AQA BIOL5 Biology Unit 5 Exam - 22nd June 2011

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Can someone please clarify what the ATP actually does in relation to the myosin head during the sliding filament mechanism? Does it just provide the energy for filaments to slide or does it provide energy to break the actin-myosin cross bridge aswell? I'm using the text book, CGP revision guide and Heck Grammar notes - but none have given me a definitive answer. Cheers lads + gals.

The way i see it the calcium ions cause the tropomyosin to move exposing the binding sites. The myosin heads then attatch to them and form a cross bridge. The calcium ions activate ATPase which breaks down ATP and the energy released cause the myosin heads to move in a rowing action and also to break the cross bridges. This cycle is then repeated.

If anyone thinks this is wrong please let me know

Reply 1301

flowerscat

Original post by -Iffy-

I have a question, with the genetic screening, one of the stages for finding the mutated gene of the individual is that the PCR technique is used to produce multiple copes of the DNA probe (referring to nelson thornes book page 272). But I thought PCR was for double stranded DNA, it separates them and forms a complementary strand on each strand. Whereas the mutated gene for genetic screening is only a single strand (as shown in the textbook). Can someone explain? :s-smilie:

You make a double-stranded probe via PCR. The primers used for PCR are labelled. It produces a mixed sample of double-labelled and single-labelled product. The single-labelled product (hybrid strand) is separated. The strands are then denatured. The labelled single-strand is used as a probe.

Now-a-days it is more common to synthetically manufacture a the probe as a single strand and label it before using it.

Reply 1302

jamest92

Original post by Thisisj

hiyaa guys,, if i look at the freexampapers, which unit from the old spec is most similar to unit 5...??

I think B

Reply 1303

Flux_Pav

Original post by mariiahgac

Can someone help me with this?

One of my biology books say that "high blood pressure is detected by baroreceptors, then impulses are sent to the medulla oblongata, sending impulses along parasympathetic newurons, which secrete acetylecholine, which then binds to receptors on the SAN"

Whereas my other biology book says that " high blood pressure is detected by baroreceptors, then impulses are sent to the center in the medulla oblongata that decreases heart rate, which then increases the frequency of impulses to the SAN via the parasympathetic nervous system"

What should I say in my exam then?? :/

when this kind of stuff happens, i would probably combine the two sets of information because both are correct and both make sense

e.g you could say 'increased frequency of impulses sent to SAN via parasympathethic nerve. and so with inceased frequency means that more AcH secreted from parasympathetic nerve endings, causing SAN to decrease the rate at whch it produces waves of electrical activity

BTW GUYS
In manual DNA sequencing, after gel electrophoresis, you end up with fragments on different lengths which end in different terminator nucleotides.
but how do you know that the fragment that travelled the furthest was a one-nucleotide fragment. is it an assumption?
because it could be 2 or 3 or maybe even 9 LOL
EXPLAIN!!!

Reply 1304

bobsaeed

Original post by arvin_infinity

Maybe they are parasympathetic neurotransmitters

slightly off the topic
Someone kindly correct me if am wrong :

Progesterone inhibits FSH - LH
In high conc. Stimulate FSH-LH

Oestrogen Inhibits LH

DUnno if there are anymore feedbacks :rolleyes:

yer AtC is the neurotransmitter in the parasympathetic nervous system governing the speed of the SAN, noradrenalin is the neurotransmitter that speeds up the SAN via the sympathetic pathways.

Adrenalin is a hormone not a neurotransmitter and is involved in glycogenisis (uptake of glucose from the blood into tissues)

Reply 1305

Destroyviruses

Original post by choc1234

i dont understand your q
i thought we just have to know for example an adenovirus will inject the normal cftr gene in to the dna of the epithelial cells ?

Yeah, thats all we have to know! But arent you curious?

Reply 1306

bobsaeed

Original post by Flux_Pav

IN electrophoresis the largest DNA fragments will travel the shortest distance (closest to the well) so the small fragments will be the ones furthest away. you usually have a mass reference as well next to the samples you are running so u can tell how large each fragment is.
the biggest ones travel the least because they are big and so get lots of friction when moving though the gel

(edited 12 years ago)

Reply 1307

flowerscat

Originally Posted by Destroyviruses
Im abit unsure about gene therapy.

How is the fragment of DNA transcrbed in the human cell if its succesfully inserted. Does it have promotor regions? Can transciption occur outside of the nucleous?

Original post by choc1234

i dont understand your q
i thought we just have to know for example an adenovirus will inject the normal cftr gene in to the dna of the epithelial cells ?

Either of two ways - either it is already in a vector which has a promoter regions, and is transcribed by the cells machinery.

or - in the case of adenovirus - the viral DNA is inserted into human DNA, then transcribed by the cell machinery.

