Chapter 10 Photosynthesis Flashcards
Mesophyll cells have how many chloroplasts?
30 to 40
Stroma is equivalent to?
Cytosol
The photosynthesis equation
6CO2 +12H2O + light energy = C6H1206+602+6 H2O
Light reactions
The light reactions are the steps of photosynthesis that convert solar energy to chemical energy. Water is split, providing a source of electrons and protons and giving off O2 as a byproduct. Light absorbed by Clore Phil drives a transfer of electrons and hydrogen ions from water to an acceptor called NADP+
Calvin cycle
The cycle begins by incorporating CO2 from the air into organic molecules already present in the chloroplast. The initial incorporation of a carbon into organic compounds is known as carbon fixation. The Calvin cycle then reduces the fixed carbon to carbohydrate by the addition of electrons. To convert CO2 to carbohydrate, the Calvin cycle also requires chemical energy in the form of ATP. The Calvin cycle makes sugar but can do so only with the help of NADPH and ATP produced by the light reaction.
Visible light
380 nm to 750 nm
Shorter wavelength to longer wavelength
Higher energy to lower energy
purple to blue to green to yellow to orange to red
Chlorophyll A and chlorophyll B
Chlorophyll A is the key like capturing pigment participates directly in the light reaction. This pigment works best with Violet blue and red light for photosynthesis.
Chlorophyll B is an accessory pigments
Carotenoids
A group of accessory pigments. And important function seems to be photoprotection. These compounds absorbent dissipate excess of light energy that would otherwise damage chlorophyll or interact with oxygen forming a reactive oxidative molecules that are dangerous to the cell.
Photosystem
A photosystem is composed of a reaction center complex surrounded by several light harvesting complexes.
When a pigment molecule of swords a photon the energy is transferred from pigment molecule to pigment molecule within a light harvesting complex until it passes into the reaction center complex. The reaction center complex also contains a molecule capable of accepting electrons and becoming reduced this is called the primary electron acceptor.
Light harvesting complex
Each light harvesting complex consists of various pigment molecules which may include chlorophyll A and chlorophyll B and multiple carotenoids.
Reaction center complex
The solar power transfer of an electron from the reaction center chlorophyll A pair to the primary electronic scepter is the first step of the light reaction. When the chlorophyll electron is excited to a higher energy level the primary electronic scepter captures it in a redox reaction.
Photosystem one and photosystem two are both located where? Which one works first in light reactions? And which wavelengths is each best at absorbing?
In the thylakoid membrane
Photosystem two works before photosystem one
Photosystem two is best at absorbing P680 wavelength and photosystem one is best at absorbing P 700.
Describe linear electron flow
- A photon of light strikes one of the pigment molecules in the light harvesting complex of PS two boosting one of its electrons to a higher energy level. This process continues until it reaches the P680 pair of chlorophyll a molecules in the PS 2 Reaction Center complex. It excites an electron in this pair of chlorophyll to a higher energy state
- The electron is transferred from the excited P680 to the electron primary acceptor.P680 becomes P680+
- An enzyme catalyzes the splitting of a water molecule into two hydrogen ions and an oxygen Adam. The electrons are supplied one by one to the P680+ pair each electron replacing one transferred to the primary electron acceptor. H+ is released to the thylakoid space. The oxygen atom immediately combines with another oxygen atom created by the splitting of another water molecule forming O2
- The electron that is photoexcited passes from the primary electronic scepter of PS2 to PS1 via the electron transport chain. This is made of PQ (plastioquinone), cytochrome complex, and PC (plastocyanin). The exergonic fall of the electron provides energy for the synthesis of ATP.
- The process again happens in photosystem one. After leaving the primary acceptor the proton goes to Fd (ferrerdoxin).
- Lastly the enzyme NADP+ reductase catalyzes the transfer of electrons from FD to NADP+. 2 electrons are required for its reduction to NADPH
Cyclic electron flow
As an electron is excited and photosystem one to the primary acceptor, The electron is past two an Fd closer to the cytochrome complex which is passed back to PC and again back into photosystem one. With each cycle one ATP is produced
Carbon dioxide enters the leaf and oxygen exits by way of microscopic pores called
Stomata
