A View of the Cell

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Chapter 8

• A View of the Cell

2
Cell History

• The microscope was invented in the 17th century
• Using a microscope, Robert Hooke discovered cells
  in 1665
• All living things are made of cells (cell theory)

3
Cell Theory

• All cells come from preexisting cells
• The cell is the basic unit of organization of
  organisms.
• All organisms are made up of one or more cells.

4

• The light microscope enables us to see the
  overall shape and structure of a cell

Image seen by viewer
Eyepiece
Ocularlens
Objective lens
Specimen
Condenser lens
Light source
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• Electron microscopes were invented in the 1950s

• They use a beam of electrons instead of light
• The greater resolving power of electron
  microscopes
• allows greater magnification
• reveals cellular details

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• Scanning electron microscope (SEM)

• Scanning electron micrograph of cilia

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• Transmission electron microscope (TEM)

• Transmission electron micrograph of cilia

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Cell sizes vary with their function

• Below is a list of the most common units of
  length biologists use (metric)

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• Cell size and shape relate to function

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Cell Types

• There are two kinds of cells prokaryotic and
  eukaryotic
• Prokaryotic cells are small, relatively simple
  cells
• They do not have a nucleus

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• A prokaryotic cell is enclosed by a plasma
  membrane and is usually encased in a rigid cell
  wall

• The cell wall may be covered by a sticky capsule

Prokaryoticflagella
Ribosomes
Capsule
Cell wall
Plasma membrane

• Inside the cell are its DNA and other parts

Nucleoid region(DNA)
Pili
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Eukaryotic cells are partitioned into functional
compartments

• All other life forms are made up of one or more
  eukaryotic cells
• These are larger and more complex than
  prokaryotic cells
• Eukaryotes are distinguished by the presence of a
  true nucleus

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• An animal cell

Smooth endoplasmicreticulum
Nucleus
Roughendoplasmicreticulum
Flagellum
Not in most plant cells
Lysosome
Centriole
Ribosomes
Peroxisome
Golgiapparatus
Microtubule
Plasma membrane
Cytoskeleton
Intermediatefilament
Mitochondrion
Microfilament
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• The plasma membrane controls the cells contact
  with the environment

• The cytoplasm contains organelles
• Many organelles have membranes as boundaries
• These compartmentalize the interior of the cell
• This allows the cell to carry out a variety of
  activities simultaneously

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• A plant cell has some structures that an animal
  cell lacks

• Chloroplasts
• A rigid cell wall

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Roughendoplasmicreticulum
Nucleus
Ribosomes
Smoothendoplasmicreticulum
Golgiapparatus
Microtubule
Centralvacuole
Not inanimalcells
Cytoskeleton
Intermediatefilament
Chloroplast
Microfilament
Cell wall
Mitochondrion
Peroxisome
Plasma membrane
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The nucleus is the cells genetic control center

• The largest organelle is usually the nucleus
• The nucleus is separated from the cytoplasm by
  the nuclear envelope
• The nucleus is the cellular control center
• It contains the DNA that directs the cells
  activities

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NUCLEUS
Chromatin
Two membranesof nuclearenvelope
Nucleolus
Pore
ROUGHENDOPLASMICRETICULUM
Ribosomes
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• The endomembrane system is a collection of
  membranous organelles
• These organelles manufacture and distribute cell
  products
• The endomembrane system divides the cell into
  compartments
• Endoplasmic reticulum (ER) is part of the
  endomembrane system

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Rough endoplasmic reticulum makes membrane and
proteins

• The rough ER manufactures membranes
• Ribosomes on its surface produce proteins

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• Smooth ER synthesizes lipids
• In some cells, it regulates carbohydrate
  metabolism and breaks down toxins and drugs

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SMOOTH ER
ROUGHER
Nuclearenvelope
Ribosomes
SMOOTH ER
ROUGH ER
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• The Golgi apparatus consists of stacks of
  membranous sacs
• These receive and modify ER products, then send
  them on to other organelles or to the cell
  membrane

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• The Golgi apparatus

Golgi apparatus
Golgiapparatus
Receiving side ofGolgi apparatus
Transportvesiclefrom ER
Newvesicleforming
Shippingside of Golgiapparatus
Transport vesiclefrom the Golgi
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Lysosomes digest the cells food and wastes
LYSOSOME

• Lysosomes are sacs of digestive enzymes budded
  off the Golgi

Nucleus
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• Lysosomal enzymes

• digest food
• destroy bacteria
• recycle damaged organelles
• function in embryonic development in animals

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Rough ER
Transport vesicle(containing inactivehydrolytic
enzymes)
Plasmamembrane
Golgiapparatus
Engulfmentof particle
Lysosomeengulfingdamagedorganelle
Food
LYSOSOMES
Digestion
Foodvacuole
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• Plant cells contain a large central vacuole
• The vacuole has lysosomal and storage functions

Centralvacuole
Nucleus
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• Protists may have contractile vacuoles

• These pump out excess water

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ENERGY-CONVERTING ORGANELLES

• Chloroplasts are found in plants and some
  protists
• Chloroplasts convert solar energy to chemical
  energy in sugars

Chloroplast
Stroma
Inner and outer membranes
Granum
Intermembranespace
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• Mitochondria carry out cellular respiration

MITOCHONDRION
Outermembrane
Intermembranespace

• This process uses the chemical energy in food to
  make ATP for cellular work

Innermembrane
Cristae
Matrix

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THE CYTOSKELETON AND RELATED STRUCTURES
The cells internal skeleton helps organize its
structure and activities

• A network of protein fibers makes up the
  cytoskeleton

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• Microfilaments of actin enable cells to change
  shape and move

• Intermediate filaments reinforce the cell and
  anchor certain organelles
• Microtubules
• give the cell rigidity
• provide anchors for organelles
• act as tracks for organelle movement