Photosynthesis Intelligent Design Biology Lesson 8 August 19, 2024
All life on Earth depends on photosynthesis, and it is the only biological process that can capture energy that originates from sunlight and convert it into chemical compounds (carbohydrates) that every organism uses to power its metabolism. It is also a source of oxygen necessary for many living organisms.
The energy of sunlight is captured to energize electrons, then this energy is stored in the covalent bonds of sugar molecules.
Photosynthesis occurs only in plants, algae, and cyanobacteria. Photoautotrophs such as these use light to manufacture their own food. Heterotrophs such as animals, fungi, and most other bacteria, rely on sugars produced by photosynthetic organisms for their energy needs. Chemoautotrophs are a group of bacteria that can build organic molecules using energy derived from inorganic chemicals instead of sunlight.
Carbohydrates produced in photoautotrophs by photosynthesis are the energy source that heterotrophs use to power the synthesis of ATP in respiration. Photosynthesis powers 99 percent of Earth's ecosystems.
Photosynthesis is a multi-step process that requires visible sunlight, carbon dioxide, and water. Photosynthesis produces oxygen and glyceraldehyde-3-phosphate (G3P), other carbohydrate molecules that can be converted into sugar molecules.
Photosynthesis Equation:
Carbon Dioxide + Water + Sunlight => Sugar + Oxygen
6CO2 (Carbon Dioxide) + 6H2O (Water) + Sunlight => C6H12O6 (Sugar) + 6O2 (Oxygen)
Plant photosynthesis occurs in a middle layer of chlorophyll-rich cells of leaves called the mesophyll. The gas exchange of carbon dioxide and oxygen occurs in small, regulated openings called stomata, which also regulate water balance. The stomata are usually located on the bottom side of the leaf, which is cooler than the top side so that water loss is minimized. The stomata open and close as a result of osmotic changes.
Chloroplasts are organelles in autotrophic eukaryotes where photosynthesis takes place. In plants, chloroplast cells are in the mesophyll. Chloroplasts have a double membrane envelope (inner and outer membrane). Inside the chloroplasts are stacked, disc-shape structures called thylakoids. Inside the thylakoid membrane is chlorophyll, a pigment molecule that absorbs light and is responsible for the initial interaction between light and plant material, and many proteins involved in the electron transport chain. The thylakoid membrane encloses an internal space called the thylakoid lumen. A stack of thylakoids is called a granum, and the liquid-filled space surrounding the granum is called stroma (not stoma).
Two Stages of Photosynthesis include Light Dependent Reactions: occur when energy from sunlight is absorbed by chlorophyll and this energy is converted into stored chemical energy. Light Independent Reactions: occur when the chemical energy harvested during the light dependent reactions drives the assembly of sugar molecules from carbon dioxide. Light dependent reactions use certain molecules to temporarily store the energy called energy carriers.
Light Energy comes from the sun in the form of electromagnetic radiation, which is solar energy in a spectrum from very short and high energy gamma rays to very long, low energy radio waves. Only a small part of this energy is visible to humans (visible light).
Solar energy travel is described in the form of waves. Shorter waves (from consecutive crest points or trough points) travel with more energy than longer waves.
The Electromagnetic Spectrum represents the total range of frequencies of radiation, from radio waves, which have the lowest energy and have the longest wavelength on the spectrum. Infrared radiation has shorter wavelengths and higher energy than radio waves, and visible light has even shorter wavelengths and higher energy.
Ultraviolet radiation light has shorter wavelengths and higher energy than visible light. X-rays has even shorter wavelength and even stronger energy. Gamma rays have the shortest wavelength and strongest energy on the electromagnetic spectrum. Ultraviolet and x-rays can be harmful to humans and organisms by penetrating and damaging skin tissues, cells, and DNA.
Light energy can excite electrons and cause it to move to a higher energy level. Different pigments exist, and each pigment only absorbs certain wavelengths or colors of light. Wavelengths not absorbed are reflected and the colors are mixed.
