Animal Cells Flashcards
Function of the skeleton
- Helps maintain cell shape
- And position of organelles within cells
- Rapidly disassembles and reassembles (unlike skeleton)
- This ability allows rapid changes in cell shape
- Highly dynamic but still provides stability
3 main components of the cytoskeleton
- Microtubules
- Microfilaments
- Intimediate filaments
Structure of Microtubules
- composed of tubulin subunits that provide shape and sturcture that resist compression
- thus help maintain shape of cell
- they radiate out from an organising centre (centrosome)
What allows Microtubules to provide cell mobility
- Flagella: ‘snake like’ motion
- Cilia : ‘rowing-like’ motion
If cells are fixed in one place beating cilia moves fluid past them
How do Microtubules provide cell mobility
- ATP powered protiens can ‘walk’ organelles along Microtubules
- allows vesicles or other organelles to be transported to specific targets within the cell
What are microfilaments made from
A double chain of actin subunits
What do microfilaments form
- linear strands
- 3D networks (using branching protiens)
Function of microfilaments
Resist tension
How do microfilaments makes the region less fluid
The cortical network under the plasma membrane helps make the region less fluid and maintain cell chape
What components of microfilaments allow muscle contraction
Actin - myosin interactions allow muscle contraction
non-animal examples of microfilaments
- ameoboid movement
- cytoplasmic streaming in plants
Intermediate filaments structure and make-up
Made up of various protiens including:
- keratins in hair
- lamins in the nucleus
- neurofilaments in neurons
Supercoiled into ‘ cables’
Intermediate filaments? R they diamic?
- less dynamic then Microtubules
- intermediate filaments form relatively permanent cellular structures
Intermediate filaments help…
- maintain cell shape
- anchor organelles
They may also remain after the cell that has made it has died, as in your hair and outer layer of skin
How cells are joined together: 3 cell junctions
- tight junctions
- desmosomes
- gap junctions
Each differ in structure and function
Tight junctions
- Hold neighbouring cells tightly pressed together - can be pulled together
- may form a continuous seal
- prevents movement of fluid across cell layers
What are Desmosomes and what do they do
- anchoring junction - held tightly together, but not as close as tight junctions
- provide attachments between sheets e.g muscle
- 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
How cells join together - ECM
- in many tissues cells do not make direct contact with other cells
- cells lie within an extracellular matrix the composition of which varies between cells
Extracellular matrix is composed of
ECM is composed of materials secreted by cells
- the secretion occurs by constitutive exocytosis
Extracellular matrix protiens
- most ECM are glycoproteins (protiens with added carbohydrates)
- the most abundant ECM glycoprotein is collagen
- collagen have great tensile strength - restists tension
Where are collagen fibres embedded
in a proteoglycan complex matrix
What are proteoglycans and what do they do
Proteins with extensive sugar additions
- they trap water within the ECM
- water resists compression and thus helps retain tissue shape
Are intermediate filaments longer lasting or shorter lasting
Longer lasting
Size of things that make up the cytoskeleton
Microfilaments - 7 nm
Microtubules - 25 nm
Intermediate filaments - 8 - 12 nm
What resists compression or tension
Tubules resist compression
Microfibriles resist tension
Intermediate filaments resist tension
