Photosynthesis Flashcards
The process of storing the energy from the sun as chemical energy in carbohydrates (ex. glucose)
- Some glucose is converted to structural carbohydrates (ex. cellulose)
- Some glucose is converted to other molecules for storage (ex. starch, glycogen)
- Some glucose is used to produce other essential substances (ex. amino acids)
- Some glucose is broken down to create ATP
Light
a form of radiant energy that makes up a small portion of the electromagnetic spectrum
Gamma
high frequency
short wavelength
high energy
Radio
low frequency
long wavelength
low energy
Pigment
a compound that absorbs some wavelengths of light and reflects others (ex. chlorophyll absorbs all wavelengths of light except green (and some yellow), which it reflects.
Why do plants appear green
-plants appear green because it is being reflected by the chlorophyll
-all other wavelengths of light are being captured and used for photosynthesis
Red
low energy
Violet
high energy
When light gets absorbed, electrons gain energy(get excited) and have 3 possible outcomes
-Dissipated as heat
-Re-emitted immediately as light of a longer wavelength
-May trigger a chemical reaction- electrons gain enough energy to move from one molecule to another (photosynthesis)
Photosynthetic pigments
Chlorophyll a: green
Chlorophyll b: yellow/green
Carotenoids: orange
Xanthophyll: yellow
Why do plants have accessory pigments instead of just chlorophyll A
Allow them to use a broader spectrum of light energy (otherwise all green light is wasted)
Why do leaves change colour in the fall
-Spring/summer: Chlorophyll dominates and “masks” other pigments
-Fall: cooler weather causes plants to stop making chlorophyll, other pigments show through instead
Two graphs are used to show how different wavelengths of light are used
- Absorbance spectrum
- Action spectrum
Absorbance spectrum
shows the efficiency of light absorption as a function of wavelength
- unique for each pigment
Action spectrum
shows the effectiveness of each wavelength of light for promoting photosynthesis
-measured as 02 production, glucose production, or C02 consumption
RF values
A ratio which can be used to determine which types of pigments are found in a solution
- distance travelled by pigment/distance travelled by solvent
Used with chromatography to identify solutes present in solution
-chromatography is used in the lab to separate components of a mixture
2 major parts of photosynthesis
- Light dependent reaction
- The Carbon fixation reaction (Light independent reaction/Calvin-Benson cycle)
-also includes a third part called the Electron Transport Chain(system)/Chemiosmosis
Electron Transport Chain(system)/Chemiosmosis
-H+ gradient
-Powers ATP production
ATP
ATP is an energy carrier(energy is stored in phosphate bonds)
ADP+P—->ATP
NADPH
(nicotinamide adenine dinucleotide phosphate) is a H+ and electron carrier, coenzyme (carries stored energy)
NADP+ + H+ —–> NADPH
The Light Independent Reaction / Calvin-Benson Cycle
-For every 12 PGAL molecules that are synthesized in the Calvin-Benson cycle, 2 leave the chloroplasts and go to the cytoplasm, used to make glucose or other high-energy compounds.
-The other 10 PGAL remain in the chloroplast and regenerate RuBP for the cycle to start over
Step 1- Carbon Fixation Reaction
C02 attaches to a 5-carbon sugar called RuBP
-creates an unstable 6-carbon molecule
-reaction is catalyzed by the enzyme rubisco
Step 2- Carbon Fixation Reaction
The unstable 6-carbon compound immediately breaks down into two
3-carbon compounds
-these 3-carbon compounds are stable (they are in a low-energy state)
-so far, C02 + RuBP —>unstable C6 —>
2 stable C3 (PGA)
Step 3- Carbon Fixation Reaction
The C3 compounds are converted to a higher energy state
-First activated by ATP (from the light reaction)
-Next, reduced by NADPH (from the light reaction)
- The H+ is transferred from the NADPH to the C3, creating PGAL
C3(stable) —-> PGAL(less stable)
