membranes Flashcards
3 types of diffusion
simple diffusion(no membrane or barrier), diffusion across membrane, facilitated diffusion
What can affect rate of diffusion and why
temperature - increased ke particles
number of channel proteins -more sites for diffusion to occur
concentration gradient - larger difference in concentration gradient=faster rate
surface area of membrane = more area to diffusion to occur.
membrane thickness
What is facilitated diffusion
Use Channel/carrier proteins to move larger polar substances across the membrane as polar molecules can’t diffuse across hydrophobic interior of membrane
With what type of difusion do we describe the membrane as partially permeable
diffusion across membranes
With what type of diffusion do we describe the membrane as selectively permeable
facilitated diffusion as the channel/ carrier proteins are specific to individual ions/molecules
What is simple diffusion
The net movement of particles from down the concentration gradient- from a high concentration to a low concentration
What happens when concentration equilibrium is reached in diffusion
The rate at which the forward and backward reaction occurs is the same (still happens- just hard to tell as occur at the same rate)
With what type of diffusion do we describe the membrane as partially permeable
difusion across membrane
What can and cannot difuse across a membrane
non polar molecules, partially polar molecules (h20)can diffuse but at low rates
polar molecules cannot pass through as ther charge repels hydrophobic interior
why is rate of difusion faster over short distances than long distances
particles move at high speeds
they are constantly colliding which slows overall movement
short distances= less collisions
long distance= increased collisions
What source of energy does diffusion rely on?
Energy from the natural random movement of particles
what is active transport
movement of molecules or ions from region of low concentration to a region of high concentration
why does active transport require atp
active process
requires atp as particles are moving against the concentration gradient
what proteins are used during active transport
carrier proteins
outline steps of active transport
- molecule binds on to carrier protein receptors on outside of cell
- ATP binds on the the carrier protein from the inside of the cell and is hydrolysed to from ADP+Pi
- The Pi attached to the carrier protein causes the carrier protein to change shape, moving the molecule into the cell
- As the Pi is released it reacts with an ADP to from ATP
- carrier protein reverts back to original shape
What is the use of bulk transport and what are the different types
bulk transport is used to transport large molecules(enzymes, cells, hormones) through membrane as they are too large to fit through carrier + channel proteins.
- Endocytosis; phagocytosis, pinocytosis
- Exocytosis
outline process of endocytosis
- cell membrane folds inwards to take in material that needs to be transported within the cell
- membrane enfold and fuses with the material to form a vesicle
- vesicle pinches off and travels into the cytoplasm to transfer material where they’re needed
outline process of exocytosis
- vesicles formed by the Golgi body move and fuse with the cell membrane
- contents of the vesicle then released outside the cell
what are the uses of atp in active transport
- move particles against concentration gradient
- movement of vesicles along cytoskeleton
- changing shape of cells to engulf materials
- fusion of membranes as vesicles form or meet the cell surface membrane
name structures in the cell membrane
phospholipid bilayer - hydrophilic phosphate group and hydrophobic core(fatty acids tail)
intrinsic proteins- (channel protein, carrier proteins, glycoproteins),Extrinsic proteins, glycolipids, cholesterol
Describe overall structure of intrinsic proteins
amino acids with hydrophobic R group that interacts with the hydrophobic core of membrane- keeping it in place
Describe the overall structure of extrinsic proteins
amino acids with hydrophilic r group attached interacting with polar head of phospholipids
function of cholesterol in plasma membrane
regulate fluidity of membrane
hydrophobic ends interact with tails of membrane and hydrophilic ends react with phosphate heads , pulling them together
difference between channel and carrier proteins
channel proteins - provide an alternative pathway for polar molecules and ions to pass through.
carrier - “carries” larger molecules through- specific to certain molecules - involves shape of protein changing
role of glycolipids
act as cell markers (antigens) to ensure immune system recognises it as a cell that belongs to the body.
role of glycoproteins
used in cell signalling. Chemicals/hormones bind to receptors on the carbohydrate chain
