Week Twelve : Cell Biology

Mitosis vs Meiosis
Simple, easy way to understand the two processes and the difference between the two. 
I also found the following neat summary online:

	Meiosis	Mitosis
Creates:	Sex cells only: Female egg cells or Male sperm cells	Makes everything other than sex cells
Definition:	A type of cellular reproduction in which the number of chromosomes are reduced by half through the separation of homologous chromosomes in a diploid cell.	A process of asexual reproduction in which the cell divides in two producing a replica, with an equal number of chromosomes in haploid cell
Produces:	four haploid daughter cells	two diploid daughter cells
Steps:	The steps of meiosis are Interphase, Prophase I, Metaphase I, Anaphase I, Telophase I, Prophase II, Metaphase II, Anaphase II and Telophase II.	The steps of mitosis are Interphase, Prophase, Metaphase, Anaphase, Telophase and Cytokinesis
Discovered by:	Oscar Hertwig	Walther Flemming
Type of Reproduction:	Sexual	Asexual
Genetically:	different	identical
Cytokenesis:	Occurs in Telophase I & Telohpase II	Occurs in Telophase
Number of Divisions:	2	1
Pairing of Homologues:	Yes	No
Function:	sexual reproduction	Cellular Reproduction & general growth and repair of the body
Chromosome Number:	Reduced by half	Remains the same
Karyokenesis:	Occurs in Interphase I	Occurs in Interphase
Crossing Over:	Mixing of chromosomes	Does not occur
Centromeres Split:	The centromeres do not separate during anaphase I, but during anaphase II	The centromeres split during Anaphase
Occurrence of Crossing Over:	Yes	No
Occurs in:	Humans, animals, plants, fungi	all organisms
Number of Daughter Cells produced:	4	2

Citric Cycle Animation
A very clear illustration of the entire citric acid cycle.  It's amazing how little cells invisible to the human eye can perform highly-complicated chemical processes to give us energy.
Below is my understanding of the cycle:  
Pyruvate supplies energy to living cells through the citric acid cycle.  Citric acid cycle is a series of chemical reactions using enzymes as catalysts.  The cycle takes place in the mitochondria.  The citric acid cycle is involved in the chemical conversion of carbohydrates, fat and proteins into carbon dioxide and water to generate ATP produced in the cycle. 

Comment on "it is the network of interactions ......not one of its components."
Although totally unrelated, but this made me think of how Chinese herbal formulas work.  TCM herbs are never prescribed individually, but always combined with other herbs to create desired effects.  One toxic herb doesn't make the entire formula toxic.  However, the word "toxic" would make many who are foreign to Chinese medicine skeptical and doubtful of the efficacy of the medicine.  There is a famous Chinese saying, "use toxin to attack toxin".  In a well-thought out formula, toxicity of herbs are reduced to minimum if not totally eliminated and each herb's strength is enhanced through the combination.  So, it's never about what a single herb can do, but the power released when it is combined with other herbs.   

Week Eleven: the Chemistry of Life

Review of Animations

I clicked on the periodic table as well as the metabolic pathways links and found both very interesting.  Periodic table is something we are familiar with.  The metabolic pathways is interesting, but all the chemistry jargon make it a little difficult to understand.  The urea cycle confirmed what we learned in pathology, urea is made in liver and not in kidneys. I'd like to revisit the links again at the end of the course, may be by then I'll have a better understanding of what all the terms mean.

Do our ends justify our means?

In the span of history, with the rise and fall of empires and kingdoms, men have learned how to defend for themselves, how to make the most out of scarce resources and most importantly, how to survive.  With the evolution of time and changes brought by the industrial revolution, survival is no longer a concern for most people.  People want more than just survival, they want to accumulate wealth, assets, material goods and whatever it is, the bigger, the better, the more, the merrier.  And so, through technology and intelligence, mankind have achieved its goal.  For most people, they now have easy access to all kinds of food and material goods, yet all this has come at a price.   One decade into the 21st century, and we've already had to deal with so many alarming natural disasters, not to mention the man-made disasters fueled by greed.  In the past, productivity was regarded more highly than sustainability, but in the wake of all the recent major disasters, it seems we should now once-again be concerned with survival and this time, not about how to get more to survive, but how to cut down and conserve. 

Mid-term paper

I chose "green chemistry" as my topic because it's so relevant to everyone of us.  With the recent change in weather patterns around the world as well as the scale of natural disasters, it is clear that Mother Nature is taking drastic measures to re-balance itself.  If we continue to ignore her cries, pretty soon we'd wipe ourselves out of existence.  If we can all just make one small change in our lifestyle, e.g meatless on Mondays, together, the effects can be dramatic!  One little step at a time...

General Chemistry - Balancing Equations - Tutorials

Detailed step-by-step tutorial illustrating how to balance a chemical equation.  I think I am beginning to like chemistry. 

Welcome to Chembalancer

The game was fun!  It was a nice, fun way to learn balancing chemical equations.  I think I've finally learned how to balance chemical equations for the first time!  despite having learned them many years back in high school...

Semiconductor of the Week - Silicon

The symbol for silicone is Si, its atomic number is 14.  It is less reactive than carbon. 


Silicon is the eighth most common element in the universe by mass, but very rarely occurs as the pure free element in nature.

Silicon is present in the sun and stars. Silicon makes up 25.7% of the earth's crust by weight, and is the second most abundant element, exceeded only by oxygen. It is found largely as silicon oxides such as sand (silica), quartz, rock crystal, amethyst, agate, flint, jasper and opal.


Silicon has many industrial uses. It is a principal component in microchips.  Silicon is widely used in semiconductors because it remains a semiconductor at higher temperatures and forms a better semiconductor/dielectric interface than any other material.