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DavidYorkshireFTW
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#3881
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#3881
(Original post by ahmmm)
plans and mark schemes for all essays or you narrowed them down?
Not narrowed them down yet but i will do, not sure how though, really unprepared for the essays :/
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rommy123
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#3882
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#3882
(Original post by WesleyT)
Oestrous Cycle

-FSH, secreted from pituitary gland, stimulates follicle development

-Oestrogen is released from the follicle and the ovaries

-Oestrogen stimulates the uterus lining to thicken and inhibits FSH

-As Oestrogen concentration increases, it stops inhibiting and stimulates the pituitary gland to secrete LH and FSH (LH surge)

-LH surge causes ovulation where the follicle ruptures and an egg is released

-LH stimulates the follicle to become the corpus luteum

-Progesterone secreted by corpus luteum

-Progesterone maintains the uterus lining and inhibits LH and FSH

If no embryo implants

-Corpus luteum breaks down

-Progesterone no longer released

-FSH concentration increases because it is no longer inhibited by progesterone

-Cycle starts again



Remember you're not a flop at Biology, you're a F.O.L.P.!

Hope this helps!
Thankyou
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DELETED ACCOUNT
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#3883
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#3883
(Original post by stoppy123)
So sorry to keep repeating myself

but, what have you got for ATP essay plan? Is this enough?

- Produced in Aerobic and Anaerobic respiration.
- Produced in light dependent and independent reactions
- Produced by phosphocreatine ssytem
- Used for Muscle contraction
- Used for active transport
- Used to create second messenger when adrenaline binds
- Used for sodium potassium pump
- Good as it's simple one step reaction
- Can be regenerated
- Does not affect osmotic potential of cell like glucose would.
- Produces energy in managable amounts.
Yep.

Maybe talk about the role of ATP on the receptors of the postsynaptic neurone?
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lcj0503
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#3884
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#3884
anyone thin chemical co-ordination in animals and plants could come up as an essay? or something like communication between cells, tissues and organs?
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s24a
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#3885
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#3885
(Original post by lcj0503)
anyone thin chemical co-ordination in animals and plants could come up as an essay? or something like communication between cells, tissues and organs?
what could you write for that?
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stoppy123
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#3886
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#3886
(Original post by frogs r everywhere)
Yep.

Maybe talk about the role of ATP on the receptors of the postsynaptic neurone?
Erm, I don't know :rolleyes:
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LitGeek94
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#3887
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#3887
(Original post by rm.xo)
You don't need any. This isn't required. That's just extra. I did this exam last year and got 23/25 on the essay without including any off spec topics.
Omg really? Thats such a relief! I really only know little things like the name of enzymes or something, no big topic things
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saba146
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#3888
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#3888
instead of trying to guess which essay titles are coming up id recommend just planning for a range of essays which cover most of the synoptic elements, ive done this for the past 2 days and familiarized myself with pretty much everything from the past units
for example the causes of variation - focuses mostly on unit 2 and 4 - with meiosis and speciation and natural selection and deletion and substitution of bases.
structure and function of proteins - structure of proteins - hemoglobin, transport proteins, hormones such as insulin and glucagon, fibrous proteins, enzymes, neurotransmitters, muscles
other essay titles are - biological importance of water, causes of diseases (yes i know this has already come up but good way to go over lung and heart diseases)
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TauMuon
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#3889
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#3889
Can someone help me clarify what voltage-gates are open during the different stages of a nerve impulse? Thanks!


Resting potential:

Sodium voltage-gates closed.
Potassium voltage-gates open.


Depolarisation:

Sodium voltage-gates open.
Potassium voltage-gates closed. (?)


Repolarisation:

Sodium voltage-gates closed.
Potassium voltage-gates open.
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DELETED ACCOUNT
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#3890
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#3890
(Original post by ropin1)
I would say that its used up in photosynthesis to create glucose or other products, Dont know if im right on that tho
You are right but:

In light dependent reaction- ATP is produced

In light independent reaction- ATP is used up



And guys it is: light dependent not light dependant
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LitGeek94
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#3891
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#3891
(Original post by TauMuon)
Potassium voltage-gated channels are closed during depolarisation, and open during repolarisation (at around +40 mV).

I THINK; can anyone clarify?
Oh, I thought both are closed during resting potential, because the sodium potassium pump helps maintain the resting potential...
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sophie15
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#3892
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#3892
What points could you include in a 'variation' essay? Please help!
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JasminC
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#3893
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#3893
(Original post by ropin1)
Someone else posted there plan to that question, there you are
Use in plants
- Water uptake in roots - apoplastic (cell wall) /symplastic (cytoplasm)
- minerals build up in root due to low water potential
- causes root pressure, evidenced by guttation

- Transpiration - is the loss of water from plant surface due to evaporation
- dependent on water potential in leaf and in air
- transpiration stream is continous flow of water from root to leaf
- Cohesion-Tension (water pulled up by transpiration replaced by more water

- Photosynthesis - water used in photolysis of water, molecule splits into
- H+ ions reduce NADP
- electrons replace electrons lost from PSII in non-cycli phosphorylation
- oxygen released as waste gas

- Xerophytic adaptions - thick waxy cuticle reduces evaporation
- close stomata in daylight to reduce transpiration
- succulent leaves store water
- smaller leaves, reduced SA:V ratio slows diffusion

