UNDERSTANDINGS
- Photosynthesis is the production of carbon compounds in cells using light energy
- Visible light has a range of wavelengths, with violet the shortest wavelength and red the largest
- Chlorophyll absorbs red and blue light most effectively, and reflects green light more than other colors
- Oxygen is produced in photosynthesis from the photolysis of water
- Energy is produced in photosynthesis from the photolysis of water
- Temperature, light intensity, and carbon dioxide concentration are possible limiting factors on the rate of photosynthesis
APPLICATIONS AND SKILLS
- Application: Changes to the Earth's atmosphere, oceans, and rock deposition due to photosynthesis
- Skill: Drawing an absorption spectrum for chlorophyll, and an action spectrum for photosynthesis
- Skill: Design of experiments to investigate the effect of listing factors on photosynthesis
- Skill: Separation of photosynthetic pigments by chromatograph
GUIDANCE
- Students should know that visible light has wavelengths between 400 and 700 nm, but they are not expected to recall wavelengths of specific colors of light
- Water free of dissolved carbon dioxide for photosynthesis experiments can be produced by boiling and cooling water
- Paper chromatography can be used to separate photosynthetic pigments but thin layer chromatography gives better results
Photosynthesis converts light energy into chemical energy;
Plants and other organisms produce foods that start food chains. We count on the Sun as a constant energy source for both warmth and food production for all of our planet. However, the sunlight that strikes Earth must be converted into a form of chemical energy in order to be useful to all non-photosynthetic organisms. The most common chemical energy produced from photosynthesis is the molecule glucose.
Plants use the pigment chlorophyll to absorb light energy;
The vast majority of plants leaves appear green to our eyes. If you were able to zoom into leaf cells and look around you, you would see that the only structures in a leaf that are actually green are the chloroplasts. Plants contain a variety of pigments in chloroplasts. The photosynthetic pigment that dominates in most plants species is the molecule chlorophyll.
Plants make use of the same part of electromagnetic spectrum that our eyes are able to see. We call this the visible portion of the spectrum. Sunlight is actually a mixture of different colors of light. You can see these colors when let sunlight pass through a prism
- Photosynthesis is the production of carbon compounds in cells using light energy
- Visible light has a range of wavelengths, with violet the shortest wavelength and red the largest
- Chlorophyll absorbs red and blue light most effectively, and reflects green light more than other colors
- Oxygen is produced in photosynthesis from the photolysis of water
- Energy is produced in photosynthesis from the photolysis of water
- Temperature, light intensity, and carbon dioxide concentration are possible limiting factors on the rate of photosynthesis
APPLICATIONS AND SKILLS
- Application: Changes to the Earth's atmosphere, oceans, and rock deposition due to photosynthesis
- Skill: Drawing an absorption spectrum for chlorophyll, and an action spectrum for photosynthesis
- Skill: Design of experiments to investigate the effect of listing factors on photosynthesis
- Skill: Separation of photosynthetic pigments by chromatograph
GUIDANCE
- Students should know that visible light has wavelengths between 400 and 700 nm, but they are not expected to recall wavelengths of specific colors of light
- Water free of dissolved carbon dioxide for photosynthesis experiments can be produced by boiling and cooling water
- Paper chromatography can be used to separate photosynthetic pigments but thin layer chromatography gives better results
Photosynthesis converts light energy into chemical energy;
Plants and other organisms produce foods that start food chains. We count on the Sun as a constant energy source for both warmth and food production for all of our planet. However, the sunlight that strikes Earth must be converted into a form of chemical energy in order to be useful to all non-photosynthetic organisms. The most common chemical energy produced from photosynthesis is the molecule glucose.
Plants use the pigment chlorophyll to absorb light energy;
The vast majority of plants leaves appear green to our eyes. If you were able to zoom into leaf cells and look around you, you would see that the only structures in a leaf that are actually green are the chloroplasts. Plants contain a variety of pigments in chloroplasts. The photosynthetic pigment that dominates in most plants species is the molecule chlorophyll.
