Photosynthesis Flashcards
(24 cards)
What autotrophs are responsible for 90% of global photosynthesis?
Algae and cyanobacteria
When was the establishment of the first chloroplasts in eukaryotes?
1.5 billion years ago
What is the chemical formula for photosynthesis?
6CO2 + 6H2O = C6H12O6 + 6O2
What are the two types of photosynthetic pigments?
Chlorophylls; absorb blue and red light
Carotenoids; absorb purple light
What are the two classes of chlorophyll pigment?
Chlorophyll a (bluish green pigment)
Chlorophyll b (yellowish green pigment)
What are the three classes of carotenoid pigments?
Xanthophyll (yellow pigment)
Carotene (orange pigment)
Phaeophytin (Grey pigment)
What is the role of pigment molecules in light harvesting in photosynthesis?
Light is collected by around 300 pigment molecules that are bound to light-harvesting protein complexes located in the thylakoid membrane.
Where in the chloroplast do the different stages of photosynthesis occur?
The light stage; In the thylakoid.
The Calvin cycle; in the stroma.
What is the latest CO2 reading?
350-450 ppm
How is water used during photosynthesis?
Water is used as an e- source and oxygen is released.
What does the light reaction generate which feeds into the Calvin cycle?
NADPH and ATP
What is Rubisco?
Most abundant protein on Earth.
Big enzyme that needs to be at high concentration.
Plants invest a lot of energy to produce it.
Not always efficient in photosynthesis.
What happens during the Carbon Fixation phase of the Calvin Cycle?
Ribulose 1,5-bisphosphate (RuBP) reacts with CO2
to form 2 x 3
carbon molecule 3-phosphoglyercate
What happens during the Reduction phase of the Calvin Cycle?
3-phosphoglyceate forms glyceraldehyde-3-phosphate via reduction
by ATP and NADPH.
One molecule of glyceraldehyde-3-phosphate is gained.
What happens during the Regeneration phase of the Calvin Cycle?
Ribulose 1,5-bisphosphate (RuBP) is regenerated by the cycle from
Glyceraldehye-3- phosphate.
What happens to the sugar synthesized in the carbon cycle?
It is transported as sucrose and stored as starch.
What happens if we don’t have CO2 during the Calvin Cycle?
Photorespiration;
1. Oxygen is consumed, not produced.
2. Carbon Dioxide is produced not consumed.
3. There is a net loss of ATP, not a gain.
What is the trade-off with stomata during hot, dry climates?
Stomata open;
Water loss
Stomata closed;
Lack of carbon dioxide
Build up of oxygen
Photorespiration
How did the Earth allow Rubisco to be inefficient?
Because the Earth’s environment was very different when Rubisco first evolved.
What are the differences in photosynthesis of C4 plants?
The Calvin cycle is physically separated from O2.
Uses a different fixation enzyme; PEP carboxylase.
CO2 is fixed twice.
What type of plant evolved convergently with C4 plants?
CAM plants (cacti)
What are the three main factors affecting photosynthesis?
Temperature
CO2 concentration
Light intensity
What factors of photosynthesis better benefit each plant type?
C3 plants benefit off high CO2 levels.
C4 benefit off of rising temperatures and light.
What will happen if CO2 doubles from preindustrial levels?
Rice (C3) yields will increase 36%.
But Corn (C4) yields will increase by only 24%.
