Transcript Title - Angelfire

Eukaryotic Membranes: Golgi
complex
• The Golgi complex
is a specialized set
of membranous
sacs derived from
the endoplasmic
reticulum.
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.
Eukaryotic Membranes: Golgi
complex
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.
Eukaryotic Membranes: Golgi
complex
•
The Golgi complex performs the
following three major functions.
1. 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.
Eukaryotic Membranes: Golgi
complex
2. It modifies some molecules – for
instance, adding sugars to proteins to
make glycoproteins
3. It packages these materials into vesicles
that are then transported to other parts of
the cell or to the plasma membrane for
export.
Eukaryotic Membranes: Golgi
complex
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.
Eukaryotic Membranes:
Lysosomes
• In the Golgi, these
enzymes are
packaged in
membraneous
vesicles called
lysosomes
Eukaryotic Membranes:
Lysosomes
• The major function of lysosomes is to digest
food particles, which range from individual
proteins to complete microorganisms
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
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
Eukaryotic Membranes:
Lysosomes
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.
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
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.
Eukaryotic Membranes:
Chloroplasts and Mitochondria
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
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
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
Eukaryotic Membranes:
Chloroplasts and Mitochondria
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.
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.
Eukaryotic Membranes:
Chloroplasts
•
•
•
•
•
Energy from sun
Thylakoid
ATP
Stroma
Sugar
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.
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.
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.
Eukaryotic Membranes:
Mitochondria
• Cistae, deep folding
loops
• Matrix, inner
compartment
• Intermembrane
Compartment,
space between
membranes
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.
Eukaryotic Membranes: Plastids
and Vacuoles
• Plastids are used as
storage containers
for various types of
molecules
• They are double
membraned
organelles
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.