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