Chapter 5: Photosynthesis
Chemicals present to initiate the Calvin cycle:
- CO2 (Carbon Dioxide) -RuBisCO (An enzyme) -RuBP (Ribulose Bisphosphate)
Chlorophyll A
-All photosynthetic organisms have it -Humans see as the common GREEN color associated with plants -Absorbs wavelengths from either end of the visible spectrum (blue and red), but not from green.
Lightdependent reactions steps
-Light energy is absorbed by a chlorophyll molecule and is passed along a pathway to other chlorophyll molecules. -The energy culminates in a molecule of chlorophyll found in the reaction center. -The energy "excites" one of its electrons enough to leave the molecule and be transferred to a nearby primary electron acceptor. - A molecule of water splits to release an electron, which is needed to replace the one donated. -Oxygen and hydrogen ions are also formed from the splitting of water.
Electromagnetic spectrum facts
-Longer the wavelength/more stretched out = Less energy -Short/tight waves = Most energy Ex: St. Bernard = Chill Chihuahua = Crackhead
The Calvin cycle reactions can be organized into three basic stages:
1. Fixation 2. Reduction 3. Regeneration.
Photosynthesis takes place in 2 stages:
1. Light-Dependent Reactions 2. Calvin Cycle ****The two reactions use carrier molecules to transport the energy from one to the other****
Cellular respiration equation
6O2 + C6 H12 O6 → 6CO2 + 6H2O
Reduction reaction
A chemical change in which electrons are gained, either by the removal of oxygen, the addition of hydrogen, or the addition of electrons
Photosystem
A grouping of pigment molecules and proteins that exist in the membranes of thylakoids. Photosystem = where lightdependent reactions begin ***EUKARYOTES two photosystems exist, the first is called photosystem II
Pigment
A molecule that absorbs light
Photon
A particle of light - a quantity or "packet" of light energy.
Photosynthesis process
STARTING REACTANTS: Requires sunlight, carbon dioxide, and water RESULTS: Releases oxygen and produces carbohydrate molecules, most commonly glucose.
The energy that these molecules carry is stored in a bond that holds a single atom to the molecule
ATP = phosphate atom NADPH = hydrogen atom. **When these molecules release energy into the Calvin cycle, they each LOSE atoms to become the lower-energy molecules ADP and NADP+**
Reduction reaction explanation
ATP and NADPH use their stored energy to convert the three-carbon compound, 3-PGA, into another three-carbon compound called G3P. The molecules of ADP and NAD+, resulting from the reduction reaction, return to the light-dependent reactions to be re-energized.
What are the two energy-carrying molecules of the light-dependent reactions?
ATP and NADPH.
Carotenoids
Accessory pigments that broaden the spectrum of colors that can drive photosynthesis.
Chlorophyll B
An accessory photosynthetic pigment that transfers energy to Chlorophyll A *Absorbs blue and red-orange light) and the carotenoids
Chloroplast
An organelle found in plant and algae cells where photosynthesis occurs ***Chloroplasts have a double (inner and outer) membrane.***
A bacterium that lives near a thermal sea vent is able to transform inorganic compounds into an energy source. This organism would be classified as a(n) _____________________
Autotroph
How do prokaryotes, such as cyanobacteria, carry out photosynthesis?
Because they lack membrane-bound organelles, prokaryotic photosynthetic autotrophic organisms have infoldings of the plasma membrane for chlorophyll attachment and photosynthesis.
Photosynthesis equation
Carbon dioxide + Water + Sun's energy = Glucose (Sugar) + Oxygen OR 6CO2 + 6H2O + light energy → C6H12O6 + 6O2
Carbon atoms used to build carbohydrate molecules comes from
Carbon dioxide, the gas that animals exhale with each breath.
