BIO 1140 Lecture Notes - Lecture 7: Gap Junction, Spindle Apparatus, Cell Membrane

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BIO1140 January 28th
Cilia & Flagellum
Movement: either to attract the surroundings (nutrients) or movement of the cell around its
Cilia, movement begins right at the plasma membrane. Flagellum have a rigid portion right at the
base but is longer, motion can be almost propeller like, rotary.
Both emerge from basal bodies- microtubules. Centrioles form basal bodies.
Length: flagella are much longer, cilia usually short
Nine doublets in a circular structure, two in the middle.
Why would doublets slide apart if there was no anchor? (Nexin)
Between each doublet are motor proteins. They’re “walking” on one doublet. As dyneins are
heading towards the plasma membrane, the doublets would slip apart. Because the the dyneins
are tied together, they don’t slide apart but rather sway back and forth in a whiplike motion.
Centrosomes are made up of 2 centrioles in an L-shape
Centrioles are made up of 9 microtubule triplets arranged in a ring structure (with no
central triplet)
Will serve as anchor to cilia and flagellum
Mitotic spindle formation
Cell to cell interactions Junctions
Tight junctions
Anchoring junctions
Gap junctions made of 6 protein subunits that span across both layers of plasma
membrane. They change how they are oriented within the membrane, which can change
the overall shape within a gap junction.
How can an axon grow to reach a target?
Microfilaments right underneath the membrane can form more rigid structures that support the
membrane. As the microtubules elongate to help the cell stretch, actin subunits add to the
microfilaments in order to help the membrane expand as well.
The axon has receptors on its membrane that can receive chemical signals from neighboring
cells. this is how the axon knows where its target is
Membranes and Membrane Transport
Why do we have membranes?
1. Boundary; selective permeability
2. Organize and scaffold
3. Regulate solute transport
4. Receive signals
5. Communication
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