BIOL 110 Labs: Photosynthesis, Population Growth & Interactions

What is the goal of the chlorophyll extraction experiment?

To extract and separate photosynthetic pigments from spinach leaves and measure their light absorption using a spectrophotometer.

Name the three pigments studied in the chlorophyll extraction lab.

Carotene, Chlorophyll a, and Chlorophyll b.

What does photosynthesis convert?

Light energy into chemical energy used to produce sugars.

What is the function of chlorophyll in photosynthesis?

It absorbs light energy for photosynthesis.

What are carotenoids?

Accessory pigments that absorb light at particular wavelengths.

Define photon.

A packet of light energy.

What is the definition of wavelength?

The distance between successive wave peaks, measured in nanometers (nm).

What does an absorption spectrum show?

How much light a pigment absorbs at different wavelengths.

What is the purpose of a spectrophotometer?

To measure how much light a substance absorbs.

What is absorbance?

The amount of light absorbed by a sample at a particular wavelength.

What is the relationship between photon energy and wavelength?

They are inversely related; shorter wavelengths have higher energy.

How does a spectrophotometer work?

It measures the amount of light absorbed by a pigment sample after white light is passed through it.

What solvents were used to separate the pigments?

95% ethanol, 92% methanol, and petroleum ether.

Which pigment remains in the ethanol layer?

Carotene.

What are the two major absorption peaks for chlorophyll b?

450 nm (blue light) and 650 nm (red light).

What happens to absorbance when pigment concentration decreases?

Absorbance decreases.

What does the Beer-Lambert Law describe?

The relationship between absorbance, concentration, and path length of light through a sample.

What is the purpose of the blank in the spectrophotometer?

To calibrate the instrument.

What happens to chlorophyll a absorbance after dilution?

It decreases.

What is the primary absorption range for carotene?

438-468 nm, primarily in the blue region of visible light.

What are the similarities between chlorophyll a and b?

Both absorb blue and red light and participate in photosynthesis.

How does concentrated pigment compare to diluted pigment?

Concentrated samples generally have greater absorbance.

What does the detector in a spectrophotometer measure?

The light passing through the sample.

What is the key takeaway regarding pigment absorption?

Chlorophyll a and b absorb strongly in blue and red regions, while carotene primarily absorbs blue light.

What is the effect of dilution on the height of absorption peaks?

Dilution lowers the height of the absorption peaks.

What does an absorption spectrum indicate?

The amount of light a pigment absorbs at different wavelengths.

What is the significance of the wavelengths of maximum absorption?

They indicate the specific wavelengths where the pigment absorbs light most effectively.

What happens to the position of absorption peaks when concentration changes?

The position of the peaks does not substantially change with concentration.

How does pigment concentration affect absorbance?

As pigment concentration decreases, absorbance decreases.

Which is more useful for identifying a substance: position or height of absorption peaks?

The position (wavelength) of the absorption peaks.

Why is the position of absorption peaks more useful?

Each pigment absorbs light at characteristic wavelengths, while peak height changes with concentration.

What would happen to photosynthesis if chlorophyll were transparent to light?

Photosynthesis would be greatly reduced or not occur, as chlorophyll would not absorb light energy.

What would the absorption spectrum of a colorless substance look like?

It would be a flat line with absorbance close to zero across the visible spectrum.

Why does chlorophyll appear green?

Chlorophyll absorbs mostly blue and red wavelengths and reflects/transmits green wavelengths.

Does chlorophyll absorb green light?

Chlorophyll absorbs very little green light compared to blue and red light.

How much photosynthesis occurs under green light?

Very little photosynthesis occurs because chlorophyll absorbs green light poorly.

How much photosynthesis occurs under blue light?

A relatively high amount of photosynthesis occurs because chlorophyll absorbs blue light effectively.

How much photosynthesis occurs under red light?

A relatively high amount of photosynthesis occurs because chlorophyll absorbs red light effectively.

What property of chlorophyll a, b, and carotenoids allows their separation?

Differences in solubility of the pigments in different solvents.

What is the relationship between pigment concentration and peak height?

Pigment concentration and absorbance have a direct relationship; as concentration increases, absorbance increases.

What happens to the position of absorption peaks when pigment concentration changes?

Changing the concentration does not substantially alter the position of the absorption peaks.

What is the effect of shorter wavelengths on photon energy?

Shorter wavelengths correspond to higher photon energy.

What happens to photon energy as wavelength increases?

Photon energy decreases as wavelength increases.

What is the fraction of a 400 nm photon's energy captured by chlorophyll if it absorbs 1 photon?

0.64

What is the key takeaway regarding pigments and light absorption?

Pigments absorb specific wavelengths of light, and the energy captured helps power photosynthesis.

