Lecture 6: Regulation of Animal Cell Shape Flashcards
What does the cytoskeleton do?
helps maintain cell shape.
and position of organelles
with in cells.
the cytoskeleton rapidly disassembles and reassembles, unlike the body’s skeletal system. this ability allows rapid changes in cell shape.
the cytoskeleton is highly
dynamic but still provides
stability.
What is the three main components of the cytoskeleton?
Microtubules
Microfilaments
Intermediate Filaments
What are microtubules made out of?
Tubulin subunits
What are microfilaments made out of?
Actin subunit
What are intermediate filaments made out of?
Keratin Proteins Fibrous subunit (keratins coiled together)
What do microtubules do?
Resist compression and help maintain cell shape.
they also provide cell motility
flagella: snake-like motion
cilia: rowing-like motion
Microtubules are also
involved in organelle
motility within the cell
ATP-powered motor
proteins can “walk”
organelles along
microtubules
Allows vesicles, or
other organelles, to be
transported to specific
targets within the cell
What do microfilaments do?
Microfilaments resist tension
The cortical network under the
plasma membrane helps make
this region less fluid and thus
maintains cell shape
Interactions between actin and
motor proteins such as myosin
support cell movement
Actin-myosin interactions allow:
- muscle contraction.
- amoeboid movement.
- cytoplasmic streaming in
plants.
What do Intermediate filaments do?
Are made of various proteins including: - keratins in hair. - lamins in the nucleus. - neurofilaments in neurons.
Supercoiled into “cables” Less dynamic than microtubules or microfilaments Intermediate Filaments form relatively permanent cellular structures
What is the name of the the three ways cells are joined together?
Tight Junctions
Desmosomes
Gap Junctions
Tight Junction
Hold neighbouring cells tightly
pressed together
May form a continuous seal
Prevents movement of fluid across cell layers
what type cell junction prevents movement of fluid across cell layers
Tight Junctions
Desmosomes
Anchoring junction
Provide attachments between
sheets of cells e.g. muscle
Act like rivets (a “torn muscle” is a torn desmosome)
Connected into the cell by
intermediate filaments
Gap Junctions
A point of cytoplasmic contact
between two cells
Ions and small molecules can
pass from cell to cell
Allows rapid cell to cell
(intercellular) communication
What cell junction allows rapid cell to cell
(intercellular) communication
Gap Junction
How are cells joined together?
In many tissues cells do not make direct contact with other cells
Cells lie within an Extracellular Matrix (ECM) the composition of which varies between tissues
What is the Extracellular Matrix made up of?
The ECM is composed of
material secreted by cells
This secretion occurs by
constitutive exocytosis
Most ECM proteins are
glycoproteins (protein with
added carbohydrates)
The most abundant ECM
glycoprotein is collagen
Collagen fibres have great
tensile strength
Where are the collegen fibres in the Extracellular matrix embedded?
The collagen fibres are Proteoglycan Matrix
embedded in a proteoglycan
complex matrix (green on figure)
What are proteoglycans? What do they do?
Proteoglycans are proteins
with extensive sugar
additions.
Proteoglycans trap water
within the ECM
Water resists compression
and thus helps retains
tissue shape.
Extracellular Matrix (ECM)
Other glycoproteins
(fibronectins)
attach cells to
ECM.
Membrane proteins
(integrins) connect
the ECM to
cytoskeleton.
Providing a
communication link
from ECM to the
cell interior
What are the three major components of the
cytoskeleton?
Microfilaments
Intermediate Filaments
Microtubules
What are the three main cell junctions
Tight Junction
Desmosomes
Gap Junction
