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  • Answered Review Questions Cell Structure and Function

    Cell Structure

    Location-Structure Function Prokaryote/ Eukaryote

    Cell membrane (Plasma membrane)

    Forms outer boundary of cell;

    Forms membrane-bound organelles

    Semi-permeable (restricts the access of certain compounds and ions)

    Aids in maintaining the complex internal organization of a cell

    Both

    Cytoplasm Everything between the nuclear envelope (nucleoid region in prokaryotes) and the cell boundary

    Site of most chemical reactions of life

    Both

    Cytosol The semi-fluid portion of the cytoplasm

    Both

    Nucleus 10% of the volume of the cell Mission control—manages protein synthesis

    Eukaryotes only

    Nucleolus Small dense spheres within the nucleus (often 2-3 visible)—tightly coiled regions of the DNA

    Genes for ribosomal RNA (building block of ribosomes)

    Eukaryotes only

    Nuclear envelope

    Porous double-membrane organelle;

    Forms outer boundary of nucleus

    Protects the DNA

    mRNA exits the nucleus through pores after transcription

    Eukaryotes only

    Bound ribosomes

    Small dense granules (each has a large and a small subunit) made of proteins and rRNA;

    Attached to endoplasmic reticulum;

    Can become free;

    Part of the endomembrane system

    Site of protein synthesis

    Ribosomes build proteins

    Eukaryotes only

    Free ribosomes

    Small dense granules (each has a large and a small subunit) made of proteins and rRNA;

    Suspended in cytosol;

    Can become bound

    Site of protein synthesis

    Ribosomes build proteins

    Both

  • Rough endoplasmic reticulum

    Network of membranous tubes dotted with bound ribosomes;

    Loosely surrounds the nucleus;

    Part of the endomembrane system

    Modify proteins

    Many proteins are modified here by cleaving the polypeptide, forming quaternary structures, removing amino acids or adding non-protein substances (e.g. enzymes often require a metallic ion to work)

    Eukaryotes only

    Smooth endoplasmic reticulum

    Network of membranous tubes;

    Loosely surrounds the nucleus;

    Part of the endomembrane system

    Makes carbohydrates and lipids

    (e.g. the SER of liver cells convert glucose to glycogen, and make triglycerides and cholesterol)

    Eukaryotes only

    Transport vesicle

    Membrane-bound bubble;

    Buds off both RER and SER;

    Part of endomembrane system

    Moves modified proteins, lipids, and carbohydrates to cis face of Golgi apparatus

    Eukaryotes only

    Golgi apparatus Network of membranous tubes;

    Located closer to cell boundary than ER;

    Cis face toward nucleus;

    Trans face toward cell membrane;

    Part of the endomembrane system

    Receives compounds from ER;

    Attaches a chemical “address label” for compounds destined for export

    Eukaryotes only

    Secretory vesicle

    Membrane-bound bubble;

    Buds off trans face of Golgi apparatus;

    Part of endomembrane system

    Moves finished compounds to cell membrane for export

    Eukaryotes only

  • Lysosome Membrane-bound bubble containing hydrolytic enzymes;

    Buds off Golgi apparatus

    Cell’s stomach;

    Merges with food vacuole and digests organic compounds;

    Autophagy (recycles old and damaged organelles and cytosol);

    Apoptosis (programmed cell death/self-destruction)

    Eukaryotes only

    Food vacuole Membrane-bound bubble;

    Buds off cell membrane

    Transports food particles and captured microbes from outside the cell into cytoplasm;

    Fuses with lysosome

    N/A

    Mitochondrion Double membrane bound organelle;

    Inner membrane called cristae;

    Semi-fluid interior called matrix;

    Has own DNA and protein- making machinery

    Descendent of free-living prokaryote

    Aerobic cellular respiration;

    Harvests chemical energy from organic monomers and stores the energy in ATP

    Eukaryotes only

    Chloroplast Double membrane bound organelle;

    Inner membrane discs called thylakoids;

    semi-fluid space surrounding thylakoids called stroma;

    Has own DNA and protein- making machinery

    Descendent of free-living prokaryote

    Photosynthesis;

    Harnesses light energy and uses it to build sugar

    Eukaryotes only

    (Plants and Photosynthes izing Protists)

  • Cytoskeleton All through cytoplasm

    Three filament types (Listed below)

    Gives shape to cell; Supports organelles;