Chlorophylls and carotenoids are the two major types of photosynthetic pigments found in plants and algae. There are five major types of chlorophylls: a, b, c, d, and in prokaryotes, bacteriochlorophyll. Chlorophylls a and b are found in higher plant chloroplasts.
Carotenoids are a much larger group of pigments. In photosynthesis, carotenoids function as photosynthetic pigments that are very efficient molecules for the disposal of excess energy by absorption and release as heat.
In the absorption spectrum, each type of pigment can be identified by the specific pattern of wavelengths that it absorbs from visible light. Each pigment has a distinct set of peaks and troughs, which reveals a distinct pattern of absorption.
A spectrophotometer is an instrument that can differentiate which wavelengths of light that a substance can absorb.
How Light-Dependent Reactions Work
A photosystem is the actual step that converts light energy into chemical energy. Two types of photosystem are found in the thylakoid membrane: Photosystem II and Photosystem I. The difference between the two is that each oxidizes and reduces (the source and delivery of electrons).
Photosystem structure: includes antenna pigments where the chlorophyll molecules are bound surround the reaction center where the photochemistry takes place.
Each photosystem has the light-harvesting complex, which passes energy from sunlight to reaction center and contains several antenna pigments with chlorophyll and carotenoids.
Absorption of a photon of light will enable a molecule into an excited state. The energy is transferred through the chlorophyll until it reaches the reaction center.
A pair of chlorophyll a molecules can undergo oxidation upon excitation, and give up an electron in a process called photoact, and light energy is converted to an excited electron.
The electron is carried by NADPH to the Calvin Cycle, where it is stored as a carbohydrate. PSII and PSI are major components of the Electron transport chain and the cytochrome complex, which is an enzyme composed of two protein complexes.
The reaction center of PSII delivers high energy electrons, one at a time, to the primary electron acceptor, and through the electron transport chain to PSI. As electrons move through the proteins that reside between PSII and PSI, they lose energy. This energy is used to move hydrogen atoms from the stromal side of the membrane to the thylakoid lumen.
Generating Energy Carrier: ATP
The buildup of hydrogen ions in the thylakoid lumen creates a concentration gradient. Diffusion of hydrogen ions from high concentration to low concentration is harnessed to create ATP.
The Calvin Cycle Stages: The Light-Independent Reactions
Stage 1: Carbon Fixation: In the stroma, in addition to CO2, plus two other components initiate the light-independent reactions: enzyme ribulose-1,5-biphosphate carboxylase/oxygenase (RuBisCo) and three molecules of ribulose biphosphate (RuBP).RuBP has five atoms of carbon, flanked by two phosphates. RuBisCO catalyzes a reaction between CO2 and RuBP. For each CO2 molecule that reacts with one RuBP, two molecules of another compound 3-phospho glyceric acid (3-PGA) form. PGA has three carbons and one phosphate.
Stage 2: Reduction: ATP and NADPH are used to convert the six molecules of 3-PGA into six molecules of a chemical called glyceraldehyde 3-phosphate (G3P) (gain of electrons)
Six molecules of both ATP and NADPH are used. For ATP, energy is released with the loss of the terminal phosphate atom, converting it into ADP; for NADPH, both energy and a hydrogen atom are lost, converting it into NADP+.
Stage 3: Regeneration: Only one of the G3P molecules leaves the Calvin cycle and is sent to the cytoplasm to contribute to the formation of other compounds needed by the plant. Because the G3P exported from the chloroplast has three carbon atoms, it takes three turns or cycles of the Calvin cycle to fix enough net carbon to export one G3P. However, each turn makes two G3Ps, thus three turns make six G3Ps. One is exported while the remaining five G3P molecules remain in the cycle and are used to regenerate RuBP, which enables the system to prepare for more CO2 to be fixed. Three more molecules of ATP are used in these regeneration reactions.
