Photosynthesis: An Overview Chapter 8 Section 2 Photosynthesis: An Overview
Photosynthesis Plants use the energy of sunlight to convert water and carbon dioxide into oxygen and high-energy carbohydrates (sugars and starches)
Investigating photosynthesis Voan Helmont’s experiments -
Investigating photosynthesis Voan Helmont’s experiments – In 1600’s, he devised a way to find out if plants grew by taking material out of the soil
Investigating photosynthesis Voan Helmont’s experiments – In 1600’s, he devised a way to find out if plants grew by taking material out of the soil Determined the mass of a pot of dry soil and a small seedling Planted the seedling in the pot of dry soil Watered the plant regularly
Investigating photosynthesis Voan Helmont’s experiments – Results –
Investigating photosynthesis Voan Helmont’s experiments – Results – At the end of 5 years the seedling had gained about 75 kg. the mass of the soil was almost unchanged
Investigating photosynthesis Voan Helmont’s experiments – Results – At the end of 5 years the seedling had gained about 75 kg. the mass of the soil was almost unchanged Conclusions –
Investigating photosynthesis Voan Helmont’s experiments – Results – At the end of 5 years the seedling had gained about 75 kg. the mass of the soil was almost unchanged Conclusions – Most of the mass gained had come from water
Investigating photosynthesis Voan Helmont’s experiments – Conclusions told part of the story of the growth. What was missing?
Investigating photosynthesis Voan Helmont’s experiments – Conclusions told part of the story of the growth. What was missing? Carbohydrate – ‘hydrate’ – water ‘carbo’ – from carbon dioxide
Investigating photosynthesis Priestley’s experiments – 100 years after Helmont’s experiments Experiment set-up
Investigating photosynthesis Priestley’s experiments – 100 years after Helmont’s experiments Experiment set-up Placed a candle under a glass jar
Investigating photosynthesis Priestley’s experiments – 100 years after Helmont’s experiments Experiment set-up Placed a candle under a glass jar Results
Investigating photosynthesis Priestley’s experiments – 100 years after Helmont’s experiments Experiment set-up Placed a candle under a glass jar Results Flame of candle eventually goes out
Investigating photosynthesis Priestley’s experiments – 100 years after Helmont’s experiments Experiment set-up Placed a candle under a glass jar Results Flame of candle eventually goes out Conclusions
Investigating photosynthesis Priestley’s experiments – 100 years after Helmont’s experiments Experiment set-up Placed a candle under a glass jar Results Flame of candle eventually goes out Conclusions Something in air was necessary to keep flame burning
Investigating photosynthesis Priestley’s experiments – Additional experiments
Investigating photosynthesis Priestley’s experiments – Additional experiments If placed a live sprig of mint under the jar and allowed a few days to pass, the candle could be relighted and remain lighted for a while
Investigating photosynthesis Priestley’s experiments – Additional experiments If placed a live sprig of mint under the jar and allowed a few days to pass, the candle could be relighted and remain lighted for a while Conclusions
Investigating photosynthesis Priestley’s experiments – Additional experiments If placed a live sprig of mint under the jar and allowed a few days to pass, the candle could be relighted and remain lighted for a while Conclusions The mint plant had produced the substance required for burning - oxygen
Investigating photosynthesis Ingenhousz experiments –
Investigating photosynthesis Ingenhousz experiments – Dutch scientist who later showed that the effect observed by Priestley occurred only when the plant was exposed to light
Investigating photosynthesis Ingenhousz experiments – Dutch scientist who later showed that the effect observed by Priestley occurred only when the plant was exposed to light Conclusion?
Investigating photosynthesis Ingenhousz experiments – Dutch scientist who later showed that the effect observed by Priestley occurred only when the plant was exposed to light Conclusion – Light is necessary for plants to produce oxygen
Investigating photosynthesis The experiments performed by these and other scientists reveal that In the presence of light
Light energy chloroplast
Investigating photosynthesis The experiments performed by these and other scientists reveal that In the presence of light Plants transform carbon dioxide and water
Light energy chloroplast Carbon dioxide + water
Investigating photosynthesis The experiments performed by these and other scientists reveal that In the presence of light Plants transform carbon dioxide and water Into carbohydrates and release oxygen
Light energy chloroplast Carbon dioxide + water Sugars + oxygen
The Photosynthesis Equation light 6CO2 + 6H2O C6H12O6 + 6O2 carbon dioxide + water sugar + oxygen
Light and Pigments In addition to water and carbon dioxide, photosynthesis requires?
Light and Pigments In addition to water and carbon dioxide, photosynthesis requires light and chlorophyll, a molecule in chloroplasts.
Light and Pigments Energy from the sun travels to the Earth in many forms. One of these forms is light (sunlight) which your eyes perceive as ‘white light’ It is actually a mixture of different wavelengths of light Many of these wavelengths are visible to your eyes and are referred to as the visible spectrum R O Y G B I V
Light and Pigments Plants gather the sun’s energy with light-absorbing molecules called pigments.
Light and Pigments Plants gather the sun’s energy with light-absorbing molecules called pigments. The plants principal pigment is chlorophyll
Light and Pigments Plants gather the sun’s energy with light-absorbing molecules called pigments. The plants principal pigment is chlorophyll There are 2 main types of chlorophyll chlorophyll a and chlorophyll b
Chlorophyll absorbs light very well in the blue and red regions Absorption of light by Chlorophyll a and chlorophyll b Chlorophyll b Chlorophyll a Chlorophyll absorbs light very well in the blue and red regions However, it does not absorb it very well in the green and yellow regions
Light and Pigment Because light is a form of energy, any compound that absorbs light also absorbs the energy from that light.
Light and Pigment Because light is a form of energy, any compound that absorbs light also absorbs the energy from that light. When chlorophyll absorbs light much of the energy is transferred directly to electrons in the chlorophyll molecules, raising the energy levels of these electrons
Light and Pigment Because light is a form of energy, any compound that absorbs light also absorbs the energy from that light. When chlorophyll absorbs light much of the energy is transferred directly to electrons in the chlorophyll molecules, raising the energy levels of these electrons These high energy electrons make photosynthesis work