multi-cellular organisation Flashcards
what is the main benefit of having multicellular organisms?
division of labor
what is the extracellular matrix and what does it do?
- extracellular matrix material is secreted from cells
- it’s a complex meshwork outside of cells
- bone and cartilage are part of it
- it forms a major component of certain parts of animal tissues
what are some of the important roles the extracellular matrix plays?
support-strength and structure
tissue organisation
cell signalling
what are the major macromolecules that form part of the extracellular matrix?
proteins- form large fibers
polysaccharides give a gel-like character
name some proteins of the extracellular matrix?
adhesive- fibronectum and laminin (they help to adhere ECM components together)
structural- collagen (provides tensile strength) and elastin (provides elasticity)
what are glycosaminoglycans (GAGs)?
they are the most abundant polysaccharides in vertebrates
- they are long unbranched ploysaccharides with a repeating disaccheride unit
- highly negative charge attracts positive ions and water
what is the function of glycosaminoglycans and proteoclycans?
-GAG and proteoglycans resist compression and form a gel like component
two GAG examples
- chondroitin sulfate (cartilige)
- hylauronic acid (found in skin, eyes, joint fluid)
what are the 3 cell junctions in animals?
anchoring junctions
tight junctions
gap junctions
describe anchoring junctions?
they are cell junctions that hold adjacent cells together or attach cells to the ECM. anchoring junctions are mechanically strong
they attach to each other and to the extracellular material and rely on cell adhasion molecules
four main categories
- adherins junctions
- desmosomes
- hemidesmosomes
- focal adhesions
describe tight junctions?
they are junctions between adjacent cells in a layer that prevent the leakage of material between cells
they’re not as mechanically strong as anchoring junctions
cells that have tight junctions also have anchoring junctions
describe gap junctions?
its a cluster of channels that permit the exchange of ions and small molecules between the cytosols of adjacent cells
they’re composed of an integral membrane protein called connnexin
6 connexin proteins required to form a channel in the mambrane of the cell
what are tissues?
they are a group of cells having similar structure or function, humans have over 200 different cell types that are grouped into a few general categories
what are the four general types of tissue and what do they do?
epithelial tissue- cells joined together forming continuous sheets to cover or line body surfaces
connective tissue- support body or connect tissue
nervous tissue- receives, generates and conducts electrical signals
muscle tissue- generates force that facilitates movement
