30 Questions
What is the main function of chloroplasts in photosynthesis?
Split H2O into hydrogen and oxygen
Which part of the chloroplast contains photosystems?
Thylakoid membranes
What is the function of photosystem II in photosynthesis?
Splits water molecules
What is the role of reaction-center complexes in photosystems?
Capture photons
Which type of chlorophyll molecule is associated with Photosystem I in photosynthesis?
P700
What process occurs in chloroplasts that results in the release of oxygen as a by-product?
Splitting H2O into hydrogen and oxygen
Why do leaves appear green?
Because chlorophyll reflects/transmits green light
What is the main photosynthetic pigment?
Chlorophyll a
What is the purpose of accessory pigments like chlorophyll b?
Broaden the light spectrum that can be used for photosynthesis
What occurs when a pigment absorbs light?
It goes from a ground state to an excited state
What is the action spectrum used for?
Profiles the relative effectiveness of different wavelengths of radiation in driving a process
What happens when excited electrons fall back to the ground state in chlorophyll?
Photons are given off, creating fluorescence
What are the two parts of photosynthesis?
The light cycle and the Calvin cycle
What is the main output of the light cycle in photosynthesis?
Oxygen
Which route for electron flow in the light cycle generates surplus ATP to satisfy the higher demand in the Calvin cycle?
Linear
What happens when a photon hits an electron in a pigment during the light cycle?
The electron is passed among pigment molecules
What is the role of Ps II in the light cycle of photosynthesis?
Splitting water into hydrogen and oxygen
What is the primary function of the Calvin cycle in photosynthesis?
To synthesize glucose using ATP and NADPH
What is the primary function of the cyclic electron flow in photosynthesis?
To generate surplus ATP
Which photosystem is exclusively involved in cyclic electron flow?
Photosystem I
What is the high-energy molecule produced during photophosphorylation?
ATP
Which component of the electron transport chain is responsible for creating an electrochemical gradient by pumping protons across the membrane?
Cytochrome complex
What evolutionary role is associated with cyclic electron flow in photosynthesis?
Protect cells from light-induced damage
What must the oxidizing power of P680+ be based on the information provided?
High
What drives ATP synthesis in mitochondria and chloroplasts?
Protons diffusing back into the matrix and stroma
Where does carbon fixation occur?
Rubisco catalyzed phase
What is the net synthesis per cycle in The Calvin Cycle for G3P?
1
Where is excess sugar stored in plants?
Starch in roots, tubers, seeds, and fruits
What does the light-independent reaction refer to in photosynthesis?
Calvin Cycle
Which process is responsible for the production of oxygen in photosynthesis?
Light reactions
Study Notes
The Light Cycle
- The light cycle has two possible routes for electron flow: linear and cyclic.
- Linear flow involves both photosystems and produces ATP and NADPH using light energy.
- Cyclic flow uses only photosystem I and produces ATP, but not NADPH.
Linear Flow
- A photon hits an electron in a pigment and the excited electron is passed among pigment molecules until it hits P680.
- The excited electron from P680 is transferred to the primary electron acceptor.
- P680+ is now missing an electron and is a strong oxidizing agent.
- Water is split by enzymes, and the electrons are transferred from the hydrogen atoms to P680+, thus reducing it to back P680.
Cyclic Flow
- Cyclic electron flow generates surplus ATP, satisfying the higher demand in the Calvin cycle.
- No oxygen is released in cyclic electron flow.
Photosynthesis
- Photosynthesis takes place in the chloroplasts.
- Chloroplasts contain thylakoid membranes, which contain photosystems.
- Photosystems contain light-harvesting complexes and reaction-center complexes.
- There are two types of photosystems: photosystem II and photosystem I.
Photosystem II
- Photosystem II functions first and best absorbs light at 680nm.
- The reaction-center chlorophyll a is called P680.
Photosystem I
- Photosystem I best absorbs light at 700nm.
- The reaction-center chlorophyll a is called P700.
- Comes after PSII.
Chlorophyll
- Chlorophyll is a pigment that absorbs visible light.
- Different pigments absorb different wavelengths.
- Chlorophyll a is the main photosynthetic pigment.
- Accessory pigments, such as chlorophyll b, broaden the light spectrum that can be used for photosynthesis.
- Accessory pigments called carotenoids absorb excessive light that would damage chlorophyll.
Chlorophyll Absorption
- An absorption spectrum is a graph plotting a pigment's light absorption versus wavelength.
- The absorption spectrum of chlorophyll a suggests that violet-blue and red light work best for photosynthesis.
- An action spectrum profiles the relative effectiveness of different wavelengths of radiation in driving a process.
Electromagnetic Spectrum
- The electromagnetic spectrum is the entire range of electromagnetic energy.
- Light is a form of electromagnetic energy, also called electromagnetic radiation.
- Light is packaged into discrete units called photons.
Calvin Cycle
- The Calvin cycle creates glucose from ATP and NADPH.
- The Calvin cycle is where carbon fixation takes place.
- Carbon fixation is the process of turning atmospheric carbon dioxide into glucose.
- The Calvin cycle has three phases: carbon fixation, reduction, and regeneration of the CO2 acceptor.
- For net synthesis of 1 G3P, the cycle must take place three times, fixing 3 molecules of CO2.
Test your knowledge on photosynthesis and light energy in this quiz. Learn about the process of photosynthesis, oxidation, reduction, and the role of light in energy production.
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