unit 3 aos 2 Flashcards
Photosynthesis equation
Carbon dioxide + water -> Glucose + oxygen + water
what is photosynthesis
is the process of converting light energy to chemical energy stored in glucose. Produces Glucose
Chloroplast
The location where photosynthesis occurs
Light Dependent Stage location, inputs, outputs
location = grana
inputs = h2o, ADP +Pi, NADP
outputs = O2, ATP, NADPH
Light dependent stage description
Light energy is captured by the chlorophyll and used to split water molecules into H+, oxygen atoms and
electrons.
● Oxygen atoms join to form O2 (oxygen gas) and NADP collects H+ and electrons forming NADPH
● The energy harnessed by chlorophyll is also used to form ATP
● The ATP and NADPH are then used in the light independent reaction.
Light Independent Stage location, inputs, outputs
Location = stroma
Inputs = CO2, ATP, NADPH
Outputs = glucose, H2O, ADP +pi, and NADP
Light independent reaction description
In a series of reactions similar to the krebs cycle, carbon dioxide is turned into glucose.
● The ATP produced in the light dependent stage provides the energy to drive the reaction
● The NADPH also provides hydrogen and electrons that are needed in the reactions
● RuBisCo is an important enzyme in the first stage of carbon fixation (the light
independent reaction) stage of photosynthesis.
Factors affecting photosynthesis rate
- Concentration of carbon dioxide
- Light intensity
- Water availability
- enzyme related factors (temp, pH)
- enzyme inhibitors
CO2 concentration
As CO2 concentration increases, the rate of photosynthesis also increases until a saturation point is hit (a limiting factor preventing increase)
light intensity
as light intensity increases, the rate of photosynthesis also increases until a saturation point is reached
water availability
In high or low temperatures, plants may close their stomata’s to reduce water loss. This prevents the uptake of CO2 and therefore lower the rate of photosynthesis
Enzyme related factors (temp)
photosynthesis rate increases as temperature increases, until reaches optimal temp and then begins to decrease as enzymes have denatured
Enzyme related factors (pH)
Enzymes involved in photosynthesis have an optimal pH, which results in an optimal rate of photosynthesis
enzyme inhibitors
reduce the rate of cellular respiration and photosynthesis by impacting the enzymes ability to bind with the substrate
- Competitive Inhibitors
- Noncompetitive inhibitors
Competitive inhibitors
- Decrease enzyme activity
- competing with the substrate for the active site
Non-competitive inhibitors
- molecule attaches to the site and changes the shape, decreasing the activity
Rubisco
Rubisco is an enzyme and the role of rubisco is to bind to CO2 and fix the carbon into organic molecules to ultimately produce glucose. Without RuBisCo plants cant undergo photosynthesis
Photorespiration
Sometimes rubisco can bind with O2, known as photorespiration. This process is wasteful as it wastes energy and reduces the rate of photorespiration
Factors affecting RuBisCo
Temperature and O2 concentartion
O2/ Rubisco
As the O2 of the plant increases Rubisco binds to O2 more easily increasing the rate of photorespiration
Plants have strategies to reduce the rate of photorespiration
- C3 Plants - Doesn’t have any features to reduce photorespiration, undergoes a normal Calvin cycle
- C4 Plants - separate Calvin cycle into 2 stages (adapted to hot dry conditions)
- CAM plants - separate Calvin cycle into 2 stages occurring at different times of the day (adapted to hot dry conditions)
C3 Plants
- Rubisco carbon from carbon dioxide during the Calvin cycle forming a 3 - carbon compound
- Occurs in mesophyll cells
- More susceptible to photorespiration in hotter/dryer conditions
- All the trees, rice, fruits and veges
C4 Plants
Calvin cycle occurs in 2 stages
- Light depended stage stays the same as C3 plants
- Carbon fixation occurs in the mesophyll cells, via an enzyme called PEP Carboxylate to produce a compound called Malate
- Malate travels to bundle sheaths and releases CO2 to rubisco for the carbon cycle to continue. Maintains high Co2 levels to reduce photorespiration
- Uses ATP, making it more energy expensive
- includes sugarcane and corn
CAM Plants
- During night hours the stomata is open to collect CO2 (forming malate)
- During the day, stomata is closed (avoiding water loss). Malate releases CO2 to rubisco for the Calvin cycle to continue.
- Maintains a high amount of CO2, reducing photorespiration
- Uses ATP and is therefore more energy expensive then C3 plants
- Cacti, pinepapples
