Questions of the Weeks Round Up

1) For the photolysis of water, we talked about the highly oxidising nature of p680+. But isn't there a Mn complex involved?

Yes it is true. The Mn Complex will interact directly with water to extract the e- to be passed to p680+. But it is not required of you to know. =)

2) SER: tubular and RER: flattened?

A pic speaks a thousand words and better than the one I drew in class


3) How polypeptides can get into the lumen of RER?



The diagram shows that a partially formed polypeptide chain is directed to the RER by the peptide signal sequence where the rest of the polypeptide chain will then continue to be formed and entered the lumen.

4)
Cell Membrane

1 D 6 C 11 D
2 C 7 B 12 D
3 B 8 A 13 B
4 A 9 D 14 B
5 A 10 A 15 C

Common Mistakes/Correction to note:

4) the width is within 10nanometers!
7) you should know the nature of the core of bilayer; having a fluid mosaic is a consequence not a reason.
9) aerobic = there is production of large amounts of ATP; from the table we can deduce that the first two rows undergo passive diffusion and active transport but active transport is halted under anerobic conditions.
11) if you choice include any of the proteins, you are not listening in class when I mentioned that the presence of proteins to affect fluidity is only a minor point and definitely not their main purposes.
14) same above in 11.
15) similar to 9 whereby air bubbled implied oxygen introduced into culture → aerobic respiration.


Cell Structure


1 D 6 C 11 B 16 D
2 E 7 A 12 C 17 B
3 D 8 E 13 D 18 D
4 C 9 C 14 A 19 A
5 C 10 D 15 B 20 C


Common Mistakes/Corrections to note:

2) sucrose: used to maintain osmotic difference of the mitochondria with its external environment so that one can view it in its native shape under microscope.
5) at the slowest speed, the most dense organelles will be spun down and that will be the nuclei/dna.
6) you should know this!
7) B is wrong. It is pointing to the RER/ribosomes where rRNA/mRNA and maybe even tRNA are present.
9) hydrolytic enzymes are found in lysosomes!
10) expected to know. It is also the site for carbohydrate synthesis and detoxification
11) B is correct; bacteria do have cell wall.
13) D: NADP is found in chloroplasts; NAD is found in mitochondria; membrane- bound enzymes refers to enzymes that are bound to the membrane e.g. ETC which is made up of a series of enzymes (although we did not go into the details) like oxidase, reductase. Try Wiki.
17) refer to 9
19) (In metabolism some substances are broken down to yield energy for vital processes while other substances, necessary for life, are synthesized) so all we need to recognise is that products can be exported out of cell via exocytosis or budded off to another site within cell where the products are needed.
20) another major featuer of prokaryotic cell; remember your essay comparing chloroplast and mitochorion?

Gen XYZ

Yesterday there was an article on Gen Y which left me thinking, which generation am I in? Found in the dead center of a crossroad of changes, my conclusion is a hybrid of X & Y.
The generation Y saw the rapid technological changes that manifested themselves in handphones, broadband computers, blogging and facebook to name a few. There is also a greater sense of individuality that prompted one to make reference to more self-confidence and possibility creativity which sometimes is really an illusion because sometimes there is a lack of maturity to handle those qualities and perhaps that is why we are seeing many more cases of youths falling into their own insecurities and turning to petty defiances. There are more venues of connections between people with facebook, friendster, myspace and maybe other virtual worlds that I am really ignorant about. For some, the gulf of human interactions did not close up because of these avenues but instead widen because relationship becomes superficial with 1000 names in your messenger but only 10 you can really turn to when you are in need - yet with 1000 names, do you make reach out to the 10 to let them know they matters? For others (like me) such avenue is a blessing as I seek out long-lost friends that dated back to primary school, overseas encounters which made a difference in my life and even just my current friends whom I cherished but went away.
If I may say, Gen Y is an exciting time when the tides may swing for each individual. It proposes a sense of purpose to create, to explore and to make a difference.

On a comparative note, Gen X is more subtle, resilient and empathetic. There wasn't so much encouraging notions and demands from the adults to the youths. We worked hard, failed with much heartbreak and moved on again. Through the failures, we gained a little bit of wisdom that we took with us through life. Without the virtual worlds, we chitchat around a real coffee table with our friends to learn not about the world issues that seemed so foreign and far away but more about things closest to us like relationships, difficulties in life and simply about life itself. There were many reflective moments that let us make connections not only with people but with life in general. These days empathy is often lacking because there are so many distractions and the fast pace at which things run, we often fail to sit down and ponder a little more about ourselves and issues around us, and that we all have social responsibility. I confess that these days I myself is losing my touch and I get a little upset about it once in a while and perform my own little rebellion against the senseless charging of life. But really, it doesn't take much to pause. Yesterday I went Toa Payoh library and I saw Ice-cream Uncle. I am not sure how many of us is a frequent patron of TP but uncle has been there for years. Years before other ice-cream men came to claim a piece of the earnings in a 10 metre radius. Uncle may not have a fancy vehicle with colorful display of various ice-cream or even look clean by other standards, but I will always buy from uncle, sometimes even when I am not sure if I want an ice-cream. I did not think uncle remember me to offer me a big cone but I will buy from him because he is getting old and I think he does not get as much business as the newcomers so if I can reach out, why not?
But I think gen x pple are a bit slow in learning not because we are less able but because we are so much more cautious with the moves we choose to take.

