OFFICIAL OCR A2 Biology - F214 Thread

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102102

Expand on what you trying to quote..maybe then i can my thinking cap on :smile:

Thank you, its a point on the specification...
"Outline the homornal and nervous mechanisms involved in the control of heart rate in humas"

Reply 3421

Remarqable M

102102

Tissue fluid.. i think..tap me sum1 if it's wrong :s-smilie:

i pretty sure its tissue fluid :p:

Reply 3422

dontkillhannah

Zahraaaa

i understand the sodium ions are activley transported out of the PCT but from there where do they go? to the capillaries? and when they move back down their concentration gradient where do they go?

The diagram from the textbook is pretty good:

So they are actively transported to the tissue fluid, so their concentration inside the cells are lower. As a result, there is a conc gradient from Na+ ions from the proximal convoluted tubule (where they are in high conc) into the cytoplasm (which now has a v. low conc of sodium ions). Therefore, the Na+ ions (with glucose/amino acids by co-transport) move in from the proximal convoluted tubule to the cells

Reply 3423

dontkillhannah

HumanNature1992

Hi, the oxygen produced during NCPP is that due to the photolysis reaction which replaces the electrons, i.e. H2O --> 2H+ + 1/202 +2e-

yup, I thiiiink so, to my knowledge the oxygen diffuses out of the chloroplast and eventually out of the leaf as the excretory product :smile:

Reply 3424

102102

NicolaBelle

Thank you, its a point on the specification...
"Outline the homornal and nervous mechanisms involved in the control of heart rate in humas"

Oh, seen well this is where u have to talk about the heart..i'll just point out few key facts which are

If heart needs more oxygen and more glucose then it will increase it’s heart rate so that it gets more oxygen pumped., it will also increase the strength of it’s contraction along with the stroke volume

U need to knw that the heart is a myogenic muscle, which means it’s can intiate it’s own contraction, without the need of an action potential.. the action potentials travels in teh form of waves of excitation in the heart from the SAN through the atria walls, to the AVN down the purkyne fibres all the way to the ventricles making them contract.
There are nerves taht are connected to the heart whom come all the way from the medulla oblongata of the brain, and affect the frequency of contractions
If you release the hormone adrenaline, then the heart rate increases, preparing you for activity. This hormone is usually released in response to shock, anticipation, stress or excitement..

Reply 3425

Remarqable M

NicolaBelle

Thank you, its a point on the specification...
"Outline the homornal and nervous mechanisms involved in the control of heart rate in humas"

Hormonal mechanism

adrenaline(hormone) mode of actions are diverse and one of the noticable effect of adrenaline is on the heart rate which it does this by changing the metabolic reactions of target tissues in the body. Adrenaline is a protein, so has specific shape which binds to a specific receptor all over the body(adrenaline and receptor bind together - complementary e.g. lock and key fit, once binded, adrenaline activates enzyme adenyl cyclase which converts ATP to cAMP which can activate other enzymes inside the target cell.) the overall of effect of adrenaline is increasing the rate of metabolic reactions of cells, because of the increase the heart pumps blood at faster rate, so more blood is pumped quicky to respiring tissues e.g. muscles so increasing the heart rate.

Nervous Mechanism

Vagus and accerator are the two nerves responsible for keeping the heart rate under control these nerves orginate from the medulla oblongata. It does this with the help of the cardiovascular centre which monitors any changes(these changes could me signals from cells asking for more glucose) in the body and feeds this information to the nerves and changes in the heart rate occur according to this information.

Reply 3426

Remarqable M

Bean_90

The descending limp is permeable to water, hence water diffuses down water potential gradient from high water potential in descending limb to low water potential in surrounding tissue of medulla by osmosis

thanks

it is all coming back and getting better :biggrin:

Reply 3427

Remarqable M

lol what happend to everyone? where are the questions?

Reply 3428

Chunkeymonkey62

Remarqable M

lol what happend to everyone? where are the questions?

Hi!

Are you retaking this as well? :p:

I remember it in january.

Reply 3429

aylasira

It's probably me being thick and pedantic, but are an amino group and an amine group the same?

Because the definition for deamination is 'removal of an amine group', but in the paragraph explaining what happens to the amino acids it refers to the 'amino group' being removed.

Reply 3430

Remarqable M

aylasira

lol its the same :p:

Reply 3431

Remarqable M

Chunkeymonkey62

Hi!

Are you retaking this as well? :p:

I remember it in january.

yeah

this unit feels so small it feels weird lol

Reply 3432

aylasira

Remarqable M

lol its the same :p:

I thought so. This new syllabus makes me paranoid :eek3:

Reply 3433

gingerfish

aylasira

When talking about deamination, I think its best to talk about the removal of the amine group, however i believe they are both the same.

Reply 3434

Remarqable M

aylasira

I thought so. This new syllabus makes me paranoid :eek3:

lol i don't feel paranoid, i admit i was in january :p:

Reply 3435

aylasira

Remarqable M

lol i don't feel paranoid, i admit i was in january :p:

I know OCR are tricksy and are out to stop me getting into medicine with their obscure questions, especially about animals that I don't care about.

Reply 3436

aylasira

gingerfish

When talking about deamination, I think its best to talk about the removal of the amine group, however i believe they are both the same.

Ah ok, thank you :smile:

Reply 3437

moneyneversleeps

Any have January paper and mark scheme??

Reply 3438

Remarqable M

i predict questions on: thermoregulation, osmoregulation, singals and messages(e.g. outline the siginificance of the frequency of impusle transmission), cAMP, nature of hormones e.g. protein/steroid, regulation of blood glucose, regulation of insulin levels e.g. outline how insulin secretion is controlled, deamination, structure of liver, hairpin countercurrent mulitplier,calvin cycle, structure and function of mitochondria, krebs/link reaction and evidence for chemiomosis

Reply 3439

TX22

this exam is going to be so applied, i am so worried.

i cant wait till this exam is over.

i dont think selective re absorption or ultrafiltration will come up.