Chapter 4 by zQXe9p

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									  Chapter 4

A Tour of the Cell




  Laura Coronado   Bio 10   Chapter 4
         Biology and Society:
    Drugs That Target Bacterial Cells
– Antibiotics were first isolated from mold in 1928.
– The widespread use of antibiotics drastically
  decreased deaths from bacterial infections.
   • Most antibiotics kill bacteria while minimally
     harming the human host by binding to structures
     found only on bacterial cells.
   • Some antibiotics bind to the bacterial ribosome,
     leaving human ribosomes unaffected.
   • Other antibiotics target enzymes found only in the
     bacterial cells.
                   Laura Coronado   Bio 10   Chapter 4
                                            Colorized TEM
Laura Coronado   Bio 10   Chapter 4
                                      Figure 4.00
  The Microscopic World of Cells
– Organisms are either
  • Single-celled, such as most prokaryotes and
    protists or
  • Multicelled, such as plants, animals, and most
    fungi




                  Laura Coronado   Bio 10   Chapter 4
Microscopes as Windows on the World
               of Cells
– Light microscopes can be used to explore the
  structures and functions of cells.
– When scientists examine a specimen on a
  microscope slide
   • Light passes through the specimen
   • Lenses enlarge, or magnify, the image
– Magnification is an increase in the specimen’s
  apparent size.
– Resolving power is the ability of an optical
  instrument to show two objects as separate.
                   Laura Coronado   Bio 10   Chapter 4
                  Cell Theory
– Cells were first described in 1665 by Robert
  Hooke.
– The accumulation of scientific evidence led to
  the cell theory.
  • All living things are composed of cells.
  • All cells come from other cells.




                   Laura Coronado   Bio 10   Chapter 4
                                                                  TYPES OF MICROGRAPHS

                  Light Micrograph (LM)                      Scanning Electron Micrograph (SEM)                             Transmission Electron Micrograph (TEM)
                 (for viewing living cells)                     (for viewing surface features)                                  (for viewing internal structures)




                                                                                                                                                                     Colorized TEM
                                                                                                    Colorized SEM
                                              LM




Light micrograph of a protist, Paramecium          Scanning electron micrograph of Paramecium                       Transmission electron micrograph of Paramecium




                                                      Laura Coronado         Bio 10     Chapter 4
                                                                                                                                                  Figure 4.1
         Electron Microscopes
– The electron microscope (EM) uses a beam of
  electrons, which results in better resolving
  power than the light microscope.
  • Magnify up to 100,000 times
  • Distinguish between objects 0.2 nanometers apart
– Scanning electron microscopes examine cell
  surfaces.
– Transmission electron microscopes (TEM) are
  useful for internal details of cells.

                  Laura Coronado   Bio 10   Chapter 4
Laura Coronado   Bio 10   Chapter 4
                                 Figure 4.2
  10 m

            Human height
   1m
            Length of some
            nerve and
            muscle cells




                                      Unaided eye
 10 cm
            Chicken egg


  1 cm

            Frog eggs
 1 mm




                                                       Light microscope
100 mm

             Plant and
             animal cells
10 mm
            Nucleus
             Most bacteria
            Mitochondrion
1 mm




                                                                           Electron microscope
            Smallest bacteria
100 nm
             Viruses

            Ribosomes
10 nm
             Proteins
             Lipids
1 nm
             Small molecules

            Atoms
0.1 nm
         Laura Coronado      Bio 10                 Chapter 4
                                                                          Figure 4.3
 The Two Major Categories of Cells
– The countless cells on earth fall into two
  categories:
  • Prokaryotic cells — Bacteria and Archaea
  • Eukaryotic cells — plants, fungi, and animals
– All cells have several basic features.
  • They are all bound by a thin plasma membrane.
  • All cells have DNA and ribosomes, tiny structures
    that build proteins.

                  Laura Coronado   Bio 10   Chapter 4
Differences Between Prokaryotic &
         Eukaryotic Cells
– Prokaryotic and eukaryotic cells have
  important differences.
– Prokaryotic cells are older than eukaryotic
  cells.
  • Prokaryotes appeared about 3.5 billion years ago.
  • Eukaryotes appeared about 2.1 billion years ago.



