AQA BIOL2 ~ 21 May 2012 ~ AS Biology
Biology exam discussion - share revision tips in preparation for GCSE, A Level and other biology exams and discuss how they went afterwards.
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Re: AQA BIOL2 ~ 21 May 2012 ~ AS BiologyI've got this word stuck in my head, but no idea what it relates to...
"peptidoglycan" Might have spelt it wrong, but does anyone know what it is... :/
I'm writing my mark scheme answers and it just came to me... ! -
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Re: AQA BIOL2 ~ 21 May 2012 ~ AS BiologyIt's what bacterial cell walls are made out of.(Original post by britash)
I've got this word stuck in my head, but no idea what it relates to...
"peptidoglycan" Might have spelt it wrong, but does anyone know what it is... :/
I'm writing my mark scheme answers and it just came to me... !
Plant cell walls are made of cellulose and bacterial cell walls are made of peptidoglycan
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Re: AQA BIOL2 ~ 21 May 2012 ~ AS BiologySo the cholera bacterium (unit 1) would have a petidoglycan cell wall? Is that all we really need to know about it? xx (and thanks!) x(Original post by nimby77)
It's what bacterial cell walls are made out of.
Plant cell walls are made of cellulose and bacterial cell walls are made of peptidoglycan
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Re: AQA BIOL2 ~ 21 May 2012 ~ AS BiologyIt's probably easier to remember the word murein.(Original post by britash)
So the cholera bacterium (unit 1) would have a petidoglycan cell wall? -
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Re: AQA BIOL2 ~ 21 May 2012 ~ AS BiologyDid pretty well(Original post by dongonaeatu)
1. index of diversity takes into account number of species present and number of different types of species 2/2
2. Light, temperature, humidity and wind 4/4 Not sure if you can call it wind - maybe just stick to air movement
3.300/3=100 3 bases per amino acid, so 900 bases.
4.i dont know, is inter between different species and intra the difference's in the same species? Yup 2/2
5. bohr effect something about co2 released when muscles respire so more haemoglobin goes to it and unloads o2 In a way. Cells respire so release more CO2, this decreases the pH and makes it more acidic causing the haemoglobin to change shape and lower its affinity to oxygen so it can release oxygen more readily at a lower PO2 of oxygen
did i do ok
1.What is a DNA made of
2. Explain 3 main differences between mitosis and meiosis
3.explain how an antibiotic can kill/inhibit a bacteria
4. Explain the function of an xylem
Spoiler:Show
1) 2 polynucleotide strands (of which are made from nucleotides consisting of a phosphate, deoxyribose sugar and organic base [A T G or C]), the strands are joined together by hydrogen bonds between A and T or G and C according to complimentary base pairing.
2) Mitosis produces genetically identical cells and meiosis genetically different
Mitosis ends up with the same number of chromosomes, Meiosis is half the number of chromosomes.
Ermm... independent segregation and crossing over can only occur in meiosis.
3) An antibiotic inhibits the peptide cross links in the cell wall of a bacteria cell causing it to weaken. This means when osmosis enters the cell, the usually rigid cell wall can withstand this, but as it is weakened the increased pressure causes it to burst - known as osmotic lysis.
4) To transport water and ions up the stem to the leaves where it is lost be transpiration. (Not really sure how to expand)
1)Explain what happens in the arteriole to control the flow of blood (2)
2)If 24% of my bases are Adenine, what % of bases are Guanine? (1)
3)What bonds join together the hydroxyl groups of cellulose? (1)
4) Explain the cohesion-tension theory -
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Re: AQA BIOL2 ~ 21 May 2012 ~ AS BiologyYes, a cholera bacterium would have a peptidoglycan cell wall.(Original post by britash)
So the cholera bacterium (unit 1) would have a petidoglycan cell wall? Is that all we really need to know about it? xx (and thanks!) x
As for what you need to know about it, I know for unit 2 you only need basic knowledge of prokaryotic ultrastructure (70s ribosomes, circular dna, etc).
Do you mean what we need to know about cholera in unit 2 or unit 1?
(and you're welcome
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Last edited by nimby77; 12-05-2012 at 15:20. Reason: bacteria have double stranded dna lol -
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Re: AQA BIOL2 ~ 21 May 2012 ~ AS BiologyHow does osmosis enter a cell, exactly?(Original post by Mocking_bird)
3) An antibiotic inhibits the peptide cross links in the cell wall of a bacteria cell causing it to weaken. This means when osmosis enters the cell, the usually rigid cell wall can withstand this, but as it is weakened the increased pressure causes it to burst - known as osmotic lysis.
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Re: AQA BIOL2 ~ 21 May 2012 ~ AS BiologyI'm a teachers pet.(Original post by Mocking_bird)
The ones you actually did were obviously right
But that shifty thing won't suffice
Slacking!
You know that someone somewhere will put something like that if they're asked to explain what the Bohr effect is though.
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Re: AQA BIOL2 ~ 21 May 2012 ~ AS Biology^ This(Original post by dongonaeatu)
she meant water enters the cell by osmosis, going down the water potential gradient.
But if osmosis wants to enter a cell, it can! alright!
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Re: AQA BIOL2 ~ 21 May 2012 ~ AS Biology(Original post by dongonaeatu)
she meant water enters the cell by osmosis, going down the water potential gradient.
