AQA BIOL2~3rd June 2013~AS Biology (Now Closed)

Hey man, thanks for answering my question!

I'll do your question now! Root pressure occurs at the xylem of roots. You know how water moves from the root hairs by the symplast and apoplast up to the endodermis, where ALL the water is taken up by endodermis cells(casparian strip forces apoplast into endodermis cells also). Now, the endodermis cells actively move ions into the xylem vessel. This lower the xylem's water potential and the water from the endodermis cells moves by osmosis into the xylem. Th pressure caused by this is root pressure

Cohesion tension - When water evaporates from the cells of the leaf, it lowers their water potential. This causes a osmotic gradient, whereby water moves across cells to replace the evaporated water. Now water molecules form h bonds between each other, so they form long chains that extend down the xylem; this is cohesion. When the water molecules move to replace the lost water, the whole chain moves up to xylem too. The movement of these chains up the xylem causes an inward pressure; this is the tension. Hence cohesion tension theory

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Ok so root pressure is really caused by actively transporting salts into xylem to get water to diffuse in from the endodermal cells?

Also, for the cohesion tension, is the tension in the xylem highest during midday when factors such as temperature and light intensity resulting in rate of transpiration being highest so meaning that choension tension is highest as well so you've got a higher rate of water flow in the xylem.

thank you so much!=P
Sorry fr wasting yr tym=]

Can someone explain immunological comparisons of proteins? Really don't understand

Serum A (has antigens) is taken from Species 1
Then injected into Species 2 which produces antibodies
Serum B from Species 2 is extracted
Then put into Species 3
If Species 3 has similar antigens to Species 1, they bind to the antibodies.
More closely related = more precipitate = because more antigens bind with the antibodies that are specific to Species 1

We are trying to look for similarities between Species 1 & 3. Species 2 only produces antibodies that are specific to the antigens/proteins of Species 1 so when it gets into Species 3, if the antigens of Species 3 is similar to species 1 then it will bind to more antibodies thus making more precipitate showing they are closely related.

Hope that made some sense! XD Please correct me if I'm wrong

Bacteria & Antibiotic Resistance

Bacteria -Genetic Variation
Adaption, the process of natural selection that allows organisms to adapt to its environment, is important for the evolution and diversity of organisms. Bacteria are particularly diverse and adaptable organisms, which allows them to become antibiotic resistant. Diversity results from changes to the DNA which occurs due to mutation and conjugation (similar to sexual reproduction).

Mutations
When the bacteria replicates, bases in the DNA sequence may be added, removed or replaced, which results in it coding for a different amino acid. This means that the polypeptide that is produced will be different and if this protein is an enzyme then it could change the metabolic pathway preventing the production of other substances (e.g. proteins which control the organisms alleles) and so the mutations alter the organisms characteristics.

Mutations are rare and occur randomly by chance (they occur independently of any changes in the environment).

Conjugation
Conjugation is when one bacteria transfers its DNA to another by producing a thin projection that connects to the other bacteria to form a thin conjugation tube. The donor bacteria sends a replicated linear version of its plasmid (normally a circular loop of DNA) down the tube. The tube disconnects before the entire plasmid passes to the other bacteria cell and so the bacteria cell only inherits some of the other characteristics from the other bacteria.

Horizontal gene transmission is where in conjugation genes are passed from one species to another.
Vertical gene transmission is where genes are passed on from generation to generation in the same species.

Antibiotics
Antibiotics are substances produced by organisms to inhibit the growth of or destroy microorganisms however the term sometimes includes synthetic drugs too. Antibiotics are primarily used to treat bacterial infections.

Bacteria cells have rigid cell walls (like plant cells) which prevent the cells from bursting when a cell has absorbed the maximum amount of water possible via osmosis. Is a cell bursts in this way it is known as osmotic lysis.

Some antibiotics inhibit the synthesis and assembly of the polypeptides that hold together the cell walls; without these cross-linkages the cell walls collapse under the osmotic pressure and so osmotic lysis occurs (killing the bacteria).

Antibiotic Resistance
After the discovery of antibiotics of antibiotics, their effectiveness reduced due to the rare event of a chance mutation in some bacteria which enabled them to produce a new protein, the enzyme penicillinase, which broke down penicillin before it could kill the bacteria.

In the presence of penicillin most of the bacteria that don't produce penicillinase will be killed, then the survivor bacteria (most of which produce penicillinase) will multiply, producing a population with an increased frequency of the allele for penicillin resistance. In this case the allele for penicillin resistance is passed from generation to generation by vertical gene transmission but it is also passed via horizontal gene transmission in conjugation to the few survivor bacteria were not penicillin resistant.

Superbugs are bacteria that gain resistance to multiple antibiotics through horizontal gene transmission.

