Forces Across Membranes Flashcards
What does it mean to say membranes are Dynamic?
Constantly formed, maintaines, dismantled or metabolised depending on the cells needs
What makes cell membranes flexible?
The fatty acids
What are the 2 classes of membrane protein?
Integral
Peripheral
What makes an integral membrane protein?
- Cant be removed without disrupting the membrane
- Amphipathic & oriented the same way as the phospholipids
What are the 4 types of integral membrane protein?
- Channels
- Carriers
- Enzymes
- Receptors
What are peripheral proteins important for?
Cell shape & motility
What makes up schwann cell membranes?
18% protein
Mainly lipid for insulation against electrical nerve signals
How much protein is in the average cell?
Around 50%
What factors aid diffusion?
Large surface area
High Permeability
High conc. gradient
What characteristics must a molecule have to diffuse through the lipid bilayer?
- Small
- Uncharged
- Hydrophobic (lipophilic)
What is a protein channel?
A trans-membranous IMP that act as an aqueous route for ion diffusion
Name the protein channels through which water goes?
Aquaporins
What are the two types of ‘gated’ channel?
Voltage gated
Ligand Gated
In general what is the electrical gradient across cell membranes?
USually the inside is relatively negative to the outside
How do carrier mediated transport systems work?
A solute binds to a transmembranous protein
The protein changes coniguration
Solute is now exposed to the other side of the membrane
Solute detaches into the cell
What are the two types of carrier mediated transprot systems?
Facilitated transport
Active Transport
Difference between facilitated & active transport?
Facilitated requires no energy
Active goes against conc. gradient
Why are active transport pumps called ATPases?
They get their energy from ATP.
What is osmolarity?
The measure of osmoles of solute per litre of solvent.
Osmolarity example:
1M glucose has an osmolarity of 1 osmole/L
Define osmotic pressure:
The pressure required to prevent water movement from high->low conc.
Explain hypo-,hyper-,iso- osmotic?
Isostomic solutions have same total number of solute particles
Hyperosmostic solution has more solute particles than the ECF
Hypoosmotic have fewer solute molecules than the ECF
What is tonicity?
Number of non-penetrating particles in solution.
Why does only tonicicty determine water movement?
Penetrating solutes will move across the membrane to equal concs.
Non-penetrating cant so the water will have to move to compensate.
Define endocytosis?
Invagination of membrane
Vesicle forms around target
Seperates from membrane on cytoplasmic side
Migrates within cell to destination
Exocytosis?
Endo but in reverse m8
