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AQA BIOL5 ~ 17th June 2013 ~ A2 Biology

Does anyone know how the relationship between oestrogen and LH positive feedback? Is it just that more oestrogen produces more LH?

I'm not sure if anyone has answered you yet, but I did a past paper where this was a question and the mark scheme was very vague (1. Vague description of positive feedback 2. Links to LH and oestrogen). I went back over my notes and what I think is that an increase in oestrogen causes an increase in LH. The peak in LH stimulates ovulation. Corpus luteum forms. Corpus luteum secretes progesterone and small amounts of oestrogen. Therefore more oestrogen = more LH = more oestrogen

Hope this helps!

Reply 3421

DrewYouTwo

Original post by stoppy123

14/20

MeRbi becoup

I'm somewhat confused about the whole two different types of neurotransmitter question? Surely both the excitatory and inhibitory AND the sympathetic and parasympathetic distinction is valid, right?

Reply 3422

TauMuon

10

Original post by Starlight94

What's the difference between a gene marker and a dna probe? :/

They're the same thing. Fluorescently/radioactively labelled DNA probes act as gene markers.

Reply 3423

stoppy123

4

Original post by Lyont

Are these right?

1) Ca2+ ions are essential to the sliding filament theory, the ions bind to troponin that then moves the tropomyosin away from the actin binding sited, this then allows the myosin head to bind to the actin. If the tropomyosin was never moved muscles (such as the heart) would not be able to contract.Correct 3/3

2) The insertion of a virus containing the gene presents the following risks; An unwanted Immune reaction to the virus causing inflammation, Infection caused by the virus as it may recover their original ability and infect the patient, and there is a possibility of causing a tumour if the gene is inserted into the wrong it of DNA.Correct 2/2

3) It requires the destruction of an embryo to start a new stem line, some people believe an embryo has protection to life. I'll give you full marks, but I think you should go on to say that an embryo has protection to life BECAUSE....people think life begins at conception

4) errm not sure about this one, acetyl choline is one and I think serotonin is another but not really sure Excitatory and Inhibitory neurotransmitters, one hyperpolarises (stopping an action potential) and the other deplorises (

5) ATPase is needed to bind ADP + Pi to make ATP, ATP is split at the myosin head providing energy for the binding and bending of the myosin head to the actin binding site, causing the muscle to contract. Another is split to unbind and 're-cock' the myosin head further along the actin. Without ATP this would not be able to happenCorrect

6) One believes that it is a slippery slope to human cloning which will cause a devaluation of human life. Another is that genetically modified food hasn't been around long enough for us to see the long term effects. Hmm, I'll give you 2/4 I was specifically looking for groups such as environmentalists and anti-globalisationists, but you made valid points :smile:

7) It is a clover shape because of homolygous base pairings, whereas mRNA is single standed. 1/2 Needed another difference

8) Mechano-receptors.Nope, baro-receptors, that might have just been what I was taught though?

Thanks (sorry for the really long post) :smile:

12/13 out of 20 :smile:

Reply 3424

Tasha_11

4

I have a question :s-smilie:

I've just been doing the specimen paper for biology and stuck on a question about action potentials. I thought that when an action potential is started, sodium ions move into the neurone and potassium to move out, in the mark scheme though it says that sodium ions move out and potassium in. This has really confused me so I would appreciate if anyone could help. Thanks :smile:

Posted from TSR Mobile

Reply 3425

Anjna

9

Original post by DrewYouTwo

Why rods see in dim light? (spatial summation)
Why cones have higher acuity?
Why cones see in colour?
Why is their a blind spot?

Think thats it really

why is their a blind spot?

Reply 3426

stoppy123

4

Original post by DrewYouTwo

MeRbi becoup

I'm somewhat confused about the whole two different types of neurotransmitter question? Surely both the excitatory and inhibitory AND the sympathetic and parasympathetic distinction is valid, right?

Basically there is two types of neurotransmitters, those which depolarise the post-synaptic neurone, and those that hyperpolarise, those that hyperpolarise will stop the action potential occuring whilst those who depolarise wil continue the action potential if you get me?

Reply 3427

Starlight94

Original post by TauMuon

They're the same thing. Fluorescently/radioactively labelled DNA probes act as gene markers.

