BIO Lab 8 - photosynthesis

Which of the following statements about chlorophyll is correct?

It reflects light in the green light spectrum. Chlorophyll is a plant pigment that absorb specific wavelengths of light energy and reflect back the green wavelengths of light that chlorophyll pigments cannot absorb.

comparing - conclusion

Plants exposed to blue light will show a greater rate of photosynthesis compared to those exposed to green light.

Photosynthesis - hypothesis

As photosynthesis progresses, the level of carbon dioxide will decrease.

Why do you cover one test tube in aluminum foil?

the foil blocks light

what are the reactants for photosynthesis

CO2 (provided by sodium bicarbonate) and H2O

Which of the following represents a reactant or input for the light reaction of photosynthesis?

H2O The photosynthesis reaction requires light, water, and carbon dioxide as reactants and produces carbohydrates (like glucose) and oxygen during the process

pigments - before you begin

Molecules of different sizes can be separated using paper chromatography. In this technique, chloroplast extract is placed at the end of chromatography paper and the end is placed in a solvent. The solvent carries the molecules as it migrates up the paper. In this way, the molecules are separated. Molecules are separated based on their chemical composition. Readily soluble molecules move the farthest compared to molecules more strongly attracted to the chromatography paper. Paper chromatography works by separating the different photosynthetic pigments into bands. Click the button below to learn more about these pigment bands.

photosynthesis - key concepts

- Plants use carbon dioxide and the energy from the sun during photosynthesis to produce glucose. - Photosynthesis is a combination of multiple chemical reactions. -A reactant of photosynthesis whose general levels can be measured is carbon dioxide. -A product of photosynthesis that can be measured is oxygen. -Carbon dioxide molecules react with water molecules using light energy to produce oxygen, water, and a glucose molecule.

photosynthesis - comparing key concepts

-Glucose produced by photosynthesis is used by plants in aerobic cellular respiration pathways to produce ATP (adenosine triphosphate), which provides energy to power many cellular reactions. Aerobic cellular respiration pathways also require oxygen. In cellular respiration oxygen reacts with glucose to produce carbon dioxide and water. -White light is made up of a range of wavelengths from red with the longest wavelength to violet with the shortest wavelength. Each group of wavelengths has a characteristic color. -Plants absorb certain wavelengths of light for photosynthesis better than others. -Plants are green because the green wavelength is mostly reflected back to our eyes.

photosynthesis comparing overview

-Light is crucial to providing the energy needed for photosynthesis. -One method to observe the progress of photosynthesis is to monitor the production of one of its products, oxygen. In this simulation, you will :Assemble a volumeter. Measure the change in the volume of oxygen produced during photosynthesis using a volumeter. Compare rate of photosynthesis in Elodea plants exposed to green or blue light in order to determine if one wavelength of light is better for photosynthesis. -Elodea is a plant that lives in water. Photosynthesis will be measured in these plants. -The reactants for photosynthesis are provided by sodium bicarbonate solution and light. -Sodium bicarbonate (NaHCO3) solution provides carbon dioxide and water, and light provides the energy needed for photosynthesis.

What would you expect to happen if you compare the rate of photosynthesis in bright white light and in darkness?

The rate of photosynthesis will be greater in bright white light than in darkness. Since photosynthesis requires light to proceed, the rate of photosynthesis would increase when exposed to white light compared to darkness.

photosynthesis pigments - key concepts

Plants use carbon dioxide and the energy from the sun during photosynthesis to produce glucose. White light is made up of a range of wavelengths from red with the longest wavelength to violet with the shortest wavelength. Each group of wavelengths has a characteristic color. Plants use multiple photosynthetic pigments to absorb light energy used in photosynthesis. The wavelengths of light absorbed can be used in photosynthesis, and the wavelengths of light reflected are what we observe.

white light graph

y axis - rate of volume change x axis - presence of light

Acidic solutions will appear what color?

yellow

photosynthesis - before you begin

-pH is a measure of the amount of hydrogen ions in a solution. The greater the amount of hydrogen ions, the more acidic the solution. As hydrogen ions are removed from a solution it becomes more basic. -Carbon dioxide combines with water to form carbonic acid. Therefore, the more carbon dioxide in a solution, the more acidic it will be. -Phenol red is a pH indicator that turns yellow in an acidic environment. -Phenol red appears pinkish-red in basic solutions.

Of the visible light spectrum, the rate of photosynthesis is worst under

green light The least amount of light absorption occurs at 550 green color range, therefore this is the lowest rate of photosynthesis.

