MG-Biology

End of testing for beta version of Biology blogging

2005-11-05T14:27:00.000+08:00

Hi all,

This will be the last post for mg-biology for the year 2005 (hopefully). To all who participated in this beta version, thank you for your time. I hope all have benefitted from this although the response have not been instantaneous as it should be.

Nontheless, if any of you wants to give feedback, you may comment on this blog after your 'A' levels.

Btw, to better benefit the students of NY, the coming year 2006, this blog will be revamp and i am looking for students (all ex-NY are welcomed) to be administrators of the blog, to share your thoughts and bio stuff.

To end off, all the best to all NY students in their bio papers!

Cheers

MG

Core Essay 2004

2005-11-05T14:24:00.000+08:00

This is the questions as requested by one student:

7 (a) Outline the differences in structure between aminoacids and nucleotides. [6]
(b) Explain, with examples, the structural differencesbetween fibrous and globular proteins. [6]
(c) Describe, with examples, the roles of proteins inmembranes. [8]

8 (a) Describe the main features of homologous chromosomes. [6]
(b) Outline the behaviour of chromosomes in meiosis. [8]
(c) Explain the need for a reduction division in meiosis. [6]

9 (a) Describe the main structural features of arteries inrelation to their functions. [8]
(b) Explain the significance of the difference in affinity foroxygen between haemoglobin and myoglobin. [6]
(c) Outline with examples, the main roles of capillaries. [6]

10 (a) Describe the main stages of the Calvin cycle. [8]
(b) Outline the role of NADP in photosynthesis. [6]
(c) Explain how ATP is synthesized using light energy in photosynthesis. [6]

11 (a) Outline the structure of xylem vessels in relation totheir function. [6]
(b) Describe the way in which water passes from root haircells to the leaves. [8]
(c) Explain why transpiration is the inevitable consequenceof gaseous exchange. [6]

MG

Energy Transfer and role of glycolipid + protein

2005-11-05T14:18:00.000+08:00

Hi all,

For vinesh: The energy transfer between trophic levels will refer to the energy that is available to the next trophic level.

For example: The energy that is available to the primary consumer from the producers will be the amount of food that is actually absorbed into the consumer.

For meng choo: Am sure there are info on that in the notes.

Glycolipids - cholesterol, etc.

Glycoproteins - Receptors, cell to cell recognition, etc.

MG

Options Paper on Tuesday

2005-09-19T08:45:00.000+08:00

Hi all,

A reminder to all that the Prelims Option Paper is on Tuesday and MCQ on Wednesday.

Vinesh: The part of the named example you need to know is for the feeding adaptations and random segregation is a mixture of the both that you mentioned.

MG

Resting potential

2005-08-25T16:51:00.000+08:00

Question: and sir, i have checked and found that u gave the answer as the outside of the membrane becomes less positive, whilst u said that the answer is more positive..so, which answer do we take? i am referring to nyjc prelims 04 mcq question 39:

To simplify things:

At resting state, the potential in the axon is less than the external environment (-70mV). This resting potential is due to the ATP pump pumping in 2 potassium ions in and 3 sodium ions out (net charged particles going out is more than those coming in).

When the pump is not working, there will be no entry of potassium in and no sodium out. Thus there will be a net decrease in charge outside due to the stopping of transporting 3 charged sodium out. Thus the environment outside will be lesser than previously (less positive) compared to the internal environment.

PS: Ignore the previous explanation of potassium diffusion, not required in this sense.

MG

PSI and PSII

2005-08-25T11:14:00.000+08:00

The questions:

1)are the lecturers implying that in PSl the ejected electrons dont enter the ETC? from my understanding... it's such tt the electrons actually enters the ETC and are transferred to protein ferredoxin before being used to reduce NADP.. is my concept wrong?

From PSI, the electrons can enter two pathways:

(i) It can leave the photophosphrylation cycle to reduce NADP, therefore the pathway of the electron is known as non-cyclic photophosphorylation. The PSI which is short of an electron will be stabilised by another electron from the ETC. That electron would have to come from PSII which have been excited by light energy. The PSII would be in turn stabilised by the electron derived from the photolysis of water.

(ii) It can re-enter the ETC, in turn drives the production of ATP and then returning back to the PSII, stabilising it. Thus this will be cyclic photophosphorylation.

2)replacement of electron loss from PSl the same in both cyclic and non-cyclic phhotophosphorylation?

Cycling photophosphorylation involves PSI (simply: electron from PSI stabalises PSI). Non-cyclic photophosphorylation involves both PSI and PSII.

In cyclic photophosphorylation, the electron comes from PSI, while in non-cyclic photophosphorylation, it comes from PSII and PSII is stabilised by electron from the photolysis of water.

MG

Transfer of energy

2005-08-25T11:02:00.000+08:00

Hi all,

You must understand that the transfer of energy is not very efficient. There are many levels of transfers from the energy derived from the sun till it reaches the top of the food chain.

You must consider first from the source of the energy, the sun. How much energy is captured from the sun by the producers and how much is converted to food (take note energy is converted in terms of glucose in plants) The way energy is transferred itself is not efficient. Only 1% of light energy is converted to glucose that will be available to the next trophic level.

Between each trophic levels, there are many ways in which energy can be lost (go and find out) and therefore the energy transfer is around 10-20% max after each trophic level.

It does not matter about the biomass of the organism, because the energy content in that mass cannot be assimilated by the next trophic level (imagine the amount of storage of glucose in consumers). Therefore, the max trophic level of a food chain can be seen.

