plasma membranes Flashcards
1
Q
role of membranes
A
- partially perm barriers between the cell + environment , organelles and the cytoplasm + within organelles
- site of chem reactions
- site of cell communication
2
Q
membrane structure
A
- plasma membrane (seperates cell from external env)
- formed from phospholipid bilayer
- hydrophilic phosphate heads form inner+outer surface
- surrounds the hysrohpohibic FA
- forms hydorphobic core inside the memebrane
3
Q
fluid mosaic model
A
- phospholipids are free to move
- giving membrane flexibility
- proteins embeeded in the bilayer
- vary in shape sixe + position
4
Q
instrinsic proteins
A
- transmembrane proteins
- embedded through both layers
- amino acids with hydrophobic R-groups on external surface
- interact with hydrophobic core keeps them in place
5
Q
channel proteins
A
- intrinsic
- hydrophilic channel
- passive movement of polar mol + ion down a CG
- held in position by hydrophobic core + R group interactions
6
Q
carrier proteins
A
- intrinsic
- passive + AT into cells
- protein can change shape
- ATP not required
7
Q
glycoproteins
A
- intrinsic proteins
- embedded
- attached carb chain with diff lengths + shapes
- role in cell adhesion
- ## receptors for chem signals
8
Q
drugs and receptors
A
- some drugs bind to cell receptors
- beta blockers reduce response of the heart to stress
9
Q
glycolipids
A
- lipids
- attached carb chain
- cell markers/antigens
- recongised by cells of immuneS as self/non-self
10
Q
extrinsic
A
- present in one side of bilayer
- hydrophilic R groups
- interact with polar heads of phospholipids / with intrinsic proteins
11
Q
cholesterol
A
- lipid / sterol
- hyrophilic end
- hydrophobic end
- regulates fluidity
- adds stability
- positioned between phospholipids
12
Q
affect of temp on CM
A
- temp inc
- phospholipids inc KE
- move more
- membrane more fluid
- loses its structure
- temp inc more : structure breaks down
- nc perm of memB
- easier for particles to cross it
- carrier/channel proteins = denatures
13
Q
solvent affect on CM
A
- water = polar solvent : essential in CM formation : nonpolar tails away = hydrophobic core and phosphate heads interact = keep bilayer intact
- organic solvent dissolve membranes
- disrupts cells
- more fluid
- more perm
14
Q
diffusion
A
- net movement of particles
- region of high to low
- passive
- continue until conc equlibrium
- occurs due to particles in g/l have KE = random movement
15
Q
factors affecting rate of diffusion
A
- temp : inc temp, inc rate : particles have more KE moving at inc speeds
- conc diff : overall movement from high to low conc will be larger
- diffusion pathway : distance the particles have to travel
- SA
in facilitated diffusion :
- number of protein channels present
16
Q
active transport
A
- movement of mol/ions in/out of cell
- from low to high conc
- requires energy
- requires carrier proteins
- process is selective - specific subs transported by specific carrier proteins.
17
Q
active transport mechanism
A
- mol/ion being transported binds to receptor on the carrier protein outside of cell
- inside of the cell ATP binds to the carrier protein
- hydrolysed into ADP + phosphate
- causes protein to change shape
- opens up inside of the cell
- mol/ion released inside of cell
- P released from carrier
- recombines with ADP = ATP
- carrier protein returns to normal shape
18
Q
bulk transport
A
- another form of AT
- large mol (enzymes) move through channel/carrier proteins
- moved in/out of cell
- by bulk transp
19
Q
endocytosis
A
- BT of material into cells
- phagocytosis = solids
- pinocytosis = liquids
- CSM bends inwards
- when it comes into contact with material to be transp
- membrane enfolds the material
- membrane fuses = vesicle
- vesicle pinches off
- moves into cytoplasm
- transfers material for further processing within cell
- E.g vesicles with bacteria go to lysosomes where bacteria digested by enzymes
20
Q
Exocytosis
A
- reverse of endocytosis
- vesicles formed in golgi
- moves towards + fuse with CSM
- contents of vesicle released outside of cell
21
Q
movement of vesicles
A
- requires energy (ATP) bc :
- move along cytoskeleton
- changes shape of cells to engulf materials
- fusion of cell membranes
22
Q
water potential values
A
- pure water = 0
- high water potential = more dilute = less negative
- low water potential = more concentrated = more negative
23
Q
osmosis in animal cells
A
- animal cell in water with high water potential (more dilute)
- water osmotes into cell
- inc hydrostatic pressure
- cells have thin CSM + no CW
- CSM can’t withstand the increased pressure
- CSM will breaks and cell will burst
- cytolysis
- animal call in sol with lower water potential (more conc)
- lose water to sol by osmosis
- volume of cell reduces
- CSM puckers
- crenation
24
Q
how to prevent crenation + cytolysis
A
- control mechanisms
- cells continuously surrounded by aq sol
- with an equal water potential
- isotonic
25
osmosis in plant cells
- high water potential
- water osmotes into cell
- inc hydrostatic pressure
- pushes memB against rigid CW = turgor
- resists entry of more water
- cell = turgid
- sol with low water potential
- water lost from cells by osmosis
- volume in cytoplasm reduces
- pulls CSM away from the CW
- cell = plasmolysis