                  Laura Coronado   Bio 10   Chapter 4
                Prokaryotes
– Are smaller than
  eukaryotic cells
– Lack internal
  structures
  surrounded by
  membranes
– Lack a nucleus
– Have a rigid cell
  wall
                  Laura Coronado   Bio 10   Chapter 4
    Plasma membrane
    (encloses cytoplasm)

Cell wall (provides rigidity)



Capsule (sticky coating)
                                                                   Prokaryotic
                                                                   flagellum
                                                                   (for propulsion)

                                                           Ribosomes
                                                           (synthesize
                                                           proteins)
                                                       Nucleoid
                                                       (contains DNA)

                                        Pili (attachment4structures)
                                Laura Coronado Bio 10 Chapter
                                                                         Figure 4.4a
                Eukaryotes
– Eukaryotes
   • Only eukaryotic cells have organelles,
     membrane-bound structures that perform
     specific functions.
   • The most important organelle is the
     nucleus, which houses most of a eukaryotic
     cell’s DNA.


                 Laura Coronado   Bio 10   Chapter 4
  An Overview of Eukaryotic Cells
– Eukaryotic cells are fundamentally similar.
– The region between the nucleus and plasma
  membrane is the cytoplasm.
– The cytoplasm consists of various organelles
  suspended in fluid.
– Make up animal & plant cells
– Unlike animal cells plant cells have
  • Protective cell walls
  • Chloroplasts, which convert light energy to the
    chemical energy of food
                   Laura Coronado   Bio 10   Chapter 4
                                    Ribosomes                             Centriole
                                                                                        Not in most
                                                                          Lysosome
                                                                                        plant cells
   Cytoskeleton                                                           Flagellum




Plasma
membrane


                                                                                            Nucleus


Mitochondrion



   Rough
   endoplasmic
   reticulum (ER)                                                                       Smooth
                        Golgi                                                           endoplasmic
                        apparatus                                                       reticulum (ER)
Idealized animal cell               Laura Coronado   Bio 10   Chapter 4
                                                                                      Figure 4.5a
      Cytoskeleton

                                                                          Central
      Mitochondrion                                                       vacuole          Not in
                                                                          Cell wall        animal cells
      Nucleus                                                             Chloroplast
 Rough endoplasmic
 reticulum (ER)

  Ribosomes




                                                                          Plasma
                                                                          membrane

Smooth
endoplasmic
reticulum (ER)                                                       Channels between
                                                                     cells
                                            Golgi apparatus
        Idealized plant cell


                               Laura Coronado   Bio 10   Chapter 4
                                                                                    Figure 4.5b
            MEMBRANE STRUCTURE
– The cell membranes are composed mostly of
  • Phospholipids & Proteins
– Phospholipids form a two-layered membrane,
  the phospholipid bilayer.
– The plasma membrane separates the living cell
  from its nonliving surroundings.
– The plasma membrane is a fluid mosaic:
  • Fluid because molecules can move freely past one
    another
  • A mosaic due to the diversity of proteins membrane
                  Laura Coronado   Bio 10   Chapter 4
                                                                                                        Proteins
                      Outside of cell                                         Outside of cell
                                                  Hydrophilic
Hydrophilic                                       region of
head                                              protein

Hydrophobic
tail                                            Hydrophilic
                                                                                                             Phospholipid
                                                head                                                         bilayer
                                                Hydrophobic
                                                tail

  Phospholipid
                 Cytoplasm (inside of cell)

                                                Hydrophobic
    (a) Phospholipid bilayer of                 regions of
                                                                      Cytoplasm (inside of cell)
    membrane                                    protein

                                                  (b) Fluid mosaic model of
                                                  membrane




                                        Laura Coronado   Bio 10   Chapter 4
                                                                                                Figure 4.6
        Cell Membrane Proteins
– Most membranes have specific proteins
  embedded in the phospholipid bilayer.
– These proteins help regulate traffic across the
  membrane and perform other functions.




