TEST 4 - PHOTOSYNTHESIS Flashcards
Photosynthesis
The process by which plants, using visible light from the sun, convert energy into chemical energy.
The Sun
Primary energy source for life, providing light for photosynthesis.
Visible Light
Component of the electromagnetic spectrum used by plants for photosynthesis, with a wavelength range of 400–700 nm
Photoautotrophs
Organisms, such as plants, that use light to produce their own food
Spectrum of Light for Photosynthesis
The range of light wavelengths from 400 nm (violet/blue) to 700 nm (red), absorbed by plants for photosynthesis
Wavelengths for Photosynthesis
400-525 nm: violet/blue
525-625 nm: green/yellow
625-700 nm: orange/red
Pigments
Chemical molecules that absorb specific wavelengths of light and reflect others, determining the color we see
Photosynthetic Pigments
Pigments like chlorophyll a and b, carotenoids, xanthophylls, and anthocyanins, which absorb light for photosynthesis
Chlorophyll A
Main pigment in photosynthesis; absorbs violet-blue and red light, converting it to chemical energy.
Chlorophyll B
Accessory pigment in photosynthesis; absorbs blue/green to orange/red light
Carotenoids, Xanthophylls, Anthocyanins
Accessory pigments that absorb various wavelengths from violet to green
Chloroplast
Organelle in plant cells where photosynthesis occurs, containing structures like thylakoids and stroma
Thylakoid
Membrane structures in chloroplasts, arranged in stacks called grana, containing chlorophyll; site of light-dependent reactions
Grana
Stacks of thylakoids within chloroplasts where light-dependent reactions occur
Stroma
Fluid-filled area within the inner membrane of chloroplasts, outside the thylakoids; site of light-independent reactions
Action Spectrum
- Wavelength of light VS efficiency of photosynthesis
- Most graphs will show: % use of light OR rate of photosynthesis
Absorption Specturm
Wavelengths of light are best absorbed by the main photosynthesis pigment.
Photosynthesis Equation
6CO2 + 12H2O → C6H12O6 + 6O2 + 6H2O
Light Energy
Energy needed in the form of photons for photosynthesis.
ATP
Used and generated during photosynthesis to store and transfer energy.
NADP⁺
Electron carrier that combines with two electrons and two hydrogen ions to form NADPH during photosynthesis.
NADPH
Reduced form of NADP⁺, produced when NADP⁺ receives electrons and is essential in the Calvin cycle for glucose production.
Glucose and Oxygen
Products of photosynthesis, where glucose is used as an energy source and oxygen is released as a byproduct.
NADP (Full Form)
Nicotinamide adenine dinucleotide phosphate; an electron carrier molecule involved in photosynthesis.
Light-Dependent Reactions
Reactions that occur in the thylakoid membranes, requiring light energy to produce ATP, NADPH, and oxygen.
Photosystem II (680 nm)
Pigment complex in chlorophyll involved in photolysis, active transport of H+ ions, and ATP synthesis.
Photosystem I (700 nm)
Pigment complex that facilitates the reduction of NADP⁺ to NADPH.
Thylakoid
Membrane structure within chloroplasts where light-dependent reactions occur.
Photolysis
Process where photon energy splits water molecules, producing oxygen, creating a 𝐻+ gradient, and replacing electrons in chlorophyll.
Electron Transport Chain (ETC) in Photosynthesis
A chain where energized electrons move and lose energy used for ATP synthesis.
Summary of Light Reactions
- Inputs: Light, water, ADP, and NADP+
- Outputs: ATP, NADPH, and 𝑂2 (waste).
Light-Independent Reactions (Calvin Cycle)
Reactions occurring in the stroma that use 𝐶𝑂2, ATP, and NADPH to produce glucose.
Carbon Fixation
The process of incorporating CO2 into organic molecules in the Calvin cycle.
Role of NADPH in Calvin Cycle
Provides electrons and energy for the reduction of carbon molecules, aiding in glucose production.
External Factors Affecting Photosynthesis
Conditions like temperature, light intensity, and CO2 concentration that impact the rate of photosynthesis.
Light Intensity
Low: Causes a shortage of NADPH and ATP, limiting the rate of photosynthesis.
High: As light intensity increases, all chlorophyll eventually becomes saturated, reaching a maximum rate of photosynthesis.
Rate Limiting Step: The reduction of G3P (glycerate-3-phosphate) is the rate-limiting step; without NADPH, reduction cannot occur.
Temperature Effect on Enzymes
Enzymes that catalyze the Calvin Cycle work more slowly at low temperatures, causing NADPH accumulation.
Optimal Temp: Photosynthesis works best at around 38°C for many plants.
High: The enzyme that fixes carbon, G3P carboxylase, may denature, limiting carbon fixation and leading to NADPH accumulation.
CO₂ Concentration
CO₂ is a substrate for the Calvin Cycle reactions. Low CO₂ concentrations limit carbon fixation, while high concentrations are not a limiting factor.
Measuring Oxygen Production
Measuring oxygen production allows for determining the volume of gas produced, indicating the rate of photosynthesis.
Measuring CO₂ Uptake
CO₂ uptake is hard to measure directly; if absorbed, it increases pH. Bromothymol blue indicates CO₂ presence by turning yellow.
Biomass Measurement
Involves taking equal-sized plant samples at intervals, measuring dry mass increase to determine photosynthetic rate. Conditions must remain consistent
