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A2 Biology OCR June 2015 Revision Thread

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Reply 1800

LA_95

Does anyone think insulin secretion from beta cells will come up?

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Reply 1801

bakedbeans247

Original post by baymax96

Please can someone give a detailed summary of selective reabsorption in the pct. I'm so confused by it :confused:

:'(

While you're waiting for a resp. check this out and see if it helps you out, pages 15-16 :wink:

http://www.thebiotutor.com/uploads/2/7/2/8/27287711/f214_2a_excretion_notes__questions.pdf

Reply 1802

bakedbeans247

Original post by LA_95

Does anyone think insulin secretion from beta cells will come up?

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YEAH i do

Reply 1803

Nat900

What's all this talk about the heart?

Reply 1804

Nat900

Oh I was thinking that testing for LH would come up? (Pregnancy test)

Reply 1805

maisie__x

Original post by Nat900

What's all this talk about the heart?

How heart rate is controlled by nervous/hormonal mechanisms and also factors that affect heart rate :smile:

Reply 1806

Asif_m96

Original post by bakedbeans247

YEAH i do

Possibly... Last time it was glucagon and increasing blood glucose conc. ya zimme

Reply 1807

kingcobra007

Original post by games211

I am not being rude or anything but why can't people just look in the book to find the answers to some of the simple qs being asked? Some of the questions being asked can easily be found in the book...................................................... like i said not being rude or anything..

exactly lool why ask somone on tsr when a better/more accurate answer is in the book

Reply 1808

mushyD

Right, so can someone summarise what theh actually think is going to come on. (Including all predictions already made) would be much appreciated.

Reply 1809

Nat900

Original post by maisie__x

How heart rate is controlled by nervous/hormonal mechanisms and also factors that affect heart rate :smile:

Please explain this to me? Where is this? I've drawn myself at point blank :O

Reply 1810

loperdoper

Original post by Nat900

Oh I was thinking that testing for LH would come up? (Pregnancy test)

The pregnancy test is actually for hCG (human chorionic gonadotrophin). LH was the ovulation test that was an application of knowledge question.

Reply 1811

bakedbeans247

Original post by Nat900

What's all this talk about the heart?

pages 28-29.

Reply 1812

Asif_m96

Original post by baymax96

Please can someone give a detailed summary of selective reabsorption in the pct. I'm so confused by it :confused:

:'(

Akhi please read the book. It explains it very well...

Reply 1813

Nat900

Original post by loperdoper

The pregnancy test is actually for hCG (human chorionic gonadotrophin). LH was the ovulation test that was an application of knowledge question.

Yeah sorry that's what I meant! :-D. I have officially lost it...

Reply 1814

abOO

Original post by baymax96

Please can someone give a detailed summary of selective reabsorption in the pct. I'm so confused by it :confused:

:'(

Sodium-potassium pumps actively transport Na ions out of the PCT wall into the blood. Therefore lowering the conc of Na ions in PCT wall cells.
So.... Na ions are bought into the PCT wall from the tubule, along with glucose and amino acids, by facilitated diffusion through co transporter proteins (uses ATP).
Then because of the high conc of Na in the walls compared the the blood, Na are pumped into the blood.
Water follows from the PCT into the PCT wall as Na are removed from the PCT (due to high water potential in tubule).
And then Water diffuses again from PCT walls into blood, down a conc gradient by osmosis.

Reply 1815

Faithams

Original post by ChoccyPhilly

Well after that part in my book, it doesn't differentiate between here the proton or electron came from, just what they do. I'm not sure then but I've be very surprised if we were tested on this exact thing

If its the revision book, then it misses out quite alot of stuff. It repeats it twice in my textbook about FAD protons but nothing about FAD is on the spec so they probably won't ask, you never know with OCR though.

Reply 1816

YouAgain

Original post by medactuary

Can someone please summarise what we need to know about Endotherms and Ectotherms?
including how they regulate body temperature

Pretty sure you have to know the physiological and behavioural adaptations they do whether they are trying to cool down or to conserve heat.

So in endotherms(practically warm blooded animals but don't use that term in the exam - quoted by OCR):

- Sweat glands in skin: If temp is too high endotherms ( an example is us humans), secrete more sweat onto skin, water in sweat eaporates. If tempt too low, less sweat is secreted and les water is evaporated.
- Lungs, mouth and nose: Panting(in dogs for example) increases evaporation of water from lungs, tongue and other moist surfaces. Temp too low, animal does not pant, less water evaporated.
- Hairs on skin: Temp too high hair lies flat providing little insulation and thus more heat is lost. If tempt too low, hairs are raised to trap a layer of insulating air, reducing loss of heat from skin.
- Arterioles leading to capillaries in skin: Temp too high, vasodilation allows more blood into capillaries near the skin surface which allows more heat to be radiated from the skin. Tempt too low, vasoconstriction reduces flow of blood through capillaries near surface of skin, which allows less heat to be radiated.

Behavioural:

- IF too hot, move into shade, hide or burrow, if too cold move into sunlight.
- If too hot orientate body to decrease surface area exposed to sun. if too cold orientate body to increase surface area exposed to sun.
-If too hot remain inactive and spread out limbs to increase surface area. If too cold move about to generate heat in muscles ( except in extreme cold where it is better to keep still and roll into a ball to reduce surface area).

Ectotherms are practically similar (behavioural wise).
It can be found in the OCR biology book pages 8-11.
:smile:

Reply 1817

bballislife

could someone please outline the control of heart rate please?
Unfortunately we haven't covered it in class and so I would be rather grateful if someone could just go through what happens, both chemically and electrically please?

Reply 1818

LA_95

Does anyone think beta oxidation will come up? If so where is the info on what we need to know because I can't find much in the book about it

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Reply 1819

maisie__x

Original post by Nat900

Please explain this to me? Where is this? I've drawn myself at point blank :O

Nervous an hormonal mechanisms;
-adrenaline in the blood causes an increase in heart rate
-the heart rate is controlled by two nerves, accelerator (releases noradrenaline), vagus nerves (releases acetyl choline which slows heart rate)
-the heart rate is also controlled by medulla oblongata which controls frequency of contractions
-worth mentioning the heart is myogenic, initiates it's own rhythm

Do you have the textbook? It's on page 29. If not I'll explain the next bit too? :smile: