AQA A2 BIOL5 22nd June 2012

the pancreas is a gland... The pancreas produces digestive enzymes, howeverr scattereed throughout these cells are the islets of langerham... theere are 2 type of these cells alpha and beta... Alpha produces glucagon and beta produces insulin...

Reply 521

EffKayy

16

Original post by Smiley Face :)

the pancreas is a gland... The pancreas produces digestive enzymes, howeverr scattereed throughout these cells are the islets of langerham... theere are 2 type of these cells alpha and beta... Alpha produces glucagon and beta produces insulin...

LOL thanks for sharing

Reply 522

. . .

How do you get 16/16 in the essay?

Reply 523

. . .

Original post by EffKayy

Question 9dii June 2010 paper http://store.aqa.org.uk/qual/gce/pdf/AQA-BIOL5-W-QP-JUN10.PDF

The markscheme says ' Mitochondria in egg/female gamete/no mitochondria come from sperm/male gamete; '

Whaat? :s-smilie:

Help please guys

Mitochondrial DNA is inherited only from the mother.

Reply 524

swiftylol

18

Original post by uzumaki1107

Specimen papers are always way harder than the actual papers so it's not the greatest benchmark for what you can actually do, try the next one, 2010 i think, grade boundaries on that were really low, ~50-60 for an A if i remember correctly

I know, that's why i'm asking... because there are no grade boundaries to compare to :tongue:

Also, could anyone explain the answer to this question?

http://www.thomas-reddington.com/uploads/7/7/8/3/778329/bio_u5_qp_specimen.pdf

Specimen (Page 9), Q5 (a)

Spoiler

(edited 11 years ago)

Reply 525

Kidneyjean

7

Original post by EffKayy

Question 9dii June 2010 paper http://store.aqa.org.uk/qual/gce/pdf/AQA-BIOL5-W-QP-JUN10.PDF

The markscheme says ' Mitochondria in egg/female gamete/no mitochondria come from sperm/male gamete; '

Whaat? :s-smilie:

Help please guys

Mitochondria in sperm are mainly in their tails (the tails' movement is used for propulsion; movement is an aerobic process and requires energy from ATP; this is synthesised in mitochondria). When the sperm fertilises the egg, its tail either falls off, or doesn't become part of the zygote, so all mitochondrial DNA comes from the egg.

But that seems like a really mean question, definitely not on the syllabus :s-smilie:

I only know about the mitochondrial DNA stuff from an article I read ages ago...

EDIT: Dang, . . . beat me to it!

Original post by . .

How do you get 16/16 in the essay?

Cover at least 5-6 areas, using two key points and an example for each one. Then add in a paragraph with content that goes 'above and beyond' the spec.

(edited 11 years ago)

Reply 526

. . .

Original post by swiftylol

I know, that's why i'm asking... because there are no grade boundaries to compare to :tongue:

Also, could anyone explain the answer to this question?

http://www.thomas-reddington.com/uploads/7/7/8/3/778329/bio_u5_qp_specimen.pdf

Specimen (Page 9), Q5 (a)

Spoiler

a i A generator potential excites the axon membrane, the generator potential is large enough to reach the threshold level so an action potential is produced. When an generator potential is produced sodium ion channels open in the axon membrane. There is a higher concentration of sodium ion in the axon than the outside so sodium ions diffuse down their concentration gradient, via facilitated diffusion into the axon. This makes the axon membrane less negative (or more positive) hence the membrane potential increase. This is known as depolarisation.

ii At about -30mV sodium ion channels close in the axon membrane and potassium channels open this causes potassium ions to diffuse out of the axon via facilitated diffusion down their concentration gradient. Making the axon membrane more negative or less positive. This is re-polarisation

(edited 11 years ago)

Reply 527

F1's Finest

21

Original post by . .

a i A generator potential excites the axon membrane, the generator potential is large enough to reach the threshold level so an action potential is produced. When an generator potential is produced sodium ion channels open in the axon membrane. There is a higher concentration of sodium ion in the axon than the outside so sodium ions diffuse down their concentration gradient, via facilitated diffusion out of the axon. This makes the axon membrane less negative (or more positive) hence the membrane potential increase. This is known as depolarisation.

ii At about -30mV sodium ion channels close in the axon membrane and potassium channels open this causes potassium ions to diffuse into the axon via facilitated diffusion down their concentration gradient. Making the axon membrane more negative or less positive. This is re-polarisation

You mean +30mV, mate.

