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Biology question someone please help!

I'm posting this here because there's 2 people in the Biology forum and i'm sure i won't get any replies so mods please keep this for a bit, i really need help...I got this question on my biology exam and i got it wrong and asked the teacher to explain when we reviewed the test in class but i still don't understand. Here's a pic of the question coz it would take ages to write down:

I don't get it..Please help..

Reply 1

Degausser

You're saying there that a tiny little chloroplast takes up roughly half of the whole plant cell they show you.

Reply 2

khalaf

Degausser

You're saying there that a tiny little chloroplast takes up roughly half of the whole plant cell they show you.

yea i know i got it wrong, i was guessing :tongue:

Reply 3

Degausser

khalaf

yea i know i got it wrong, i was guessing :tongue:

Can you see where you went wrong now?

Reply 4

Azer

The chloroplast is about 5 nanometers big, so A. This is because I think you mistook the entire cell for being a chloroplast in the question (?).

The chloroplast is the little dark-stained ball. There are a bunch of them, and each one seems to be about 5 nanometers big on that scale.

Reply 5

khalaf

Degausser

Can you see where you went wrong now?

. To me, those numbers have no meaning whatsoever. Why is the graticule there, surely there's a use for it isn't there? i don't get how to do all the conversions. The answer, which is 10nm btw (according to the teacher :eyeball:

) has nothing to do with either of them.

Reply 6

Alisa25

Well first of all - count up how many "small divisions" the chloroplast take up. From what i can see its about 3-4 divisions - that means its 0.3 or 0.4 mm. (according to the "key" in the beginning of the question).

Then you just convert mm to um. You can convert mm to m. And then convert m to um.
Then choose the answer that is remotely similar.

Hope that helps.

Reply 7

khalaf

Alisa25

So the answer's supposed to be 5? and what's the ocular micrometer there for?

Reply 8

Alisa25

khalaf

So the answer's supposed to be 5? and what's the ocular micrometer there for?

Well i think its 5 but i havent actually worked it out yet... :rolleyes:

Micrometer is there to measure the WHOLE cell whilst the graticule is there to hlp you measure organelles as the micrometer doesnt have the accuracy.

:smile:

Reply 9

khalaf

Alisa25

Well i think its 5 but i havent actually worked it out yet... :rolleyes:

Micrometer is there to measure the WHOLE cell whilst the graticule is there to hlp you measure organelles as the micrometer doesnt have the accuracy.

:smile:

Thanks, i hope i don't get a micrometer question on the exam, i screwed them all up even though they're all multiple choice :redface:

Reply 10

Alisa25

khalaf

Thanks, i hope i don't get a micrometer question on the exam, i screwed them all up even though they're all multiple choice :redface:

multiple choice?????? :eek3:

You are soooo lucky!!!

Last year i didnt have that luxury, all our questions were written and LONNNG! :frown:

yOU'RE welcome btw. :smile:

Reply 11

cowsgoquack

The top image tells you that: 10<->90 on the graticule is equal to 0.2mm

Therefore 1 graticule unit = 0.0025mm = 2.5μm

Bottom picture shows that a chloroplast is about 4 graticule units

2.5μm * 4 = 10μm

Reply 12

cowsgoquack

Alisa25

Micrometer is there to measure the WHOLE cell whilst the graticule is there to hlp you measure organelles as the micrometer doesnt have the accuracy.

:smile:

the ocular micrometer is used to judge the scale that the graticule represents - the graticule on its own doesn't measure anything, it's divisions are arbitrary.