gen x or y?
I learnt how to type when I was 20 while in NS. I got my first hp after my first Uni exams, I am unclear about the notion of LAN but started on my first proper blog because of my students 2 years ago. I suppose I am catching up to a certain extent and learning but the cautious me will take a step back each time to remind me not to get overwhelmed and to get back to basics.

caught at a crossroad, life is not necessarily bad. I want to teach my kids the good and bad things of both generations. There are values that we should not forget lest the fabrics of the world collapse. Already I am seeing it.
I want to remind them that they are entering into the world of gen x when they come out of their studies...only to remind myself that I too will become obselete in 20 years' time.

Sad or Angry

I reprimanded my class today. Mmm.. maybe reprimanding is the wrong word because I am real lousy at that. I was speaking from my heart would be more accurate. I told my friends that I am always weary after such a session. Then he reminded me that my tiredness did not come from an outburst/anger but from sadness. Sadness he said, is more tiring than anger. After all the effort, all the reminders and all the giving, it was sadness not anger.

I looked at these kids and thought, regardless how they did in their previous schools, here in the college it is a fresh new start. I was sad because I worried that they belittle themselves when they can be so much more. I have seen some bright sparks but their fires always dimmed before they have a chance to burn. I do not think they realise it themselves. And if we have a weaker foundation, it just means that we have to work harder to catch up, to be more responsible with ourselves and our goals at the end of the day. Slowly but surely together as a class we will make it there unless we choose not to work at it.
A friend said that I worried too much and perhaps I do but only because they meant something to me even when they waddle through the lessons with playfulness and some cheekiness. A time to play and a time to pay attention, we all need to work on that.

The day passes and while the sadness loses its core after seeing these silly kids with their grins at their ccas in the evening, I have to continue making some worksheets that I decided to create after much contemplation since last week.


*It is not my first heartbreak but perhaps there is more because of greater expectations of myself this year. When I first came in to teach a class of 07, they told me that they have learnt nothing from the relief teacher for a whole semester except that she loves char siew bun. And it was reflected in their fundamental in biological molecules and earlier topics which somehow, some never ever recovered from. I thought I will work hard this time to make sure that that doesn't happen to my kids. but I can only hope so.

Losses and Gains

The teams lost to HC-I on Wednesday. While the girls are through to the finals for a 1-2 finish, the guys will have to settle for a 3-4 placing - the sadness is palpable for the boys. Yet I wasn't too upset because from the first time I screamed at them for their horrible team work and absence of expected basic skill to the game that day, I had seen improvement & hard work which I am proud of. Not of myself but of them... until recently when I heard that a handful want to throw in the towel at this point, before the season even ended and that stirred up the red eye monster in me because how can you throw it away when you have teammates who are willing to fight? What kind of selfish, self-centered person are you doing in a team sports? Are you being even fair to your coach or teachers who have to stay up on those late nights and Saturdays? As much as I want to sympathise the 'loss', betrayal and such selfishness are definitely intolerable. I think I am a nice person. But not that nice.

NICENESS
Yet sometimes i think I am too nice in school. I played along, I laughed and I gave encouragement but sometimes I am not sure if the kid know that he/she is going too far and know when to cut off as part of decorum and respect. Immaturity or ignorance or both? I think I have high tolerance because of my work with youth outside where I often closed one eye and choose to look at the heart beneath. But didn't my kids realise that these are life-skills? Sometimes you think you are being taken for granted

FOr all the woes and miseries, I am glad to have a friend who called me up for dinner on Wed because he spotted a distressed msg on one of my online platforms. We consoled each other over pasta and mudpies, reminding each other that there are still roses in the path and we just do the best we can as we learn.

From SER or RER

Just a thought to clarify

This post is made in response to a question I posted to L 2 weeks back when I asked if all polypeptide made on in the lumun of RER will pass through RER or SER or both. I highlighted that most will pass through via the SER.

I would like to clarify that there are two polypeptides that we can considered here:
1) those that are meant to be secreted out of the cell (thus exists in its entirety in the lumen)
2) proteins embedded in the membranes e.g transmembrane proteins.

In the case of 1, polypeptides formed may bud off from SER
In the case of 2, the transmembrane proteins are already embedded in the membrane of RER when they are synthesized so it make more sense to bud off directly from there