b2.2 membrane transport

Question 1

what is the basic structure of a membrane?

Answer 1

membranes are essential components of cells - the plasma membrane forms the border between a cell and its environment.
the basic structure of all biological membranes is the same - a bilayer of phospholipids and other amphipathic molecules form a continuous sheet that controls the passage of substances

Question 2

what is the structure of a phospholipid?

Answer 2

phospholipids are formed by a hydrophilic phosphate head bonding with two hydrophobic hydrocarbon (fatty acid) tails. as they have both polar and non-polar parts, they are known as amphipathic

Question 3

how do lipid bilayers work as barriers?

Answer 3

the bilayer has two regions: a hydrophobic core and a hydrophilic outer layer. these properties allow the bilayer to form a barrier.
- large molecules cannot pass through the barrier as the hydrophobic region is tightly packed and has low permeability to larger molecules
- polar molecules and ions cannot pass through the hydrophobic tails. the polar nature of these molecules means that they won’t interact with the non-polar fatty acid tails