2010 biology unit three exam

[akira88]

Have we got any word on the blue vs. red light question?

In the Heinemann book is has the peak absorption at red..

[shinny]

thanks

shinny, let me explain q21 to you.

the graph shows that as solute conc. increases outside the cell, the rate of movement of solute across the membrane increases.
okay lets get that straight.

this thus means that there is a higher solute conc. (lower water conc.) outside the side and a lower solute conc. (higher water conc.) inside the cell. Thus the movement would be from inside to outside.

However [regarding option D] as solute R is metabolised in the cell (increasing solutes within the cell), there will be a higher solute conc. inside the cell.

This will then even out the conc. gradient, thus the rate of movement across the membrane decreases.

HOWEVER, in all due respect I also agree with option B so I'm not saying you're wrong Shinny, but I'm hoping the VCAA Biology examiners pick up on the countless errors that were in this paper.

(:

I'm well aware of the principles. It's just your interpretation of 'is metabolised' that differs. Generally metabolism refers to the breakdown of a substance; not creation. Given that it's a past tense verb, it's having the process of metabolism (any bodily reaction really) done to it. Hence, it's a reactant; not a product, meaning that it's referring to the breakdown of the substance. Hence, the amount will decrease, increasing the concentration gradient.

[jcheah12]

initially the movement of solutes is from inside to outside the cell.

but if solute R metabolises inside the cell (breakdown of solutes) there would be thus more solutes in the cell.

with more solutes inside the cell, this will initially decrease the rate of movement from inside to outside te cell

as more solutes are being broken down, the conc. gradient increases on the other side.

so therfore, the conc gradient is evened out then it increases on the other side as more solutes are broken down.

that means the rate of movement decreases from inside the cell to outside, then increases again from outside to inside.

ultimately there is still a decrease in the rate of movement   

[shinny]

initially the movement of solutes is from inside to outside the cell.

but if solute R metabolises inside the cell (breakdown of solutes) there would be thus more solutes in the cell.

with more solutes inside the cell, this will initially decrease the rate of movement from inside to outside te cell

as more solutes are being broken down, the conc. gradient increases on the other side.

so therfore, the conc gradient is evened out then it increases on the other side as more solutes are broken down.

that means the rate of movement decreases from inside the cell to outside, then increases again from outside to inside.

ultimately there is still a decrease in the rate of movement   

If you look at the graph, at the 0 point, you can conclude that there is no solute R inside the cell at all. The cell isn't producing solute R, it's eating it up. The question states that the movement is purely from outside the cell to inside. I don't know why you're assuming that the 'initial movement is inside to outside'. Thus, you'll never get this apparently inside to outside movement. It's a simple case of eating up solute R, and thus increasing the concentration gradient from outside to inside, thus increasing solute R.

[Keine]

Quote for the red and blue light:
I picked blue light because I reasoned that water would
distort the frequency wavelength of light, making it closer
to the colour blue than red, and because plants generally
photosynthesize well with red *and* blue (I was never told
which one was better), I thought blue based on that reasoning.
(I also had some stupid support logic that helped a little: "oh, water
is blue so when light goes through it, the light turns blue too!")

Also, for the first multiple choice question, who here put 'C'?
I thought it was 'C' because it asked which one could infect
'body cells'. Keyword here, because bacteria and most other
pathogens just damage or destroy body cells, but the virus
is the only one that actually 'infects' it and ruptures it in the end.
But according to this, its 'D: Gram-negative Bacteria'. Can anyone explain?

Lastly, for the first short answer question, I put 'Grace' instead of Emily.
I thought it was Grace because.. well how can the same meal affect
Grace's blood sugar level so insignificantly, while Emily's blood glucose
level soared up? The control was the exact food given, so one same
meal cant have more carbohydrates than the other. Grace's blood glucose
level also goes *below* the original starting point which really says something,
as Emily's blood glucose still hasnt gone below the starting point.

Can anyone correct me if im wrong ?

[Keine]

Oh, nevermind about the glucose one :\
I just re-read the question and realised that
the blood glucose levels are supposed to drop
sharply after a meal, so Emily should be correct
Q__Q three marks are gone

[shinny]

Also, for the first multiple choice question, who here put 'C'?
I thought it was 'C' because it asked which one could infect
'body cells'. Keyword here, because bacteria and most other
pathogens just damage or destroy body cells, but the virus
is the only one that actually 'infects' it and ruptures it in the end.
But according to this, its 'D: Gram-negative Bacteria'. Can anyone explain?

Key word here was cellular agents in the stem. I see where you're coming from, but the keyword cellular really rules out everything else.

[Keine]

ah, crap
four marks down :\
thanks for explaining it to me : )

[shinny]

Quote for the red and blue light:
I picked blue light because I reasoned that water would
distort the frequency wavelength of light, making it closer
to the colour blue than red, and because plants generally
photosynthesize well with red *and* blue (I was never told
which one was better), I thought blue based on that reasoning.
(I also had some stupid support logic that helped a little: "oh, water
is blue so when light goes through it, the light turns blue too!")

Water is actually colourless. The blue in the ocean we see is due to other reasons (was it actually the sky? I vaguely remember someone saying that explanation was wrong). Anyway, I don't remember what's taught in VCE, but Wiki says chlorophyll absorbs blue the most. And we all know Wiki is always right.

[Russ]

Water is actually colourless. The blue in the ocean we see is due to other reasons (was it actually the sky? I vaguely remember someone saying that explanation was wrong). Anyway, I don't remember what's taught in VCE, but Wiki says chlorophyll absorbs blue the most. And we all know Wiki is always right.

Cyanobacteria isn't it? But I haven't done that for years so :S

[Keine]

yes I know water is colourless, but it was just a joke
to myself : )
anyway, heres hoping that blue is correct
in our school, a lot of people went with red

[mikee65]

Dayum, just realised you were supposed to weigh the mice before and after :/
I used an infared camera to monitor metabolism in the mice :/

what if you just said if group A mice are heavier than group B mice?

[Milkshake]

Dayum, just realised you were supposed to weigh the mice before and after :/
I used an infared camera to monitor metabolism in the mice :/

what if you just said if group A mice are heavier than group B mice?

Not exactly sure, I went with weight change percentage, to account for differences in weight before treatment

EDIT: Mavis just looked at your solutions, would I get marked down for not saying the experiment can be repeated...? I used 20 mice in each group, so 40 mice total

[simpak]

Dayum, just realised you were supposed to weigh the mice before and after :/
I used an infared camera to monitor metabolism in the mice :/

what if you just said if group A mice are heavier than group B mice?

Not exactly sure, I went with weight change percentage, to account for differences in weight before treatment

EDIT: Mavis just looked at your solutions, would I get marked down for not saying the experiment can be repeated...? I used 20 mice in each group, so 40 mice total

large sample is similar to repeating since it kinda is repeating the experiment 20 times on different mice, get me?

No a large sample is a different mark to a repeated measures experiment.
I was always taught you had to have both.
20 mice is fine, but you need to repeat the experiment under different extraneous variable conditions.
So it is plausible that you may be marked down.
However, what was the Q worth?
4 marks?
One for hyp, one for results, two for experimental design.
You would lose one mark tops, and perhaps none at all because usually experimental design without a hypothesis is worth like, 4 marks.

[stonecold]

... june 09:
Following is an example of a suitable set up.
• Large numbers of plants are used or the experiment is repeated many times.

Or both to cover your ass