Plants make use of the same part of electromagnetic spectrum that our eyes are able to see. We call this the visible portion of the spectrum. Sunlight is actually a mixture of different colors of light. You can see these colors when let sunlight pass through a prism
The visible light spectrum includes many colors, but, for the purpose of considering how chlorophyll absorbs light energy, we are going to consider three regions of the spectrum:
- The red end of the spectrum
- The green middle of the spectrum
- The blue end of the spectrum
Substances can do one of only two things when they are struck by a particular wavelength (color) of light. They can:
- Absorb that wavelength (if so, energy is being absorbed and may be used)
- Reflect that wavelength (if so, the energy is not being absorbed and you will see that color)
Let's apply this information to how chlorophyll absorbs light for photosynthesis. Chlorophyll is a green pigment. This means that chlorophyll reflects green light and therefore must absorb the other wavelengths of the visible light spectrum. When a plant leaf is hit by sunlight, the red and blue wavelengths of light are absorbed by chlorophyll and used for photosynthesis. Almost all the energy of the green wavelengths is reflected, not absorbed.
Photosynthesis occurs in two stages;
Photosynthesis produces sugar molecules as a food source for the plant. Sugars, such as glucose, are held together by the covalent bonds. It requires energy to create those covalent bonds, and the source of that energy can ultimately be traced back to the sun.
The first stage of photosynthesis is a set of reactions that "trap" light energy and convert it to the chemical energy of ATP. The second stage of photosynthesis is a set of reactions in which ATP is used to help bond carbon dioxide and water molecules together to create a sugar, such as a glucose
- The first stage of photosynthesis:
The first stage of photosynthesis is a set of reactions typically referred to as the light-dependent reactions. In this set of reactions, chlorophyll absorbs light energy and convert that energy to a form of chemical energy (ATP). In addition, light energy is used to accomplish a reaction that is called photolysis of water. In this reaction, a water molecule is split into its component elements: hydrogen and oxygen.
The oxygen that is split away due to the photolysis of water is typically released from the plant leaf as a waste product. From the plant's perspective, the useful products formed during this stage of photosynthesis are ATP and hydrogen.
- The second stage of photosynthesis:
This stage is a series of reactions collectively referred to as the light-independent reactions. ATP and hydrogen are used as forms of chemical energy to convert carbon dioxide and water into useful organic molecules for the plant. Glucose, a typical product of photosynthesis, is an organic molecule. It requires six inorganic carbon dioxide molecules to form one glucose molecule: 6CO2+6H20-->C6H12O6+6O2
This conversion of an inorganic form of an element to an organic form is known as fixation. Therefore, photosynthesis can be described as a series of reactions in which carbon dioxide and water are fixed into glucose, and oxygen is produced as a by-product.
The fixation reaction described above requires energy. The energy to create the glucose comes directly from the ATP and hydrogen created in the first stage of photosynthesis. Ultimately, this energy can be traced back to sunlight. It is also important to not the that glucose is only one of the many possible organic molecules that can be formed from photosynthesis.
Measuring the rate of photosynthesis;
Look again at the summary reaction of photosynthesis:
6CO2+6H20-->C6H12O6+6O2
This balanced equation shows us that carbon dioxide molecules are reactants and oxygen molecules are products of photosynthesis. In cell respiration, oxygen is a reactant and carbon dioxide is a product.
At any given time of the year, any one plant has fairly consistent rate of cell respiration. Not only is this rate consistent throughout the day and night, it is also at a relatively low level. Plants need ATP for various biochemical processes, but the level is typically far lower than any animal needs.
The same consistency is not true regarding the rate of photosynthesis. The photosynthetic rate is highly dependent on many environmental factors, including the intensity of light and air temperature. During the daytime, especially on a warm sunny day, the rate of photosynthesis ay be very high for a particular plant. If so, the rate of carbon dioxide take in by the plant and the rate of oxygen released will also be very high. Because the plant is also carrying out cell respiration, the rate of photosynthesis may drop to zero. At that time, a particular plant may be giving off carbon dioxide and taking in oxygen to maintain its relatively low and consistent rate of cell respiration.
Measuring the rate of oxygen production or carbon dioxide intake is considered to be a direct measurement of photosynthetic rate as along as correction is made for cell respiration. Another common method for measuring photosynthesis is to keep track of the change in biomass of experimental plants. However, the mass of plants is considered to be an indirect reflection of photosynthetic rate, as an increase or decrease in biomass may be caused by a whole variety of factors as well as the photosynthetic rate.
The effects of changing environmental factors on the rate of photosynthesis;
Look now at the patterns that can be seen when three common environmental factors are varied, and how these factors are predicted to change the rate of photosynthesis in a generalized plant.
