M2 - cell membranes Flashcards
(12 cards)
plasma membranes functions
partially permeable physical barrier preventing entrance of pathogens
cell recognition - glycoproteins on surface acts as antigen to tell what’s foreign and not
cell communication - receptors on surface of membrane which chemicals from other cells attach to
intracellular membrane functions
act as vesicles to transport substances through the cell via cytoplasm
decides what goes in and out of organelles
compartmentalise - seperate contents of organelle from cytoplasm
site of chemical reactions
components of phospholipid bilayer
glycoproteins
glycolipids
cholesterol
intrinsic proteins
extrinsic proteins
what do glycoproteins do
protein attached to sugar molecule
act as recognition site and antigen to flag as self
what do glycolipids do
phospholipid attached to a sugar molecule
act as recognition site and antigen
also contributes to membrane stability by forming hydrogen bonds with water
what do cholesterol do
lipid between phospholipid tails, pushing them closer together
regulates membrane fluidity
what do intrinsic proteins do
they span both the bilayers and usually act as carrier or channel proteins
what do extrinsic proteins do
small proteins on surface of membrane
usually acts as enzyme to catalyse reactions inside cells
beetroot practical
- beetroot cylinders same size
- set different water baths at diff temp
- water in different boiling tubes
- put one beetroot in each boiling tube
- take beetroot out and put water into cuvette
- put into colorimeter and the darker solution (more permeable), the more light absorbed
what happens to membrane permeability below freezing
- decreases because proteins unfold and deform
- molecules have less energy and don’t move much
- phospholipids tight packed - membrane rigid
membrane permeability 0-45 degrees
partially permeable
high temp = high kinetic energy and higher fluidity
membrane fluidity above 45 degrees
proteins denature so permeability increases rapidly
