Sunday, September 04, 2005
BIOLOGY - Cell membrane and Specialised Cells
1.31 Importance of cell membrane
separate cell contents from external environment
control exchange between cell and environment
enable separate compartments to be formed within a cell (for specialized metabolic reactions)
some chemical reactions take place on the membrane
act as receptor sites of recognizing external stimuli
1.32 Structure of cell membrane
bi-layer structure: phospholipids
matrix of cholesterol, phospholipids, glycolipids, and glycoproteins
fluid mosaic model—cell membrane is formed from double layers of lipids in which proteins are embeddedà some form channels that allow certain molecules to pass into and out of cell
some act as small pumps that push molecules from one side to another
1.33 Glycocalyx= glycoproteins/glycolipids
cell-cell recognition
receptor sites for chemical signals
assisting in binding together of cells to form tissues
1.4 Specialised cells
1.41 Red blood cell
no nucleus
contains haemoglobin—for oxygen absorption and to transport oxygen from lungs to other parts of body
biconcave shape—increase surface area to volume ratio and increase rate of diffusion
flexible; can squeeze through the narrow width of capillary
1.42 Muscle fibres
· elongated
· cylindrical in shape
· can contract and shorten
· thus bring about movement
1.43 Root hair cell
long and narrow
increase surface area to volume ratio
for absorption of water and dissolved mineral salts from soil into plant
1.44 Xylem vessel
absence of cross wall
absence of protoplasm; dead
hollow—for the transport of water and dissolved mineral salts from roots to other parts of the plant
has lignin—strengthens wall, thus providing mechanical support to plant
separate cell contents from external environment
control exchange between cell and environment
enable separate compartments to be formed within a cell (for specialized metabolic reactions)
some chemical reactions take place on the membrane
act as receptor sites of recognizing external stimuli
1.32 Structure of cell membrane
bi-layer structure: phospholipids
matrix of cholesterol, phospholipids, glycolipids, and glycoproteins
fluid mosaic model—cell membrane is formed from double layers of lipids in which proteins are embeddedà some form channels that allow certain molecules to pass into and out of cell
some act as small pumps that push molecules from one side to another
1.33 Glycocalyx= glycoproteins/glycolipids
cell-cell recognition
receptor sites for chemical signals
assisting in binding together of cells to form tissues
1.4 Specialised cells
1.41 Red blood cell
no nucleus
contains haemoglobin—for oxygen absorption and to transport oxygen from lungs to other parts of body
biconcave shape—increase surface area to volume ratio and increase rate of diffusion
flexible; can squeeze through the narrow width of capillary
1.42 Muscle fibres
· elongated
· cylindrical in shape
· can contract and shorten
· thus bring about movement
1.43 Root hair cell
long and narrow
increase surface area to volume ratio
for absorption of water and dissolved mineral salts from soil into plant
1.44 Xylem vessel
absence of cross wall
absence of protoplasm; dead
hollow—for the transport of water and dissolved mineral salts from roots to other parts of the plant
has lignin—strengthens wall, thus providing mechanical support to plant
# we mugged! @ 8:36 PM 