Why is a 3% sodium bicarbonate (NaHCO3) solution added to each test tube?

it is a source of water and carbon dioxide

pigments - why does chlorophyll b appear to be yellow?

it reflects light in those wavelengths and absorbs violet and red

comparing - Strategy

I will compare the rate of photosynthesis of green light and blue light.

photosynthesis comparing - before you begin

A volumeter allows the measurement of volume change due to displacement of a liquid. The liquid may be displaced by addition or removal of a substance, such as oxygen.

pigments - pigment colors

During paper chromatography, the different photosynthetic pigments of the chloroplast extract migrate up the chromatography paper. The pigments that are more soluble will migrate farther than those that are less soluble. Examine the bands produced on your chromatography paper. Each band represents a different pigment of your starting extract. Chlorophyll a is blue-green. Chlorophyll b is yellow-green. Carotenes are orange. Xanthophylls are yellow.

white light strategy

I will compare the rate of photosynthesis with and without white ligh

white light method

I will measure the volume change due to O2 production using a volumeter.

photosynthesis - strategy

I will place a plant in an environment with carbon dioxide and light for photosynthesis to occur. I will use a pH indicator to monitor the level of carbon dioxide. I will compare the results to a negative control without a plant.

photosynthesis - overview

One method to observe the progress of photosynthesis is to monitor the removal of one of its reactants, carbon dioxide. In this simulation, you will:Identify the uptake of carbon dioxide due to photosynthesis and compare it to a negative control.

pigments - What is the purpose of using extract from chloroplasts?

chloroplasts contain the photosynthetic pigments. To separate the photosynthetic pigments, we must collect them where they are located in the chloroplasts.

comparing - Why does blue light lead to a greater rate of photosynthesis compared to green light?

Plants absorb certain wavelengths of light better than others for use in photosynthesis. Green light is reflected back and its energy is not fully available for use in photosynthesis.

A new plant species has a unique photosynthetic pigment. The leaves of this plant appear to be blue-green. What wavelengths of visible light does this pigment reflect?

green and blue Plant pigments absorb specific wavelengths of light energy and reflect back the wavelengths of light that they cannot absorb. The reflected wavelengths of light give the plant or flower its color, in this case green and blue were reflected back making the flower appear green/blue.

How does a phenol red-containing solution look if CO2 level is low?

red Phenol red solution is red if carbon dioxide levels are low (alkaline pH). Phenol red solution is yellow if the carbon dioxide level is high (acidic pH).

Which of the following is NOT a product of the light reaction?

carbon dioxide the photosynthesis reaction requires light, water, and carbon dioxide as reactants and produces carbohydrates (like glucose) and oxygen during the process.

In paper chromatography, photosynthetic pigments from a plant pigment extract will separate due to their (Check all that apply)

differences in solubility in a chromatography transport solution (mobile phase). differences in affinity for the chromatography paper (stationary phase). Pigments responsible for photosynthesis can be separated based on their chemical composition on chromatography paper. Molecules that are soluble in the transport solution will move up the chromatography paper more quickly than the molecules that are attracted to the paper.

photosynthesis - Why are carbon dioxide levels changing in the tube with Elodea?

Carbon dioxide levels are dropping because carbon dioxide is a reactant in photosynthesis.

photosynthesis pigments - overview

Chlorophyll extract appears green, hiding the presence of multiple pigments. It is possible to visualize the different pigments found in chlorophyll by separating them. One method of separation is paper chromatography. In this simulation, you will:Use paper chromatography to separate different photosynthetic pigments in a chloroplast solution.Identify different photosynthetic pigments based on their color. There are four distinct groups of photosynthetic pigments that each absorb different wavelengths of light:Chlorophyll a (absorbs red-violet light, appears blue-green)Chlorophyll b (absorbs red-violet light, appears yellow-green)Carotenes (absorb blue-violet light, appear orange)Xanthophylls (absorb blue light, appear yellow)

photosynthesis - What is happening to the level of carbon dioxide in the experimental test tube with the Elodea leaf as indicated by the red color in the tube?

The level of carbon dioxide is decreasing.

Photosynthesis - What is happening to the level of carbon dioxide in the negative control test tube without the Elodea leaf as indicated by the yellow color in the tube?

The level of carbon dioxide is unchanged.

A student set up a test tube containing sodium bicarbonate and topped it with a volumeter, but forgot to add the Elodea plant! Which of the statements below gives the result that the student would be likely to observe?

The level of the liquid in the volumeter would remain constant since gas is neither being produced nor being used.

pigments - What is the purpose of the chromatography solvent?

The pigments dissolve in the chromatography solvent, which allows them to be separated. As the solvent moves up the paper, the pigments are carried along and are separated.

comparing - hypothesis

The rate of photosynthesis is greater for blue light than for green light.

white light hypothesis

The rate of photosynthesis is greater in white light than in darkness.

do you expect photosynthesis to occur without light

no. light energy is needed

photosynthesis - Why is phenol red added to the test tubes?

phenol reed is a pH indicator

photosynthesis - What is the initial color of the test tube?

pinkish - red

based on your results, what can you conclude from this experiment

plants exposed to white light will undergo photosynthesis and produce oxygen

pigments - why did the different photosynthetic pigments migrate to different points on the chromatography paper

the pigments differ in their solubility in the solvent and affinity for the paper

Why is the volume level for the Elodea covered with foil decreasing

the plant is undergoing cellular respiration and is consuming oxygen. A plant in darkness will consume oxygen when it conducts aerobic cellular respiration using glucose reserves, and new oxygen is not produced because photosynthesis is not occurring.

Why is the volume level for the Elodea exposed to white light increasing?

the plant is undergoing photosynthesis and producing oxygen. The addition of oxygen is displacing the liquid in the volumeter.

what do the white light (solid red) and darkness (stripped orange) bars represent

the solid red bar shows how oxygen volume increases due to photosynthesis, and the striped orange bar shows how oxygen volume decreases to due aerobic cellular respiration and a lack of photosynthesis