Cell Membrane And Transport
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What are the functions of the cell membrane
1 ) barrier between the living cell and the non living surroundings 2) allows molecules to cross and enter / leave the cell ( selectively permeable) but barrier for other molecules
What are the structural components of the cell membrane
• phospholipids -proteins -carbohydrates -cholesterol
What is the function of phospholipids in the cell membrane
Form bi layers as the head is pointing out wards (hydrophilic) and the tail is pointing inwards (hydrophobic)
Why do the tails point inwards
They repel water in the cytoplasm and the extra cellular fluid
What is the actual width of a cell membrane
7-8nm in an electron microscope
What type os molecules can diffuse directly across the phospholipid bi layer
Small ,lipid souble, uncharged , non polar (oxygen)
What type os molecules can’t diffuse directly across the phospholipid bi layer in the fatty acids tails
Larger , lipid insoluble , charged and polar molecules
What are the two types of membrane proteins
Extrinsic and intrinsic
What type of protein is it
Globular
What are extrinsic proteins
Associated with one bilayer , acts as a receptor
what 2 types of intrinsic proteins are there
channel or carrier proteins
what are channel (intrinsic) proteins
water filled pore that allow specific ions to be transported across the membrane . Many are gated requiring open and closing in response to the cells need
what are carrier (intrinsic ) proteins
this allows larger polar molecules to be transported across the membrane and when the molecule attaches to a binding site the carrier protein changes shape and releases the molecule on the other side
where are carbohydrates found in the cell membrane
found pionting out the cell which is attached to either proteins (glyproteins) or to the phospholipids (glycolipids )
what is the carbohydrates function
cell to cell recognition and signalling and are collectively known as glycocalyx
what is cholesterol ?
a lipid based compound that fits between the phospholipids in animal cell membrane and helps the stability
what is the cholesterol function
controls membrane fluidity - how permeable the membrane
what is the fluid mosaic model
a model that describes the structure and behaviour of biological membranes
why is it called the fluid mosaic model
fluid - the individual phospholipid molecules can move around mosaic - the proteins are embedded in the bilayer vary in size and shape and arranged in a random pattern
how is the method of transport determined across a membrane
determined by size and properties
what affects the permeability of a membrane
temperature organic solvents level of cholestrol
how does temperature effect the permaebility of a membrane
higher temp cause both the membrane molecules and molecules moving through it have a greater kinetic energy meaning faster diffusion
how does organic solvents affect the permeability of a membrane
they dissolve or emulsify phospholipids and potentially denature the proteins which disrupts the cell mem creating gaps or holes
how does the level of cholesterol affect the permeability of a membrane
increases the stability in the membrane