Edexcel Biology (Unofficial) B2 Mark Scheme.

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For the very first question about the differences between the bacteria cells and the shown yeast cell, I wrote about the bacteria cell not having a nucleus - that the chromosomal DNA just 'floats around' in the cytoplasm, I wrote that a bacteria cell can sometimes have a flagella and that the yeast cell did not, that a bacteria cell's wall is not made from cellulose and that a bacteria cell does not have a vacuole but the yeast cell does. This question was 2 marks.

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For the second question I wrote 'mitochondria'. This was a one mark question.

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For question three, I wrote down 42, although I now believe this to be incorrect. I believe the answer to be 17 or 21. This was a one mark question (I don't know why there is so much controversy surrounding this one mark!).

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For question 2a the answer was peristalsis. The exact phrase I wrote was: "peristalsis - a wave of muscle contraction", this was to secure the mark. This was a one mark question.

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For the disadvantage question I wrote that the food had not been churned by the stomach and that the bacteria had not been killed by the stomach acid. This was a one mark question.

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For the amylase question I wrote the following: "The amylase, a biological enzyme, will break down the starch in the white bread into simple sugars. White bread is easier to break down than brown bread". This was either a two or a three mark question.

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For the multi-choice fossils question I selected D. This, obviously, was a one mark question.

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For the question of why the numbers of species A were lessened I wrote the following: a natural disaster such as an ice age, volcanic eruption or an earthquake could have occurred - destroying the habitat, that the species A might have been competing with other species (namely species C) and that the estimates were based on the fossil records - meaning that gaps or decreases in numbers could be due to the fact that some fossils simply had not been discovered yet or were even there in the first place. I'm pretty sure that this question was a three marker.

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For the question about bases in amino acids, I multiplied the number given by three (because three bases code for an amino acid) to get an answer in the 1800's (don't remember the number exactly). This was a two mark question.

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For the question about pentadactyl limbs, I wrote that the two bones above the wrist allow for rotation, and that the pentadactyl limb features five fingers. This question was a two or three marker, and because I had just looked at my watch I realised I didn't have much time left so I rushed it.

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For the question about the DNA from pea cells, I wrote that the first step was required in order to break open the cells and to release the DNA (by breaking open the nucleus). I didn't actually revise the second part of this question (the part about adding in detergent) so I just made up that you are adding biological enzymes to remove unwanted parts of the cell and to soften the DNA. This was a two mark question.

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For the question about comparing cells produced by mitosis and meiosis, I wrote that mitosis produces two diploid genetically identical cells, whereas meiosis produces four haploid gamete cells. This was a three mark question.

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For the first circulatory systems question, I can confirm that the answer was the pulmonary vein. This was a one mark question (I think).

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For the question immediately after the question above, about how de-oxygenated blood moves from the atrium to the lung, I wrote that it goes through the atrium, a valve, then into the ventricle, and then another valve, and that when the heart beats the valves open and the blood moves in a beat. The blood then moves along the pulmonary artery before reaching the lung. This was either a two or a three mark question.

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For the first six mark question about the blocking of the coronary arteries, I wrote that they can be blocked by excess cholesterol in the blood, meaning that the muscle cells in the heart can't respire as efficiently, meaning a lower cardiac output. To compensate, the heart has to beat faster, which can cause cardiac arrest or a heart attack, and it could even lead to death. I also wrote that the person who suffered from this would suffer from shortness of breath, and that they would build up an oxygen debt very quickly. Another point is that this could cause the heart to beat irregularly, which may cause a stroke. I also wrote that less blood pumping can limit how much other cells can respire because the heart can't supply them with oxygen quickly enough.

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For the second six mark question I wrote about how the root hair cells of the plant absorb water through osmosis - because the water molecules move from the area of high concentration (soil) to the area of low concentration (root hair cell) through the root hair cell's partially permeable (cell) membrane. I then wrote about transpiration, and how the evaporation of water in the leaves through the stomata causes water to be pulled up from the xylem, which pulls water from the roots. I then compared this chain of transpiration to sucking on a straw. I also talked about active transport, and how it requires energy from respiration, and how osmosis and transpiration require no energy, but I don't think active transport would be on the mark scheme.

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I think that the mark scheme will be quite tough for this exam, meaning lower grade boundaries. This test rewarded those who revised, so people who crammed last minute probably won't get a good mark as they probably didn't go into enough detail and they didn't revise all of the topics. Fortunately for people like us that plan ahead, this means that we will probably get higher grades even though we got lower marks. I am personally quite confident that I definitely got an A, and I'm about 70% sure that I got an A*. This is because in the past, the A* boundary has been as low as 45 (!) in March 2013. The A grade was 40 however, and the B grade was 35. This was a difficult paper. However, the June 2012 paper was really a breeze, and when I did it in a home revision session I scored 55 out of 60 marks. The grade boundary here however was 53 marks for an A*, and 46 for an A. This shows that the boundaries can and will vary, and as this was a harder paper I do think that the boundaries will be lower. One reason I think for this paper being harder than the past two years is because Edexcel may be switching to the new GCSE style paper, so that people next year can do our paper and know to expect something similar (this would explain the weird layout and the copious amounts of suggest questions).

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Don't worry, if you are browsing this forum it shows that you actually care about your education and grade. You are probably fine and you will probably get an A or an A*.

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I guess is that the grade boundaries would be similar to March 2013: A* is 45 marks, A is 40 marks, B is 35 marks, and a C is 30 marks.

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Phew. That's a lot of text I just typed.