Transcript The significance of size

Size Matters!
Size Matters!
Size Matters!
Compare the relative sizes of molecules, cell membrane thickness, viruses, bacteria,
organelles and cells, using the appropriate SI unit.
A molecule
1nm
http://mendosa.com/glucose_molecule.jpg
Glucose (1nm)
A molecule
10nm
http://www.biolibogy.com/images/structure_of_plasma_membrane.JPG
A virus – the T
bacteriophage
100nm
10nm
http://oceanworld.tamu.edu/resources/oceanography-book/Images/BacteriophageCartoon.jpg
Bacteriophage (virus)
E.coli (bacteria cell)
100nm
0.1µm
1000nm
1µm
http://bio1903.nicerweb.com/doc/class/bio1903/Locked/media/ch18/18_01T4PhageEColi_LP.jpg
Bacteria (1µm)
Eukaryote
Cell (100µm)
http://www.cic-caracas.org/departments/science/images/08eukaryote.jpg
Organelle (10µm)
• In the last sequence of slides every thing
increased by a magnitude of 10x each time.
The IB requires you to remember the sizes.
• Make up a mnemonic to help you to
remember the order!
• My Crazy Mum Visits Bieber Outside Concerts.
• My Money Vanishes Beautifully On Cars.
• My Most Valued subject is BiO ! Cool!
Lets look at Surface areas and
volumes………
• Fill in the table below:
a
Size of
side (a)
a
a
Surface
area of
the box
(a x a x 6)
Volume of Surface
the box
area to
(a x a x a) volume
ratio
1
6
1
6:1
2
24
8
3:1
3
54
27
2:1
4
96
64
1.5 : 1
5
150
125
1.2 : 1
6
216
216
1:1
7
294
343
0.9 : 1
• What trend did you notice?
– What happened to the area as side size increased?
The area increased much faster than the side size.
– What happened to the volume?
The volume increased much faster than the side size
– Which one (area or volume) increased the fastest?
Why is this important?
• The surface area relates to how much material
can enter a cell at a time.
The bigger the area is the more material can enter
in an amount of time
• The volume relates to how much material is
needed at a time.
The bigger the volume is the more material is
needed to maintain it for an amount of time.
• Assume that a volume of 1 needs 1 lot of material to
sustain it….And an area of 1 can provide 1 lot of material:
a
a
a
• Look at cell size where a=1. Is it able to supply
= 6 Volume =1 ….It can provide 6x as much
its needs? Area
material than it needs
• Look at cell size where a=6. Is it able to supply
= 216 Volume =216 ….It can just provide as
its needs? Area
much material than it needs
• What about a=7?
• The same idea is relevant for heat and waste
needing to be given out by an organism.
Can you think of some organisms that
have to deal with this problem?
1. Elephant – a very big organism produces lots
of heat. How does it get rid of all the heat
with a relatively low SA : Vol ratio?
– Find out about elephant ears.
2. The Shrew – A very small organism with a
relatively large SA : Vol ratio. How does it
manage to stay warm in winter?
– Find out about changes in metabolism.