5) Biological Membranes Flashcards
What is the role of membranes at the surface of cells
-Barrier between cell and environment
-control what substances enter and leave
-Allow recongnition eg , immune system
-Cell communication
Whar is the role of membranes within cells
-Compartmentalisation
-Form vesicles for transportation
-Control substances that enter and leave
-Allow to be site of chemical reactions
Whar is the role of Phospholipid bilayer
Hydrophilic head , Hydrophobic tail .
Head face out where fatty acid tails are on the inside.
Centre is hydrophobic so it doesn’t allow water-soluble substances though , but fat- soluble is able to
What is the role of cholestrol
Gives the membrane stability
Bind to the hydrophobic tail to make them pack more closely together , Make membrane less fluid and more rigid
What is the difference between Channel and carrier proteins
Channel Protien - Allow small or charged particles through ,
Carrier proteins - Transport molecules and ions by active transport and facilitated diffusion.
What is the role of glyvoproteins and glycolipids
Stabiilise membranes by forming hydrogen bonds.
Site where drugs, hormones and antibodies bind to.
Act as receptors for cell signaling.
How do cell membrane receptors plays an important role in cell signalling
Have specific shapes, only messenger molecules with a complementary shape bind to them .
What response can drugs cause when binding to cell membrane receptors.
Either trigger a response, block their response and prevent it from working
How does temperature increase membrane permeablity
Temp below 0 ack
How does temperature increase membrane permeablity
Temp below 0 - Packed closely together , rigid .
Deform, increase the permeability of the membrane. Ice crystals may form and pierce the membrane making it highly permeable.
**Temp 0 - 45 ** - Phospholipids, move and aren’t packed tightly , partially permeable.
Temp inc , move more , inc permeability.
**Temp above 45 **
Starts to melt , more permeable , water inside of cell expands , Channel proteins and carrier proteins deform so theyy can’t control what enters or leave cells .
How does solvents affects membrne permeability
Dissolve lipids and disrupt structure of membrane.
Increase cell permeability
What factors can affect the rate of diffusion
- Higher concn gradient
- Thinner thickness exchange surface - short diffusion distance.
- Large surface area
- Higher temp - more kinetic enrgy so particles move faster
How do carrier proteins move large molecules
Facilitated diffusion
Molecule attatch to the protein
Protein changes shape
Release molecule on opposite side
How do channel prroteins move molecules
Form pores
Move charged particles
Use facilitated diffusion
How does Active Transport move
Attatch to carrier protein
Change shape allow to release on the other side
Energy is used in the form of ATP.