Free-floating DNA and RNA is not transcribed by the cell and usually broken down rapidly by enzymes.

More at:

http://ghr.nlm.nih.gov/handbook/therapy/procedures

Reply 1308

-Iffy-

Original post by flowerscat

Thank you, I get it now :smile:

Reply 1309

flowerscat

Original post by bobsaeed

Adrenaline is both - a neurotransmitter and a hormone.

In the AQA syllabus, it is used in the context of a hormone.What is not mentioned is that it also acts as a neurotransmitter for the sympathetic nervous system.

Reply 1310

flowerscat

Original post by choc1234

can someone please reassure me veryone on the this thread is amazingly clever
because i thought i was well prepared after reading some of the stuff on here :\
need an A in this ir no university for me :frown:

for the synoptic essay ive just made plans for about 30 possible essay titles
how much detail do we need to know about the uses of recombinant dna technology?..its really boring lol

A lot of it is background information to help people understand the topic better - not all of it is needed for the exams, so don't get stressed :-)

Reply 1311

choc1234

off too bed
solid revision tomrow hopefully

Reply 1312

bobsaeed

Original post by flowerscat

im pretty sure noradrenalin is the neurotransmitter in sympathetic nervous system and adrenaline is the hormone

Reply 1313

flf

Original post by Jasmine_009

you can talk about stuff like making medicines(herbs) , agriculture, plants are needed to remove CO2 so less global warming effect, needed for stable food chain, maintain constant climate (like transpiration), they provide shelter....i am not sure about some of the points but i would suggest you to try and relate as much as u can.

Great, thanks!

Reply 1314

bobsaeed

Original post by mariiahgac

help hahaha

Can someone help me with this?

One of my biology books say that "high blood pressure is detected by baroreceptors, then impulses are sent to the medulla oblongata, sending impulses along parasympathetic newurons, which secrete acetylecholine, which then binds to receptors on the SAN"

Whereas my other biology book says that " high blood pressure is detected by baroreceptors, then impulses are sent to the center in the medulla oblongata that decreases heart rate, which then increases the frequency of impulses to the SAN via the parasympathetic nervous system"

What should I say in my exam then?? :/

they are both right but acetylecholine is defiantly released so i would say the first one is more what they want in an exam

Reply 1315

Destroyviruses

Original post by bobsaeed

im pretty sure noradrenalin is the neurotransmitter in sympathetic nervous system and adrenaline is the hormone

yes if you allow your knowledge to be limited by this spec.

However adrenalin also acts as a neurotransmitter.

Reply 1316

flf

Original post by percy93

talk about how plants affect CO2 concentration- and link that to the effect on heart rate, haemoglobin activity etc etc

great idea, would not have thought of that!

Could anyone briefly explain the effect of CO2 on haemoglobin please? I know it was in unit 1, WAY back and there was some kind of oxygen association graph but i can't remember what it means?

Thanks in advance

Reply 1317

arvin_infinity

Original post by janet9

Menstrual Cycle Feedbacks

POSITIVE FEEDBACK

•

LH stimulates the production of the corpus leuteum, which produced progesterone but also a bit of oestrogen, which stimulates the further production of LH, which means further oestrogen is produced. This causes ovulation.

NEGATIVE FEEDBACK

•

FSH stimulates follicle development, which stimulates the ovaries to produce oestrogen, which inhibits FSH, so only that ONLY ONE follicle is developed.

•

LH produces the corpus leuteum, which produces progesterone, which inhibits LH production.

•

More oestrogen inhibits FSH, which results in less oestrogen being produced.

•

More progesterone inhibits LH so less progesterone is produced by the Corpus Luteum.

Why is positive feedback not considered to not be a part of homeostasis?

•

Because postive feedback doesn't keep internal environments constant;
It amplifies the departure - effectors work to further increase the departure away from normal levels.

Oestrogen's a funny one. It inhibits FSH and LH, but at high levels, stimulates FSH and LH production, so that's both negative feedback at first and positive feedback at high levels.

Oestrogen is produced by a follicle when there is not corpus luteum
In +ve feedback for Oestrogen ---> release of LH is stimulated
Just to make sure ovulation occurs

Just ignore my previous post (it was worst summary ever :wink:

)

Reply 1318

arvin_infinity

Original post by bobsaeed

Thought its a hormone!!!!! :s-smilie:

Reply 1319

flowerscat

@flf

When a tissue is active, it produces more CO2.

CO2 diffuses into the red blood cells and bonds with water forming carbonic acid which dissociates into hydrogen carbonate ions and releases protons (hydrogen ions)

hydrogen ions lower the pH of the RBC. To prevent a drastic fall in pH, haemoglobin releases its oxygen and takes up the proton.

Overall effect: more CO2 = more oxygen released at that site.

This is called the Bohr effect

(edited 12 years ago)