                 Laura Coronado   Bio 10   Chapter 4
         The Process of Science:
        What Makes a Superbug?
– Observation: Bacteria use a protein called PSM
  to disable human immune cells by forming
  holes in the plasma membrane.
– Question: Does PSM play a role in MRSA
  infections?
– Hypothesis: MRSA bacteria lacking the ability
  to produce PSM would be less deadly than
  normal MRSA strains.

                 Laura Coronado   Bio 10   Chapter 4
        The Process of Science:
       What Makes a Superbug?
– Experiment: Researchers infected
  • Seven mice with normal MRSA
  • Eight mice with MRSA that does not produce PSM
– Results:
  • All seven mice infected with normal MRSA died.
  • Five of the eight mice infected with MRSA that
    does not produce PSM survived.


                  Laura Coronado   Bio 10   Chapter 4
       The Process of Science:
      What Makes a Superbug?
– Conclusions:
  • MRSA strains appear to use the membrane-
    destroying PSM protein, but
  • Factors other than PSM protein contributed to the
    death of mice




                  Laura Coronado   Bio 10   Chapter 4
                                                                               Colorized SEM
MRSA bacterium
producing PSM
proteins

                                                Methicillin-resistant
                                                Staphylococcus aureus (MRSA)



PSM proteins
forming hole
in human
                                                                PSM
immune cell                                                     protein
plasma
membrane                                                           Pore
                                                Plasma
                                                membrane




Cell bursting,
losing its
contents
through
the pores

                 Laura Coronado   Bio 10   Chapter 4
                                                                          Figure 4.7-3
                    Cell Wall
– Plant cells have rigid cell walls surrounding
  the membrane.
– Plant cell walls
  • Are made of cellulose
  • Protect the cells
  • Maintain cell shape
  • Keep the cells from absorbing too much water




               Laura Coronado   Bio 10   Chapter 4
                 Animal Cells
– Animal cells
  • Lack cell walls
  • Have an extracellular matrix, which
     –Helps hold cells together in tissues
     –Protects and supports them
– The surfaces of most animal cells contain cell
  junctions, structures that connect to other
  cells.

                   Laura Coronado   Bio 10   Chapter 4
                  THE NUCLEUS

– The nucleus is the chief executive of the cell.
  • Genes in the nucleus store information necessary
    to produce proteins.
  • Proteins do most of the work of the cell.




                  Laura Coronado   Bio 10   Chapter 4
  Nucleus Structure and Function
– Nuclear envelope borders the nucleus and is a
  double membrane.
– Pores in the envelope allow materials to move
  between the nucleus and cytoplasm.
– The nucleus contains a nucleolus where ribosomes
  are made.
– Chromatin are long DNA molecules and associated
  proteins that form fibers.
  • Stored in the nucleus
  • Each chromatin fiber equals one chromosome.
                  Laura Coronado   Bio 10   Chapter 4
                                    Nuclear
  Ribosomes         Chromatin       envelope         Nucleolus   Pore




TEM




                                                                        TEM
      Surface of nuclear envelope          Nuclear pores
                      Laura Coronado   Bio 10   Chapter 4
                                                                         Figure 4.8
  DNA molecule


                                                  Proteins




Chromatin
fiber                Chromosome



            Laura Coronado   Bio 10   Chapter 4
                                                        Figure 4.9
                  Ribosomes
– Ribosomes are responsible for protein
  synthesis.
– Ribosome components are made in the
  nucleolus but assembled in the cytoplasm.
– Ribosomes may assemble proteins:
• Suspended in the fluid of the cytoplasm or
• Attached to the outside of an organelle called the
  endoplasmic reticulum

                   Laura Coronado   Bio 10   Chapter 4
                                             Ribosome




mRNA




                                 Protein


       Laura Coronado   Bio 10   Chapter 4
                                              Figure 4.10
                                      TEM
                                            Ribosomes in
                                            cytoplasm




                                            Ribosomes attached
                                            to endoplasmic
                                            reticulum




Laura Coronado   Bio 10   Chapter 4
                                                   Figure 4.11
      How DNA Directs Protein Production

– DNA directs protein production by transferring its
  coded information into messenger RNA (mRNA).
– Messenger RNA exits the nucleus through pores in
  the nuclear envelope.
– A ribosome moves along the mRNA translating the
  genetic message into a protein with a specific amino
  acid sequence.




