Active and Bulk Transport

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Active and Bulk Transport
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Active Transport

• passive transport is useful for many metabolic
  functions, but often materials need to be
  concentrated
• ?this requires moving them against a
  concentration gradient
• adenosine triphosphate (ATP) provides the energy
  needed in this and many other processes of living
  cells

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ATP

• ATP is similar to the structure of a nucleotide,
  except that it contains 3 phosphate groups
  attached to a ribose sugar
• ?energy is released when the high-E bond between
  the 2nd and 3rd phosphate group is broken

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Adenosine Triphosphate
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Active Transport Mechanism

• active transport is the movement of molecules and
  ions against a concentration gradient
• ?molecules and ions bind to a protein carrier
  which uses energy from ATP to pump molecules or
  ions across the cell membrane
• ?the molecule to be transported attaches to an
  open binding site on one side of the carrier
  protein
• ?ATP is converted to ADP P on the carrier
  protein and releases energy
• ?the energy causes a change in the shape of the
  protein that carries the solute to the other side
  of the membrane

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Na/K Pump

• The Na/K pump is utilized in neurons (nerve
  cells)
• ?Na ions must be higher outside the cell, while
  K ions must be lower outside the cell for a
  nerve transmission to occur
• ?Binding of the phosphate from ATP changes the
  shape of the protein, alternately providing
  binding sites for three Na ions to be
  transported out for every two K ions to be
  transported into the cell

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http//www.youtube.com/watch?vKd3LorZcJewfeature
related
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Cystic Fibrosis

• Cystic fibrosis is a disease in which the protein
  for active transport of Cl- ions out of cells is
  faulty, resulting in a buildup of Cl- ions and
  reduced reabsorption of Na ions
• This results in dehydration of lung and digestive
  tissue, increased mucous, and reduced ability to
  defend against bacteria.

http//www.youtube.com/watch?v5n29ZCvtCI8feature
related
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Bulk Transport

• vesicles are required for movement of large
  particles (i.e. proteins, polysaccharides) in and
  out of cells, requiring energy from ATP.

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Endocytosis

• endocytosis involves the pinching in of a portion
  of the cell membrane to form a vesicle inside the
  cytoplasm which then travels to the needed
  location within the cell.
• two types phagocytosis and pinocytosis

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Phagocytosis

• Phagocytosis (cell eating) is the bulk transport
  of solids into the cell
• Involves the use of pseudopods to engulf
  particles (i.e. macrophages WBC engulf entire
  bacteria) which eventually encloses them in a
  vesicle within the cells cytoplasm
• Lysosomes containing digestive enzymes may fuse
  with the phagocytic vesicle to digest the
  particles it contains

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Electron Micrograph of Macrophage Phagocytosis of
E. coli
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Pinocytosis

• pinocytosis (cell drinking) is the bulk transport
  of (liquid) extracellular fluid into vesicles in
  the cell, forming a pinocytic vesicle

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Receptor-Mediated Endocytosis

• molecule binds to receptor protein on cell
  membrane exterior

?receptor-molecule complexes move within
membrane ?vesicles form when enough accumulate
(i.e. insulin)
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Hypercholesterolemia

• Hypercholesterolemia is a condition in which
  receptor proteins on liver cells used to remove
  excess cholesterol is absent or reduced in
  number.
• This leads to heart and artery disease

http//www.youtube.com/watch?vUIjkAPn2CRE
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Exocytosis

• exocytosis moves large amounts of material out of
  the cell in a process which is the reverse of
  endocytosis
• some cells produce substances for export like
  proteins (i.e. hormones, enzymes)
• ?vesicles form around proteins created in the
  endoplasmic reticulum
• ?vesicles merge with the Golgi body where the
  protein is modified and packaged for export
• ?new vesicles are formed by the Golgi body which
  move to and merge with the cell membrane,
  expelling the protein from the cell (i.e.
  hormones expelled into blood, digestive enzymes
  into lumen of small intestine)

http//www.youtube.com/watch?vbD4z27ASN1Mfeature
fvsr
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