Photosynthesis Flashcards
What is photosynthesis?
A complex series of reactions that can be summarized as the following equation:
6 CO2 + 12 H2O + Light energy → C6H12O6 + 6 O2 + 6 H2O
Photosynthesis ____ the direction of electron flow compared to ____
reverses ; respiration
What type of process is photosynthesis?
A redox process in which H2O is oxidized and CO2 is reduced
Is photosynthesis an endergonic process?
Yes, meaning the energy boost is provided by light
What is a wavelength?
A measure of the distance between crests of the waves, ranging from less than a nanometer to more than a kilometer
Light is what type of energy?
Electromagnetic energy, also called electromagnetic radiation
What are pigments?
Substances that absorb visible light
What happens to the wavelengths that are absorbed?
They disappear
What happens to the wavelengths that are not absorbed?
They are reflected or transmitted
The absorption spectrum of chlorophyll a indicated that what colors will work best for photosynthesis and what color is the least effective?
violet-blue and red will work best while green is the least effective
What is the action spectrum?
A profile of the relative effectiveness of different wavelengths that confirms the effectiveness of violent-blue and red light
How do chlorophyll a and b differ?
CH3: chlorophyll a
CHO: chlorophyll b
What happens when a pigment molecule absorbs light?
One of its electrons goes from a ground state to an excited state, which is unstable
How do electrons fall back to the ground state?
In isolation, releasing excess energy as heat or light, an afterglow called fluorescence
What does a photosystem consist of?
A reaction-center complex surrounded by light-harvesting complexes
What is the reaction-center complex?
An association of proteins holding a special pair of chlorophyll a molecules and a primary electron acceptor
What is the light-harvesting complex?
Pigment molecules bound to proteins ; transfer energy of photons to the chlorophyll a molecules in the reaction-center complex
What are the two types of photosystems in the thylakoid membrane, numbered in order of their discovery
Photosystem II (PS II)
Photosystem I (PS I)
In mitochondria, protons are pumped to the ____ and drive ATP synthesis as they diffuse back into ______ ____
Intermembrane space ; mitochondrial matrix
In chloroplasts, protons are pumped into the ___ ___ and drive ATP synthesis on the ____ ____ of the membrane as they diffuse back into the ___
Thylakoid space ; stroma side ; stroma
Is the Calvin cycle anabolic or catablic?
Anabolic ; it builds sugar from smaller molecules using ATP and the electrons carried by NADPH
Where have alternative mechanisms of carbon fixation evolved?
In hot, arid climates
Most plants are what?
C3 plants, in which the initial fixation of CO2, via rubisco, forms a three-carbon compound
What is photorespiration?
When rubisco binds with O2 instead of CO2, producing a two-carbon compound
