Download PHYS-2030 Tutorial 1 1. A protein molecule has a molar mass of

PHYS-2030
Tutorial 1
1. A protein molecule has a molar mass of 40,000 (i.e., Avogadro's number of these molecules
has a total mass of 40,000 g). The official name for the unit of molar mass is the Dalton (1 Dalton
= 1 g/mole, abbreviation = Da). So this protein has a molar mass of 40 kDa. The average density
of proteins is about 1300 kg m-3. If the protein molecule is spherical, what is
(A) its radius, and
(B) its surface-to-volume ratio?
2. Repeat Problem 1 for a protein with molar mass equal to 400 kDa.
3. The amino acid residues in a protein chain have an average molar mass of 120 Da. If all of the
residues of the protein in Problem 1 were in a single α-helix, how long would the helix be?
4. Water has a molar mass of 18 Da and a density of 1000 kg m-3. How many water molecules are
there in each cubic nanometer? Make a simple assumption to estimate how far it is from a
particular water molecule to any of its nearest neighbouring water molecules.
5. A colony of bacteria are subjected to a toxic agent which reduces the population by a factor of
2 every 3.5 days. The initial population is 5.1x107 cells. Plot the population as a function of time.
What kind of time dependence does the population have? Find a way of plotting the population so
that it is easy to answer the following question graphically:
How long does it take for the agent to reduce the population to 0.2% of its original value?