Unit 10 Photosynthesis
• Plants use energy from the sun and convert it to
chemical energy
– Glucose
• Photosynthesis occurs in chloroplasts
• Capture of light energy (light dependent rxn)
– In chlorophyll molecule in the thylakoid membrane
• Carbon fixation (light independent rxn)
– In stroma, carbon dioxide is “fixed” into a
carbohydrate molecule
Exercise 10.1
Wavelengths of transmitted light
• Wavelengths of light that are seen are reflected,
or transmitted.
• Wavelengths that are absorbed are not seen by
human eye.
• Pigments absorb wavelengths of light to spilt
water during the Light Reaction.
– Chlorophyll a- reflect green
– Chlorophyll b- reflect green
– Carotenoids- reflect red-orange-yellow
• What wavelengths do these pigments absorb?
• Use spectroscope to view white light.
• What wavelengths are absorbed by
different colored filters?
• What wavelengths are absorbed by
spinach extract?
Exercise 10.2 Determine absorption
spectrum of photosynthetic pigments
•
•
•
•
Review use of spectrophotometer (Unit 3)
Spinach extract
Carrot extract
Measure the absorbance of extracts at
varying wavelengths.
– Start with 525 nm, then vary.
– Must calibrate spec with blank each time
wavelength is changed
• Hint: Measure spinach and carrot at a
particular wavelength, then move to next
wavelength.
• Graph results.
– Graph both % transmittance and absorbance
• Determine at which wavelengths the
pigments in spinach and carrot has
maximum absorption.
10.3 Pigment chromatography
• Use the process of paper chromatography to separate
the various pigments in spinach.
• Drop spinach extract onto a piece of chromatography
paper. Let dry and repeat 4 times in order to get a
concentrated amount of extract.
• Have instructor add solvent to the large chromatography
tube.
• Place paper in tube, put stopper in place and put tube in
dark place for 20 minutes.
• Remove paper and look at record the colors you see.
http://www.phschool.com/science/biology_place/labbench/lab4/intro.html
Starch Distribution
• See demo
• Coleus leaves were tested for the
presence of starch using the iodine test.
• Compare the production of starch in
leaves that have been covered with foil for
several days and in uncovered leaves.
• Where is starch stored?
10.5 Chloroplast structure
• Study the sketch in lab
book AND the
chloroplast model!
• Know these locations in
the chloroplast:
–
–
–
–
–
–
Thylakoid
Granum
Outer membrane
Inner membrane
Stroma
Where light reactions
occur
– Where chlorophyll
molecules are located