Reproduction
- sexually reproducing organisms use water to bring male and female gametes together in fertilisation
- in mammals foetus develops in water filled sac which provides thermal and physical stability

Hydrolysis and condensation
- ATP -> ADP + Pi
- restriction endonucleases use hydrolysis
- hydrolysis/condensation reactions of biopolymers (polysaccharides, polypeptides, nucleic acids)

Osmosis
- movement of water molecules from a high water potential to low water potential through partially permeable membrane
- water potential in cells (if isotonic no net diffusion, if in hypotonic soln cell swells/plant cell turgid, if in hypertonic soln cell crenates/plant cell undergoes plasmolysis)

Blood Glucose

- Blood glucose conc too high - water potential too low
- causes water to leaves surrounding cells to increase water potential, cells my dehydrate/die
- Diabetes - blood has lower water potential, leads to thirst, copious urine produced due to XS water in blood, poor vision due to osmotic loss of water from eye, blood pH falls leading to acidosis

Cholera
- bacterial cell adheres to epithelia and secretes exotoxin, which enters cell and opens chloride ion channels
- chloride ions diffuse out of cells into lumen, lowering lumen's water potential
- water osmotically diffuses into lumen, produces diarrhoea
- treat with ORS salts

Cystic Fibrosis
- in healthy cells CFTP protein carries Cl ions out of cell, increases water potential of cytoplasm
- water leaves cell by osmosis, makes mucus watery
- CFTP protein absent due to genetic mutation
- Cl ions cannot leave cell, water remains in cell
- produces thick sticky mucus which blocks airways, leads to coughing, wheezing, bacterial infection

OTHER TOPICS could be considered
- water as a habitat (oceans, lakes, rivers) for marine life (fish gills, counter-current exchange)
- adaptions of hydrophytic plants
- Role of water in thermoregulation
- Osmoregulation (TBH this is quite complicated)
thank you sooooo much! do you know anything about what to put on a question asking the importance of hydrogen bonds in living organisms?x
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kitkat95
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#3894
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#3894
Anyone got any thoughts on what to include in an essay about polymers? All I can think of so far is:
- Starch- amylose and amylopectin
- Cellulose
- Structure of proteins
- DNA
- could the chain of water molecules in the cohesion of water count as a polymer?
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DrewYouTwo
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#3895
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#3895
Ok, practice question guys:

Explain how chemical mediators like histamines differ from hormonal control?

Why can oestrogen and progesterone be taken as an oral pill but not LH or FSh?

Explain how the strucure of siRNA differs from mRNA?

Why is PCR heated to 72 degrees after primers bond?

Describe the second messenger system, with reference to adrenaline?

Why do cones see in colour?
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DavidYorkshireFTW
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#3896
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#3896
(Original post by WesleyT)
Oestrous Cycle

-FSH, secreted from pituitary gland, stimulates follicle development

-Oestrogen is released from the follicle and the ovaries

-Oestrogen stimulates the uterus lining to thicken and inhibits FSH

-As Oestrogen concentration increases, it stops inhibiting and stimulates the pituitary gland to secrete LH and FSH (LH surge)

-LH surge causes ovulation where the follicle ruptures and an egg is released

-LH stimulates the follicle to become the corpus luteum

-Progesterone secreted by corpus luteum

-Progesterone maintains the uterus lining and inhibits LH and FSH

If no embryo implants

-Corpus luteum breaks down

-Progesterone no longer released

-FSH concentration increases because it is no longer inhibited by progesterone

-Cycle starts again



Remember you're not a flop at Biology, you're a F.O.L.P.!

Hope this helps!
Dude, you're awesome- i reckon hopefully the word F.O.L.P will help me remember all of that!
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asdfasdfasdfasdf
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#3897
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#3897
has anyone got any links to any essay plans? thanks in advance!
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lcj0503
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#3898
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#3898
(Original post by s24a)
what could you write for that?
for chemical co ordination in animals/plants:

Hormones- Oestrous cycle
Glucose Regulation
Adrenaline
Second messenger model
Growth Factors- IAA/tropisms
Chemical Mediators
Osmoregulation and ADH

its just in my essay plan booklet and i was wondering if it could come up because its mainly unit 5? but i think sometimes they have a general essay then one more relating to unit 5-thats what i have been told :/
x
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F1's Finest
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#3899
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#3899
http://filestore.aqa.org.uk/subjects...W-QP-JUN11.PDF

Can anyone explain 5)c)ii

I just haven't got a clue what's going on.

I thought it wouldn't matter how many times your restriction enzyme cuts the DNA, surely when you add up the pieces again, you would get the same number
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problematic
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#3900
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#3900
(Original post by JasminC)
also what would you include if hey asked about the importance of hydrogen bonds?

Cohesion Tension theory (Xylem)

Base pairs AT CG (include how many of each to be fancy lol C-G is 3 Hbonds and AT is 2)

Cellulose structure - The point of myofibrils helping it's strength

The big enzyme topic - Helping it to form its specific active site

I also have a special one, classification lol so when scientists want to see how closely related two animals are, they use DNA hybridisation
(Seperating two strands at high temperature which breaks their H-bonds, then allowing complementary bases to join)

And PCR (the use of temperature to break the H-bonds to allow exposed nucleotides)

Hope that helps
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