    Aids in motion and cell division;

    Moves material (organelles) through cytoplasm

    Actin Filaments One kind of cytoskeletal element;

    Most often located just below cell membrane;

    Twisting strand of globular actin subunits

    Movement (e.g. Amoeba pseudopods, cytoplasmic streaming, formation of cleavage furrow, microvilli extension and retraction)

    Eukaryotes only

    Microtubules One kind of cytoskeletal element;

    Spread through out cytoplasm;

    Small hollow tube built of tubulin dimers

    Internal monorail system for moving organelles through cytoplasm;

    components of centrosome, centrioles, cilia, and flagella;

    Microtubules are the spindle fibers that move the chromosomes in cell division

    Eukaryotes only

    Intermediate filaments

    One kind of cytoskeletal element;

    Spread through out cytoplasm;

    Anchored to cell membrane and organelles

    Scaffolding that supports organelles;

    Gives shape to cells

    Eukaryotes only

    Centrosome (Microtubule Organizing Center [MTOC])

    Within cytoplasm;

    In animal cells the location is covered by a pair of centrioles

    Region of the cytoplasm that makes spindle fibers for cell division

    Eukaryotes

    Centriole Small pair of hollow tubes;

    Built of microtubules

    Organized into a 9+0 arrangement

    Covers centrosome in animal cells

    Associated with cell division but not necessary

    Eukaryotes (Animal cells)

  • Cilia Small oar-like structure projecting outside the cell membrane;

    Built of microtubules (9+2 arrangement);

    Basal body has 9+0 arrangement like centriole

    Synchronized rhythmic rowing;

    Movement for single-celled microbes;

    Ciliary escalator in trachea

    Eukaryotes

    Flagella Long whip-like tail projecting outside the cell membrane;

    Built of microtubules (9+2 arrangement);

    Basal body has 9+0 arrangement like centriole

    Wiggles back and forth moving cell through liquid;

    Sperm cells have a flagellum

    Both (prokaryotic flagella are different in

    structure and motion [rotary])

    Central Vacuole

    Large membranous sac in plant cells;

    Takes up most of the space in cytoplasm

    Maintains structural integrity of plant cells (turgidity);

    Water storage;

    Alkaloid storage;

    Pigment storage

    Eukaryotes (Plants only)

    Perioxisome Small membrane bound organelle in aerobic eukaryotes

    Catalase enzymes in organelle convert hydrogen peroxide (slightly toxic intermediate metabolite of superoxide free radical breakdown) to water and oxygen gas

    Eukaryotes

    PLASMA MEMBRANE

  • NUCLEUS, NUCLEAR ENVELOPE, NUCLEAR PORES

  • GENERALIZED ANIMAL CELL

  • GENERALIZED PLANT CELL

    BOUND AND FREE RIBOSOMES

  • RER AND SER

    GOLGI APPARATUS

  • LYSOSOME

    MITOCHONDRION

  • CHLOROPLAST

    PEROXISOME

    CENTRIOLES

  • FLAGELLA AND CILIA

    MICROTUBULES

  • ACTIN FILAMENT

    INTERMEDIATE FILAMENT

    Trace the path of the production of a protein from the DNA in the nucleus to its secretion outside the cell. (endomembrane system). Explain the function of each member.

    Proteins are synthesized by the bound ribosome. The resulting protein is modified (glycoprotein is attached, plus any other modifications) by the rough endoplasmic reticulum. A small section of the RER containing the protein pinches off the end enclosing the protein inside a transport vesicle. The transport vesicle moves to the Golgi apparatus where it fuses with the cis face of the Golgi apparatus. The protein receives a chemical address label (glycoprotein is modified) as it is moved through the layers of membranous sacs of the Golgi apparatus. On the trans face of the Golgi apparatus the finished protein is enclosed inside a secretory vesicle that moves to the cell membrane and dumps the protein out of the cell.

    Secretory vesicle

  • Lipids or carbohydrates are synthesized by the smooth endoplasmic reticulum. A small section of the SER containing the compound pinches off the end enclosing the protein inside a transport vesicle. The transport vesicle moves to the Golgi apparatus where it fuses with the cis face of the Golgi apparatus. The compound receives a chemical address label (glycoprotein is modified) as it is moved through the layers of membranous sacs of the Golgi apparatus. On the trans face of the Golgi apparatus the finished compound