All life on Earth depends on photosynthesis, and it is the only biological process that can capture energy that originates from sunlight and convert it into chemical compounds (carbohydrates) that every organism uses to power its metabolism. It is also a source of oxygen necessary for many living organisms.
The energy of sunlight is captured to energize electrons, then this energy is stored in the covalent bonds of sugar molecules.
Photosynthesis occurs only in plants, algae, and cyanobacteria. Photoautotrophs such as these use light to manufacture their own food. Heterotrophs such as animals, fungi, and most other bacteria, rely on sugars produced by photosynthetic organisms for their energy needs. Chemoautotrophs are a group of bacteria that can build organic molecules using energy derived from inorganic chemicals instead of sunlight.
Carbohydrates produced in photoautotrophs by photosynthesis are the energy source that heterotrophs use to power the synthesis of ATP in respiration. Photosynthesis powers 99 percent of Earth's ecosystems.
Photosynthesis is a multi-step process that requires visible sunlight, carbon dioxide, and water. Photosynthesis produces oxygen and glyceraldehyde-3-phosphate (G3P), other carbohydrate molecules that can be converted into sugar molecules.
Photosynthesis Equation:
Carbon Dioxide + Water + Sunlight => Sugar + Oxygen
6CO2 (Carbon Dioxide) + 6H2O (Water) + Sunlight => C6H12O6 (Sugar) + 6O2 (Oxygen)
Plant photosynthesis occurs in a middle layer of chlorophyll-rich cells of leaves called the mesophyll. The gas exchange of carbon dioxide and oxygen occurs in small, regulated openings called stomata, which also regulate water balance. The stomata are usually located on the bottom side of the leaf, which is cooler than the top side so that water loss is minimized. The stomata open and close as a result of osmotic changes.
Chloroplasts are organelles in autotrophic eukaryotes where photosynthesis takes place. In plants, chloroplast cells are in the mesophyll. Chloroplasts have a double membrane envelope (inner and outer membrane). Inside the chloroplasts are stacked, disc-shape structures called thylakoids. Inside the thylakoid membrane is chlorophyll, a pigment molecule that absorbs light and is responsible for the initial interaction between light and plant material, and many proteins involved in the electron transport chain. The thylakoid membrane encloses an internal space called the thylakoid lumen. A stack of thylakoids is called a granum, and the liquid-filled space surrounding the granum is called stroma (not stoma).
Two Stages of Photosynthesis include Light Dependent Reactions: occur when energy from sunlight is absorbed by chlorophyll and this energy is converted into stored chemical energy. Light Independent Reactions: occur when the chemical energy harvested during the light dependent reactions drives the assembly of sugar molecules from carbon dioxide. Light dependent reactions use certain molecules to temporarily store the energy called energy carriers.
Light Energy comes from the sun in the form of electromagnetic radiation, which is solar energy in a spectrum from very short and high energy gamma rays to very long, low energy radio waves. Only a small part of this energy is visible to humans (visible light).
Solar energy travel is described in the form of waves. Shorter waves (from consecutive crest points or trough points) travel with more energy than longer waves.
The Electromagnetic Spectrum represents the total range of frequencies of radiation, from radio waves, which have the lowest energy and have the longest wavelength on the spectrum. Infrared radiation has shorter wavelengths and higher energy than radio waves, and visible light has even shorter wavelengths and higher energy.
Ultraviolet radiation light has shorter wavelengths and higher energy than visible light. X-rays has even shorter wavelength and even stronger energy. Gamma rays have the shortest wavelength and strongest energy on the electromagnetic spectrum. Ultraviolet and x-rays can be harmful to humans and organisms by penetrating and damaging skin tissues, cells, and DNA.
Light energy can excite electrons and cause it to move to a higher energy level. Different pigments exist, and each pigment only absorbs certain wavelengths or colors of light. Wavelengths not absorbed are reflected and the colors are mixed.
