OCR 2010 A2 Biology Unit 2 - Control, Genome and Environment Watch

tgr141291
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Can someone explain what we need to know with regards to the experimental evidence for the role of auxins in the control of apical dominance and the role of gibberellin in the control of stem elongation. There seems to be loads of waffle in the textbook - but what are the points we need to learn?

Thanks
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ViolinGirl
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#922
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(Original post by ibysaiyan)
Hi there yea.... Its to do with the production of penicillin at one place it says its made up by feed batch process while the next para. states Batch process only :confused:
By feed batch I assume you mean continuous culture method?

Well anyway. I know for sure than penicillin is produced by batch culture method, because the fungus penicillium produces penicillin as a by product of their metabolism that is not part of its normal growth, so penicillin is a secondary metabolite, so the fungus would need to be under 'stress' conditions in order to produce it. With a batch culture, a set amount of nutreints are added to the culture so it will follow the typical growth curve, and secondary metabolites will start to be produced during the stationary phase where the nutrients begin to run out.
If it was continous culture then the nutrients and conditions would constantly be altered to suit the fungus, and the secondary metaolite would not be produced.
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Chunkeymonkey62
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#923
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****

I have to do F21 - 2,4 and 5 as well.

Im really struggling in terms of revision. Its like I cant be bothered and nothing is going in!
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TX22
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#924
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#924
What did everyone get for their A2 OCR biology ISA grades?
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ACDC
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#925
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#925
Anyone have any good succint notes on the gene sequencing/gene technology/genetic engineering topic?
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ibysaiyan
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(Original post by ACDC)
Anyone have any good succint notes on the gene sequencing/gene technology/genetic engineering topic?
Yep most my and other folks posts on it I will collect them later or you could scavenge around or if i got time I will make them up again.
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ibysaiyan
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#927
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(Original post by tgr141291)
Can someone explain what we need to know with regards to the experimental evidence for the role of auxins in the control of apical dominance and the role of gibberellin in the control of stem elongation. There seems to be loads of waffle in the textbook - but what are the points we need to learn?

Thanks
Things to know about auxin aka 2,4Di or IAA .
Is produced in the apex of the plants.All you need to know in terms of experimental points is that the flow of Auxin is downward.Starting from darwin until 60's various experiments were performed to find out the role of auxin.At first it was thought that the auxins were destroyed by the sunlight which in some way caused the growth but later it was found out that the sunlight provides Kinetic energy to auxins to flow from one side to the other.How auxins work? e.g Say the left side of the stem has been cut-off so what happens is that the stem bends towards the left side due to the expansion-elongation of the cells on the right side. Basically they attach on to the complementary receptors on the cell walls of the plants by which a chain reaction goes on within (the whole process is not known yet) which causes cell wall to expand.

Now on to the apical dominance: Its the phenomena which occurs with few species of plants for example: Christmas tree xD where auxin act as "inhibitor".How this works? On a normal plant you would expect the growth of the plant to be uniform by which we mean more on the top side and less on the lower but this doesn't occur rather the opposite.The auxins attach themselves to the terminal buds in these plants which inhibits their growth.So top being more in auxin conc. = Very low growth.
Mid-stem = Low growth.
Bottom= Max. growth as the auxin concentration is low to inhibit terminal buds.


Role of gibberlins: Well from what I can recall is that they provide food to the seed. There was a past paper question on it which I did in my lesson. Where a diagram of seed was shwo. arghh cant remember what it was but it was to do with the conversion of the food within the seed into energy i.e ATP by enzymes in a chain reaction . I think giberrlin first within the embryo goes out to this "X-layer" where it activates enzymes such as amylase to convert "endosperm" which is food source into glucose + aerobic respiration = > net. 32ATP
Not 100% sure if its accurate
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ViolinGirl
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#928
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(Original post by tgr141291)
Can someone explain what we need to know with regards to the experimental evidence for the role of auxins in the control of apical dominance and the role of gibberellin in the control of stem elongation. There seems to be loads of waffle in the textbook - but what are the points we need to learn?

