Energy and Photosynthesis
Chapter 5: Energy and Photosynthesis
Authors
Michèle Shuster • Janet Vigna • Matthew Tontonoz
Biology for a Changing World, 4th ed
Macmillan Learning © 2021
Driving Questions
Why are photosynthetic organisms like algae so important?
What are the different types of energy, and what transformations of energy do organisms carry out?
How do plants and algae convert the energy in sunlight into energy-rich organic molecules?
An exploration of why organisms like humans cannot perform this function.
How do algal biofuels compare to other fuels in terms of costs, benefits, and sustainability?
Fossil Fuels Are Limited
The demand for oil is projected to increase over the next 25 years, but sources of oil are finite.
It takes millions of years for oil deposits to replenish, leading to concerns about long-term availability.
Algae as Fuel
Algae possess the ability to capture sunlight and convert it into usable energy forms.
A significant portion of this energy is stored as oils, which are particularly suitable for fuel production.
The Future of Fuel
Biofuels are defined as renewable fuels sourced from living organisms, with algae being a major contributor to this category.
U.S. Energy Consumption
The United States is the largest consumer of fossil fuels, highlighting the urgent need for developing new energy sources to reduce this demand.
Interpreting Data
(1 of 6) Daily Petroleum Use
The United States consumes approximately 19 million barrels of petroleum per day, with around 8 million barrels per day imported.
Cost Analysis:
U.S. Sources (including biofuels), average cost: $65.00 per barrel.
Canada, average cost: $91.00 per barrel.
Saudi Arabia, average cost: $3.00 per barrel.
Venezuela, average cost: $20.00 per barrel.
Iraq, average cost: $6.00 per barrel.
Algal biofuel, approximate cost: $273 per barrel.
(2 of 6) Cost Reduction Strategies
Questions raised regarding how algal biofuel companies could reduce their production costs given the high cost compared to other petroleum sources.
(3 of 6) Impact of Domestic Production
Hypothetical scenario where the U.S. replaces half of its oil imports from OPEC and Persian Gulf countries with domestically produced algal biofuel.
Examination of the potential effects on production costs for daily needs.
Energy Basics
Algae and plants harness energy from sunlight, which is then stored in chemical compounds.
The biofuels produced through this process contain high levels of chemical energy.
What is Energy?
Definition: Energy is the capacity to do work.
Energy exists in various forms, including potential energy stored in chemical bonds.
The law of conservation of energy states that energy is neither created nor destroyed; it can only change forms.
Energy Concepts
Potential Energy:
Stored energy, particularly in the form of chemical bonds.
Kinetic Energy:
Energy of motion, such as thermal energy produced from moving molecules or atoms.
Heat:
A form of kinetic energy generated by the random movement of particles.
Energy Transformation
Example: A cyclist consumes an energy bar, which contains potential chemical energy.
After digestion, the chemical bonds are broken, releasing stored potential energy.
As the cyclist climbs uphill, potential energy converts into kinetic energy and heat.
Energy Transformation Efficiency
It is vital to note that energy transformation processes are not fully efficient, as some energy dissipates as heat.
Constant energy supply is necessary to maintain any system.
The Process of Photosynthesis
Photosynthesis is defined as the process by which plants and other autotrophic organisms capture the energy of sunlight to synthesize energy-rich molecules.
How Organisms Gain Energy
Autotrophs:
Organisms that capture and transform sunlight through photosynthesis.
Heterotrophs:
Organisms that derive energy by consuming other organisms.
Inputs and Outputs of Photosynthesis
The chemical equation for photosynthesis can be summarized as follows:
Inputs:
Sunlight, Water (H₂O), Carbon dioxide (CO₂)
Outputs:
Oxygen (O₂), Glucose (C₆H₁₂O₆)
Location of Photosynthesis
Photosynthesis takes place in chloroplasts, which are specialized organelles found in the cells of plants and algae.
Note: While the internal structure of chloroplasts is interesting, understanding the overall function is essential without needing to memorize all details.
Parts of Photosynthesis
“Photo” Step:
Chloroplasts absorb sunlight, splitting water molecules and releasing oxygen as a by-product.
“Synthesis” Step:
The energy captured is utilized to convert CO₂ into glucose, effectively transforming sunlight into chemical energy.
From Sun to Fuel
When the products from plants and algae are converted into fuel and combusted, they release CO₂, which is the same gas these organisms absorbed during photosynthesis.
Light Energy
Light energy is described as the energy carried by the electromagnetic spectrum and is composed of particles known as photons.
Light Wavelengths
Photons vary in wavelengths, which determine different energy levels and contribute to the colors of visible light.
Absorption of Light Energy by Plants
Chlorophyll is the pigment present in the green parts of plants, capable of absorbing photons from various colors of light while primarily reflecting green light.
Photosynthesis: Transformation of Light Energy into Chemical Energy
Light reactions occur when photons are absorbed by chlorophyll, resulting in the excitation of electrons.
This process leads to the generation of energy-carrying molecules such as ATP (adenosine triphosphate).
Photosynthesis: Storing Energy in Carbon Compounds
Photosynthesis incorporates carbon dioxide into organic molecules through a process known as carbon fixation, effectively storing energy in the form of carbohydrates.
Practical Hurdles in Algal Biofuels
Current production of algal biofuels is still in the prototype stage.
Algae can be utilized for various applications, suggesting their potential beyond fuel; for example, researchers at UC San Diego have successfully created sustainably developed boards from algae.
Summary of Key Points
Importance of Photosynthetic Organisms
Photosynthetic organisms, such as algae, are crucial as they transform sunlight into energy-rich food molecules, fundamental for all living organisms.
Types of Energy and Transformations
Energy is conserved and transformed from one form to another.
Kinetic energy (e.g., heat) and potential energy (e.g., chemical energy) are key forms of energy in biological systems.
Energy flows within ecosystems, returning to the environment mainly as heat, with losses occurring during energy transformations.
Conversion of Sunlight into Organic Molecules by Plants and Algae
Photosynthesis encapsulates the process where light energy is converted into chemical energy, with two primary phases: light capture and glucose synthesis.
Autotrophic organisms perform photosynthesis, while heterotrophic organisms depend on these autotrophs for energy.
Comparison of Algal Biofuels and Other Fuels
Algal biofuels have the potential to serve as an alternative to fossil fuels by transforming glucose into energy-rich oils suitable for powering vehicles.