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4.3 The Endoplasmic
Reticulum, Golgi
Apparatus, and
Lysosomes are part of an
extensive
endomembrane
- Overview
- Cells have extensive sets of intracellular
membranes which compose the
endomembrane system
- First discovered in the late 1800s
- Contains: the ER, golgi, and lysosomes.
- First discovered in the late 1800s
- Cells have extensive sets of intracellular
membranes which compose the
endomembrane system
- How are the cell membranes synthesized?
- Membranes and proteins assembled in the ER
- ER: contains the enzymes involved
in lipid synthesis (lipids
manufactured in the ER and inserted
into the organelle's own
membranes_
- ER: contains the enzymes involved
in lipid synthesis (lipids
manufactured in the ER and inserted
into the organelle's own
membranes_
- Transpermeable proteins have enough
hydrophobic surfaces that they are also
inserted into the ER membrane while
being made
- Lumen: proteins that will be
secreted by a cell end up in this
internal cavity where they are then
packaged for vesicular release from
the cell
- Membranes and proteins assembled in the ER
- How are organelle membranes maintained?
- Membrane lipids and proteins
synthesized in ER must be transported
through the network to the vesicles
- Vesicles: cargo-bearing, pinch off of one
set of membranes and travel along
microtubule tracks to the next set of
membranes where they fuse with these
structures
- Vesicles: cargo-bearing, pinch off of one
set of membranes and travel along
microtubule tracks to the next set of
membranes where they fuse with these
structures
- Membrane lipids and proteins
synthesized in ER must be transported
through the network to the vesicles
- Golgi apparatus
- Functions as a molecular assembly line in which
membrane proteins undergo extensive
post-translational modification
- Many reactions involve the addition of sugar
residues to membrane proteins and secreted
proteins
- cis-Golgi: vesicles that bud off from the ER fuse
with the closet golgi membranes
- trans-Golgi: cis-golgi until reach the end of
the assembly line at the farthest sacs from
the ER
- Functions as a molecular assembly line in which
membrane proteins undergo extensive
post-translational modification
- Lysosomes
- Break down molecules into smaller parts which are then recycled
- Have enzymes called hydrolases that can digest proteins, nucleic acids, lipids, and other complex sugars
- Endocytosis: Vesicles that bud off from the plasma
membrane via this are also sent to lysosomes where
their extracts are procceds
- Break down molecules into smaller parts which are then recycled
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