3. Week One
Li Tao, Zheng Mengjia, Bai Fan, Zhang Yicheng and Fang Yuliang is responsible for week one.
Besides this part, this week's course includes:
Instructed by Prof. Wouter D. Hoff, Tuesday, April 4, 2015.
How do people learn? Neurobiology study of learning shows that fMRI of human brain picture is different during passive learning or active learning(fMRI：功能性核磁共振成像). Different part of brain are activated. So active learning can make our brain learn better.
There are many theories in textbooks. One way to judge if this theory is good is its prediction ability(If the theory has the ability to predict). And another judgement is its consistency ability.
Let's search for consistent theory with examples.
The atom model in chemistry can prove and predict many phenomenon.
How can the protons come close to each other and don't seperate?
This is inconsistent in atom model.
With the development of physics, we know there is another fundamental force with atom nucleus: strong interaction. Strong interaction is much stronger than coulombian force, so protons can come close to each other and don't seperate.
In Newtonian mechanics, time is reversible.
Is time reversible?
If time is reversible, why can't we go back to past years? So this is inconsistent.
We alreadly know Boltzman statics won huge success in physics. And he predicted that entropy will entropy only increase with time without outer pertubation.
Does entropy only increase with time without outer pertubation?
Maybe this is inconsistent.
If entropy only increase with time, our universe will go to heat death(热寂) finally. But this prediction didn't consider the Universal Gravitation in our universe. Universal Gravitation will make stars close to each other and make our universe in order(take solar system as an example). So Boltzman Statics must have something wrong.
And how can we measure the entropy of a cell? Is it low or high?
If salt crystal has low entropy and salt water has high entropy, maybe the cell entropy is just colse to the salt entropy:
Not very low and relatively high. And another question is
How do we define the complexity of cells?
We already know that cell is complex and salt crystal & salt water are not complex, so how to define the complexity of cells?
Due to the diffraction of light, the resolution of conventional light microscopy is limited to about 300nm.
Is the limiting resolution of light microscopy 300nm?
Maybe not! Or not completed.
Super-resolution techniques allow the capture of images with a higher resolution than the diffraction limit.
On 8 October 2014, the Nobel Prize in Chemistry was awarded to Eric Betzig, W.E. Moerner and Stefan Hell for "the development of super-resolved fluorescence microscopy," which brings "optical microscopy into the nanodimension".
In the proposed method, so-called stimulated emission depletion (STED), a light pulse excites all the fluorescent molecules, while another light pulse quenches fluorescence from all molecules except those in a nanometre-sized volume in the middle . Only this volume is then registered. By sweeping along the sample and continuously measuring light levels, it is possible to get a comprehensive image. The smaller the volume allowed to fluoresce at a single moment, the higher the resolution of the final image. Hence, there is, in principle, no longer any limit to the resolution of optical microscopes.
We have developed Green Fluorescent Proteins(GFP) that can emits green fluorescent under UV-vis light.
With the development of Super-resolution microscopy and GFP, single molecule science in biology come true.
In short, it works because of the overlap of many spectrum of fluorescence blinking patterns when time goes.
We have known that some of theories in textbook is non-coexisting or uncompleted. And textbooks always tells us that there is truth and hide many problems.
Textbooks like using cartoons to demonstrate some items, such as nature of chemical bonds, which is illustrated by Linus Pauling and has won great success.
And this cartoon shows human's deeply understanding of nature of chemical bonds. However, some of cartoons are just drawn here and mislead our understanding of nature.
Take the water tank as an example.
If the system is in equilibrium, “no work” out. With outer work, one system can stay in steady state. Hence, equilibrium ≠ steady state.
And people know a lot about systems in equlibrium like chemical reaction equlibrium. We can use thermal dynamics to study it.
For exmaple, we use △G,△H,△S in thermal dynamics to quantify the energy of reactions like: ATP↔ADP+Pi.
BUT, are we in equilibrium or in steady state? None of them. we are getting older and older. So we are in non-equilibirum.
What about non-equlibrium dynamics?
Non-equilibrium dynamics is relatively unknown and is hidden in textbook. Lars Onsager and Lya Prigogine won Nobel Prize for the study of non-equilibrium models.
Big open area is still in non-equilibrium.
What is a biological species?
There are two kinds of biological species:
- Sexual reproduction with offspring
- Homo species(e.g. Escherichia coli)
These organisms generating through mitosis and meiosis while cross - overs having occurred independently of each other between pair of homologous chromosomes. Reproductive isolation exists between different species, and the gene pool ensures we stay similar.
Take E.Coli as an example. E.Coli don't get married and they reproduce just by spliting themselves to 2 parts->chromosome copy:
And just like the movie in our main page:
After reproduction, bacterial stay similar because of the gene pool.
We have know a lot about sexual reproduction while know a little about bacterials. Maybe only 1% bacteria are already discovered.
Yep, bacterial can swim. And different bacterail swim through different ways.
One kind of bacterail swim is to use the motor protein(motor motif) in the connection part of its tail and body and it acts like a rotary engine, powered by proton motive force. This is similar to the mechanism of propeller.
Flowchart of bacterial flagellar movement is shown below:
The mechanism of rotary engine is similar with ATP synthase.
Another kind of bacterial swim is sperm's shaking its tail. The structure of human sperm is shown below:
The proximal part (mid-piece) of the flagella moved little, whereas the distal part moved with very large transverse amplitude.
The observation also suggests that human spermatozoon beats with a cone-shaped helical wave having an elliptical cross section just like this:
Why do we need science?
Under the energy budget, we need science to study our environment and ecology, as well as to treat our dieases(like cancer).
But, maybe the best answer is human's curiosity.
Our work of science can be described as two major parts:
- Answer questions
- answer old questions
- answer new questions
- Ask questions
- ask old questions
- ask new questions
Maybe our current state is to answer & ask old questions.