Chlorophylls and carotenoids are the two major types of photosynthetic pigments found in plants and algae. There are five major types of chlorophylls: a, b, c, d, and in prokaryotes, bacteriochlorophyll. Chlorophylls a and b are found in higher plant chloroplasts.
Carotenoids are a much larger group of pigments. In photosynthesis, carotenoids function as photosynthetic pigments that are very efficient molecules for the disposal of excess energy by absorption and release as heat.
In the absorption spectrum, each type of pigment can be identified by the specific pattern of wavelengths that it absorbs from visible light. Each pigment has a distinct set of peaks and troughs, which reveals a distinct pattern of absorption.
A spectrophotometer is an instrument that can differentiate which wavelengths of light that a substance can absorb.
How Light-Dependent Reactions Work
A photosystem is the actual step that converts light energy into chemical energy. Two types of photosystem are found in the thylakoid membrane: Photosystem II and Photosystem I. The difference between the two is that each oxidizes and reduces (the source and delivery of electrons).
Photosystem structure: includes antenna pigments where the chlorophyll molecules are bound surround the reaction center where the photochemistry takes place.
Each photosystem has the light-harvesting complex, which passes energy from sunlight to reaction center and contains several antenna pigments with chlorophyll and carotenoids.
Absorption of a photon of light will enable a molecule into an excited state. The energy is transferred through the chlorophyll until it reaches the reaction center.
A pair of chlorophyll a molecules can undergo oxidation upon excitation, and give up an electron in a process called photoact, and light energy is converted to an excited electron.
The electron is carried by NADPH to the Calvin Cycle, where it is stored as a carbohydrate. PSII and PSI are major components of the Electron transport chain and the cytochrome complex, which is an enzyme composed of two protein complexes.
The reaction center of PSII delivers high energy electrons, one at a time, to the primary electron acceptor, and through the electron transport chain to PSI. As electrons move through the proteins that reside between PSII and PSI, they lose energy. This energy is used to move hydrogen atoms from the stromal side of the membrane to the thylakoid lumen.
Generating Energy Carrier: ATP
The buildup of hydrogen ions in the thylakoid lumen creates a concentration gradient. Diffusion of hydrogen ions from high concentration to low concentration is harnessed to create ATP.
The Calvin Cycle Stages: The Light-Independent Reactions
Stage 1: Carbon Fixation: In the stroma, in addition to CO2, plus two other components initiate the light-independent reactions: enzyme ribulose-1,5-biphosphate carboxylase/oxygenase (RuBisCo) and three molecules of ribulose biphosphate (RuBP).RuBP has five atoms of carbon, flanked by two phosphates. RuBisCO catalyzes a reaction between CO2 and RuBP. For each CO2 molecule that reacts with one RuBP, two molecules of another compound 3-phospho glyceric acid (3-PGA) form. PGA has three carbons and one phosphate.
Stage 2: Reduction: ATP and NADPH are used to convert the six molecules of 3-PGA into six molecules of a chemical called glyceraldehyde 3-phosphate (G3P) (gain of electrons)
Six molecules of both ATP and NADPH are used. For ATP, energy is released with the loss of the terminal phosphate atom, converting it into ADP; for NADPH, both energy and a hydrogen atom are lost, converting it into NADP+.
Stage 3: Regeneration: Only one of the G3P molecules leaves the Calvin cycle and is sent to the cytoplasm to contribute to the formation of other compounds needed by the plant. Because the G3P exported from the chloroplast has three carbon atoms, it takes three turns or cycles of the Calvin cycle to fix enough net carbon to export one G3P. However, each turn makes two G3Ps, thus three turns make six G3Ps. One is exported while the remaining five G3P molecules remain in the cycle and are used to regenerate RuBP, which enables the system to prepare for more CO2 to be fixed. Three more molecules of ATP are used in these regeneration reactions.