                   Laura Coronado   Bio 10   Chapter 4
                                      DNA



Synthesis of
mRNA in the
nucleus
                                      mRNA




Nucleus


                                              Cytoplasm

                              mRNA
Movement of
mRNA into                                      Ribosome
cytoplasm
via
nuclear pore


Synthesis of
protein in the
cytoplasm                               Protein
        Laura Coronado   Bio 10   Chapter 4
                                                          Figure 4.12-3
  THE ENDOMEMBRANE SYSTEM
– Many membranous organelles forming the
  endomembrane system in a cell are
  interconnected either
  • Directly or
  • Through the transfer of membrane segments
    between them
– The endoplasmic reticulum (ER) is one of
  the main manufacturing facilities in a cell.
  • Produces an enormous variety of molecules
  • Is composed of smooth and rough ER
               Laura Coronado   Bio 10   Chapter 4
                                       Nuclear
                                      envelope




      Ribosomes
      Rough ER           Smooth ER
TEM




                  Laura Coronado   Bio 10
                                            Ribosomes
                                            Chapter 4
                                                        Figure 4.13
        Endoplasmic Reticulum
– Rough ER (RER) is due to ribosomes that stud
  the outside of the ER membrane.
  • RER produce membrane proteins and secretory
    proteins.
  • After the rough ER synthesizes a molecule, it
    packages the molecule into transport vesicles.
– Smooth ER (SER) lacks surface ribosomes
  • Produces lipids, including steroids
  • Helps liver cells detoxify circulating drugs

                    Laura Coronado   Bio 10   Chapter 4
      Proteins are                  Secretory                     Vesicles bud off
      often modified in             proteins depart in            from the ER.
      the ER.                       transport vesicles.




       Ribosome
                                                                    Transport
                                                                    vesicle




                                                       Protein
A ribosome                                                        Rough ER
links amino acids
into a
polypeptide.
                      Polypeptide

                            Laura Coronado   Bio 10   Chapter 4
                                                                  Figure 4.14
           The Golgi Apparatus
– The Golgi apparatus
   • Works in partnership with the ER
   • Receives, refines, stores, and distributes
     chemical products of the cell




                                   Video: Euglena

                  Laura Coronado   Bio 10   Chapter 4
                      “Receiving” side of
                       Golgi apparatus




                                                                      Transport vesicle   “Receiving” side
                                                                      from rough ER       of Golgi
                                                                                          apparatus

                                                                                                             New
                                                                                                             vesicle
                                                                                                             forming




                                                                                                             Transport
                                                                                                             vesicle
                                                                                                             from the
                                                                                                             Golgi
                                                    “Shipping” side
                                                    of Golgi
                                                    apparatus
                                                                                                             Plasma
                                                                                                             membrane

New vesicle forming




                                Laura Coronado   Bio 10   Chapter 4
                                                                                             Figure 4.15
               Transport vesicle             “Receiving” side of
               from rough ER                 Golgi apparatus


                                                                      New
                                                                      vesicle
                                                                      forming




                                                                     Transport
                                                                     vesicle
                                                                     from the
                                                                     Golgi


“Shipping” side of
Golgi apparatus
                                                                      Plasma
                          Laura Coronado   Bio 10   Chapter 4
                                                                      membrane
                                                                   Figure 4.15a
                 Lysosomes
– A lysosome is a sac of digestive enzymes found
  in animal cells.
– Enzymes in a lysosome can break down large
  molecules such as
  • Proteins
  • Polysaccharides
  • Fats
  • Nucleic acids

