Microscopes provide windows to the world of the cell

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Microscopes provide windows to the world of the
cell

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

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Electron microscopes

• They use a beam of electrons instead of light
• The greater resolving power of electron
  microscopes

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The Cell Theory

• Robert Hooke (1600s/ English)) used a compound
  light microscope to study cork, the dead cells of
  oak bark.
• Cells are the basic building blocks of all
  living things.
• Schleiden Schwann (1830s, German) their
  observations conclusions are summarized as the
  cell theory

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The cell theory is made up of three main ideas

• 1.All organisms are composed of one or more
  cells.
• 2. The cell is the basic unit of
  organization of organisms.
• 3. All cells come from preexisting cells.

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Cell sizes vary with their function

• Cell size and shape relate to function

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Natural laws limit cell size

• a cell must be large enough to house the parts it
  needs to survive and reproduce
• The maximum size of a cell is limited by the
  amount of surface needed to obtain nutrients from
  the environment and dispose of wastes

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A small cell has a greater ratio of surface area
to volume than a large cell of the same shape
10 µm
30 µm
Total surface areaof 27 small cubes 16,200 µm2
Surface areaof one large cube 5,400 µm2
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2 Types of cells 1. Prokaryotic 2. Eukaryotic
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Prokaryotic cells-Bacteria

• small, relatively simple cells

• They do not have a nucleus

• enclosed by a plasma membrane and is usually
  encased in a rigid cell wall
• Inside the cell are its DNA and other parts

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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
• 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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Animal Cell
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Plant Cell
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The nucleus

• 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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Endoplasmic reticulum (ER)

• The rough ER manufactures membranes
• Ribosomes on its surface produce proteins
• Smooth ER synthesizes lipids
• In some cells, it regulates carbohydrate
  metabolism and breaks down toxins and drugs

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The Golgi apparatus

• finishes, sorts, and ships cell products
• 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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Lysosomes

• sacs of digestive enzymes budded off the Golgi
• Lysosomal enzymes
• digest food
• destroy bacteria
• recycle damaged organelles
• function in embryonic development in animals

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Connection Abnormal lysosomes can cause fatal
diseases

• Lysosomal storage diseases are hereditary
• They interfere with other cellular functions
• Examples Pompes disease, Tay-Sachs disease

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Vacuoles have diverse functions in cell
maintenance

• membrane-bound sacs with varied functions.
• Food vacuoles, from phagocytosis, fuse with
  lysosomes.
• Contractile vacuoles, found in freshwater
  protists, pump excess water out of the cell.
• Central vacuoles are found in many mature plant
  cells.

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ENERGY-CONVERTING ORGANELLES
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Chloroplasts

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

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Mitochondria harvest chemical energy from food

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

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THE CYTOSKELETON

• The cells internal skeleton helps organize its
  structure and activities
• A network of protein fibers makes up the
  cytoskeleton

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three main types of fibers in the cytoskeleton
microtubules, microfilaments, and intermediate
filaments.

• Microfilaments 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

INTERMEDIATEFILAMENT
MICROFILAMENT
MICROTUBULE
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Cilia and flagella

• locomotor appendages that protrude from certain
  cells
• Clusters of microtubules drive the whipping
  action of these organelles