3A plasma membrane Flashcards
what does the cell membrane do?
controls what enters and exits the cell to maintain homeostasis
structure of plasma membrane
made out of phospholipid molecules, 2 layers of these molecules form a phospholipid biolayer
what are phospholipids made out of
phosphate head and 2 fatty acid tails
phosphate head
polar, hydrophilic (water loving)
lipid tail
non-polar, hydrophobic (water fearing)
what are the roles of proteins associated with the membrane?
proteins are embedded throughout the membrane. they provide support (structural proteins), allow cells to recognise (receptor) other structures, allows cells to communicate (secretory) and assist with the transport (channel/carrier) of substances across the membrane
fatty acids in the membrane can be
saturated- have straight tails
unsaturated- have a kink in the tail (these kinks create space in the bilayer which increases the fluidity of the membrane)
what does cholesterol do
embedded between/spread amongst the fatty acid tails in the membrane to keep it flexible (provides fluidity), is hydrophobic
attached to carbohydrates
glycolipids and glycoproteins
glycolipid
not attached to protein
glycoproteins
attached to proteins
describe the importance of the phospholipids in the structure of phospholipid bilayers
The hydrophilic heads and hydrophobic tails of phospholipids allow them to form a bilayer, with the heads facing the extracellular (outside) environment and the tails facing the intracellular (inside) environment, forming the basis of the plasma membrane
why is it called the fluid mosaic model
- It is fluid because phospholipids continually move side to side
- Mosaic refers to the proteins and carbohydrates embedded in the membrane - like mosaic that is made up of many parts
cell membranes are selectively …
permeable, this allows certain molecules (PERMEABLE) eg hydrophilic molecules and ions to cross whilst other molecules cannot. (IMPERMEABLE) eg large molecules such as proteins.
