Presentation on theme: "Photosynthesis Energy, from light to sugar. Photosynthesis Photosynthesis is the process by which the energy of a photon is captured and stored in the."— Presentation transcript:
Photosynthesis Photosynthesis is the process by which the energy of a photon is captured and stored in the chemical bonds of a carbohydrate.
Light ‘All around us, moving through us, are countless photons, little packets of pure energy, each moving as fast as possible, and each riding a wave…’
Light Light, or visible light, is electromagnetic radiation of a wavelength that is visible to the human eye (about 400–700 nm) In a scientific context, the word light is sometimes used to refer to the entire electromagnetic spectrum Light is composed of an elementary particle called a photon
Photons Photons are packets of energy, moving at 3x10 8 m/s. As they travel they move in a waveform The distance between two peaks is a called the wavelength The number of wavelengths that pass in a given time period is the frequency
Electromagnetic Radiation Higher frequency = short wavelength = higher energy photon
Pigment A pigment is a material that changes the color of light it reflects as the result of selective color absorption (it absorbs specific photons of certain wavelengths and reflects other photons) Living organisms use pigment molecules transfer light energy to electrons chlorophyll The main photosynthetic pigment found in plants is chlorophyll
Plant Pigments Plants use a variety of pigments to capture a larger range of the light spectrum
Light Dependent Reaction 1.Water is split, O 2 is released electrons pass to chlorophyll at reaction center protons are released into thylakoid lumen 2.Photons strike photosystem II resonance energy excites electrons 3.Excited electrons are passed through electron transport chain to photosystem I protons pumped into thylakoid lumen ATP synthesized through chemiosmosis 4.Photons strike photosystem I 5.Excited electrons are passed to NADP+
Redox and Resonance redox Electrons can be donated – redox resonance Electrons can transfer energy to nearby electrons - resonance
Light dependent reaction Photolysis –water molecule is lysed by enzyme Photoactivation –e - are excited by photon energy Photophosphorylation –e - are passed through electron transport chain –ATP generated by chemiosmosis Photoreduction –e - are accepted by NADP+, it is reduced to NADPH
Also known as the Calvin cycle Occurs in the stroma of the chloroplast Combines CO 2 with electrons from NADPH and energy supplied by ATP Ribulose biphospate (RuBp) is the initial reactant and the final product Rubisco adds CO 2 to RuBp (carbon fixation) Each turn creates 1 G3P (3 carbons) that exits the cycle 2 G3Ps are then combined to make 1 glucose
The Light Independent Reaction : The Calvin Cycle
Factors affecting rate of photosynthesis The rate of photosynthesis can be measured directly by oxygen production, or indirectly by increase in biomass Several variables will influence the rate of photosynthesis 1.Light intensity – amount of sunlight 2.Atmospheric carbon dioxide concentration 3.Temperature
Limiting Factor The variable which determines the rate of photosynthesis is called the limiting factor The limiting factor will vary between environments
Factors affecting rate of photosynthesis Can you give a reasoned explanation for the shape of these curves?
Review Write a description of the light dependent reaction, include… –Photolysis, photoactivation, photophosphorylation, and photoreduction Explain how the light independent reaction (calvin cycle) uses the products of the light dependent reaction. From memory draw the graphs showing the effects of the three factors that limit the rate of photosynthesis.