                  Laura Coronado   Bio 10   Chapter 4
           Lysosome Functions
– Lysosomes have several of digestive functions.
  • Many cells engulf nutrients in tiny cytoplasmic sacs
    called food vacuoles.
  • These food vacuoles fuse with lysosomes, exposing
    food to enzymes to digest the food.
  • Small molecules from digestion leave the lysosome
    and nourish the cell.
– Lysosomes can also
  • Destroy harmful bacteria
  • Break down damaged organelles
                   Laura Coronado   Bio 10   Chapter 4
Plasma membrane                Digestive enzymes




          Lysosome                                                       Lysosome

                                                     Digestion
                                                                                                                     Digestion
                     Food vacuole                                                             Vesicle containing
                                                                                              damaged organelle

(a) Lysosome digesting food                                         (b) Lysosome breaking down the molecules of damaged
                                                                     organelles
                                                                                                                 Organelle fragment




                          Vesicle containing two
                          damaged organelles




                              Organelle fragment
                                                       TEM




                                                   Laura Coronado     Bio 10   Chapter 4
                                                                                                             Figure 4.16
Plasma membrane                  Digestive enzymes




              Lysosome

                                                                      Digestion

                          Food vacuole



(a) Lysosome digesting food



                              Laura Coronado   Bio 10   Chapter 4
                                                                    Figure 4.16a
        Lysosome



                                                                   Digestion
                                    Vesicle containing
                                    damaged organelle

(b) Lysosome breaking down the molecules of damaged organelles



                            Laura Coronado   Bio 10   Chapter 4
                                                                  Figure 4.16b
                   Vacuoles
– Vacuoles are membranous sacs that bud from:
  • ER
  • Golgi
  • Plasma membrane
– Contractile vacuoles of protists pump out excess
  water in the cell.
– Central vacuoles of plants
  • Store nutrients
  • Absorb water
  • May contain pigments or poisons
                 Laura Coronado   Bio 10   Chapter 4
                       Vacuole filling with water




                                                      LM
Vacuole contracting




                                                      LM
     (a) Contractile vacuole in Paramecium




                                      Colorized TEM
                Central vacuole



                                 a Chapter 4
     (b) Central vacuole in 10 plant cell
              Laura Coronado Bio
                                                           Figure 4.17
                                Vacuole filling with water




                                                                            TEM
Vacuole contracting




                                                                            TEM
                           in Coronado Bio 10
  (a) Contractile vacuole LauraParamecium       Chapter 4
                                                             Figure 4.17a
          Endomembrane System
– To review, the endomembrane system interconnects
  the
  •   Nuclear envelope
  •   ER
  •   Golgi
  •   Lysosomes
  •   Vacuoles
  •   Plasma membrane

                                 Video: Chlamydomonas


                  Blast Animation : Vesicle Transport Along Microtubules

                       Laura Coronado   Bio 10   Chapter 4
                  Rough ER
              Transport
              vesicle
Golgi
apparatus
                                                               Transport vesicles
Transport
                                                               carry enzymes and
vesicle
                                                               other proteins from
                                                               the rough ER to the
                                                               Golgi for processing.
Plasma
membrane
  Secretory             Vacuole                                Lysosomes carrying
  protein                                                      digestive enzymes can
                                          Lysosome             fuse with other vesicles.
  Some products      Vacuoles store some
  are secreted       cell products.
  from the cell.
                         Laura Coronado   Bio 10   Chapter 4
                                                                            Figure 4.18a
     CHLOROPLASTS AND MITOCHONDRIA:
           ENERGY CONVERSION
– Cells require a constant energy supply to perform the
  work of life.




                   Laura Coronado   Bio 10   Chapter 4
                  Chloroplasts
– Most of the living world runs on the energy provided
  by photosynthesis.
– Photosynthesis is the conversion of light energy from
  the sun to the chemical energy of sugar.
– Chloroplasts are the organelles that perform
  photosynthesis.
– Chloroplasts have three major compartments:
   • The space between the two membranes
   • The stroma, a thick fluid within the chloroplast
   • The space within grana, the structures that trap
     light energy and convert it to chemical energy
                   Laura Coronado   Bio 10   Chapter 4
        Inner and outer
        membranes




Space between
membranes
 Stroma (fluid in chloroplast)                                                    Granum




