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AS biology help...Calcuations! AGHHHHH

hey im doing AS and A2 biology! Im doing fine where it comes to facts and stuff but the calcuations are driving me crazy!
i cant seem to find any websites or books that explain how to do them!

I have done loads of past papers n keep falling on calcuations and reading graphs.
Can any one help exxplain..
how to read a pressure or volume graph for heart/lungs
how to read a breathing of heart beat graph
how to calcuate heart rate, breathing rate, stroke volume, cardiac output ect.
any sort of magnifaction, observed size, acual size calcuations
jus any sort of math question!
there were also other questions like...

1)show how much the hypha had grwon during the session. the diagram showed it was 2.6 at the begining and 5.5mm at the end and had a scale that said 4.7mm = 500um. How are you ment to figure that out? the answer was 300um but dont know how you get there!?

OR

2) the diameter of the artery was 4mm. calcuate the diameter of the luman of this artery show your working? again what the..!? the table showed - endothemlium - 20um
smooth muscle - 490um
elastic tissue - 370um
connective tissue 120um
so how am i ment to figure out the diamter of the luman? the aswer is 2000um and the mark scheme said 2 x thickness of wall. but why?

Or..now this REALLY confused me!

3) what is the MINIMUM distance the molecule of CO2 diffues from the blood plasma to the air space in avolus.
the diagram showed this
cell layer A thickness 0.04-0.2um
space between cell layers 0.02um
cell layer B - 0.05 - 0.3um
so coz its the minimum i added up all the minimum thickness and got 0.7um but the answer was 0.11um which is all the maximum? WHYYYYY

this is the last one and the worst for me anyways..

4) at rest the rate of blood flow to the heart muscle is 0.9cm3 g-1 per min (dont know what g-1 is but hey!) calcuate the volume of blood 1g of heart muscle would recieve in 5 mins of excerise.
On the table it said
rate of blood flow/cm3 minute-1 heart muscle 300(at rest) 1200 (during excerise)
the answer was 18cm3 again how do you work this out and what goes g-1 mean?!

this goes on, so if there is anyone who can do these with ease please help, or if there are any websites tht explain all this that would help me so much!
please please please
thanks for your time
kaytieee xx

Reply 1

M.A.H

Arghh wish i could help but i have the same problem, maths in biology seems likes its all bogus to me

Reply 2

rahmed

Kaytieee

2) the diameter of the artery was 4mm. calcuate the diameter of the luman of this artery show your working? again what the..!? the table showed - endothemlium - 20um
smooth muscle - 490um
elastic tissue - 370um
connective tissue 120um
so how am i ment to figure out the diamter of the luman? the aswer is 2000um and the mark scheme said 2 x thickness of wall. but why?

Or..now this REALLY confused me!

Believe me when I say this is one of the easiest questions you'll come across. It's really simple to work out, they practically give you the answer.

So they have told you that the diameter of the artery is 4mm which is equal to 4000 um (micrometers). I've converted it to 4000 because those are the units of the other components in the question. (1000 um is equal to 1 mm).

Ok so they've given you the diameters of all the components that make up the lumen of the artery, so add them all together: 20 + 490 + 370 + 120 = 1000 um. -> Easy, right?

So, you mentioned that the markscheme said 2 times the thickness of the wall. Well, it's really simple when you think about it. The artery is like a circle when cut in cross section, so it has a wall on either side. On one side this equals 1000 um and the other is also 1000 um = 2000 um in total. (See the diagram below).

So: total diameter - diameter of the wall = Diameter of the Lumen.

=

4000 um - 2000 um = 2000 um.

Easy!

Here's a diagram I've drawn to help you visualise the answer:

lumen.jpg58.8KB

Reply 3

rahmed

Kaytieee

Or..now this REALLY confused me!

3) what is the MINIMUM distance the molecule of CO2 diffues from the blood plasma to the air space in avolus.
the diagram showed this
cell layer A thickness 0.04-0.2um
space between cell layers 0.02um
cell layer B - 0.05 - 0.3um
so coz its the minimum i added up all the minimum thickness and got 0.7um but the answer was 0.11um which is all the maximum? WHYYYYY

Edit: See answer below

Reply 4

Miss_Scarlett

Listen to Rahmed, he gives good advice. I agree with both answers he has given. :smile:

lol thanks :smile:

cheers guys thats really great!!! woo exam on the 9th lol!!
But im still a bit confused on the CO2 question, i understand that they want the minimum distance, but when they give the diameter of a certain thing they say like 0.2-0.4
so would the minimum diamter for that be 0.2 and the maximum be 0.4?
but you are adding up all the maximum diameters which would give the maximum distance for the CO2 to travel?

Reply 7

Mth15

Actually, i think you do add up all the minimum distances, i see your logic but remember this is AS, so the answer is just found by 0.04 + 0.02 + 0.05, which equals the answer of 0.11

Reply 8

rahmed

lol, you're right - I should have done the calculations myself.... :redface:

Reply 9

Speedbird2008

Gahhh, I HATE explaining graphs for Biology and doing those bloody magnification calculations. :mad:

Reply 10

iainmacn

Kaytieee

4) at rest the rate of blood flow to the heart muscle is 0.9cm3 g-1 per min (dont know what g-1 is but hey!) calcuate the volume of blood 1g of heart muscle would recieve in 5 mins of excerise.
On the table it said
rate of blood flow/cm3 minute-1 heart muscle 300(at rest) 1200 (during excerise)
the answer was 18cm3 again how do you work this out and what goes g-1 mean?!

I assume g-1 means "per gram". Generally where there's something to a negative power like g-1 it's like dividing by the positive version - so it's like /g, or if it was (say) m-2 then dividing by m squared.

Assuming that - it's telling you that each gram receives 0.9 cm^3 per minute at rest.

It also says that when exercising the blood flow goes up by a factor of 4 (300 to 1200 for the whole heart).

So exercising - each gram will receive 0.9 x 4 cm3 per minute = 3.6cm3

So in 5 minutes - multiply that by 5 giving you

5 x 3.6 = 18cm3 :smile:

HTH

Reply 11

Venom123

Which exam board is this for mine doesn't seem that many calculations

Reply 12

Jenny fur may

Thank you soooo much Katie for asking the question! And thank you sooo much To iain for that answer 🙏🏼👏🏼 I'm also having a small nightmare but this really helped!!