2.9 (Energy Metabolism) Flashcards
Define photosynthesis.
- Photosynthesis is the production of carbon compounds in cells using light energy.
- The process in which cells synthesize organic compounds (eg. glucose) from inorganic compounds (H2O + CO2) in the presence of sunlight.
State the chemical equation for photosynthesis.
6CO2 + H2O ———> C6H12O6 + 6O2
Define visible light.
Electromagnetic radiation in the range of 400-700nm, which can be detected by the eye and used by plants.
State the relationship between wavelength and energy.
The shorter the wavelengths, the more energy there is. The longer the wavelengths, the less energy there is.
State the range of wavelengths that fall within the visible spectrum.
Visible light range from 700 nm - 400 nm. The colors from long to short wavelengths are red, orange, yellow, green, blue, indigo, and violet
Define pigment
Substances, often proteins, which absorbs light and therefore color appears to us the ones that the pigment doesn’t absorb
State the primary and accessory pigments found in chloroplasts.
- The primary pigment in the chloroplast is the chlorophyll (green).
- Chlorophyll-A is the most abundant and has a darker green.
- Chlorophyll-B is the less abundant and has a lighter green.
- Carotenes are orange.
- Protective pigments (red, violet, blue) attracts pollinators and protects DNA from UV light.
Explain why plants are green.
Sunlight contains all the wavelengths of visible light. The main photosynthetic pigment in plants is the chlorophyll, which appears green because it reflects light most strongly in the green portion of the spectrum. Chlorophyll absorbs light most strongly in the blue portion followed by the red portion of the spectrum.
Define photolysis.
- Photolysis means water splitting. During photosynthesis, light energy is used to split water molecules as represented by the following equation: 2H2O → 4H+ + 4e- + O2
State the equation for photolysis.
2H2O → 4H+ + 4e- + O2
State that the oxygen produced in photolysis is a waste product of photosynthesis
Oxygen (O2) is released as a waste product in this process. The H+ and e- continue on in the photosynthesis light reactions.
State the energy conversion that occurs during photosynthesis.
Energy can’t be created/destroyed. The energy in the form of light is converted into chemical energy in the bonds of carbohydrates.
Define “limiting factor.”
A limiting factor is a variable of a system that can limit the rate of a reaction.
Either the amount of light, temperature or CO2 concentration will limit the rate of photosynthesis. Whichever of the three is furthest from its optimal will be the limiting factor.
Explain how the following factors limit the rate of photosynthesis: temperature, light intensity, CO2 concentration.
Temperature
- Photosynthesis is an enzyme-catalyzed reaction, and like with other enzyme reactions, photosynthesis rate will increase as the temperature is raised until an optimal temperature is reached.
- After the optimum, the rate of photosynthesis abruptly declines with further increase of temperature. The decline is because most enzymes involved in photosynthesis rapidly denature at higher temperatures.
Light intensity
- Without enough light, a plant cannot perform photosynthesis because light energy is required in the light dependent reactions.
Increasing the light intensity will increase the rate of photosynthesis. - -
- However, at a certain point the photosynthetic rate will plateau. The leveling off is because all available chlorophyll pigments are being used.
CO2 concentration
- Without carbon dioxide, a plant cannot perform photosynthesis because CO2 is required in the light independent reactions.
- Increasing carbon dioxide concentration will increases the rate of photosynthesis.
- However, at a certain point the photosynthetic rate will plateau. The leveling off is because all enzymes used in the reactions are being used.
State that (some) prokaryotes, algae and plants carry out photosynthesis.
Prokaryotes were the first to perform photosynthesis around 3.5 billion years ago, they became a part of the algae and plants million of years later.