Transcript Cell Physiology lab - Orange Coast College

Cell Physiology lab
Outline of the day
1. Turn in your lab reports at the front
–
More than 10 minutes late = bad
Any questions on last week’s lab?
Quiz
Introduction to the lab
Lab!
Check out
2.
3.
4.
5.
6.
•
•
Get a stamp
Make sure I mark you down for attendance
Quiz
• Ends 10 minutes after it’s started
– Ends at: ____
Lab this week!
• Exploring cell physiology
– How membranes work
• Using beets!
– The affect of surface area to volume ratio on
diffusion
• Using potatoes!
Plant
Cells
Plasma membrane
(lipid bilayer)
Animal
Cell wall
(only on plants, fungi,
protists, and bacteria)
Animal cell - ccasa by MesserWoland at http://en.wikipedia.org/wiki/Image:Biological_cell.svg
Plant cell - PD by Mariana Ruiz - LadyofHats at http://en.wikipedia.org/wiki/Image:Plant_cell_structure_svg.svg
Membranes
• Membranes separate the cell from the
outside
– If the membranes break, the cell dies
Cell diagram from Wellcome images http://images.wellcome.ac.uk/: N0021944 Credit Medical Art Service, Munich /, Wellcome Images
Today
• We want to look at how pH affects
membranes
– Does pH damage membranes?
• But we can’t actually see membranes
under a microscope to see if they’ve been
damaged!
That’s where
beets come in!
• Beet cells are filled with
a red pigment
• When beet cell
membranes are
damaged, they release
the red pigment
Images from: http://flickr.com/photos/fotodawg/111040816/;
http://flickr.com/photos/sushiesque/204490212/;
http://flickr.com/photos/niznoz/8725134/ - all cc licensed
Beets
• We’re going to put beet cores in different
pH solutions
– And observe what happens
Strong Acid
Neutral
Strong Base
?
Photos from: http://flickr.com/photos/niznoz/8725134/; http://flickr.com/photos/sushiesque/204490212/; both cc licensed; art by Marc Pe
How will we measure the color change?
• Spectrophotomers!
– Machines that measure how much light is
absorbed by (or transmitted through) a
solution
Missing image:
Image showing light passing
through a sample in a spec
to demonstrate physics of
what is going on.
Missing image:
Image of OCC’s specs.
Calibrating the spectrophotometer
1. Turn spec on, let it warm up (>10 minutes).
2. Select the wavelength you want to use.
3. With nothing in the meter, adjust the meter to
read  using the infinity control knob (left
knob / power switch).
4. Place a cuvette filled with the blank solution
into the sample holder. The blank solution
has only the solvent in it (water today).
5. Adjust the meter to read 0 absorbance (full
scale) using the zero control knob (right
knob).
6. Put your sample tube in the sample holder!
(Repeat this procedure whenever you adjust the wavelength)
Surface area to volume ratio
• A factor that can affect the rate of diffusion
into a substance
• Questions:
– Which cube(s) have the highest surface area
to volume ratio?
– Which cube(s) will gain the most water?
Cube diagrams by Marc Perkins
Addition to the potato section!
• Calculate the % weight change for each
treatment
– % weight change = (weight change) / (initial weight) * 100
Time (minutes)
Initial
Final
Weight change
% weight change
Before you leave
• Clean up your work area
– Wash glassware and store upside down
• Show me your lab report so I can stamp it
– Need to have all data fields filled in
– Complete at home and then turn in at the beginning of
next lab
• Remember that we’ll have a quiz at the
beginning of the next class
– 6-7 questions on today’s lab
– 3-4 questions on the lab we’ll do next week
Calibrating the spectrophotometer
1. Turn spec on, let it warm up (>10 minutes).
2. Select the wavelength you want to use.
3. With nothing in the meter, adjust the meter to
read  using the infinity control knob (left
knob / power switch).
4. Place a cuvette filled with the blank solution
into the sample holder. The blank solution
has only the solvent in it (water today).
5. Adjust the meter to read 0 absorbance (full
scale) using the zero control knob (right
knob).
6. Put your sample tube in the sample holder!
(Repeat this procedure whenever you adjust the wavelength)
Notes for the instructor:
• I’d add in an image of OCC’s specs to the presentation,
as well as an image of how specs work.
• You could either break the calibration procedure up into
multiple slides, illustrating them with images, or walk the
students through the calibration on their specs with a
single-page slide (being sure to have the students do
everything on their specs as you explain it). I waffle
between how I prefer to do it, though I do like being able
to leave up a single-page version of the calibration
proceedure during lab.
• I’d prefer to find better images of plant and animal cells,
though the ones included are good enough for the
purpose (to demonstrate that plant and animal cells are
similar, but that plants have cell walls, which animals
don’t).
License information
• This work is licensed under the Creative Commons AttributionNonCommercial-ShareAlike 3.0 License. To view a copy of this
license, visit http://creativecommons.org/licenses/by-ncsa/3.0/us/ or send a letter to Creative Commons, 171 Second
Street, Suite 300, San Francisco, California, 94105, USA.
• The slides in this presentation were originally created by Marc
C. Perkins (http://faculty.orangecoastcollege.edu/mperkins).
• You are free to use, modify, and distribute these slides
according to the terms of the Creative Commons license (e.g.,
you must attribute the slides, no commercial uses are allowed,
and future distributions must be licensed under a similar
license).
• Attribution should be given to Marc C. Perkins (and any later
editors), including a link back to Marc’s current website. This
applies both while distributing the slides and during use of the
slides; attribution during use can be satisfied by, for instance,
placing small text on at least one of the slides that has been
shown (see below for an example).
History
• August 2007: Marc Perkins released first
version.
http://faculty.orangecoastcollege.edu/mperkins
(If you modify these slides and redistribute them, add your information to the list)