primary function of mitochondria?

    <p>To generate energy for the cell through ATP production</p> Signup and view all the answers

    What is the term for the process by which a cell takes in large molecules from the outside environment?

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

    What is the term for the process by which a cell releases large molecules from the inside to the outside environment?

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

    Which organelle is responsible for modifying and packaging proteins produced in the RER?

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

    What is the type of transport that uses vesicles rather than channel or transport proteins?

    <p>Bulk transport</p> Signup and view all the answers

    What is the primary function of the Golgi complex in a cell?

    <p>To synthesize and package proteins for secretion</p> Signup and view all the answers

    Which type of endocytosis involves the ingestion of solid particles, such as bacteria or dead cell remnants?

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

    What is the main difference between passive transport and facilitated transport?

    <p>Passive transport requires energy, while facilitated transport does not</p> Signup and view all the answers

    What is the primary mechanism by which lipid-soluble molecules enter a cell?

    <p>Diffusion through the plasma membrane</p> Signup and view all the answers

    Which type of transport involves the movement of molecules from an area of higher concentration to an area of lower concentration?

    <p>Passive transport</p> Signup and view all the answers

    What is the function of a transporter protein in facilitated transport?

    <p>To bind to specific molecules and facilitate their transport across the plasma membrane</p> Signup and view all the answers

    Which type of endocytosis involves the binding of specific substances to plasma membrane receptors?

    <p>Receptor-mediated endocytosis</p> Signup and view all the answers

    What is the direction of molecule movement during facilitated transport?

    <p>From an area of higher concentration to an area of lower concentration</p> Signup and view all the answers

    Study Notes

    Cell Structure and Function

    • Cells are the basic structural and functional units of life, and all organisms are composed of either one cell (unicellular) or more cells (multicellular).
    • The branch of biology that deals with the structure and function of cells is called Cytology.
    • Cells are classified into two groups: prokaryotes and eukaryotes, with the primary difference being the presence or absence of a nucleus, a membrane-bound structure that houses the DNA.

    Prokaryotes vs Eukaryotes

    • Prokaryotes are unicellular microorganisms that have no nuclear membrane or any other membrane-bound organelles (e.g. bacteria).
    • Prokaryotic DNA is found in the central part of the cell, a darkened region called the nucleoid.
    • Prokaryotes have a cell wall similar to plant cells.
    • Eukaryotic cells are cells that contain a membrane-bound nucleus and other membrane-bound compartments called organelles, which have specialized functions (e.g. animals, plants, and fungi).

    Cell Size and Shape

    • Cells come in different sizes and shapes, but most cells are very small and require a microscope to examine.
    • The size and shape of cells can vary greatly, with some cells having cube-shaped, long column-shaped, spindle-shaped, or having long projections.

    Cell Structures

    Protoplasm

    • The living part of the cell is called protoplasm, which is composed of water, proteins, lipids, carbohydrates, and electrolytes.
    • Protoplasm consists of two distinct regions: cytoplasm, which lies outside the nucleus, and nucleoplasm, which lies inside the nucleus.
    • Cells also contain inclusions, which consist of metabolic by-products, storage forms of various nutrients and pigments.

    Three Main Components of Cells

    • Plasma membrane: an outer membrane that separates the cell's interior from its surrounding environment.
    • Cytoplasm: the fluid present in the cell and surrounded by the cell membrane, which contains water, enzymes, salts, and various organelles.
    • Nucleus: a large organelle that may or may not be centrally located within the cytoplasm.

    Plasma Membrane

    Principal Components

    • Phospholipid bilayer: a "sandwich" made of two layers of phospholipids, with polar phosphate molecules forming the top and bottom surfaces, and nonpolar lipid tails in between.
    • Proteins: scattered throughout the plasma membrane, playing important roles in allowing substances to enter the cell.
    • Carbohydrates: attached to some of the lipids (glycolipids) and proteins (glycoproteins), forming specialized sites on the cell surface that allow cells to recognize each other.

    Functions

    • Isolates the interior of the cell from the external environment (physical barrier).
    • Allows only certain molecules and ions to enter and exit the cytoplasm freely, making it selectively permeable.

    Cytoplasm and Its Organelles

    • The cytoplasm includes the contents of a cell between the plasma membrane and the nuclear envelope.
    • It contains organelles and cytoskeleton suspended in the gel-like cytosol, which consists of 70-80% water.
    • Many metabolic reactions, including protein synthesis, take place in the cytoplasm.

    Nucleus

    • A prominent structure in eukaryotic cells, the nucleus is a large organelle that may or may not be centrally located within the cytoplasm.
    • It is enveloped in a double membrane called the nuclear envelope, which has nuclear pores to control the passage of ions, molecules, and RNA between the nucleoplasm and the cytoplasm.
    • It stores genetic information as DNA organized into linear structures called chromosomes.
    • Most nuclei contain at least one nucleolus, which consists of ribonucleic acid (RNA) and helps in producing structures called ribosomes.

    Ribosomes

    • Organelles composed of proteins and rRNA (nucleoproteins), where protein synthesis occurs.
    • Ribosomes exist as free ribosomes within the cytoplasm or attached to the membrane of the endoplasmic reticulum.

    Golgi Complexes

    • Located near the nucleus in most cells, the Golgi complex consists of many smooth membranous saccules, some vesicular, others flattened, containing enzymes and proteins being processed.
    • It completes posttranslational modifications of proteins produced in the RER and then packages and addresses these proteins to their proper destinations.

    Lysosomes

    • Membranous sacs produced by the Golgi apparatus, containing hydrolytic enzymes.
    • Found in all cells of the body, but particularly numerous in white blood cells that engulf disease-causing microbes.
    • When a lysosome fuses with such an endocytic vesicle, its contents are digested by lysosomal enzymes into simpler subunits, which then enter the cytoplasm.

    Mitochondria

    • Often called the powerhouses or energy factories of a cell, as they are responsible for making adenosine triphosphate (ATP), the cell's main energy-carrying molecule.
    • Mitochondria are oval-shaped, double-membrane organelles, with an outer membrane enclosing the intermembrane space, and an inner membrane with many folds (cristae) enclosing a gel-like matrix.
    • Abundant in cells or cytoplasmic regions where large amounts of energy are expended.

    Mechanisms of Transport Across the Plasma Membrane

    Bulk Transport (Vesicular Transport)

    • Cells use bulk transport to move large molecules, such as polysaccharides or polypeptides, across the membrane.
    • These processes use vesicles rather than channel or transport proteins.
    • Includes exocytosis and endocytosis.

    Diffusion

    • The random movement of molecules from an area of higher concentration to an area of lower concentration, until they are equally distributed.
    • A passive way for molecules to enter or exit a cell, requiring no energy to move substances.

    Facilitated Transport

    • Many solutes do not simply diffuse across a plasma membrane, but are transported by means of protein carriers within the membrane called transporters, which bind only to a particular molecule, such as glucose.
    • During facilitated transport, a molecule is transported across the plasma membrane from the side of higher concentration to the side of lower concentration.

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