Biology 107 Cell III

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Biology 107Cell III

• September 27, 2004

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Cell III

• Student Objectives As a result of this lecture
  and the assigned reading, you should understand
  the following
• 1. The mitochondria carry out cellular
  respiration in which the chemical energy of
  foods, such as sugars, is converted to useful
  chemical energy in the form of the molecule ATP.
  Mitochondria are double membrane containing
  structures.
• a. The inner membrane encloses a fluid-filled
  space called the mitochondrial matrix.
• b. The space between the inner and outer
  membrane is the intermembrane space.

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Cell III

• c. The intermembrane space contains one set of
  enzymes, while the mitochondrial matrix contains
  a different set of enzymes. Also, the inner cell
  membrane is highly folded and contains enzymes
  that are responsible for ATP production. Each
  fold is called a crista (plural, cristae) and
  the folding increase the membrane surface area
  for the enzymes.
• d. Mitochondria contain circular DNA and
  prokaryote-like ribosomes, suggesting they arose
  from symbiotic association between aerobic
  organisms (the precursors of mitochondria) and
  anaerobic organisms (the precursors of the cell
  in which the mitochondria reside).

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Cell III

• 2. Like mitochondria, chloroplasts are double
  membrane structures with their own DNA and
  ribosomes. Like mitochondria, chloroplasts are
  fuel processors, but they convert solar energy
  into chemical energy, while mitochondria convert
  one form of chemical energy into another form of
  chemical energy. The membranes partition the
  chloroplast into three major compartments
  involved in photosynthesis.
• a. The intermembrane space is between the outer
  and inner chloroplast membranes.
• b. The space enclosed by the inner membrane, the
  stroma, contains the thylakoid membranes, a the
  network of tubules and hollow discs.
• c. The space inside thylakoid membranes.

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Cell III

• The cytoskeleton is a supportive network of
  intracellular linear polymers. These
  cytoskeletal elements are important in
  maintaining cell shape and motility of cells and
  their organelles.
• a. Microfilaments are long polar filaments
  composed of actin. These filaments are involved
  in cell shape changes through interaction with
  other proteins (e.g., myosin), they participate
  in cellular contractility.
• b. Intermediate filaments constitute a class of
  proteins rather than a single protein species.
  Intermediate filaments are very stable linear,
  rope-like structures that help to anchor
  structures.
• c. Microtubules are composed of tubulin that
  forms long straight polymers that are easily
  assembled and disassembled. These dynamic
  structures are involved in the movement of
  organelles around the cell.

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Cell III

• Cells are dynamic structures - they are
  continually moving components around and
  transferring substances between compartments and
  regions. Examples of how cells segregate
  materials include protein sorting and vesicular
  transport.
• a. Protein sorting relates to the different
  regions specific proteins must localize to
  provide proper functioning in the cell. Some
  proteins must enter the nucleus, others enter
  membranous organelles such as mitochondria,
  lysosomes, or chloroplasts, and still others
  become integral membrane proteins or secreted
  proteins.
• b. Vesicular transport carries vesicle contents
  and membrane to intracellular sites or to sites
  on the plasma membrane for release to the
  outside of the cell. The various vesicular
  transport and secretion pathways use molecular
  signals or "tags" to designate the proper
  sorting.

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Structure of a Mitochondrion
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Mitochondria are Double-membrane Structures
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Chloroplasts are Double-membrane Structures
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Chloroplast
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Cytoskeleton Consist of Three Elements
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Examples of Microfilament Function
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Micrographs of Microfilaments and Intermediate
Filaments
Intermediate filaments
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Microtubule Organizing Centers (MTOCs)
Actin
MTOC
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Microtubules and Accessory Proteins are Involved
with Intracellular Movement of Organelles
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Cells are Dynamic Structures
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Review - Pathway for Movement of Proteins and
Membranes