Thanks
Ok. Apical dominance refers to how the growth of the apical bud prevents the growth of lateral buds further down the stem. It is known that auxins are produced at the shoot tip, and that they are involved in cell elongation. It is suggested that auxins are also involved in inhibiting the growth of side shoots.
To test this experiments were done where the tip of the shoot is cut off, and left to grow, in this case lateral buds do grow. The explantion is that auxin levels drop when the tip is cut off and no longer inhibit the growth of lateral stems. To further test this, the tip was cut off, and a paste of auxins were placed onto the tip, but in this case, lateral stems did not grow.

But, more experiments had to be carried out to ensure that there were not other factors causing the growth when tip was cut off, for example the exposure of the plant tip to oxygen which could then cause the production of a hormone that causes lateral stems to grow. From further anaylsis of other species of plant, it was concluded that there are 2 other hormones that are involved as well, cytokinins and absinsic acid.
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ibysaiyan
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#929
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(Original post by ViolinGirl)
By feed batch I assume you mean continuous culture method?

Well anyway. I know for sure than penicillin is produced by batch culture method, because the fungus penicillium produces penicillin as a by product of their metabolism that is not part of its normal growth, so penicillin is a secondary metabolite, so the fungus would need to be under 'stress' conditions in order to produce it. With a batch culture, a set amount of nutreints are added to the culture so it will follow the typical growth curve, and secondary metabolites will start to be produced during the stationary phase where the nutrients begin to run out.
If it was continous culture then the nutrients and conditions would constantly be altered to suit the fungus, and the secondary metaolite would not be produced.
Ok so penicillin is made by feed Batch culture only? does that mean the food source is limited and once too much toxin starts to generate or another limiting factor kicks in- The whole set-up needs to be sterilized again ?
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ViolinGirl
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#930
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(Original post by ibysaiyan)
Ok so penicillin is made by feed Batch culture only? does that mean the food source is limited and once too much toxin starts to generate or another limiting factor kicks in- The whole set-up needs to be sterilized again ?
No. In a batch culture the process is run once. The supply of nutrients are provided, conditions are set and fungus will be placed in the fermentor, at the end of the process when pencillin is produced, it is harvested, the tank is emptied and process is repeated from scratch as necessary. This is in contrast to a continuous culture fermentor where nutrients are constantly being added and the fungus/bacteria etc would not be under stress so not produce secondary metabolites. This process is used for primary metabolite production. It can keep running forever as long as conditions and nutrients are supplied and products are harvested, in this case, if there does happen to be a contamination, such as foreign bacteria entering the sample, then the whole set up needs to be shut down, and the tanks steralised and set up again, which is extremely costly and one of the down sides to this prodcution method. For that reason many aspectic techniques are put in place to attempt to prevent contamination which you prob already known about.
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ibysaiyan
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#931
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(Original post by ViolinGirl)
No. In a batch culture the process is run once. The supply of nutrients are provided, conditions are set and fungus will be placed in the fermentor, at the end of the process when pencillin is produced, it is harvested, the tank is emptied and process is repeated from scratch as necessary. This is in contrast to a continuous culture fermentor where nutrients are constantly being added and the fungus/bacteria etc would not be under stress so not produce secondary metabolites. This process is used for primary metabolite production. It can keep running forever as long as conditions and nutrients are supplied and products are harvested, in this case, if there does happen to be a contamination, such as foreign bacteria entering the sample, then the whole set up needs to be shut down, and the tanks steralised and set up again, which is extremely costly and one of the down sides to this prodcution method. For that reason many aspectic techniques are put in place to attempt to prevent contamination which you prob already known about.
Alright I think I get it now but isnt penicillin a secondary metabolite?
Oh is it because of the microbes being stress-less that it becomes a primary?
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ViolinGirl
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#932
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(Original post by ibysaiyan)

