CH 4 LEDs and Photosynthesis Flashcards
Photosynthesis is the process by which plants convert light energy into the ______________they use as building blocks and —_________________stores.
Sugars
Energy
Membranes in plants called __________________do the heavy lifting, collecting ___________ ____________and passing it along to chemical processes inside the leaves that convert light, water, and carbon dioxide (CO2) from the air into _________________.
Chlorophylls
Light energy
Sugars
Water (H2O) + light (hv) + Carbon Dioxide (CO2) → ___________+ __________________.
→ Sugars + Oxygen (O2)
Again……..
Water (H2O) + _____________+ Carbon Dioxide (CO2) → Sugars + Oxygen (O2)
light (hv)
Photosynthesis can be broken down into two sub-processes: ________________ reactions and __________________ reactions.
light-dependent reactions
light-independent reactions.
It might be simpler to consider the light-dependent reactions _______________reactions because they use __________________ to break up a water molecule (H2O).
“water side”
light energy
The energy produced from these reactions is captured in two compounds that fuel the rest of the photosynthetic process:
________________________
Below is the simplified reaction: H20 + light → ATP + NADPH + O2
ATP (adenosine triphosphate)
NADPH (nicotinamide adenine dinucleotide phosphate).
As with everything in biology, the names can be confusing. “Light-independent reactions” are more commonly called “dark reactions,” though they don’t only occur at night as their name might imply. They just don’t require light, so it’s better to call them ____________________.
Light independent reactions
Light-independent reactions are also called the “_________________.” Melvin Calvin, James Bassham, and Andrew Benson discovered it while working together at University of California, Berkeley, but Calvin gets the name recognition.
“Calvin Cycle.”
In these reactions, ___________ is converted into sugars with the aid of the energy building blocks produced by the light-dependent reactions, ___________and ______________.
CO2
ATP and NADPH.
Because these reactions consume CO2, they can be considered
_____________________reactions.
Simplified, the carbon fixation reaction looks like this: ATP + NADPH + CO2 → Sugars + O2
Carbon Fixation
Simplified, the carbon fixation reaction looks like this:
______+ ________+ ___________→ Sugars + O2
ATP + NADPH + CO2
Both halves put together:
Light-Dependent Cycle H20 + light → ATP + NADPH + O2
Light-Independent Cycle ATP + NADPH + CO2 → Sugars Total
Two-Step Reaction?
Total Two-Step Reaction
H20 + light → ATP + NADPH + CO2 → Sugars + O2
There are several types of chlorophyll? Most green plants use chlorophyll _____and chlorophyll ______plus compounds called____________ to capture light for photosynthesis. There are also C1, C2, D, and F chlorophylls, but these are generally found in lower
A
B
Caretines
Chlorophyll is probably the best-known plant pigment. It’s _____________ in color and found in all plants and algae.
Chlorophyll’s job is to absorb ____________from the light _________to which the plant is exposed.
Green
Energy
Photons
In plants, chlorophylls absorb in the __________and ________ regions of visible light.
This may be why early LED manufacturers, who didn’t know better, produced grow lights with only red and blue emitters.
Red
Blue
One curiosity about chlorophyll is its close resemblance to hemoglobin, the human molecule that provides oxygen and carbon dioxide transport throughout the body. The primary difference between chlorophyll and hemoglobin is their center ion: hemoglobin has iron (Fe) at its center, while chlorophyll centers on ____________________otherwise, the molecules are strikingly similar.
Magnesium (Mg)
While partially true, plants don’t reflect 100% of the ___________________they receive—some is absorbed and some is reflected.
The reflected __________________can be absorbed by another leaf; thus, ____________________ scatters further into the garden’s canopy than red and blue.
Green light 3x
Many plants absorb as much as _________________of the green light they are given.
70% to 90%
Green light is absorbed deep within the leaf tissue by a group of compounds called ___________________ among which lycopene and beta-carotene are most well-known.
Carotenoids
lycopene and beta-carotene are two well-known well known carotenoids
lycopene and beta-carotene
Carotenoids cause plant leaves to ________________, increasing their ability to capture more light.
Thicken
should a plant begin to shut down chlorophyll absorption due to light overexposure, _____________________can continue to drive photosynthesis.
Green light
____________, ______________, and ______________are the primary colors of light;
when they are mixed together in computer monitors and televisions, they can recreate every color including white.
Including 5% to 10% green emitters in an LED grow light makes it easier for the gardener to see problems that might otherwise be masked by the light’s purplish-pink color.
Red, blue, and green
Infrared: Emerson Enhancement Effect
In 1957, Robert Emerson conducted experiments regarding what wavelengths most efficiently drive photosynthesis.
He noticed that photosynthesis dramatically drops off at ___________nm and above. This was considered strange since chlorophyll isolated in a beaker absorbs light well above this point.
Photosynthesis reductions above __________nm became known as the “___________________.”
680nm
680nm
Red drop effect
This led Emerson to additional experiments showing that plants respond disproportionately to the combination of ___________________ and ___________________.
infrared light and red wavelengths.
