Eukaryotic Membranes: Golgi complex

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Eukaryotic Membranes Golgi complex

• The Golgi complex is a specialized set of
  membranous sacs derived from the endoplasmic
  reticulum.

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Eukaryotic Membranes Golgi complex

• In fact it looks like discs of smooth ER stacked
  on top of one another.
• The vesicles that we talked about budding off
  from the smooth ER now fuse with the sacs on one
  side of the Golgi complex.
• Adding membrane to the Golgi complex
• Emptying their context into the Golgi complex.

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Eukaryotic Membranes Golgi complex
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Eukaryotic Membranes Golgi complex

• While some vesicles are joining the Golgi complex
  on one side others are leaving the other side.
• These vesicles are carrying proteins, lipids and
  other complex molecules.

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Eukaryotic Membranes Golgi complex

• The Golgi complex performs the following three
  major functions.
• It separates proteins and lipids received from
  the ER according to their destinations for
  esample, the Golgi separates digestive enzymes
  that are bound for lysosomes from hormones that
  will be secreted from the cell.

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Eukaryotic Membranes Golgi complex

1. It modifies some molecules for instance, adding
   sugars to proteins to make glycoproteins
2. It packages these materials into vesicles that
   are then transported to other parts of the cell
   or to the plasma membrane for export.

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Eukaryotic Membranes Golgi complex
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Eukaryotic Membranes Lysosomes

• Some of the proteins manufactured in the ER and
  sent to the Golgi are intracellular digestive
  enzymes that can break down proteins, fats, and
  carbohydrates into their component subunits.

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Eukaryotic Membranes Lysosomes

• In the Golgi, these enzymes are packaged in
  membraneous vesicles called lysosomes

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Eukaryotic Membranes Lysosomes

• The major function of lysosomes is to digest food
  particles, which range from individual proteins
  to complete microorganisms

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Eukaryotic Membranes Lysosomes

• As we will discuss in the future many cells eat
  by phagocytosis (engulfing extracellular
  particles with extensions of the plasma membrane.
• These membranous sacs are called food vacuoles

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Eukaryotic Membranes Lysosomes

• Lysosomes recognize these food vacuoles and fuse
  with them.
• The contents of the two vesicles mixes, and the
  lysosomal enzymes digest the food into amino
  acids, monosaccharides, fatty acids, and other
  small molecules, which then diffuse into the
  cytoplasm

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Eukaryotic Membranes Lysosomes
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Eukaryotic Membranes Lysosomes

• It is still not understood how lysosomes
  recognize these food vacuoles, but research is
  being done in this field
• Lysosomes also digest defective or malfunctioning
  organelles, such as mitochondria or chloroplasts.
  Doing so in the same manner as food vacuoles.

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Eukaryotic Membranes Chloroplasts and
Mitochondria

• Each cell has specific needs
• manufacture materials,
• pick things up from the environment
• throw other things out
• to move
• to reporduce

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Eukaryotic Membranes Chloroplasts and
Mitochondria

• Mitochondria and chloroplasts are responsible for
  providing energy for the cell.
• They are exxentially foreign creatures thought to
  have evovled from bacteria that took up residence
  long ago within a fortunate eukaryotic cell.

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Eukaryotic Membranes Chloroplasts and
Mitochondria
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Eukaryotic Membranes Chloroplasts and
Mitochondria

• There are many similarities between the two
  organelles
• Both are usually oblong
• Surrounded by double membranes
• Have enzyme assemblies that synthesize ATP
• DNA unique to themselves

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Eukaryotic Membranes Chloroplasts and
Mitochondria

• At the same time they are different due to
  different functions.
• Chloroplasts capture the energy of sunlight
  during photosynthesis and store it in sugar
• Mitochondria convert the energy of sugar into ATP
  for use by the cell

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Eukaryotic Membranes Chloroplasts and
Mitochondria

• The endosymbiotic hypothesis gives an explanation
  of the possible incorporation of bacteria into
  the cytoplasm of host cells, and the possible
  origin of the double membrane surrounding
  mitochondria and chloroplasts

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Eukaryotic Membranes Chloroplasts and
Mitochondria
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Eukaryotic Membranes Chloroplasts

• Chloroplasts are found only in plants and certain
  protist, notable the unicellular algae.
• They are surrounded by two membranes, though
  there is very little space between them
• The inner membrane encloses a semifluid material
  called the stroma.

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Eukaryotic Membranes Chloroplasts

• Embedded within the stroma are interconnected
  stacks of hollow membranous sacs.
• The individual sacs are called thylakoids and a
  stack of sacs is a granum
• The green pigment, chlorophyll, which captures
  light energy is stored in the thylakoid.

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Eukaryotic Membranes Chloroplasts

• Energy from sun
• Thylakoid
• ATP
• Stroma
• Sugar

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Eukaryotic Membranes Mitochondria

• Whereas chloroplasts convert solar energy into
  chemical energy, mitochondria extract energy from
  food molecules and tore it in the high-energy
  bonds of ATP
• A cell digests food by both aerobic and anaerobic
  metabolism.

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Eukaryotic Membranes Mitochondria

• Anaerobic (without oxygen) occurs in the cytosol.
• Aerobic (with oxygen) occurs with in the
  mitochondria, and is 18-19 times more efficient.

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Eukaryotic Membranes Mitochondria

• Because mitochondria are energy producing they
  are found in higher concentrations in certain
  cells such as muscle, and less abundant in others
  such as bone.
• Mitochondria are the power house of the cell and
  will be discusses further later in the course.

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Eukaryotic Membranes Mitochondria

• Cistae, deep folding loops
• Matrix, inner compartment
• Intermembrane Compartment, space between membranes

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Eukaryotic Membranes Plastids and Vacuoles

• There are times when a cell will find itself in a
  favourable environment, where food can be stored
  rather than used.
• Because of this cells have evolved organelles in
  which to store such valuable molecules.

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Eukaryotic Membranes Plastids and Vacuoles

• Plastids are used as storage containers for
  various types of molecules
• They are double membraned organelles

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Eukaryotic Membranes Plastids and Vacuoles

• Especially important, particularly for perennial
  plants (year after year) are plastids that store
  photosynthetic products from the summer for use
  during the following winter and spring.
• Starch is usually the means of storage, potatoes
  being an example of this.