-30mV wouldn't be a significant enough polarisation of the membrane for K+ channels to open.

(edited 11 years ago)

Reply 528

swiftylol

18

Original post by . .

a i A generator potential excites the axon membrane, the generator potential is large enough to reach the threshold level so an action potential is produced. When an generator potential is produced sodium ion channels open in the axon membrane. There is a higher concentration of sodium ion in the axon than the outside so sodium ions diffuse down their concentration gradient, via facilitated diffusion out of the axon. This makes the axon membrane less negative (or more positive) hence the membrane potential increase. This is known as depolarisation.

I thought sodium ions enter the neruone axon when an action potential occurs :confused:

ii At about -30mV sodium ion channels close in the axon membrane and potassium channels open this causes potassium ions to diffuse into the axon via facilitated diffusion down their concentration gradient. Making the axon membrane more negative or less positive. This is re-polarisation

And i thought potassium diffused out of the axon when re-polarising :s-smilie:

What the ****?

Reply 529

. . .

Original post by James A

You mean +30mV, mate.

-30mV wouldn't be a significant enough polarisation of the membrane for K+ channels so open.

Yeah.

Original post by swiftylol

I thought sodium ions enter the neruone axon when an action potential occurs :confused:

And i thought potassium diffused out of the axon when re-polarising :s-smilie:

What the ****?

They do. My error. The mark scheme is wrong.

Reply 530

freddy

Original post by NutterFrutter

It's LH (at least that's what the textbook says). Is this question from a past paper?

yes i think so

Reply 531

freddy

Original post by uzumaki1107

First chunk of bite size biology notes, feel free to take a look :smile:

http://www.scribd.com/doc/95762183/Biology

thankssss these notes are amazing. it would be v. nice if you could upload the pdf. file? :smile:

Reply 532

rss.914

shouldn't the answer to this question be C?

Reply 533

Bugsy

1

Original post by rss.914

shouldn't the answer to this question be C?

Ovulation occurs when oestrogen levels start to fall and progesterone levels begin to rise, this occurs in B. Progesterone levels peak in C which imply that the egg has already been released at this stage, i.e. is not being released if that makes sense?

Reply 534

swiftylol

18

Original post by rss.914

shouldn't the answer to this question be C?

Looks like B to me, since progesterone starts to increase (it's caused by the corpus thingy which comes after ovulation) and oestrogen decreases (just caused LH secretion)

This was posted from The Student Room's iPhone/iPad App

Reply 535

rss.914

Original post by Bugsy

Ovulation occurs when oestrogen levels start to fall and progesterone levels begin to rise, this occurs in B. Progesterone levels peak in C which imply that the egg has already been released at this stage, i.e. is not being released if that makes sense?

ahh ok, i thought it's normally meant to occur on day 14

Reply 536

Bugsy

1

Original post by rss.914

ahh ok, i thought it's normally meant to occur on day 14

In humans it does, yes. But you can't always assume it's the same for different types of mammals. Just make sure you're always looking at the axis, as most often on these types of questions they want to see you know what happens to hormone levels at different stages in the cycle, not just simply remembering what day it happens on :smile:

Reply 537

rss.914

Original post by Bugsy

In humans it does, yes. But you can't always assume it's the same for different types of mammals. Just make sure you're always looking at the axis, as most often on these types of questions they want to see you know what happens to hormone levels at different stages in the cycle, not just simply remembering what day it happens on :smile: