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A level Biology: Post your doubts here!

oahmed64

oahmed64

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Hey could anyone PLEASE give me a model answer for how bacteria is used in extracting metals?
 
Mahmood Magdy

Mahmood Magdy

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oahmed64 said:
Hey could anyone PLEASE give me a model answer for how bacteria is used in extracting metals?
Click to expand...
The process of extraction of metals using bacteria is known as Bio-leaching. Chemoautotrophic bacteria, which obtain their energy from oxidation reactions, such as A.ferrooxidans are used to extract the metals of Copper, zinc, gold, silver etc from their low grade ores. The insoluble ore is turned to soluble ore. First of all, the ore is piled up, followed by creating acidic conditions (pH 1.5-3). Different types of bacteria can be used, not just one. The reaction is highly exothermic. The reaction could be direct oxidation from Sulfide to Sulfate , Ferrous to Ferric. Products are washed in pools and the metal is displaced by adding scrap iron.
 
Mahmood Magdy

Mahmood Magdy

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liptonice said:
and also from May june 2007 paper 4, question 4a : Describe the role of insulin in the regualtion of blood glucose concentration ?

why in the MS its written about K+ ions pump and Ca2+ ions ?????????
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Because when there is a change in stimulus, the generator potential has to exceed the threshold level first. For this to happen, energy conversion takes place at the receptor, in this case the beta- cells, which leads to a series of processes which leads to insulin being secreted. If we take the case of the Pacinian capsule (pressure receptor), it gets squeezed out of shape which opens the Na+ channels which eventually leads to an action potential. Every receptor has it own 'skip' and if you are doing A2 CIE you do not have to study those. Just the basic concept of the energy conversion(from light, pressure, heat, chemical etc to electrical potential), threshold level and the generator potential.
 
C

cadburrylover

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can someone tell me when to use membrane and when to use neuron/cell when answering questions about nerve impulses?
 
M

My Name

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qwertypoiu said:
guys plz help,
What is the difference between collagen molecules and collagen fibres?
Click to expand...
collagen.jpg

This might help you :)
Pic shared by FranticAmaze
 
qwertypoiu

qwertypoiu

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upload_2015-4-20_18-7-23.png
So, answer is A. What does cohesive tension force even mean? Someone please explain this and also how/why it increases/decreases during day and night, and how it affects diameter of tree. Thanks
 
Mahmood Magdy

Mahmood Magdy

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qwertypoiu said:
View attachment 52236
So, answer is A. What does cohesive tension force even mean? Someone please explain this and also how/why it increases/decreases during day and night, and how it affects diameter of tree. Thanks
Click to expand...
Try thinking about it this way, at night there is no sun and obviously less/no transpiration. Now you studied that the movement of water in the xylem depends upon the low hydrostatic pressure created at the leaves due to loss of water. This creates a transpirational pull and thus water moves up the xylem. Back to night-time, no sun=no transpiration, thus water moves slowly if at all in the xylem and thus the diameter increases. The same concept applies during day time and thus the diameter is much less during the day as most of the water is constantly moving due to the cohesion-tension theory and transpirational pull.
 
qwertypoiu

qwertypoiu

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Mahmood Magdy said:
Try thinking about it this way, at night there is no sun and obviously less/no transpiration. Now you studied that the movement of water in the xylem depends upon the low hydrostatic pressure created at the leaves due to loss of water. This creates a transpirational pull and thus water moves up the xylem. Back to night-time, no sun=no transpiration, thus water moves slowly if at all in the xylem and thus the diameter increases. The same concept applies during day time and thus the diameter is much less during the day as most of the water is constantly moving due to the cohesion-tension theory and transpirational pull.
Click to expand...
Mahmood Magdy said:
The answer will be B probably HIV/AIDS, I believe this is due to the working of the enzyme reverse transcriptase. Therefore, to prevent it, drugs that have structures similar to DNA nucleotides are used to act as competitive inhibitors etc. I guess this is a pretty fair assumption :D
Click to expand...
THANK YOU BRO!!! :)
 
qwertypoiu

qwertypoiu

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Hi, I have a question about tertiary structures of proteins. Their shapes are affected by:
  • hydrogen bonds
  • ionic bonds
  • disulphide bonds
  • hydrophobic interactions
between the different amino acids.

Somebody please explain which of these bonds are the strongest and which are the weak ones. (please order them from strongest to weakest)
Also, please explain, for each of them, how they can be broken? I mean which onees are broken by pH changes, which ones by temperature changes, etc.
Thank you!
 
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