Photosynthesis 2.0 Flashcards
What is photosynthesis?
The way in which plants make their own food using light.
What are plants classified as?
Autotrophs.
Is photosynthesis anabolic or catabolic?
Anabolic.
What is the aim of photosynthesis?
To get plants to make food.
How is light absorbed in photosynthesis?
Chlorophyll in the leaf.
What are the reactants of photosynthesis?
Carbon dioxide, water, and light.
What are the products of photosynthesis?
Glucose and oxygen.
Where does CO2 come from in photosynthesis?
Through stomata from the atmosphere.
Where does water come from in photosynthesis?
Through roots - osmosis.
Where does light come from in photosynthesis?
Sun and artificial light (lamps, etc.).
What impacts the rate of photosynthesis?
Temperature (enzymes), light intensity, and CO2 levels.
What is the effect of increasing light intensity in a greenhouse on plants?
Supplies more light which stimulates plant crop growth, increasing the growth rate for plants.
What is the effect of adding artificial CO2 to a greenhouse on plants?
Supplies more carbon atoms to the dark stage of photosynthesis for glucose formation.
What is the effect of increasing temperature of a greenhouse on plants?
Increases the rate of photosynthesis as it increases enzyme activity.
What does ADP stand for?
Adenosine diphosphate.
What is ADP?
Low energy molecule made from adenosine & 2 phosphates.
How is ATP formed?
Add one phosphate to ADP.
What is phosphorylation?
Adding a phosphate.
What does ATP stand for?
Adenosine triphosphate.
What is Stage 1 of photosynthesis?
The light stage (Cyclic phosphorylation).
Why is the light stage called ‘the light stage’?
As it requires light.
What is the summary of the light stage (Cyclic phosphorylation)?
Light energy is absorbed by chlorophyll molecules, high energy electrons leave chlorophyll, are passed through electron acceptors & lose energy, combining with ADP + P to form ATP & H2O, and low energy electrons return to chlorophyll.
Why is it referred to as cyclic phosphorylation?
As electrons return to the chlorophyll at the end (low energy).
What are the products formed in the light stage and their fate?
ATP (used in dark stage), H2O (used in photolysis or lost via stomata in transpiration).
Why is oxygen a waste product of the light stage?
As it is not needed for the light stage to occur.
What is Pathway 2 of the light stage of photosynthesis?
Non-cyclic phosphorylation.
What is the summary of the light stage (Non-Cyclic phosphorylation)?
✔ Light energy excites electrons in chlorophyll.
✔ Water is split → Electrons replace lost ones, O₂ released.
✔ Electrons move through the ETC, pumping H⁺ ions into the thylakoid.
✔ ATP is made as H⁺ flows through ATP synthase.
✔ Electrons are re-energized and used to form NADPH.
Produces ATP, NADPH, and O₂
Why is it referred to as non-cyclic phosphorylation?
As electrons do not return to chlorophyll.
What are the products formed during the light stage?
NADPH (supplies protons & electrons for dark stage), ATP (supplies energy for dark stage), and oxygen (used for respiration or released into the atmosphere).
What is the fate of high energy electrons?
Used to make NADPH and return to chlorophyll.
What are the two functions of NADPH?
Supply electrons and supply protons.
What is the source of protons (+) to make NADPH?
Photolysis (4e+).
Name another molecule other than chlorophyll that provides electrons in photosynthesis.
H2O.
What is photolysis?
The splitting of water using light energy during photosynthesis.
Why is it good that chlorophyll contains many chemicals?
Can absorb more energy.
What is the role of stomata in photosynthesis?
Allows CO2 into the plant which is required for photosynthesis.
What is the fate of the end products of the dark stage?
Return to light stage.
What are the functions of glucose?
Food for the plant and respiration.
What is the stage of photosynthesis controlled by enzymes?
The dark stage.
What is the method for investigating the effect of light intensity on the rate of photosynthesis?
Cut stem of Elodea, attach a paperclip, switch off lights, use sodium hydrogen carbonate, place in water bath at 25 degrees, count bubbles for 1 min, and repeat.
Why was Elodea used?
As it’s a green aquatic plant that can produce bubbles underwater.
Why was sodium hydrogen carbonate used?
To maintain CO2 levels.
What is the optimum temperature for enzyme activity?
Water bath at 25 degrees.
What factor was kept constant in the experiment?
CO2 levels - using sodium hydrogen carbonate.
What factor was varied in the experiment?
Light intensity - moved lamp a set distance closer to the plant each time.
Explain the shape of the graph drawn up from the experiment.
As light intensity increases, so does the number of bubbles, leveling off after reaching saturation point.
What does saturation point mean?
Point where the plant cannot photosynthesize any faster.
What is the importance of eliminating external light in the experiment?
To ensure the amount of bubbles produced is accurate due to the variable.
What are the X and Y axes of the graph for the rate of photosynthesis light intensity experiment?
X = light intensity, Y = rate.
What is the role of NADPH in the dark stage?
Transfer protons & electrons. CO2 is reduced to glucose.
What occurs in the dark stage
Energy from ATP
NADPH releases electrons and protons
CO2 combines with electrons and protons
to form glucose
