Tam 6 Photosynthesis

LAB 6

Today’s Lab

I. Photosynthesis Review

II. Plant Pigments

III. Process of Photosynthesis

IV. Reactants and ProductsA. Light

B. Carbon Dioxide

C. Chlorophyll

Photosynthesis

•the process by which plant cells containing chlorophyll combine carbon dioxide and water in the presence of lightenergy to form carbohydrates and release oxygen

light

6CO2 + 12H2O C6H12O6 + 6O2+ 6H2O

Photosynthesis

•Glucose (monosaccharide) is one of the main products

•Most commonly, the end-product is a 3-carbon sugar that is converted directly into sucrose (disaccharide = Glucose + Fructose) or starch

•Therefore, the presence of starch is indirect evidence of photosynthesis.

Equations

•Photosynthesis

6CO2 + 6H2O C6H12O6 + 6O2

•Respiration

C6H12O6 + 6O2 6CO2 + 6H2O

chlorophyllsunlight

Photosynthesis & Respiration

Photosynthetic Rates

•Gross Photosynthetic RateRate at which only photosynthesis proceeds

•Net Photosynthetic RateGross photosynthetic rate minus the rate of respiration•Accounts for the difference cellular respiration makes in

photosynthetic rate and ATP production

•Actual production of new sugar and oxygen after accounting for sugar lost simultaneously during cellular respiration

Photosynthesis:Chloroplasts

•Organelles enclosed by a double membrane

•Site of photosynthesis

•Located primarily within mesophyll cells inside leaves

Photosynthesis:Geography

a) Inner tissue of the leaf, called mesophyll,

is specialized for photosynthesis

b) The Chloroplasts occur in the narrow

layer of protein- rich cytoplasm that

surround a large central vacuole

c) Three- dimensional structure of the

chloroplast The stack of thylakoids are

interconnected by the stroma.

d) The arrangement of the pigment- containing

thylakoid membranes.

Photosynthesis:Two Phases

1. Light-dependent- In thylakoids

- Electrons energized by light used to generate ATP and NADPH

2. Carbon fixation/light independent- In stroma

- Sugars synthesized from CO2 and H from NADPH

Photosynthesis

•Light-

dependent in

thylakoid

•Light-

independent

in the stroma

Today’s Lab


II. Plant Pigments



B. Carbon Dioxide

C. Chlorophyll

Plant Pigments

•Three main types of light-capturing pigments1. Chlorophylls (a, b)

2. Carotenoids (xanthophyll, carotene)

3. Phycobilins

•Primary pigment is Chlorophyll a

•Secondary pigments include chlorophyll b, xanthophylls, and carotenes

•Accessory pigments- capture energy from other wavelengths and then

transfer it to chlorophyll a

Plant Pigments•Light = energy and is composed of photons

•Visible light - small portion of electromagnetic spectrum

•All energy travels as waves

•Shorter wavelengths have more energy than longer wavelengths

•Different pigments absorb different wavelengths of light

Higher energy

Lower energy

Plant Pigments:The Electromagnetic Spectrum

The wavelengths

of visible light

for humans range

from 400 – 700

nanometers (nm)

Plant Pigments:Absorption & Photosynthetic Rate

Plant Pigments:Chlorophylls

•Absorb in the blue and red spectrum, reflecting a green/yellow color

•Chlorophyll a - Absorbs in violet-blue and orange-red spectra- Found in most photosynthetic organisms

•Chlorophyll b- Absorbs primarily in blue spectrum, reflects yellow

- Usually found in land plants

Plant Pigments:Carotenoids

•Absorb in the blue spectrum, reflecting a red/orange/yellow color

•Important in human health- Antioxidants – fight free radicals- Lycopene helps prevent prostate cancer- Carotenoids help block formation of LDL cholesterol

- Lutein protects eye health- Carotenoids are precursors to Vitamin A

Plant Pigments:Phycobilins

•Absorb in red, orange, yellow, and green spectrum

•Found in cyanobacteria and algae

•Water soluble; found in cytoplasm / stroma of chloroplast

•Fluoresce at certain wavelength making them useful in immunofluorescence assays

Today’s Lab


II. Plant Pigments



B. Carbon Dioxide

C. Chlorophyll

Process of Photosynthesis:Elodea Experiments

•Goal: test the effects of light on photosynthetic rate using Elodea•Elodea in NaHCO3 solution in tubes

•One tube in light, the other in dark

•Place jar of water in between light and tubes to help absorb heat

•Let reaction proceed for 20-30 minutes, then measure distance solution traveled

•Distance divided by time is photosynthetic rate

•Record data in excel

Photosynthetic Rate = D/t


Di Df

o2

time (t)


•Create your own experiment

•Write hypothesis in notebook and draw a sketch of the setup

•Follow the same procedure for measuring net photosynthetic rate

Today’s Lab


II. Plant Pigments



B. Carbon Dioxide

C. Chlorophyll

Reactants & Products:Light Experiment Tips

•Test two geranium plants, one that’s been in light and one that’s been in the dark

•Follow procedure for removing chlorophyll- Why is this important?

•Test for presence of starch

•Sketch and explain results in your notebook

Reactants & Products:Carbon Dioxide Experiment Tips

•Use coleus leaf that’s been deprived of CO2

•Remove chlorophyll and test for presence of starch

•Sketch and explain your results

Reactants & Products:Chlorophyll Experiment Tips

•Use coleus leaf with variegated leaves

•Test for the presence of starch

•Sketch leaves both before and after!

For Next Time

•Review lab 6

•Read lab 7

•Finish plant growth lab report

Documents

Tam 6 Photosynthesis