1Outline how light energy is converted to chemical energy in carbon compounds.
Light energy is absorbed by chlorophyll in chloroplasts, which then converts carbon dioxide and water into glucose and oxygen.
2Draw a flowchart to illustrate the energy conversions performed by living organisms.
Input energy (sunlight) -> Photosynthesis -> Chemical energy (glucose) -> Cellular respiration -> ATP (usable energy)
3List three reasons why living organisms need energy for cell activities.
1. To perform metabolic processes, 2. To maintain homeostasis, 3. To carry out growth and reproduction.
4State that sunlight is the principal energy source in most ecosystems.
Sunlight is the primary source of energy for photosynthesis, which fuels most ecosystems.
5State the chemical equation for photosynthesis.
6CO2 + 6H2O –> C6H12O6 + 6O2
6Outline the source of the atoms used to form glucose (C6H12O6) during photosynthesis.
The carbon atoms in glucose come from carbon dioxide, while the hydrogen atoms come from water.
7Define photolysis.
The splitting of water molecules using light energy during the light-dependent reactions of photosynthesis.
Releases: O2, e- and Protons
8State the source of the oxygen produced as a by-product in photosynthesis.
The oxygen is produced by the splitting of water molecules during photolysis.
9State the equation for photolysis
2H2O –> 4H+ + O2 + 4e-
10State which parts of paper chromatography are the stationary phase and mobile phase
Stationary phase: the paper
Mobile phase: the solvent used to develop the chromatogram
11Outline the process of separating pigments using chromatography.
Can be separated using paper chromatography
Pigments are first extracted from leaves using a suitable solvent that dissolves most of the plant pigments
A sample of the extract (fluid) is placed on chromatography paper and transferred to a container with the chromatography solvent
Pigments move at diff rates on the stationary phase and separate according their solubility and affinity for the stationary phase.
12Identify pigments that result from chromatography by color and calculated Rf value.
By comparing the color and Rf values of the separated pigments to known standards, the specific pigments can be identified.
Rf = Retention Factor
Formula: Rf = sample distance / solvent distance
13State the range of wavelengths that fall within the visible spectrum.
400nm to 750nm
14Outline the function of pigments.
Absorb the photons in the visible light spectrum and reflect the colour that we see
15State the primary and accessory pigments found in chloroplasts.
Primary pigments: Chlorophylls - Chlorophyll a and Chlorophyll b (reflect green light)
Absorb wavelengths in the blue-violet and red regions
Accessory pigments: Carotenoids - Xanthophyll and b carotene (reflect yellow and orange light respectively)
Absorb wavelengths in the blue-violet regions
16Explain why most plants look green.
Chlorophyll a and b, the main pigments capturing the photons, reflect green light and absorb wavelengths in the blue-violet and red regions of the light spectrum
17Sketch the chlorophyll pigment absorption spectrum, including both wavelengths and colors of light on the X-axis.
See slide 9
X-axis: wavelength of light, Y-axis: Amount of light absorbed
Chlorophyll a:
- 2 peaks; one at 425 and one at 660
- remains somewhat constant in between
Chlorophyll b:
- 2 peaks; one exponential slope turning into a large one at 550 and one medium one at 625
- remains somewhat constant in between
- X-axis: wavelength of light, Y-axis: Amount of light absorbed
Carotenoid:
- one small trough after a straight line at 450 then a large narrow peak at 475
- goes back down to x-axis at 525
18Compare the action spectrum and absorption spectrum.
Both:
- highest rates are at the blue and red wavelengths while the lowest rates occur at the green
19 contrast the action spectrum and absorption spectrum.
Action spectrum:
- measures the overall rate of photosynthesis against the wavelength of light
- X-axis is wavelength of light (nm)
- Y-axis is the rate of photosynthesis
Absorption spectrum:
- measures the wavelengths of light absorbed by each pigment
- X-axis is wavelength of light (nm)
- Y-axis is amount of light absorbed
20Explain the shape of the curve of the photosynthesis action spectrum.
highest rates are at the blue and red wavelengths while the lowest rates occur at the green
This matches the absorption spectra of the photosynthetic pigments closely as it’s their ability to absorb light energy that allows photosynthesis to occur
21Outline a technique for calculating the rate of photosynthesis by measuring either oxygen production or carbon dioxide consumption.
Measure either oxygen production or carbon dioxide consumption.
22Define “limiting factor.”
A factor that restricts the rate of a process.
23Explain how temperature limits the rate of photosynthesis.
High temperatures can denature enzymes, while low temperatures can slow down enzyme activite
24Explain how light intensity limits the rate of photosynthesis.
Low light intensity reduces the energy available for photosynthesis, while high light intensity can damage the photosynthetic apparatus.
25Explain how CO2 concentration limits the rate of photosynthesis.
Low CO2 concentration reduces the availability of carbon for photosynthesis, while high CO2 concentration can saturate the photosynthetic process.
26Identify manipulated (independent), responding (dependent) and controlled variables in experiments testing limiting factors on the rate of photosynthesis.
Manipulated variable: temperature, light intensity, or CO2 concentration; Responding variable: rate of photosynthesis; Controlled variables: other environmental factors such as humidity, pH, etc.
27Outline techniques for measuring the rate of photosynthesis while manipulating either temperature, light intensity, or CO2 concentration.
Manipulate temperature by:
- changing the temperature in the water bath
Manipulate light intensity by:
- moving a primary light source closer or further away from the plant
Manipulate CO2 conc. by:
- using sodium hydrogen carbonate which can be dissolved in the water containing the plant
28State the source of atmospheric carbon dioxide beyond the historical average of about 300 ppm.
Fossil Fuels
29Compare enclosed greenhouse and free-air carbon dioxide enrichment (FACE) experiments.
enclosed greenhouse experiments are conducted in controlled environments, while FACE experiments are conducted in open-air settings.
30List the questions that are addressed in carbon dioxide enrichment experiments.
How does increased CO2 concentration affect photosynthesis, plant growth, and ecosystem dynamics?