What is the energy of a 400 nm photon?

Calculated in Step 1 of the lab.

What is the key takeaway regarding wavelength and photon energy?

Shorter wavelength = higher photon energy.

What does absorbance measure?

How much light is absorbed by a substance.

What is the relationship between concentration and absorbance?

Higher concentration generally means higher absorbance.

What does peak position help identify?

The pigment present in the sample.

What light does chlorophyll absorb?

Blue and red light; reflects/transmits green.

What light does carotene primarily absorb?

Primarily blue light.

What is the main concept connecting the entire lab?

Pigments absorb specific wavelengths of light, powering photosynthesis.

What is photosynthesis?

Process that converts light energy into chemical energy.

What is an autotroph?

An organism that produces its own organic food.

What is chlorophyll?

Green pigment that absorbs light energy.

What is a photon?

A packet of light energy.

What is a wavelength?

Distance between successive peaks of a light wave, measured in nanometers.

What is an absorption spectrum?

Graph showing how much light a pigment absorbs at different wavelengths.

What are the three major pigments studied?

Chlorophyll a, Chlorophyll b, and Carotene.

Why do plants appear green?

Chlorophyll absorbs blue and red light but reflects/transmits green light.

What does a spectrophotometer measure?

How much light a substance absorbs.

What is transmittance?

Amount of light that passes through a substance.

What is a blank in spectrophotometry?

Solvent used to calibrate the spectrophotometer.

What is the purpose of chromatography in this lab?

To separate pigments based on their solubility.

What is the Beer-Lambert Law?

A = εlc, relating absorbance to concentration.

What happens to DPIP in the second experiment?

It loses its blue color as it is reduced.

What occurs during the light-dependent reactions of photosynthesis?

Chlorophyll absorbs light, exciting electrons and oxidizing water.

What is the effect of dilution on absorbance?

Dilution substantially decreases absorbance.

What does the peak position indicate in absorption spectrum results?

It helps identify the pigment based on wavelengths absorbed.

What is the primary photosynthetic pigment?

Chlorophyll a.

What is the accessory pigment that expands light absorption?

Chlorophyll b.

What color light has the highest energy?

Blue light (450 nm).

What color light has the lowest energy?

Red light (650 nm).

What is produced during water oxidation?

Oxygen, electrons, and protons.

What is the role of Photosystem II?

It oxidizes water and produces oxygen.

What happens to electrons in the electron transport chain?

They move through carriers and help establish a proton gradient for ATP synthesis.

What is DPIP?

2,6-dichlorophenol indophenol, an artificial electron acceptor used to measure photosynthetic electron transfer.

What color is oxidized DPIP?

Blue.

What color is reduced DPIP?

Colorless.

What does a decrease in DPIP absorbance indicate?

DPIP is being reduced, indicating electron transfer.

What is the independent variable in the chloroplast experiment?

Amount of chloroplast suspension.

What is the dependent variable in the chloroplast experiment?

Rate of water oxidation, measured indirectly by DPIP reduction.

What happens to chlorophyll electrons when they absorb light?

They become excited to higher energy levels.

What is the relationship between pigment concentration and absorbance?

As pigment concentration increases, absorbance increases.

What is the significance of the spectrophotometer in the experiment?

It measures the amount of blue DPIP remaining, indicating the rate of electron transfer.

What is the role of NADP+ in photosynthesis?

It is reduced to NADPH during the process.

What is the purpose of the electron transport chain?

To generate a proton gradient for ATP production.

What is the expected result of increasing chloroplast suspension amounts?

An increase in the rate of DPIP reduction.

What misconception about plants and light absorption is common?

That plants use green light most effectively; they actually absorb blue and red light more effectively.

What is the first step in the photosynthesis process?

Light absorption by chlorophyll.

What happens during water oxidation in photosynthesis?

Water loses electrons, producing oxygen and protons.

How do chlorophyll pigments differ?

They have different solubility properties and absorption peaks.

What is the expected outcome when chloroplast suspension is 0 mL?

Little or no photosynthetic reduction; DPIP remains high.

What does a rapid decrease in DPIP absorbance suggest?

A faster rate of photosynthetic electron transfer.

What is the relationship between wavelength and photon energy?

As wavelength increases, photon energy decreases.

What is the significance of the Z-scheme in photosynthesis?

It describes the flow of electrons through the photosystems and electron transport chain.

What is the role of light in the photosynthesis process?

It excites electrons in chlorophyll, initiating the process.

What is the expected absorbance for 0.4 mL of chloroplast suspension?

It is expected to decrease the fastest, indicating the greatest reduction of DPIP.

What is the final product of the Calvin cycle?

Glucose, produced from the reduction of CO2 using ATP and NADPH.