Problems
25
• An impressive application in biological research is the instrument put together by
Prof. Akos Vertes (Chemistry Dept., GWU). With his device, he can analyze the
proteins taking part in some action in a live cell. First, he knocks the molecules
out of a particular cell region or organelle with a highly focused infrared laser.
Then, he collects the vaporized material in a micro-vacuum cleaner hovering over
the cell, and sends the material to a mass spectrometer. Knowing the masses of
various proteins, he can tell which ones were present in the cell region at the time
of vaporization.
As we have indicated, by expending energy (and releasing heat), life systems also
have dynamical processes for substance separation and transport. These processes
effect separation against opposing forces and diffusion. The pumping of sodium out
of a biologic cell (via ‘active transport’) is a good example. The transport by motor
proteins of molecules (‘cargo’) along intracellular filaments of the cytoskeleton is
another.
Problems
2.1 Based on the mechanisms for geological differentiation and the solubility of
metals in metal, argue that at the center of the Earth’s core, the iron may contain
more than 50% gold.
2.2 Explain why natural diamonds could not have been formed in the Earth by
the compression of plant carbon deposits. Describe the current theory on natural
diamond formation, and how we are able to find diamonds near the surface of the
Earth.
2.3 In short, what is the current scientific view on how life started on Earth?
2.4 Describe the microscopic changes that cause a homogeneous mixture of
dispersed microspheres of oil in water to naturally separate.
2.5 In the measurements of Wong and Wiltzius, a large number of microscopic
particles of uniform size were mixed into glycerol (index of refraction of 1.473,
temperature of 51 ◦ C, viscosity 137 cp) to create a semi-transparent colloidal
suspension. The mixture was then put into a 1 mL cuvette sample holder. Light
from a Helium-Neon laser beam was scattered from the sample. The scattered light
was then focused with a lens onto a CCD detector containing pixels spread over
an area. The direction of the light rays to a given pixel determined the scattering
wave number q = (4πnf/c) sin (θ/2). From the intensity of the light measured
over time, the autocorrelation function G(τ ) was calculated, and then fitted to
1 + β exp (−2 ) to find for several values of q 2 . Assuming = Dq 2 , a value
for the diffusion constant for the Brownian motion of the particles in glycerol can
be found. Using the graphs in the text and the Stokes-Einstein Relation, find the
diameter of the colloidal particles.
2.6 Argue the feasibility of using the principles behind a mass spectrometer to
separate garbage and other waste material into usable elements.
25
• An impressive application in biological research is the instrument put together by
Prof. Akos Vertes (Chemistry Dept., GWU). With his device, he can analyze the
proteins taking part in some action in a live cell. First, he knocks the molecules
out of a particular cell region or organelle with a highly focused infrared laser.
Then, he collects the vaporized material in a micro-vacuum cleaner hovering over
the cell, and sends the material to a mass spectrometer. Knowing the masses of
various proteins, he can tell which ones were present in the cell region at the time
of vaporization.
As we have indicated, by expending energy (and releasing heat), life systems also
have dynamical processes for substance separation and transport. These processes
effect separation against opposing forces and diffusion. The pumping of sodium out
of a biologic cell (via ‘active transport’) is a good example. The transport by motor
proteins of molecules (‘cargo’) along intracellular filaments of the cytoskeleton is
another.
Problems
2.1 Based on the mechanisms for geological differentiation and the solubility of
metals in metal, argue that at the center of the Earth’s core, the iron may contain
more than 50% gold.
2.2 Explain why natural diamonds could not have been formed in the Earth by
the compression of plant carbon deposits. Describe the current theory on natural
diamond formation, and how we are able to find diamonds near the surface of the
Earth.
2.3 In short, what is the current scientific view on how life started on Earth?
2.4 Describe the microscopic changes that cause a homogeneous mixture of
dispersed microspheres of oil in water to naturally separate.
2.5 In the measurements of Wong and Wiltzius, a large number of microscopic
particles of uniform size were mixed into glycerol (index of refraction of 1.473,
temperature of 51 ◦ C, viscosity 137 cp) to create a semi-transparent colloidal
suspension. The mixture was then put into a 1 mL cuvette sample holder. Light
from a Helium-Neon laser beam was scattered from the sample. The scattered light
was then focused with a lens onto a CCD detector containing pixels spread over
an area. The direction of the light rays to a given pixel determined the scattering
wave number q = (4πnf/c) sin (θ/2). From the intensity of the light measured
over time, the autocorrelation function G(τ ) was calculated, and then fitted to
1 + β exp (−2 ) to find for several values of q 2 . Assuming = Dq 2 , a value
for the diffusion constant for the Brownian motion of the particles in glycerol can
be found. Using the graphs in the text and the Stokes-Einstein Relation, find the
diameter of the colloidal particles.
2.6 Argue the feasibility of using the principles behind a mass spectrometer to
separate garbage and other waste material into usable elements.