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AS Biology Question

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kratos009:
Hey everyone,
I got two Biology questions. They were from the May/ June 2007 Paper 1.

1. Membranous sacs containing products of metabolism are formed by the endoplasmic reticulum in cells.
   Where are these products used?
   A. inside and outside the cell
   B. inside lysosomes only
   C. inside the cells only
   D. Outside the cell only

 the answer was A. could you explain to me what they mean by products of metabolism, do they mean metabolic wastes such as CO2? And if that is what they meant how and why are they used inside and outside the cells? ???

2. This molecule is a polymer of reducing sugars.
Which of the following procedures could be carried out in order to test for the presence of the
reducing sugars in this molecule?
1 add hydrolytic enzyme and then heat with Benedict’s reagent
2 dissolve in water, neutralise and then heat with Benedict’s reagent
3 boil with ethanol and then heat with Benedict’s reagent
4 boil with hydrochloric acid, neutralise and then heat with Benedict’s reagent

A 1 and 2
B 1 and 4
C 1, 2 and 4
D 1, 2, 3 and 4

The answer is B. I was just wondering how and why is Hydrochloric acid used for the breakdown of polymers?

Thank you very much ;D

nid404:
For the first one metabolism could be synthesis of proteins and lipids and so on too.....in fact if u study function of cell organelles

Smooth Endoplasmic Reticulum (SER). Series of membrane channels involved in synthesising and transporting materials, mainly lipids, needed by the cell.

Rough Endoplasmic Reticulum (RER). Similar to the SER, but studded with numerous ribosomes, which give it its rough appearance. The ribosomes synthesise proteins, which are processed in the RER (e.g. by enzymatically modifying the polypeptide chain, or adding carbohydrates), before being exported from the cell via the Golgi Body.


So they are used both within the cell and outside


for the 2nd one......HCl hydrolysis the glycosidic bond.

kratos009:
Thanks a lot for answering so quickly ;D

Oh right I get the first one. So lipids are used in the cells for energy reserves, while the proteins are exported out of the cell to form other useful substances like antibodies etc.
For the second one how does HCl hydrolyse the glycosidic bond? Is it like dilute HCl acid which has aspects of water which hydrolyses the glycosidic bond while the HCl acid acts as a sort of a catalyst? Would it be alright if you could explain the mechanism of the hydrolysis or find a link that explains it if its not too much to ask. Thanks a lot.

I also got another question from that paper :D

In mammals, some carbon dioxide is transported by red blood cells in combination with
haemoglobin.
What is the product of this combination?
A carbamino-haemoglobin
B carbonic acid
C carboxyhaemoglobin
D haemoglobinic acid

the answer is A. I don't find the question very clear, so are they saying how is CO2 transported if it remains as just CO2 or if otherwise I was just wondering isn't most of the CO2 that is transported in the red blood cell in the form of carbonic acid as the CO2 reacts with the water and is stored in the red blood cell during the transportation until it reaches the lungs where the reaction is reversed to form CO2 again?

Thanks, I hope that made sense ;D

nid404:
the mechanism of hydrolysis....will have to look for summin

and they are askin what is the compound that forms when CO2 combines with Hb........it's called carbamino-heamoglobin...like how O2 forms oxyhaemoglobin...


By the way ur concept of loading and unloadin doesn't seem clear.....I'll look for a video tutorial......ur under the wrong impression that Hb carried CO2 in the form of carbonate ion

nid404:
check this   http://www.youtube.com/watch?v=Qrvrs6RXxwY&feature=related

&& http://www.youtube.com/watch?v=wLPgxfBqtOM

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