What happens at cell membranes? Flashcards
Describe the structure of the plasma membrane?
The plasma membrane has a phospholipid bilayer. the heads of the phospholipids in the bilayer face out wards as they are hydrophilic and the tails face inwards as they are hydrophobic.
what is a property of the phosoplipids in the bilayer?
They are amphipathic- heads are polar and tails are non polar
Why is cholestrol important in the phospholipid bilayer?
Cholestrol maintains the membrane rigidity and prevents the tails in the membrane from clumping and melting due to changes in temperature.
what are glycoproteins?
carbohydrate chain attached to a protein inbeded in the membrane. its function is to serve as receptors for chemical signals.
what are glycolipids?
A glycolipid is a carbohydrate chain attached to a phospohlipid. The function of glycolipids is to facilitate cellular recognition ( cells are able to recognise the cell as self).
What is the difference between intergral and peripheral?
Peripheral means attched to a structure on the plasma membrane and intergral means is within the plasma membrane.
what is a uniporter?
transports one molecule in one direction down its concentration gradient
what is a symproter?
A symporter transports two molecules or more in the same direction. they could be moving in differnt concentration gradients.
what is an antiporter?
A antiporter transports two molecules or more in the opposite direction. they could be moving in differnt concentration gradients.
How does the membrane remain fluid?
Typically each phospholipid in the bilayer has one saturated fatty acid and one unsaturated fatty acid. The unsaturated fatty acid gives the fatty acid a kink which reduces the van der waals forces as they are less packed together, so therefore reducing the melting point.
what is the properties of the membrane?
partilally permeable
flexability and deformability
key role in signal transduction
what is facilitated diffusion?
faciliated diffusion can occur using a channel or carrier protein. it does not require energy and it allows the entry of molecules in and out of the membrane that cannot cross the bilayer. ( entry down their concentration graident)
What is passive diffusion?
passive diffusion is the free movement of substances that can cross the plasma membrane.
what is active transport?
Active transport is the movement of molecules against their concentration gradient using ATP.
what is the rate limiting step in passive diffusion?
The rate limiting step is the hydrophobic portion of the membrane.
