Water and Movement Across the Membrane Flashcards
What does amphipathic mean?
- A molecule containing an area of hydrophobic and of hydrophilic nature
How do water soluble molecules arrange themselves in solution?
- Water- water H bonding of the water is replaced by
- Water- solute bonding
What do water soluble molecules arrange themselves like this?
- Water-solute hydrogen bonding is more favourable
How do uncharged molecules arrange themselves in water?
In such a way that will bring the least amount of disruption to the water-water bonds
What are uncharged molecules said to form in solution?
Cages
What do phospholipids form to minimise water disruption?
- Micelles
- Bilayers
What are buffers?
Solutions of weak acids that dissociate to form a conjugate acid-base
What 3 things aid diffusion?
- Large surface area
- High permeability
- High conc. gradient
What 3 properties do molecules need to have to diffuse across the membrane?
- Small
- Uncharged
- Lipophobic
What 2 elements can cross the membrane easily?
- N2
- O2
Because they are small and uncharged (symmetry)
What two waste compounds can easily cross the membrane?
- Urea
- CO2
What are the 2 classes of membrane proteins?
- Integral
- Peripheral
4 types of integral proteins?
- Channels
- Carriers
- Enzymes
- Receptors
What happens to the plasma membrane if integral proteins are removed?
It is disrupted
Relative “amphipathicness” of integral and peripheral proteins
Integral = amphipathic Peripheral = not
Where are peripheral proteins found?
Inner side of the membrane
What do peripheral proteins tend to be?
Enzymes
What do peripheral proteins play a key role in?
Cell shape and motility
What is an example of a peripheral protein that is important for cell shape and motility (hint: the gene for its coding is lost in duchennes dystrophy)
Dystrophin
Name two cells and their membrane protein percentage to show how different membranes can be
- Schwann cells (18%)
- Mitochondria (75%)
What protein does water use to enter/exit the cell?
Aquaporin
What are the 2 types of gated channels
- Voltage gated
- Ligand gated
How does voltage changes cause voltage gated channels to open??
- It acts on charged regions of the protein
- Causes a conformational change
Define osmolarity
- Number of osmoles of solute per litre of solution
Define osmolality
- Number of osmoles of solute per kg of solvent
Osmolarity of 1M of glucose?
1 osmol/L
Osmolarity of 1M of NaCl
2osmol/L
What determines the tonicity?
Conc of non penetrating solutes on 2 sides of the membrane
What happens if the ECF has a higher tonicity than the ICF?
- Cell is hypotonic
- Cell will swell as water enter
What happens if the ECF has a lower tonicity than the ICF?
- Cell is hypertonic
- Cell will shrink as water leaves
What is an isosmotic solution?
Equal number of both penetration and non penetrating solutes on either side of the membrane
Isotonic?
Equal number of non penetrating solutes on each side
