plasma membranes Flashcards
what is meant my compartmentalisation
the formation of separate membrane bound areas in a cell
what are membranes formed by
phospholipid bilayer
what does a phospholipid consist of?
hydrophobic fatty acid tails - inside
hydrophilic phosphate heads - outside
what was the fluid mosaic model and when was it
it was in 1972 by singer and Nicholson
this model describes how phospholipids are free to move within the layer relative to each other
giving the membrane flexibility
what are intrinsic proteins
trans membrane proteins that are embedded through both layers of the membrane
they have hydrophobic r groups on their external surfaces
give 2 examples of intrinsic proteins
channel proteins
carrier proteins
what are channel proteins
passive movement of hydrophilic channel
polar molecules
ions down a concentration gradient
what are carrier proteins
active transport
passive transport
protein usually changes shape
what are glycoproteins
intrinsic proteins
embedded in membrane with attached carbohydrate chains
play a role in cell adhesion
and receptors in cell signalling when chemical binds to a receptor
receptors of neurotransmitters and hormones
what are glycolipids
attached with carbohydrate chains
these molecules are called cell markers or antigens
peripheral proteins
hydrophilic R groups on their outer surfaces
what is cholesterol
hydrophilic and phobic end
regulates the fluidity of membrane
cholesterol add stability to membranes without making them too rigid
how does temperature affect membrane structure
when temperature is increased the phospholipids will have more kinetic energy and will move more
and the membrane will lose its structure
this will cause particles to across the membrane easier
define diffusion?
is the net, or overall movement of particles from a region of higher concentration to a region of lower concentration
passive movement
what affects the rate of diffusion
temperature - kinetic energy particles move faster
concentration difference - the bigger the difference between them faster rate of diffusion
what 2 things affect diffusion across membranes
surface area- the larger the higher rate of diffusion
thickness of membrane- the thinner the exchange surface the higher the rate of diffusion
define facilitated diffusion
diffusion across a membrane through protein channels
allows polar molecules and ions to pass
passive movement down a conc gradient
what is meant by passive movement
no metabolic - ATP energy is required
what is meant by active transport
movment of ions or molecules into or out of a cell from a region of low conc to a region of high conc
requires energy and carrier proteins
describe the process of active transport in steps
1) the molecule or ion to be transported binds to the receptors of the carrier protein on the outside of the cell
2) on the inside ATP binds to the carrier protein and is hydrolysed into ADP and Phosphate
3) protein changes shape opening up the inside of the cell
4) molecule is released to the inside of the cell
5) phosphate molecule is released from the carrier protein and recombines with ADP to from ATP
6) carrier protein return to its original shape
define bulk transport
another form of active transport
large molecules and whole cells are transported by bulk transport through channel or carrier protein
define endocytosis
is the bulk transport of material into cells
what are the 2 types of endocytosis
phagocytosis - for solids
pinocytosis - for liquids
