AQA Biology AS New Spec - 26th May and 7th June

On a question it asked how the reduced elasticity of the lungs causes breathing difficulties, and one of the marking points was that lungs cannot fully inflate (reduced lung capacity)- which I understand.
However the other marking but was that breathing out would no longer be passive? Which i don't understand at all

could someone explain the process of hybridisation please???

could someone explain the process of hybridisation please???

Hybridisation is what we use to determine the degree of 'relatedness' between two organisms. The first step is to obtain DNA from the two organisms. We then break the hydrogen bonds and separate the DNA strands by heating. We then allow the separated DNA strands to mix. Hybrid DNA forms which contains strand of DNA from one organism and a strand of DNA from the other. We now attempt to separate these two strands via heating. The higher the temperature required to separate the strand, the more closely related the two organisms are as their must be more Hydrogen bonds so there must be more complementary base pairs and so the base sequences of dna must be more similar

How can Biologists use protein structure to investigate the relationship between differentspecies?

Look at sequence of amino acid - primary structure, in same protein . The more similar the sequence , the closer the relationship

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Am I correcting in thinking the first paper was only on the first 2 units (even though AQA said the papers would be mixed) and so paper 2 will be on Unit 3 and 4?

Am I correcting in thinking the first paper was only on the first 2 units (even though AQA said the papers would be mixed) and so paper 2 will be on Unit 3 and 4?

I think what this means is that normally we don't use forced expiration: our intercostal muscles do not normally contract during expiration. This is because the elasticity of the alveoli is enough to push the air out: the alveloi sort of recoil. However, reduced elasticity renders this mechanism ineffective and so we need to rely on forced expiriation which means expiration is no longer passive

The paper seemed to be almost solely on Unit 1 and 2, but that's purely a coincidence. But, that does mean that there is a high chance that this paper tomorrow will contain mostly Unit 3 and 4 content.
(Saying that, it's hard to tell as AQA are very unpredictable, they may surprise us with even more enzymes).

Wait... I seem to be missing something. What is in Unit 3 and 4? Is it not A2 content?

Does anyone know the key points of how tissue fluid is formed?

1. High hydrostatic pressure at the arteriole end of the capillary bed causes fluid and small molecules to be pushed out of the capillary into the surrounding tissue, (as the pressure is lower there)

2. Plasma proteins are too large and are therefore not pushed through the capillary and remain inside it. These are soluble and therefore lower the water potential.

3. Some water will therefore move back into the capillary via osmosis

Also as a side note it is good to know that any excess tissue fluid is drained by the lymphatic system

What ****ed me over in the specimen papers we've had for the new specification was how strict the mark scheme was! I literally know the majority of the content but I just don't write answers in the way they want me to 😡 It's so annoying. I've basically just accepted that I'm getting a U in these exams no matter what the paper or the grade boundaries are🙄