Thanks

was getting so confused

Reply 3428

master y

12

Anyone have any synoptic examples for protoctista? Really struggling here

Reply 3429

F Hopeful

Rhodopsin the pigment in rod cells is a protein thought that may come in handy :biggrin:

Reply 3430

F Hopeful

Original post by Tasha_11

I have a question :s-smilie:

I've just been doing the specimen paper for biology and stuck on a question about action potentials. I thought that when an action potential is started, sodium ions move into the neurone and potassium to move out, in the mark scheme though it says that sodium ions move out and potassium in. This has really confused me so I would appreciate if anyone could help. Thanks :smile:

Posted from TSR Mobile

Yeah the markscheme is wrong :biggrin:

Reply 3431

DrewYouTwo

Original post by stoppy123

Basically there is two types of neurotransmitters, those which depolarise the post-synaptic neurone, and those that hyperpolarise, those that hyperpolarise will stop the action potential occuring whilst those who depolarise wil continue the action potential if you get me?

Sorry wasn't clear enough :tongue:

my fault . I get the idea of antagonistic synapses, just I was unclear on why my answer about neuroadrenaline and avcetylcholine couldn't be counted as right?

Reply 3432

mariposaa

8

Original post by Tasha_11

I have a question :s-smilie:

I've just been doing the specimen paper for biology and stuck on a question about action potentials. I thought that when an action potential is started, sodium ions move into the neurone and potassium to move out, in the mark scheme though it says that sodium ions move out and potassium in. This has really confused me so I would appreciate if anyone could help. Thanks :smile:

Posted from TSR Mobile

Specimen mark scheme is wrong

Reply 3433

TauMuon

10

Original post by sophie15

Could somebody summarise temperature regulation please? I have a feeling it is going to come up as it isn't on recent papers! Thanks :smile:

Endotherms:

Too Hot:
1) Vasodilation
2) Lowering of body hair
3) Sweating
4) Behavioural mechanisms (moving to shade etc.)

Too Cold:
1) Vasoconstriction
2) Raising of body hair
3) Shivering
4) Increased metabolic rate
5) Behavioural mechanisms (moving out of shade etc.)

A change in blood temperature is detected by thermoreceptors in the hypothalamus. These send impulses to the heat loss/heat gain centre of the hypothalamus which in turn sends nervous impulses to perform the appropriate responses (above).

Reply 3434

DrewYouTwo

Original post by Anjna

why is their a blind spot?

No pHotoreceptors

Reply 3435

mackie0088

Original post by stoppy123

Questions to refresh your memory!

Poison X removes Ca2+ ions in muscle fibres, explain why this person will die when poisoned with Poison X(3)

Ca2+ in vital in allowing muscle contraction, Ca2+ bind to troponin on actin moving tropomyosin away from binding sites. Ca2+ also stimulates ATPase which hydrolyses ATP and allows myosin heads to recock. Without Ca2+ intercostal muscles cannot contract, a person cannot breathe. 02 is not supplied to cells so respiration stops.

The insertation of genes through gene therapy can have dangerous consequences, explain why (2)

When genes are added, it changes the amino acid sequence and therefore the protein coded for. This may lead to the formation of non-functional proteins which can lead to cancer :confused:

Explain why there is ethical issues around stem cells research (2)

Stem cell research is carried out on animals, there are many issues surrounding animal rights. Stem cells are harvested from human zygotes there are often issues surrounding the viability of the potential embryo

Describe and explain the two types of neurotransmitter (4)

There are 2 types of neurotransmitter acetylcholine which is involved in the sympathetic nerve which increases the response and nor adrenaline which is involved with the parasympathetic nerve which has an inhibitory response

Inhibitor Y inhibits ATPase in muscle cells, explain why they are unable to contract (2)

ATP binds to the actin myosin crossbridge causing the myosin head to detach, ATPase hydrolyzes the ATP to ADP and Pi. Causing the myosin head to return to it original position. Without ATPase the myosin head cannot return to its original position, so the muscle cannot contract.

Certain pressure groups have problems with GMOs, describe and explain two of these groups (4)

:confused:

I dont think we need to know about specific groups just disadvantages?

tRNA is structurally different from mRNA, give 2 reasons why (2)

tRNA has an amino acid attached as it has an amino acid attachment site, mRNA has no attachment site. tRNA is a clover shape as there is H bonds bonds, mRNA is single stranded so there is no H bonds in mRNA

Name the receptors in the blood that respond to high blood pressure (1)
Chemoreceptors

:smile:

Reply 3436

stoppy123

4

Original post by DrewYouTwo

Sorry wasn't clear enough :tongue:

my fault . I get the idea of antagonistic synapses, just I was unclear on why my answer about neuroadrenaline and avcetylcholine couldn't be counted as right?

Oh right, well, those are examples of each type, but not the type themselves, it's like saying, what is the part of the reflex arc that responds to the stimulus (effector) and saying muscle and glands, although they are effectors, I wanted the broader term, but still, you understood it which is correct :P