Increasing the use of antibiotics and killing off only the non-resistant bacteria leaves resistant bacteria to multiply producing a population of resistant only bacteria that replaces the original population.

Antibiotic Resistance & TB
TB (Tuberculosis) is a disease affecting the lungs caused by the bacterium Mycobacterium. Treatment of TB requires the patient to take antibiotics for approximately 6-9 months. Initially the antibiotics kill off the least resistant strains of Mycobacterium and after several months the majority of Mycobacterium will have been killed (and the patient may feel better) however a few of the most resistant bacteria will still be alive. If the patient completes their course of antibiotics the bacterium will eventually be killed off. In patients who don't finish their course of antibiotics, the resistant strains of Mycobacterium multiply and spread to others. These resistant strains may then receive resistance to other bacterium via conjugation. Patients with these strains of bacterium must take a 'cocktail' course of antibiotics to ensure that at least 1 of the antibiotics work.

Antibiotic Resistance & MRSA
Staphylococcus aureus is a species belonging to the genus staphylococcus which resides in humans thoughts. Mostly it doesn't present a major health risk however in cases where it does antibiotics are used to treat it. MRSA (Methicillin-resistant Staphylococcus aureus) is a strain of the bacterium, resistant to one or more antibiotics. MRSA can be particularly dangerous as it is mostly found in hospitals; as patients in hospitals tend to be weaker and more vulnerable to infection; transmission of MRSA is made easy as the people stay closed together and are examined by doctors who move from patient to patient. Different strains of MRSA swap resistances which lead to some strains being resistant to nearly all antibiotics; these strains are very difficult to treat.

Biodiversity

Biodiversity describes the variety of living organisms referring to the number and variety of organisms in a particular area, taking into consideration the species diversity (number of species in the area and number of individuals of one species in that community, the genetic diversity (variety of genes a species possesses) and the ecosystem diversity (the range of habitats within the area).

Species Diversity
Species diversity is the measure of biodiversity that looks at the number of species and the proportion of the community that each species represents. Here is my Dr. Patricia Tannis' nice how to calculate species diversity guide on Pandora (How to calculate species diversity with references to Borderlands) ;3
https://twitter.com/shinusuke_akki/status/313822509768261633/photo/1

Species Diversity & Human Activities

The human populations immense size has increased their need for the earths resources and as a result of their activities, such as agriculture and deforestation, the earths biodiversity has been reduced.

Impact of Agriculture
Communities of natural ecosystems have a large number of individual organisms and a large number of species.
Communities of agricultural ecosystems are controlled by humans using selective breeding, reducing the number of species and their genetic variety of alleles.

Any single area can only support a certain amount of biomass; in agricultural land most of the space is taken up by the chosen species/crop. The species diversity is reduced by the lack of space for other species, the competition for this space and the use of pesticides by humans.

Impact of Deforestation
In forests the species diversity is high, as many different species adapt to the forests numerous habitats. Tropical rainforests have the highest species diversity of any ecosystem and contain approximately half the worlds species within them, despite only covering approximately 7% of the worlds surface.

Deforestation results in the loss of habitat and hence the loss of biodiversity; it is estimated that 50,000 species are lost per year as a result. Deforestation can be a result of humans harvesting its trees for wood, clearing it for agriculture, settlement etc. and partially is as a result of man-made pollution.

THE END OF PART 5/5 MEANING THE ABSOLUTE END OF MY BIOL1 NOTES!!!!! note: I will be writing up notes for BIOL1, If you would like me to send you a copy of these in an email just ask or PM me and I'll send them as I write each part or as a whole when all the notes are complete complete, add your your preference when you request the notes. I can also send you a copy of the BIOL2 notes now they are complete if you would like, feel free to ask ^.^

Thank-you to my partner who has supported me, whom without I would have never produced these notes as I'd have dropped out of A Levels a long time ago. A Levels are hard, don't let anyone make you feel like you're not working hard, regardless of how much work you're doing!

Yeah, that's right Active transport of mineral ions into the xylem that causes osmosis into the xylem. Its the osmosis that causes the pressure

Absolutely right When transpiration is high, water flow is high. And when water flow through the xylem is high, the tension in the vessels are high too, so it will become narrower. And as you said, this typically occurs the most at midday, when transpiration is at the highest

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Not wasting my time at all, helps me revise Good luck


I answered this earlier in the thread, hope this helps!

Marry me .....

Can someone explain immunological comparisons of proteins? Really don't understand

This has probably been asked lots of time but cant find replies but does anyone have any predictions for the 6 marker. Tissue fluid is ruled out.

does anybody have like a list of all the definitions we need to know for this exam? Thank you.

Hi, does anyone know whether we have to learn the names of the amino acids?

The answer being 209.1 is as incorrect as adding 0.9th of a person. There's no way to argue with AQA -.-


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