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Re: AQA BIOL2 ~ 21 May 2012 ~ AS BiologyCould someone please help me I'm so confused!
Why is it that some places with low oxygen, the animals living there have an oxygen dissociation curve to the right and some have it to the left?
Because if it has a higher affinity then more oxygen can be picked up, and if it's a lower affinity more oxygen can be released into the cells/ tissue...
So how do you know what to say in an exam if they ask if the curve will be to the left or right!?!? AHHHH!
Attached two questions.. do you see what I mean? -
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Re: AQA BIOL2 ~ 21 May 2012 ~ AS Biologyokay, listen. When the curve is to the right, it has a low affinity for oxygen. This is because the animal lives in places with a high partial pressure of oxygen (e.g a bird) and so it is MORE important for the animal to be able to unload the oxygen rather than load it ( as a bird is very active so muscles are respiring and so it needs the oxyhaemoglobin to be unloaded)(Original post by thescientist17)
Could someone please help me I'm so confused!
Why is it that some places with low oxygen, the animals living there have an oxygen dissociation curve to the right and some have it to the left?
Because if it has a higher affinity then more oxygen can be picked up, and if it's a lower affinity more oxygen can be released into the cells/ tissue...
So how do you know what to say in an exam if they ask if the curve will be to the left or right!?!? AHHHH!
Attached two questions.. do you see what I mean?
If it is to the left is has a HIGH affinity for oxygen. E.g a lug worm. This is because the lug worm lives in a place with a low partial pressure of oxygen (e.g the soil) and the lugworm is not very active. Therefore it is more important for the lug worm to be able to load oxygen to the haemoglobin, rather than unload it ( as the lugworm is not very active)
do you understand -
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Re: AQA BIOL2 ~ 21 May 2012 ~ AS Biology(Original post by Mocking_bird)
Spoiler:Show1)Explain what happens in the arteriole to control the flow of blood (2)
Well, they have this smooth muscle malarkey and it contracts and relaxes and so reduces and increases the diameter and this regulates the flow of blood to the capillaries.
2)If 24% of my bases are Adenine, what % of bases are Guanine? (1)
A loves T, and C loves G. This means that A & T have the same and so 24%, meaning that the rest of it is split between C & G. Given that my limited Math stretches to this just about, I know that the remainder is 52%. My Mum would be proud of me knowing that this means there is 26% G, as that is what 52/2 is.
3)What bonds join together the hydroxyl groups of cellulose? (1)
I think these are hydrogen bonds.
4) Explain the cohesion-tension theory.
Are you being sarcastic? You nabbed MY notes!
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Re: AQA BIOL2 ~ 21 May 2012 ~ AS BiologyNo, because earlier on in the question it says that in the atmosphere there is a low partial pressure of oxygen.(Original post by dongonaeatu)
okay, listen. When the curve is to the right, it has a low affinity for oxygen. This is because the animal lives in places with a high partial pressure of oxygen (e.g a bird) and so it is MORE important for the animal to be able to unload the oxygen rather than load it ( as a bird is very active so muscles are respiring and so it needs the oxyhaemoglobin to be unloaded)
If it is to the left is has a HIGH affinity for oxygen. E.g a lug worm. This is because the lug worm lives in a place with a low partial pressure of oxygen (e.g the soil) and the lugworm is not very active. Therefore it is more important for the lug worm to be able to load oxygen to the haemoglobin, rather than unload it ( as the lugworm is not very active)
do you understand -
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Re: AQA BIOL2 ~ 21 May 2012 ~ AS Biologywhat? Are you kidding me?(Original post by thescientist17)
No, because earlier on in the question it says that in the atmosphere there is a low partial pressure of oxygen.
listen, to the right there is a low affinity for oxygen and to the left there is a high affinity for oxygen. Are you saying this is wrong? -
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Re: AQA BIOL2 ~ 21 May 2012 ~ AS BiologyI know this is unit 2, but you guys' answers are much quicker than the unit 1 board,
From January, do any of you have a mark scheme points for the differences between Pulmonary Fibroisis and Emphysema.
I'm really struggling with making mark scheme points between the two.. :/
Whats the main points / Thanks x -
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Re: AQA BIOL2 ~ 21 May 2012 ~ AS Biologyemphysema is caused by smoking or exposure to foreign particles- which become trapped in the alveoli. This causes inflammation, where phagocytes go to the area. The phagocytes produce an enzyme that breaks down elastin ( found in walls of alveoli)(Original post by britash)
I know this is unit 2, but you guys' answers are much quicker than the unit 1 board,
From January, do any of you have a mark scheme points for the differences between Pulmonary Fibroisis and Emphysema.
I'm really struggling with making mark scheme points between the two.. :/
Whats the main points / Thanks x
so the alveolar walls are destroyed and elasticity of lungs is lost- so this reduces surface area of alveoli and rate of gaseous exhange decreases.
fibrosis- is formation of scar tissue in lungs. Result of exposure to asbestos or dust. Scar tissue is thicker and less elastic than normal lung tissue. so lungs less able to expand and cant hold as much air as normal- tidal volume is reduced. So a reduction in gaseous exchange- diffusion is slower across a thicker scarred membrane. Basically it, both have to increase breathing rate to get enough air in.
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