- The red end of the spectrum
- The green middle of the spectrum
- The blue end of the spectrum
Substances can do one of only two things when they are struck by a particular wavelength (color) of light. They can:
- Absorb that wavelength (if so, energy is being absorbed and may be used)
- Reflect that wavelength (if so, the energy is not being absorbed and you will see that color)
Let's apply this information to how chlorophyll absorbs light for photosynthesis. Chlorophyll is a green pigment. This means that chlorophyll reflects green light and therefore must absorb the other wavelengths of the visible light spectrum. When a plant leaf is hit by sunlight, the red and blue wavelengths of light are absorbed by chlorophyll and used for photosynthesis. Almost all the energy of the green wavelengths is reflected, not absorbed.
Photosynthesis occurs in two stages;
Photosynthesis produces sugar molecules as a food source for the plant. Sugars, such as glucose, are held together by the covalent bonds. It requires energy to create those covalent bonds, and the source of that energy can ultimately be traced back to the sun.
The first stage of photosynthesis is a set of reactions that "trap" light energy and convert it to the chemical energy of ATP. The second stage of photosynthesis is a set of reactions in which ATP is used to help bond carbon dioxide and water molecules together to create a sugar, such as a glucose
- The first stage of photosynthesis:
The first stage of photosynthesis is a set of reactions typically referred to as the light-dependent reactions. In this set of reactions, chlorophyll absorbs light energy and convert that energy to a form of chemical energy (ATP). In addition, light energy is used to accomplish a reaction that is called photolysis of water. In this reaction, a water molecule is split into its component elements: hydrogen and oxygen.
The oxygen that is split away due to the photolysis of water is typically released from the plant leaf as a waste product. From the plant's perspective, the useful products formed during this stage of photosynthesis are ATP and hydrogen.
- The second stage of photosynthesis:
This stage is a series of reactions collectively referred to as the light-independent reactions. ATP and hydrogen are used as forms of chemical energy to convert carbon dioxide and water into useful organic molecules for the plant. Glucose, a typical product of photosynthesis, is an organic molecule. It requires six inorganic carbon dioxide molecules to form one glucose molecule: 6CO2+6H20-->C6H12O6+6O2
This conversion of an inorganic form of an element to an organic form is known as fixation. Therefore, photosynthesis can be described as a series of reactions in which carbon dioxide and water are fixed into glucose, and oxygen is produced as a by-product.
The fixation reaction described above requires energy. The energy to create the glucose comes directly from the ATP and hydrogen created in the first stage of photosynthesis. Ultimately, this energy can be traced back to sunlight. It is also important to not the that glucose is only one of the many possible organic molecules that can be formed from photosynthesis.
Measuring the rate of photosynthesis;
Look again at the summary reaction of photosynthesis:
6CO2+6H20-->C6H12O6+6O2
This balanced equation shows us that carbon dioxide molecules are reactants and oxygen molecules are products of photosynthesis. In cell respiration, oxygen is a reactant and carbon dioxide is a product.
At any given time of the year, any one plant has fairly consistent rate of cell respiration. Not only is this rate consistent throughout the day and night, it is also at a relatively low level. Plants need ATP for various biochemical processes, but the level is typically far lower than any animal needs.
The same consistency is not true regarding the rate of photosynthesis. The photosynthetic rate is highly dependent on many environmental factors, including the intensity of light and air temperature. During the daytime, especially on a warm sunny day, the rate of photosynthesis ay be very high for a particular plant. If so, the rate of carbon dioxide take in by the plant and the rate of oxygen released will also be very high. Because the plant is also carrying out cell respiration, the rate of photosynthesis may drop to zero. At that time, a particular plant may be giving off carbon dioxide and taking in oxygen to maintain its relatively low and consistent rate of cell respiration.
Measuring the rate of oxygen production or carbon dioxide intake is considered to be a direct measurement of photosynthetic rate as along as correction is made for cell respiration. Another common method for measuring photosynthesis is to keep track of the change in biomass of experimental plants. However, the mass of plants is considered to be an indirect reflection of photosynthetic rate, as an increase or decrease in biomass may be caused by a whole variety of factors as well as the photosynthetic rate.
The effects of changing environmental factors on the rate of photosynthesis;
Look now at the patterns that can be seen when three common environmental factors are varied, and how these factors are predicted to change the rate of photosynthesis in a generalized plant.