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peebs123
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#2421
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#2421
(Original post by mogg)
right so when you are doing restriction mapping you want the strand to be completely digested by the restriction endonuclease enzyme. This mean that all the possible restriction sites have been used and there are the maximum number of fragments are produced. If it only has been partially digested, it means you will get some random larger fragments where a restriction site has not been recognised and broken apart. does that help?
Yes that helps, thanks!
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Anjna
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#2422
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#2422
if ach isn't broken down and remains in the synaptic cleft longer than it should? what does this result to?
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simstaaar
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#2423
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(Original post by YWArtist)
Which sexy person on here has a list of essay names, with bullet points as to topics to include in each essay?

I hope they bring you as much pleasure as they have given me...
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Ghost95
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#2424
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#2424
(Original post by s24a)
i thought an ADP molecule is used for formation, and ATP is used for detachment? :confused:
ATP binding to the head causes DETACHMENT, then hydrolysis of ATP by ATPase provides energy for the head to revert back to it's original position. Then ADP binding to the head causes FORMATION of a cross-bridge another actin-myosin binding site further along the actin filament, head changes angle (power stroke) and ATP binds again so it detaches...cycle repeats
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Lizzie232
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#2425
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(Original post by s24a)
i thought an ADP molecule is used for formation, and ATP is used for detachment? :confused:
The ADP is used so the fibre is in the right state to bind.

Once they attach they change their angle and pull the actin filament, releasing a molecule of ADP.

ATP attaches to detach it from the actin filament.

Hydrolysis of this ATP molecule provides the energy for the myosin head to return to its original position
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SamEastie
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#2426
(Original post by MLogan)
Formation, the detachment is caused by a new ATP molecule binding to the myosin head ..I think!
not sure it is for formation.. adp and p are attached to the myosin head at the point when it binds. the head has energy from previous hydrolysis of atp in a cycle before, but im not sure atp actually causes it to bind. its due to the angle of the head with adp.. i may be wrong .. :')
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MLogan
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#2427
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#2427
(Original post by s24a)
i thought an ADP molecule is used for formation, and ATP is used for detachment? :confused:
The energy used from hydrolysis of ATP to ADP + P is used to bind the myosin head to actin and causes it to be pulled along. When a new ATP binds to the myosin head, this causes the detatchment of the myosin head from Actin filament. Does that make sense? If not ask me
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MLogan
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(Original post by Anjna)
if ach isn't broken down and remains in the synaptic cleft longer than it should? what does this result to?
This will mean constant action potentials to the post synaptic membrane, this can cause muscular spasms. I think...
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safis
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#2429
(Original post by master y)
how/who told you this?
A teacher who attended aqa conference last year.. Chief examiner mentioned it there will be a future question on this but didn't say when.
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MLogan
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#2430
(Original post by safis)
A teacher who attended aqa conference last year.. Chief examiner mentioned it there will be a future question on this but didn't say when.
on what?
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Anjna
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#2431
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"Plant responses to environmental changes are co-ordinated by plant growth factors . Explain how." how would you answer this Q?
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peebs123
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#2432
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#2432
how does the structure of a muscle cell relate to its function?
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Andrewjames6
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#2433
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#2433
Chapter 11 MS 3B(i) states 'ATPase breaks down ATP yielding energy' which i get... however the second mark says 'energy is used to break actomyosin bridge' which i dont get.. i thought the energy allows the mysoin head to reattach....
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Andrewjames6
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#2434
fast twitch or slow?
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F1's Finest
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(Original post by simstaaar)
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I hope they bring you as much pleasure as they have given me...
No 19 caught my eye.

'The part played by the movement of substances across cell surface membranes in the functioning of different organs and organ systems'

This one is tricky.

Bullet points:

Carrier Proteins - outline and give examples
Glucose Co-Transport
Hormones
Secretory cells - e.g. pancreas

Can't think of any more.




Can water molecules be referred to as substances?

Guys, any help would be appreciated.
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laser174572
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#2436
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#2436
(Original post by James A)
No 19 caught my eye.

'The part played by the movement of substances across cell surface membranes in the functioning of different organs and organ systems'

This one is tricky.

Bullet points:

Carrier Proteins - outline and give examples
Glucose Co-Transport
Hormones
Secretory cells - e.g. pancreas

Can't think of any more.




Can water molecules be referred to as substances?

Guys, any help would be appreciated.
Sodium and potassium ions during the passage of an action potential would seem to be a relevant point, plus Saprobiontic organisms might be relevant...it's difficult to think of anything I know beyond the syllabus to get the extra marks for that one, though...


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flyylikejetz
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#2437
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#2437
(Original post by Anjna)
"Plant responses to environmental changes are co-ordinated by plant growth factors . Explain how." how would you answer this Q?
My guess would be...

you have to consider auxins and in particular IAA with tropism.
For instance with light, plants tips will show positive phototropism given that IAA accumulates on the shaded side and inhibited cell elongation so tip elongates bending towards light.

Environmental changes could be as said before light, and water (roots) etc...
there is temperature, CO2 etc.. but i don't think they would fit in with the growth factors theme of the question
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Ghost95
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#2438
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#2438
(Original post by James A)
No 19 caught my eye.

'The part played by the movement of substances across cell surface membranes in the functioning of different organs and organ systems'

This one is tricky.

Bullet points:

Carrier Proteins - outline and give examples
Glucose Co-Transport
Hormones
Secretory cells - e.g. pancreas

Can't think of any more.




Can water molecules be referred to as substances?

Guys, any help would be appreciated.


That's a tough one... I don't see why you couldn't write about water, just be careful what it is. Maybe counter-current flow mechanism in gills? It's a movement of oxygen across a cell membrane vital for respiration in fish so maybe. Look for the exam paper mark scheme for that question they always give a breakdown of what is acceptable to write about
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kiyubi
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#2439
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#2439
(Original post by James A)
No 19 caught my eye.

'The part played by the movement of substances across cell surface membranes in the functioning of different organs and organ systems'

This one is tricky.

Bullet points:

Carrier Proteins - outline and give examples
Glucose Co-Transport
Hormones
Secretory cells - e.g. pancreas

Can't think of any more.




Can water molecules be referred to as substances?

Guys, any help would be appreciated.
Polar and non polar molecules oxygen, co2, ions eg nitrate too many!
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F1's Finest
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#2440
Cheers guys

(Original post by laser174572)
Sodium and potassium ions during the passage of an action potential would seem to be a relevant point, plus Saprobiontic organisms might be relevant...it's difficult to think of anything I know beyond the syllabus to get the extra marks for that one, though...


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Yeah, I almost forgot about that one!

Why Sapribiotic microorganisms?

Do you mean as in when they respire? The gases exchanged across their cell membrane?

(Original post by Ghost95)
That's a tough one... I don't see why you couldn't write about water, just be careful what it is. Maybe counter-current flow mechanism in gills? It's a movement of oxygen across a cell membrane vital for respiration in fish so maybe. Look for the exam paper mark scheme for that question they always give a breakdown of what is acceptable to write about
The thing with counter current flow is that there's no movement across a cell membrane. All it really is though is blood and water flowing in the opposite direction.

I appreciate the responses though
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