MG

Identification!

2005-08-25T10:54:00.000+08:00

Hi all,

I would stress again that the information here is reserved for students who will identify themselves. You are welcomed to read, but if you are to comment, please identify yourself.

As such, all comments made without identification will be deleted at first instant starting from now.

Do not expect to score well unless you put in the effort that is required.

Thank you for your cooperation.

MG

Health vs Study

2005-08-16T16:13:00.000+08:00

There seems to be an increasing rate of absentism for classes. To many who burnt the midnight oil to cramp a few more hours beware. You body needs a good amount of rest, especially when you are fully utilising your brains (i hope so).

As such, please include in your study plan, a suitable amount of time for some light exercise (NOT long hours of soccer and basketball games) and have a good amount of sleep (~ 7 hours).

You do the maths, if you get sick because of squeezing the extra hours, you lose out in a few days of work. Plus, insufficient sleep leads to ineffective studying as well.

PS: Those who know this site, do intro to those who have spare time and have questions to ask.

MG

Synapsis VS Crossing over

2005-08-11T22:32:00.000+08:00

Synapsis happens at prophase of meiosis I. It refers to the homologous choromosomes coming close together. Chiasma formation then takes place and bivalents are then formed.

Crossing over refers to the breakage and rejoining of segments of non-sister chromatids during prohase (of meiosis I) after bivalents are formed.

As such, synapsis is not equivalent to crossing over.

The pairing (formation of bivalents) allows crossing over to take place and this enables genetic variations in the gametes.

MG

Adaptation of thylakoid to its function

2005-08-11T22:22:00.000+08:00

To answer this question, first of all you must take note of the marks allocation. Always attempt a question with a plan. Break the questions into parts that you understand.

The key to the question is asking about adaptation and function, in terms of thylakoid it will refer to structure related to function.

Firstly you will have to identify the structure of the thylakoid and its location.

Next you have to identify its function. Here we know that it is involved in photosynthesis. You have to be familiar with photosynthesis to know what role does the thylakoid plays (and thus how is it adapted to perform its role)

(i) Light Harvesting - what is the role played by the thylakoid membrane and adaptation

(ii) Electron transfer

(iii) Cyclic and non-cyclic photophosphorylation

(iv) ATP synthesis.

With these you are more able to attempt the questions.

Do take note that adaptations need not be specialized features, it will also include features that enable the thylakoid to perform its function.

MG

Codominance & Incomplete dominance

2005-08-05T21:32:00.000+08:00

The difference between Incomplete dominance and Co-dominance:

The lecture is taken as the lastest and correct version.

For Incomplete dominance, neither allele has complete dominace over the other and hence both allele will NOT FULLY expressed themselves, instead, both allele express intermediate characteristic.

Example: Snap dragon

One allele codes for red flowers
One allele codes for white flowers

When bothe alleles are together, the phenotype expressed will be pink, which means both allele did NOT FULLY expressed themselves but expressed intermediate characteristic.

For Codominance, both allele expressed themselves FULLY as shown in the phenotype.

Example: ABO Blood group

I(superscipt A) codes for the production of antigen A
I(superscript B) codes for the production of antigen B

When both alleles are together, both characteristics are expressed FULLY, meaning that antigen A and B are produced in the blood. Hence co-dominance.

Example 2: Coat colour

One allele codes for white patches
One allele codes for red patches

When both alleles are together,
(i) pink patches indicate....?
(ii) white and red patches found together indicates...?

Answer:
(i) Incomplete dominace
(ii) Co-dominance

Final note: To differentiate look at the final expression and take note of FULL or Intermediate expression.

Genetics definitons

2005-07-31T19:28:00.000+08:00

a)Allele Frequency
b)Gene Pool
c)Selective Advantage
d)Selective Disadvantage
e)Selection Pressure
f)Allopolyploidy
g)Autopolyploidy

(a) The frequency of a particular allele among all versions of a particular gene.

(b) The total aggregate of genes in a population at any one time.

(c)(d) Traits or conditions that allow an organism to become more competitive in a given
environment

(e) A measure of the effectiveness of natural selection in altering the genetic composition of a population

(f) A common type of polyploid species resulting from two different species interbreeding and combining their chromosomes.

(g) A type of polyploid species resulting from one species doubling its chromosome number to become tetraploids, which may self fertilize or mate with other tetraploids.

Do check out the glossary in Campbell Biology (6th Edition) for more definitive terms.

MG

Instructions

2005-07-28T10:17:00.000+08:00

Hi all,

Here is how you would make use of this blog. WE will share questions/ concepts that are common. Post your question/query under the comments in this post. If suitable, i will answer the question and post it in a new post.

You need to be a member to post comments, so follow the 3 step instructions and start posting

PS: Identify yourself or your queries will not be entertained.

MG-Biology

2005-07-28T10:15:00.000+08:00

Hi all,

Welcome to MG-Biology. First of all, a disclaimer that the blog site is designed for discussion of Biology within students and it should not under no circumstances be reproduced for other purposes. It reflect the view of the administrator and does not reflect the views of any organisation.

Some basic rules to take note:

(i) All discussion should be strictly educational in basis

(ii) No vulgarities are to be used at any time

(iii) Provide a theme for your posting and keep it to the point.

(iv) The administor reserves the right to post/unpost at his discretion.

(v) Identify yourself or posting will not be published.

Thank you for your cooperation, learn and work hard