BIO 1140 Lecture Notes - Lecture 6: Gap Junction, Centriole, Dynein

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Membranes
BIO1140 Introduction to Cell Biology: Lecture 6
Cilia and agellum use microtubules to exert dierent
motion
Cilia and agellum are dierent; they have dierent
functions and structures, you typically have more cilia
than you do agella
Basic structure of each is similar (9+2 structure)
9+2 structure: Ring of 9 circular doublet pairs and another
doublet in the center
Anchored inside the cell: In animal cells they’re connected
to the centriole, acts as an anchor/base for cilia or agella
Cilia goal: Trying to get particles stuck into the cilia (for
food) as well as moving the cell around/the environment
around them. Moving the environment is their main
function. Objective is to move the surroundings
away/forward from the cell. This can be useful to get rid of
pathogens/bacteria. Idea is to move the environment away
from the cells surrounding (can get rid of harmful things or
can bring the environment around the cell to incorporate
nutrients). Cilia exercise their movement to move their
surroundings
Flagella goal: Initial portion of agella is typically
0xed/more rigid (cilia already have a movement imposed)
agella has a dierent movement than cilia, they move
like an S wave. Structure looks more like a propeller. This
helps to move the cell from point A to B. End result will be
dierent because of the dierence in the shape of
movement.
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If there was no anchor for cilia and agella: Nexin is a
cross linker protein that holds together the 9 doublets,
without it you wouldn’t have the circular shape. The
doublets would slide apart because the dynein would slide
apart (dynein is walking towards the cell), as it’s walking
between each doublet if there’s no link between the
doublets then the motor end, on each of the 9 doublets
and they need to be attached together. You also need
them to be able to bend and come back. Otherwise you
would just be getting one way and you need it to go back
and forth to get the motility.
Without you would dyenin’s walking and microtubules
sliding apart. Coming back you get the reverse motion.
Need to be able to explain and demonstrate this.
Centrosome/Centrioles: Centrioles are made of two
centrosomes placed in an L shape. Centrioles separate by
pulling apart. They’re the anchor for cilia and agellum.
Microtubule organization centre: Centrioles organize the
microtubules. Having the structure as an L with 9 tirplets
organized in circulation allows microtubueles to be
organized. 9+2 can be reorganized to form doublets and
one in the centre. In centrioles theree’s no triplet or
doublet
How do cells interact?: Should be able to dierentiate
between the dierent junctions
oTight Junctions:
oAnchoring Junctions:
oGap Junctions: Junctions talking about when talking
about cells communicating with one another by
sending ions across the membrane. Gap junctions
are proteins that form a ring, six subunits span the
membrane (need to be able to be in a hydrophobic
2
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Document Summary

Cilia and flagellum use microtubules to exert different motion. Cilia and flagellum are different; they have different functions and structures, you typically have more cilia than you do flagella. Basic structure of each is similar (9+2 structure) 9+2 structure: ring of 9 circular doublet pairs and another doublet in the center. Anchored inside the cell: in animal cells they"re connected to the centriole, acts as an anchor/base for cilia or flagella. Cilia goal: trying to get particles stuck into the cilia (for food) as well as moving the cell around/the environment around them. Objective is to move the surroundings away/forward from the cell. This can be useful to get rid of pathogens/bacteria. Idea is to move the environment away from the cells surrounding (can get rid of harmful things or can bring the environment around the cell to incorporate nutrients). Cilia exercise their movement to move their surroundings.

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