                                                                                TEM
                            Laura Coronado   Bio 10   Chapter 4
                                                                  Figure 4.19
               Mitochondria
– Mitochondria are the sites of cellular
  respiration, which produce ATP from the
  energy of food molecules.
– Mitochondria are found in almost all
  eukaryotic cells.
– An envelope of two membranes encloses the
  mitochondrion. These consist of
  • An outer smooth membrane
  • An inner membrane that has numerous infoldings
    called cristae
                 Laura Coronado   Bio 10   Chapter 4
                Outer




                                                         TEM
              membrane




   Inner
 membrane


    Cristae

    Matrix

Space between
 membranes



     Laura Coronado   Bio 10   Chapter 4
                                           Figure 4.20
     Mitochondria & Chloroplasts
– Mitochondria and chloroplasts contain their own
  DNA, which encodes some of their proteins.
– This DNA is evidence that mitochondria and
  chloroplasts evolved from free-living prokaryotes in
  the distant past.




                    Laura Coronado   Bio 10   Chapter 4
            THE CYTOSKELETON
– A network of fibers extending throughout the
 cytoplasm.
  • Provides mechanical support to the cell
  • Maintains its shape
  • Contains several types of fibers made from different
    proteins:
     –Microtubules are straight and hollow & guide the
       movement of organelles and chromosomes
     –Intermediate filaments and microfilaments are
       thinner and solid.

                  Laura Coronado   Bio 10   Chapter 4
LM




 (a) Microtubules
 in the cytoskeleton




     (b) Microtubules
     and movement
                        LM




                             Laura Coronado   Bio 10   Chapter 4
                                                                   Figure 4.21
                Cilia and Flagella
– Cilia and flagella aid in movement.
   • Flagella propel the cell in a whiplike motion.
   • Cilia move in a coordinated back-and-forth motion.
   • Cilia and flagella have the same basic architecture.
– Cilia may extend from nonmoving cells.
– On cells lining the human trachea, cilia help sweep
  mucus out of the lungs.
                  Video: Prokaryotic Flagella (Salmonella typhimurium)


                                Video: Paramecium Cilia


                              Animation: Cilia and Flagella

                      Laura Coronado   Bio 10   Chapter 4
                                                                                            Colorized SEM
                                                                   (b) Cilia on a protist




                                                                                            Colorized SEM
                                                   Colorized SEM




                                                         (c) Cilia lining the
(a) Flagellum of a human sperm cell                      respiratory tract
                       Laura Coronado   Bio 10   Chapter 4
                                                                         Figure 4.22
             Evolution Connection:
      The Evolution of Antibiotic Resistance
– Many antibiotics disrupt cellular structures of invading
  microorganisms.
– Introduced in the 1940s, penicillin worked well against
  such infections.
– But over time, bacteria that were resistant to
  antibiotics were favored.
– The widespread use and abuse of antibiotics continues
  to favor bacteria that resist antibiotics.


                    Laura Coronado   Bio 10   Chapter 4
Laura Coronado   Bio 10   Chapter 4
                                      Figure 4.23
                              CATEGORIES OF CELLS

          Prokaryotic Cells                                         Eukaryotic Cells




• Smaller                                        • Larger
• Simpler                                        • More complex
• Most do not have organelles                    • Have organelles
• Found in bacteria and archaea                  • Found in protists, plants,
                                                  fungi, animals



                              Laura Coronado   Bio 10   Chapter 4
                                                                          Figure 4.UN12
Outside of cell
                                              Phospholipid


                                                                            Hydrophilic



                         Protein                                            Hydrophobic



                                                                            Hydrophilic



Cytoplasm (inside of cell)


                             Laura Coronado   Bio 10   Chapter 4
                                                                   Figure 4.UN13
                                                                 Mitochondrion

                 Chloroplast

Light energy                                Chemical
                                                                CELLULAR
               PHOTOSYNTHESIS                energy                              ATP
                                                               RESPIRATION
                                             (food)




                         Laura Coronado   Bio 10   Chapter 4
                                                                 Figure 4.UN14

								
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