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Edexcel Biology Unit 1 Revision Questions

Seeing as i've just started revising unit 1 over easter holidays, i thought it would be a good idea to have a thread where people post questions fron unit 1 exams they have or questions they've been set for hwk etc and i will type up the questions and their answers from markschemes etc onto a word document which i will then upload for anyone taking the exam. I believe this would be an effective way of revising and people who dont know the answers to the questions can find out what the answers are.

So i'd be grateful for people to start posting questions asap.

Regards, Asad

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Reply 1
Yea thats a good idea
Ok it seems noone is really contributing anything to this thread..and i have to cover unit 1 for my synoptic paper anyway so i'll start off. Explain the process of DNA replication stating clearly why it is referred to as "semin-conservative replication"
Reply 3
asadtamimi
Seeing as i've just started revising unit 1 over easter holidays, i thought it would be a good idea to have a thread where people post questions fron unit 1 exams they have or questions they've been set for hwk etc and i will type up the questions and their answers from markschemes etc onto a word document which i will then upload for anyone taking the exam. I believe this would be an effective way of revising and people who dont know the answers to the questions can find out what the answers are.

So i'd be grateful for people to start posting questions asap.

Regards, Asad


Easier to get a hold of past papers...

Anyway:

List 4 functions of lipids and one benefit over charbohydrates in respiration.
Energy stores (adipose tissue) underneath the skin of most organisms.
They may also aid as a boyancy aid to keep organisms afloat in water Waterproofing layer on the feathers of ducks for example and the waxy cuticle on leaves.
Phopholipids are the important structural components in cell membranes
The only benefit over carbohydrates is that lipis release twice as much energy per gram. thats all i can think of atm
btw whats MATHS papers doing in your sig lol
Reply 6
I like maths
ROFL your a joker - btw did i get your q right ?
Reply 8
yes, congratulations
Reply 9
Iceman can you clearly explain to me the process of DNA replication - i never seem to include all the major points - it would be of great use to me

Regards, Asad
asadtamimi
Iceman can you clearly explain to me the process of DNA replication - i never seem to include all the major points - it would be of great use to me

Regards, Asad



sure thing asad... DNA replication is commonly referred to as "semi-conservative replication" because half of the original DNA molecule is kept and is a part of the new on that is made. DNA replication occurs during the interphase part of the cell cycle. Firstly the hydrogen bonds holding the complementary bases together are disrupted allwoing the double helix to unwind and the two strands to separate exposes the bases. Free nuclotides which are present in the cell pair up with the exposes complementary bases of one strand. The whole process is catalysed by the enzyme DNA polymerase which joins together the deoxyribose and phosphate groups (and also helps with the initial unzipping of the dna molecule in the first place) Hydrogen bonds form between the bases...and BEHOLD ! your DNA has been replicated :smile:
seeing that my original q had been answered heres another one for all you happy people :smile:.......explain the process of transcription and translation stating why it happens...also define the term GENE
Reply 12
iceman_jondoe
sure thing asad... DNA replication is commonly referred to as "semi-conservative replication" because half of the original DNA molecule is kept and is a part of the new on that is made. DNA replication occurs during the interphase part of the cell cycle. Firstly the hydrogen bonds holding the complementary bases together are disrupted allwoing the double helix to unwind and the two strands to separate exposes the bases. Free nuclotides which are present in the cell pair up with the exposes complementary bases of one strand. The whole process is catalysed by the enzyme DNA polymerase which joins together the deoxyribose and phosphate groups (and also helps with the initial unzipping of the dna molecule in the first place) Hydrogen bonds form between the bases...and BEHOLD ! your DNA has been replicated :smile:


Yeah, you'd got the idea... I won't go into the details you don't need for A-level

Though one thing you do need to know is that DNA polymerase only completely synthesises DNA on one strand (works only in the 5' to 3' direction)

This means on the other strand DNA polymerse incompletely synthesises DNA and so it only forms fragments of DNA on that strand. These fragments are then joined together by another enzyme DNA ligase.
o yeah i had something written down about that, DNA ligase works in the 3 to 5 direction ?
Reply 14
Give an account of the structure and function of the polysaccharides cellulose, starch and glycogen. [10 marks]
starch is actually made up of two polysaccharides amylose and amylopectin. Btoh amylose and amylopectin are polymers made up of alpha glucose monomers linked by 1,4 glycosidic bonds. However amylopectin has branches where the bonds are. Starch molecule often curl up due to hydrogen bonds forming between the OH groups of molecules. As it is a polysaccharide it is insoluble and therefore doesnt affect the water potential of cells making an excellent storage compound. It froms granules inside cells e.g. within chloroplasts. Glycogen has a similar structure to amlopectin and is the main storage compound in animals. Cellulose is made up of Beta glucose monomers linked by 1,4 glycosidic bonds...its molecules do not curl up but form long stragith chains :biggrin:. hydrogen bonds form between adjacent chains forming bundles of molecules called microfibrils. These microfibrils provide great tensile strength and is the main componnet of celss walls. As many organisms do not produce the enzymes required to break down the links in cellulose it is an excellent choice for plant cells to provide strength to plant cell walls.

NB i think there should be more than 10 marks for that
Reply 16
Ok thanks, so what does DNA helicase do if DNA polymersase is involved in the breaking up of the hydrogen bonds and then the joining of the nucelotides?
DNA helicase? ive never come across that enzyme before....you dont need it for the edexcel syllabus which i am sure off. Perhaps DNA helixase catalyses the disruption of the H-bonds at the start or something ? to help the double helix unwind ?.
Reply 18
asadtamimi
Ok thanks, so what does DNA helicase do if DNA polymersase is involved in the breaking up of the hydrogen bonds and then the joining of the nucelotides?


Helicase - unwinds the double stranded DNA

DNA polymerase - synthesises DNA on both strands but only works in one direction 5' to 3'

DNA ligase - joins fragments of DNA on one strand
Reply 19


DNA helicase? ive never come across that enzyme before....you dont need it for the edexcel syllabus which i am sure off.
My teacher said you do need to know about it.