Forces Across Membranes 1 Flashcards
In simple terms, what does the cell membrane do?
Seperates the ECF and the ICF, is responsible for the composition difference between the two
Give an example of some concentration differences between the ECF and the ICF?
Na+ > in ECF
K+ > in ICF
Cl- > in ECF
HCO3- > in ECF
Phosphate/Sulphate > in ICF
Protein > in ICF
How do cell membranes acts as a selective barrier?
Permeable and impermeable to different substances
What substances can freely cross the cell membrane?
O2
Nutrients
CO2
Waste
H2O
What substances cannot cross the cell membrane and the capillary wall?
Ions cannot cross the cell membrane
Plasma proteins cannot cross the capillary wall
Does permeability of the cell membrane change at different times?
Yes
How are membranes dynamic?
They are constantly being formed, changed or dismantled
What forms most of the cell membrane?
Thin layer of phopholipids as a bilayer
Why are membranes flexible?
Fatty acids behave like oil
What could happen to membranes if they are overstretched?
They could rupture
Why are membranes a good insulator against electrical charge?
They prevent the passage of electrons
How to proteins and carbohydrates relate to membranes?
Membranes are embedded with proteins and associated with carbohydrates
Are membrane carbohydrates intra or extra cellular
Extracellular, they are linked to proteins and lipid
What are the carbohydrates of the cell membrane linked to?
Proteins and lipids
What are the carbohydrates of the membrane important for?
Cell-cell communication
What are glycoproteins?
Proteins with carbohydrate groups attatched to the polypeptide chain
What are glycolipids?
Lipids with a carbohydrate group attatched
What are the four classes of membrane proteins?
Receptor
Transporters (carrier and channel proteins)
Enzymes
Peripheral proteins
What are integral membrane proteins?
Proteins which are integrated into the structure of the membranes, such as receptors, transporters and enzymes
Are peripherial proteins embedded into the membrane?
No, they are associated with the membrane byt not embedded in it
What are receptors?
Allows communication of an extracellular signal to an intraceullular space to create an intracellular response
Why is the cellular response of a receptor specific?
Not all receptors are present on all cells, with receptors being unique to different substances
What are transporters?
Proteins which allow movement of ions or molecules across the membrane
What are the two types of transporters?
Channel proteins
Carrier proteins
How do channel proteins operate?
They create a pore through the membrane which molecules (usually water and ions) can flow through
What are the two types of channel proteins?
Open (water) or gated (ions) which open in response to signals
How do carrier proteins work?
They do not create a continuous pore, they are only open at one side at any time
What is an enzyme?
Catalyses reactions on the cell membrane
What are enzymes often associated to?
Receptors
What are some roles of peropheral proteins?
Maintain structure of cells by anchoring the membrane to intracellular cytoskeleton
Attatches cells to the extracellular matrix
Perform signilling functions within cells
Give some examples of how membranes differ in their protein content to suit their function?
Myelin 18% protein as lipids are better for insulation
Most cells are 50% proteins
Membranes involved in energy transduction such as mitochondria inner membrane are 75% proteins