Role of gibberlins: Well from what I can recall is that they provide food to the seed. There was a past paper question on it which I did in my lesson. Where a diagram of seed was shwo. arghh cant remember what it was but it was to do with the conversion of the food within the seed into energy i.e ATP by enzymes in a chain reaction . I think giberrlin first within the embryo goes out to this "X-layer" where it activates enzymes such as amylase to convert "endosperm" which is food source into glucose + aerobic respiration = > net. 32ATP
Not 100% sure if its accurate
What?! Never heard of this. Gibberellins are associated with stem elongation in plants, and they also promote seed germination.
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ViolinGirl
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#933
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(Original post by ibysaiyan)
Alright I think I get it now but isnt penicillin a secondary metabolite?
Oh is it because of the microbes being stress-less that it becomes a primary?
You still seem confused here. Ok...

yes penicillin is a secondary metabolite.

There are 2 fermentor methods for large scale production:
Batch culture- carried out once with no addition of nutrients and repeated as necessary.

Continuous culture- ongoing process with nutrients continually supplied and products harvested.

Batch method is used to produce secondary metabolites.

I was only referring to continuous to show the contrast.
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ibysaiyan
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#934
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#934
(Original post by ViolinGirl)
What?! Never heard of this. Gibberellins are associated with stem elongation in plants, and they also promote seed germination.
Yep I will post up the question later. =}
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ibysaiyan
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#935
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(Original post by ViolinGirl)
You still seem confused here. Ok...

yes penicillin is a secondary metabolite.

There are 2 fermentor methods for large scale production:
Batch culture- carried out once with no addition of nutrients and repeated as necessary.

Continuous culture- ongoing process with nutrients continually supplied and products harvested.

Batch method is used to produce secondary metabolites.

I was only referring to continuous to show the contrast.
Oh k. Thanks makes sense now :yep:
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ViolinGirl
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#936
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I'd like to know if we need to know the specific regions of the brain within the cerebral cortex such as broca's area...

Anyone know?

Also if we do, please explain!
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ViolinGirl
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#937
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Oh- If anyone wants to-I'd appreciate a summary of the commercial use of plant hormones.
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ibysaiyan
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#938
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(Original post by ViolinGirl)
I'd like to know if we need to know the specific regions of the brain within the cerebral cortex such as broca's area...

Anyone know?

Also if we do, please explain!
Yep.The stuff worth knowing is the CSF- Cerebro spinal fluid,Thalamus (the primitive or the reptilian brain),hypothalamus,cerebrum and cerebellum,medulla oblongata.The linkages of two hemispheres.Meninges being form of protective layer.Oh also you must know that how the development of human brain started and that limbic system deals with memory and emotions.The part is called hippo campus which has an important role in memory,autonomic co-ordination .It is just underneath your eye socket.
Difference btw. hemispheres: Left hemisphere is known to deal with verbal actions.The brocas area is involved in the production of speaking an writing languages. Wernickes area helps in Understanding a language.
Right hemisphere deals with stuff visually thats why scientist are said to be left users while artists right.

P.S: Just wanted to mention that about 5 years ago i had a terrible car accident in which i was literally juiced over by a car xD as a result of which my cerebrum shook.Thank god it wasn't too violent but it left some scars such as when I am exhausted I cant co-ordinate balance.My vision circles 360 around me.. jeez Nightmare I say! Its as if you are pushed over the cliff or sucked into a black hole.
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TX22
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#939
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so is this right about batch and continuous culture:

batch culture- nutrients are added to the culture at the beginning in the fermenter and the microorganisms are allowed to grow for certain time. The products are harvested from the fermenter at the end.

continuous culture - nutrients are added to the culture in the fermenter continuosuly and the products are harvested at regular intervals
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TX22
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#940
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#940
sorry for spelling
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