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AQA BIOL5 Biology Unit 5 Exam - 22nd June 2011

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Reply 1440

kingsmod1

how many minutes do we have for essay guys
and hw many mins should i plan???

Reply 1441

IFondledAGibbon

Original post by sleungs

So if you were asked to define a "stem cell" or a "totipotent cell" what would you say?

Just read the Wiki article and it seems to me that a zygote is a totipotent cell. There are no other cells which are totipotent. When it divides and develops into an embryo, the cells are then called stem cells? Basically I have no idea what I'm talking about!

Stem cells are just undifferentiated cells. Totipotent, pluripotent and multipotent cells are types of stem cells. Totipotent stem cells can become all cells, and are present in the early zygote. This ability is lost and cells become pluripotent because these cells can't become placental cells, though they can become all body cells. Multipotent cells are found in adult mammals and can only differentiate into a smaller number of cells E.G. the stem cells in the bone marrow can't become brain cells.

I think that's right.

Reply 1442

Sparkly-Star

I would say 5 - 10 minutes planning for an essay, a good fairly detailed plan will give help you write a better essay, 20 - 30 minutes writing.

(edited 12 years ago)

Reply 1443

Sparkly-Star

I think tomorrow, I will spend 30 minutes on questions then 30 minutes on the essay. Switch back to finish the questions off and then finally finish the essay as well. That way you have done at least a bit of both.

Reply 1444

Flux_Pav

how many marks do you need for full UMS out of 100?

Reply 1445

vickidougal

possible essay..
1.) importance enzymes
Digestion: amylase, maltase, sucrase lactase --> glucose for cells to respire

Enzyme ATPase to hydrolyse ATP--> movement of myosin heads (contraction), sodium potassium pump, building smaller molecules into larger molecules, secretion (ATP needed to form lysosomes for exocytosis, autolysis, break down of phagocytic vacuole, reuse of useful cell products), Activation of molecues (phosphorylation of glucose in glycolysis)

Breaking down acetycholine via acetylcholinesterase in muscle contractrion --> recycled/prevent over stimulation

uses of enzymes in DNA technology: DNA polymerase (add nucleotides in PCR, Sanger method, obtained from bacteria), RNA polymerase (during transcription DNA--> pre mRNA), DNA helicase (during DNA hybridisation when testing how closely related two organisms are)

Food industry: proteases, lipases and amylase

talk about enzmes themselves: globular proteins, biological catalysts to lower activation energy

can anyone think of anything else?
(i would say that one of the essays could be on DNA tech, but because it has to be synoptic, they're aren't really any synoptic elements we could draw in from other units..)

Reply 1446

User544981

Original post by Sparkly-Star

*Chemo receptors
*Pressure receptors
*Influx of sodium ions
*Temperature
*Blood glucose conc.
*Menstrual cycle

I don't know about the other units haha! :p:

oh yeah completely forgot about those i feel like ive forgotten everything
hope this exam goes well otherwise its goodbye uni

Reply 1447

User544981

Original post by booooom

its a past questio. my teacher gave me a list of past essay questions which have come up, what bout the bohr effect frm unit 2--negative feedback??

what on earth is the bohr effect

Reply 1448

sleungs

Original post by IFondledAGibbon

Yes thanks! That's made it really clear :smile:

Reply 1449

Nadine2010

Original post by hahaff

oh yeah completely forgot about those i feel like ive forgotten everything
hope this exam goes well otherwise its goodbye uni

also, lungs- expiration, inspiration.. atm pressure vs pulmonary pressure..
and respiration and photosynthesis i guess.. eg, in photosynthesis as RuBP is used up to make GP, TP regenarates it using ATP.. as far as i can remember?

Reply 1450

Vidja

Original post by hahaff

what on earth is the bohr effect

Carbon dioxide reducing haemoglobin's ffinity for oxygen.

When dissolved in solution, CO2 becomes HCO3, carbonic acid, which can partially denature the haemoglobin, reducing it's oxygen affinity.

Reply 1451

User544981

Original post by Flux_Pav

how many marks do you need for full UMS out of 100?

depends on the grade boundaries
hope they are really low this time round

Reply 1452

User544981

Original post by Vidja

Carbon dioxide reducing haemoglobin's ffinity for oxygen.

When dissolved in solution, CO2 becomes HCO3, carbonic acid, which can partially denature the haemoglobin, reducing it's oxygen affinity.

i knew that but i didnt knw it was called the bohr effect

Reply 1453

Vidja

Original post by hahaff

i knew that but i didnt knw it was called the bohr effect

Page 152 of the AS textbook if you're interested

Reply 1454

Abby :)

Urgh panicking big time for this exam.
Although its my last one <3 Horrayy!

Reply 1455

flowerscat

Original post by Vidja

Carbon dioxide reducing haemoglobin's ffinity for oxygen.

When dissolved in solution, CO2 becomes HCO3, carbonic acid, which can partially denature the haemoglobin, reducing it's oxygen affinity.

It does not denature the haemoglobin, it just displaces the oxygen

Reply 1456

Sparkly-Star

I am really scared about the weird HSW questions, often the last few questions. :frown:

Reply 1457

Vidja

Original post by flowerscat

It does not denature the haemoglobin, it just displaces the oxygen

Oh, really? Thanks. Is it the actual carbonic acid molecule that displaces the oxyegn, or does a CO from the acid displace it or something?

EDIT: The textbook says the low pH of the acid causes the haemoglobin to change shape?

(edited 12 years ago)

Reply 1458

flowerscat

Original post by Flux_Pav

in DNA sequencing, do you pick out only one piece of dna and clone it by PCR ?
or do you sequence the whole genome by cutting it into pieces ?

In DNA sequencing, you can do either. As long as you can design some primers that can start off the sequencing. If you were sequencing an entire genome, then it is first cut into pieces by restriction enzymes, inserted into vector, then sequenced. Since you know the sequence of the vector, you will always be able to design primers to start off sequencing.

and also, how do you know that the fragment that moved the furthest only consisted of one nucleotide? :s-smilie:

it could be any size as long as its the smallest, isn't it?

Because you are adding four terminator nucleotides.

The synthesis of the completmentary base to the first base of the sequence can be either by a "normal" base or a terminator base.

If the terminator base is added, then the first band will correspond to one nucleotide.

In practice, this does not happen, as you will also have the sequence of the (radiolabelled) primer to account for. So the lowest band = (length of primer + first base)

Hope this helps.

Reply 1459

flowerscat