chapter 10 photosynthesis Flashcards
What are autotrophs?
Self-sufficient organisms that synthesize organic materials from inorganic sources like CO2 or nitrates.
What are photoautotrophs?
Autotrophs that use energy from the sun to make organic molecules from water and CO2.
What role do photoautotrophs play in ecosystems?
They are primary producers that feed themselves and most of the living world.
What are heterotrophs?
Organisms that derive energy from the intake and digestion of organic substances produced by other organisms.
What is the significance of bacteria in photosynthesis?
Bacteria started producing photosynthetic elements and oxygen about 2.5 billion years ago.
Where does photosynthesis occur?
In chloroplasts of plants, algae, some eukaryotes, and prokaryotes.
What are chloroplasts?
Sites of photosynthesis that evolved from photosynthetic bacteria, specifically cyanobacteria.
What is the stroma?
Dense fluid within chloroplasts that surrounds the thylakoid membrane and contains ribosomes and DNA.
What is a thylakoid?
Flattened membranous sac inside chloroplasts, often stacked in grana, containing molecular machinery for converting light energy to chemical energy.
What are the two processes of photosynthesis?
Light reactions and the Calvin cycle.
What occurs during light reactions?
Light is absorbed, water is split, O2 is released, and ATP and NADPH are produced.
What is chlorophyll’s role in photosynthesis?
Chlorophyll absorbs light; chlorophyll a and b have different functional groups and absorb different wavelengths.
What is the difference between absorbance spectrum and action spectrum?
- Absorbance spectrum shows which pigments absorb which wavelengths best
- Action spectrum shows which wavelengths are best for photosynthesis.
What are photosystems?
Complexes composed of a reaction center surrounded by light harvesting complexes; there are two types: PSI and PSII.
What happens to electrons during linear electron flow?
Electrons are absorbed by P680, passed to a primary electron acceptor, and then transferred through an electron transport chain.
What does P680 do in the photosystem?
Absorbs light and gives up an electron to a primary electron acceptor, requiring a new electron from water.
What is photophosphorylation?
The process of adding a phosphate group to ADP to form ATP using energy derived from the proton gradient.
What is P700’s role in photosystem I?
P700 donates electrons to NADP, resulting in the formation of NADPH.
What is the Calvin cycle?
A process that uses ATP and NADPH to fix CO2 and produce sugars.
What is the role of the enzyme rubisco in the Calvin cycle?
Rubisco is crucial for bringing carbon into the reaction by fixing CO2 with RuBP.
What are the three stages of the Calvin cycle?
- Fixation * Reduction * Regeneration
What is the function of stomata?
Allow CO2 to enter and O2 to exit, facilitating gas exchange.
What happens to stomata in hot, dry conditions?
They close to save water, which reduces CO2 access and photosynthesis.
What are C4 plants?
Plants that spatially separate carboxylases and evolved in hot, dry regions to increase biomass accumulation.
Give examples of C4 plants.
- Corn * Sugar cane * Sorghum * Pearl millet * Foxtail millet * Tef
What are CAM plants?
Plants that temporarily separate carboxylases, performing carbon fixation and the Calvin cycle at different times.
Give examples of CAM plants.
- Cactus * Orchid * Pineapple * Aloe vera
What is the main difference between C4 and CAM plants?
C4 plants spatially separate steps; CAM plants temporally separate steps.
What is the primary function of photosynthesis?
Photosynthesis converts light energy to the chemical energy of food
This process is essential for sustaining life on Earth.
What are the two major processes of photosynthesis?
The light reactions and the Calvin cycle
These processes work together to convert solar energy into chemical energy and produce sugars.
Where do chloroplasts likely originate from?
Chloroplasts likely evolved from photosynthetic bacteria
This endosymbiotic theory explains the origin of chloroplasts.
What is the stroma in chloroplasts?
The dense fluid within the chloroplast surrounding the thylakoid membrane
It contains ribosomes and DNA and is involved in organic molecule synthesis.
What happens during the light reactions of photosynthesis?
Light is absorbed, water is split, oxygen is released, and ATP and NADPH are produced
This stage occurs in the thylakoid membranes.
What are photosystems?
Composed of a reaction centre and light-harvesting complexes that absorb light
There are two types of photosystems: PSI and PSII.
What is the function of the Calvin cycle?
Uses ATP and NADPH to fix CO2 and produce sugars
This cycle occurs in the stroma of chloroplasts.
What are the three main steps of the Calvin cycle?
Fixation, Reduction, Regeneration
These steps are crucial for converting CO2 into carbohydrates.
What is a characteristic of C4 plants?
They spatially separate carboxylase from the Calvin cycle
C4 photosynthesis is advantageous in hot, dry climates.
What is the role of stomata in photosynthesis?
Allow CO2 to enter and O2 to exit, facilitating gas exchange
Stomata also contribute to water loss through evaporation.
What is CAM photosynthesis?
A mechanism that temporally separates carbon fixation and the Calvin cycle
Stomata open at night to reduce water loss.
Which plant is considered the most economically important C4 plant?
Corn
It is the fourth most economically important crop plant.
True or False: The Calvin cycle occurs in the thylakoid membranes.
False
The Calvin cycle takes place in the stroma.
Fill in the blank: Photosynthetic pigments absorb light at different _______.
[wavelengths]
This allows for a range of light absorption for photosynthesis.
What does the linear electron flow in photosynthesis generate?
ATP and NADPH
This process occurs during the light reactions.
True or False: All plants are photoautotrophs.
False
While most plants are photoautotrophs, there are exceptions.
What is the main pigment in photosynthesis?
Chlorophyll A
Chlorophyll B and carotenoids are accessory pigments.