Photosynthesis
Certain organisms convert solar energy (sunlight) into chemical energy, which is then used to build carbohydrate molecules
In ALL autotrophic EUKARYOTES, photosynthesis takes place inside an organelle called the __________________
Chloroplast
Pigment facts
Different kinds of pigments exist, and each absorbs only certain wavelengths (colors) of visible light. Pigments reflect the color of the wavelengths that they cannot absorb.
Photosystem II and I (II Comes FIRST)
From photosystem II, the excited electron travels along a series of proteins. This electron transport system (chain) uses the energy from the electron to pump hydrogen ions into the interior of the thylakoid. A pigment molecule in photosystem I accepts the electron.
Because the carbohydrate molecule has six carbon atoms....
It takes six turns of the Calvin cycle to make one carbohydrate molecule (one for each carbon dioxide molecule fixed).
In plants, photosynthesis takes place primarily in the _________________
Leaves, specifically the mesophyll
Lightdependent reactions facts
MAIN PURPOSE: To convert light energy into chemical energy. -This chemical energy will be used by the Calvin cycle to fuel the assembly of sugar molecules.
In plants, chloroplast-containing cells exist in the _____________
Mesophyll
Autotroph (Producers)
Organism that can produce its own food. *Plants are the best-known autotrophs, but others exist, including certain types of bacteria and algae.
Heterotrophs (Consumers)
Organisms incapable of photosynthesis that must therefore obtain energy and carbon from food by consuming other organisms. *Humans and all animals are heterotrophs
Photosynthesis produces _____________ as a byproduct, and respiration produces _____________ as a byproduct.
Oxygen Carbon Dioxide
Calvin Cycle
Reactions of photosynthesis that use the energy stored by the lightdependent reactions to form glucose and other carbohydrate molecules.
Carbon fixation explanation
RuBisCO catalyzes a reaction between CO2 and RuBP, which forms a six-carbon compound that is immediately converted into two three-carbon compounds. *CO2 is "fixed" from its inorganic form into organic molecules.
Stomata
Small, regulated openings of the leaf where the gas exchange of carbon dioxide and oxygen occurs.
Granum
Stack of thylakoids
Thylakoids
Stacked, disc-shaped structures inside the chloroplast, used to convert light energy to chemical energy. **Located within the chloroplasts**
Calvin Cycle simplified
Stage 1. Enzyme RuBisCO incorporates carbon dioxide into an organic molecule Stage 2. The organic molecule is reduced Stage 3. RuBP (the molecule that starts the cycle) is regenerated so the cycle can continue.
Lightdependent reactions
TAKES PLACE IN THYKALOID MEMBRANE 1. Chlorophyll absorbs energy from sunlight 2. Converts it into chemical energy with the use of water. 3. Oxygen released from the hydrolysis of water as a byproduct.
More on Calvin Cycle
Takes six turns of the Calvin cycle to fix six carbon atoms from CO2. These six turns require energy input from 12 ATP molecules and 12 NADPH molecules in the reduction step and 6 ATP molecules in the regeneration step.
Wavelength
The distance between two consecutive, similar points in a series of waves, such as from crest to crest or trough to trough *The wavelength of a single wave is the distance between two consecutive points along the wave.
Reduction
The gain of an electron by an atom or molecule.
Carbon fixation
The initial incorporation of carbon into organic compounds.
The Energy Cycle
The movement of energy into and out of the earth system.
Clorophyll
The pigment through which the entire process of photosynthesis begins. *Chlorophyll is responsible for the green color of plants* **Located within the thylakoids**
Absorption spectrum
The range of a pigment's ability to absorb various wavelengths of light.
Electromagnetic spectrum
The range of all possible wavelengths of radiation. *Each wavelength corresponds to a different amount of energy carried.
Stroma
The space surrounding the granum
Photoautotrophs
Type of autotroph that uses sunlight and carbon from carbon dioxide to synthesize chemical energy in the form of carbohydrates. *Plants, algae, and certain bacteria, called cyanobacteria, are photoautotrophs that can carry out photosynthesis.
Mesophyll
the tissue in the interior of the leaf where photosynthesis occurs.