Chapter 8 Flashcards
What is the overall equation for photosynthesis?
6CO2 + 12H2O → C6H12O6 + 6H2O + 6O2
Which organisms carry out oxygenic photosynthesis?
Cyanobacteria, 7 groups of algae, and all land plants.
What are the two main stages of photosynthesis?
Light-dependent reactions and carbon fixation reactions (light-independent reactions).
What occurs during light-dependent reactions?
They require light to capture energy from sunlight, make ATP, and reduce NADP+ to NADPH.
What occurs during carbon fixation reactions?
They do not require light and use ATP and NADPH to synthesize organic molecules from CO2.
What is the thylakoid membrane?
The internal membrane of chloroplasts that contains chlorophyll and other photosynthetic pigments.
What are grana?
Stacks of flattened sacs of thylakoid membrane.
Who demonstrated that plant substance is not solely derived from soil?
Jan Baptista van Helmont.
What did Joseph Priestly discover about vegetation?
Living vegetation adds something to the air.
What did Jan Ingenhousz propose about plants?
Plants carry out a process that uses sunlight to split carbon dioxide into carbon and oxygen (O2 gas).
What was F.F. Blackman’s conclusion about photosynthesis?
Photosynthesis is a multistage process, only one portion of which uses light directly.
What did C. B. van Niel find about purple sulfur bacteria?
They do not release O2 but accumulate sulfur.
What is the absorption spectrum?
The range and efficiency of photons a molecule is capable of absorbing.
What are pigments?
Molecules that absorb light energy in the visible range.
What is the role of chlorophyll a?
It is the main pigment in plants and cyanobacteria that can convert light energy to chemical energy.
What is the structure of chlorophyll?
It contains a porphyrin ring with a magnesium ion at the center.
What is the action spectrum?
The relative effectiveness of different wavelengths of light in promoting photosynthesis.
What are carotenoids?
Accessory pigments that can absorb photons with a wide range of energies and scavenge free radicals.
What is the function of the antenna complex in photosystems?
It captures photons and feeds the captured light energy to the reaction center.
What happens when a chlorophyll in the reaction center absorbs a photon?
An electron is excited to a higher energy level and can be transferred to the primary electron acceptor.
What is cyclic photophosphorylation?
A process in sulfur bacteria that generates ATP via electron transport using only one photosystem.
What is the role of photosystem II?
It can generate an oxidation potential high enough to oxidize water.
What is the Calvin cycle?
A process that uses ATP and NADPH to build carbohydrates from CO2.
What is the key step in the Calvin cycle?
The attachment of CO2 to RuBP to form PGA.
What are the three phases of the Calvin cycle?
Carbon fixation, reduction, and regeneration of RuBP.
What are the three phases of the Calvin cycle?
- Carbon fixation: RuBP + CO2 → PGA
- Reduction: PGA is reduced to G3P
- Regeneration of RuBP: PGA is used to regenerate RuBP
How many turns of the Calvin cycle are needed to produce G3P and glucose?
3 turns incorporate enough carbon to produce a new G3P.
6 turns incorporate enough carbon for 1 glucose.
What is the direct product of the Calvin cycle?
Glucose is not a direct product of the Calvin cycle.
G3P is a 3 carbon sugar used to form sucrose.
What is G3P used for in plants?
G3P is used to form sucrose, the major transport sugar in plants, and to make starch, an insoluble glucose polymer stored for later use.
How do photosynthesis and respiration interact?
Photosynthesis uses the products of respiration as starting substrates, while respiration uses the products of photosynthesis as starting substrates.
What are the two enzymatic activities of Rubisco?
- Carboxylation: Addition of CO2 to RuBP, favored under normal conditions.
- Photorespiration: Oxidation of RuBP by the addition of O2, favored when stomata are closed in hot conditions.
What are the types of photosynthesis?
- C3: Plants that fix carbon using only C3 photosynthesis (the Calvin cycle).
- C4 and CAM: Add CO2 to PEP to form a 4 carbon molecule using PEP carboxylase.
What is the process of carbon fixation in C4 plants?
C4 plants initially fix carbon using PEP carboxylase in mesophyll cells, producing oxaloacetate, which is converted to malate and transported to bundle-sheath cells.
What is a disadvantage of the C4 pathway?
To produce a single glucose requires 12 additional ATP compared with the Calvin cycle alone.
What is unique about CAM plants?
CAM plants, such as cacti and pineapples, open their stomata at night and close them during the day, fixing CO2 using PEP carboxylase during the night.
How do CAM plants minimize photorespiration?
When stomata are closed during the day, organic acids are decarboxylated to yield high levels of CO2, driving the Calvin cycle.
How do C4 and CAM pathways differ?
C4: Two pathways occur in different cells. CAM: C4 pathway at night and the C3 pathway during the day.
