Biomolecules Revision questions

Hi, i was given about 10 question sheets revising all of the biomolecules studied in class but i am stuck on a few questions. Please help with the following and i will give rep.

1) Why is it important to have two differeing forms of glucose (alpha + beta) (2marks)

2)What do the terms saturated and unsaturated mean? (2 marks)
Now there is a question below it saying in what ways do the properties of saturated and unsaturated fats differ and that is wheere i wrote about C-C and C=C bonds so that shudnt be written for the answer i have asked

3) DNA base are Cytosine.... etc

Using this information explain the term complementary base pairs (2 marks)
I know that A goes with T because they are both purines but i dont know how to word this answer for 2 marks

4) Suggest why it is an advantage that glycogen molecule is branched (2)

5) State two ways in which a cellulose molecule differs from a glycogen molecule. (2)

Thanks in advance,

Regards, Asad

Reply 1

Cirsium

19

Ok well the most obvious one as it were where I won't give you a wishy-washy answer is number 4. By being branched the glycogen molecule offers several hundred sites at which hydrolysis or synthesis can occur. This means that enzymes have easy access to the molecule and that blood sugar can very quickly be regulated by breaking down the branches, or building them up. Were it a linear molecule then hydrolysis could only occur at 2 sites

Umm as for the DNA bases... I see what you mean, it's obvious but hard to explain. Although I'd kinda like to correct you quickly about A and T - they're not both purines because each pair includes one purine and one pyrimidine. They bond together because they both form 2 bonds - C and G form 3. I guess you talk about the fact that each base can only bond with one other and this is specified by whether it is pur/pyr and how many bonds it can form, leading to the constant distance between the strands of DNA.

Not sure about why it's important to have 2 types of glucose. I mean you use alpha in sucr, lac, malt, amylose/amylopectin, glycogen and then beta in cellulose but hmm not sure that's what they're after

I think you're wrong - I think you do need to talk about that bit in the first question because sat/unsat MEANS whether it has single or double bonds there's no other definition for it

And for the last one... well cell is beta glucose where glyc is alpha. Umm glycogen is a branched globular type molecule, cellulose is formed in sheets... hmmm I've forgotten so much :confused:

Reply 2

Nabqueen

1) It's important so that different polysaccharides can be made. Eg, starch and glycogen are made from alpha glucose whereas cellulose is made from beta glucose.

2) Saturated can't bond to anything else, Unsaturated have available electrons

3) cytosine, adenine, thymine, guanine
In a DNA molecule, there is just enough room between the 2 sugar-phosphate backbones for one purine and one pyrimidine molecule, so a purine in one strand must always be opposite a pyrimidine in the other.

4) Loads of branches mean that stored glucose can be released quickly, which is important for energy release in animals.

5) Cellulose is unbranched, and its made from beta glucose. (there's loads of other stuff too, but thats just two) :biggrin:

Reply 3

asadtamimi

OP

13

Nabqueen

1) It's important so that different polysaccharides can be made. Eg, starch and glycogen are made from alpha glucose whereas cellulose is made from beta glucose.

2) Saturated can't bond to anything else, Unsaturated have available electrons

3) cytosine, adenine, thymine, guanine
In a DNA molecule, there is just enough room between the 2 sugar-phosphate backbones for one purine and one pyrimidine molecule, so a purine in one strand must always be opposite a pyrimidine in the other.

4) Loads of branches mean that stored glucose can be released quickly, which is important for energy release in animals.

5) Cellulose is unbranched, and its made from beta glucose. (there's loads of other stuff too, but thats just two) :biggrin:

Thank you both so much - just saw now there is a sort of maths based question that i dont think i can answer because i dont have enough data:

A biochemical analysis of a DNA sample showed that 27% of the nitrogenous base was cytosine. Calculate the percentage of the bases in teh sample which would be thymine. Show your working.

How am i supposed to answer this? Am i meant to know the relationship of percentages between the four bases?

Reply 4

rishman

13

ATCG so 27% cytosine so 27% guanine so 23% A and 23% thymine

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