Photosynthesis!
Even Spongebob likes it!
Homeostasis takes energy. Where does it come from?
Energy is the ability to do work.
Organisms are doing work all the time. Even when at rest, organisms are using energy for things such as transporting molecules across the cell membrane, building proteins, responses to chemical signals, and contracting muscles. The sodium-potassium pump is a protein pump commonly found in cell membranes. ATP keeps this pump working.
Energy can be found in many forms including light, sound, heat, and chemical. Living organisms use chemical fuel. One of the most widely used chemical used for energy in organisms is ATP, or adenosine triphosphate. ATP consists of adenine, a 5-carbon sugar called ribose, and three phosphate groups.
The energy used in ATP is found in the bonds between the phosphate groups.
ADP (adenosine diphosphate) is a compound that looks almost like ATP, except that it has two phosphate groups instead of three.
Small amounts of energy are stored in the bonds which hold the phosphate molecules together. When cells have extra energy, phosphates are added to ADP to make ATP. When energy is needed, the third phosphate is broken off and energy is released and used by the cell.
This characteristic of ATP makes it exceptionally useful as a basic energy source for all cells. Most cells only have a small amount of ATP, enough to last for a few seconds of activity. ATP is a great molecule for transferring energy, but, it is not a good one for storing large amounts of energy over the long term. After ATP is used up, cells must turn to breaking down glucose molecule in the presence of oxygen (respiration). With foods like glucose, cells can regenerate ATP from ADP as needed.
Analogy
When a phosphate group is added to an ADP molecule, ATP is produced. ADP contains some energy, but not as much as ATP. In this way, ADP is like a partially charged battery that can be fully charged by the addition of a phosphate group.
For Powerpoint 8.1 click here!
Homeostasis takes energy. Where does it come from?
Energy is the ability to do work.
Organisms are doing work all the time. Even when at rest, organisms are using energy for things such as transporting molecules across the cell membrane, building proteins, responses to chemical signals, and contracting muscles. The sodium-potassium pump is a protein pump commonly found in cell membranes. ATP keeps this pump working.
Energy can be found in many forms including light, sound, heat, and chemical. Living organisms use chemical fuel. One of the most widely used chemical used for energy in organisms is ATP, or adenosine triphosphate. ATP consists of adenine, a 5-carbon sugar called ribose, and three phosphate groups.
The energy used in ATP is found in the bonds between the phosphate groups.
Storing Energy
ADP (adenosine diphosphate) is a compound that looks almost like ATP, except that it has two phosphate groups instead of three.
Small amounts of energy are stored in the bonds which hold the phosphate molecules together. When cells have extra energy, phosphates are added to ADP to make ATP. When energy is needed, the third phosphate is broken off and energy is released and used by the cell.
This characteristic of ATP makes it exceptionally useful as a basic energy source for all cells. Most cells only have a small amount of ATP, enough to last for a few seconds of activity. ATP is a great molecule for transferring energy, but, it is not a good one for storing large amounts of energy over the long term. After ATP is used up, cells must turn to breaking down glucose molecule in the presence of oxygen (respiration). With foods like glucose, cells can regenerate ATP from ADP as needed.
Analogy
When a phosphate group is added to an ADP molecule, ATP is produced. ADP contains some energy, but not as much as ATP. In this way, ADP is like a partially charged battery that can be fully charged by the addition of a phosphate group.
Heterotrophs and Autotrophs
The energy for all organisms to live ultimately comes from the sun. Plants, algae, and some bacteria are able to use light energy from the sun to produce food.
Autotroph - organisms that make their own food from the sun's energy.
The process by which autotrophs use energy of sunlight to produce high-energy carbohydrates - sugars and starches - that can be used as food is known as photosynthesis.
Photosynthesis comes from the Greek words photo, meaning "light" and synthesis, meaning "putting together".
In the process of photosynthesis, plants convert the energy of sunlight into chemical energy stored in the bonds of carbohydrates.
Organisms that obtain energy from food by consuming other living things are known as heterotrophs.
Some heterotrophs get food by eating plants, while others get their food by eating animals that eat plants. Still others, like mushrooms, obtain food by absorbing nutrients from decomposing organisms in the environment.
For Powerpoint 8.1 click here!
Lesson 8.2
Energy from the sun travels to the Earth in the form of light. Our eyes perceive this as "white light" which is made up of the visible spectrum of colors with different wavelengths. Plants gather the suns energy with light-absorbing molecules called pigments. Photosynthetic organisms capture energy from sunlight with pigments call chlorophyll.
As shown here, the pigment chlorophyll absorbs energy from wavelengths of violet, blue, and some from orange and red while reflecting the green and yellow wavelenths. This reflection is what gives chlorophyll and the plants containing them their green color.
Only certain organisms, called photo-autotrophs, can perform photosynthesis. These include plants, cyanobacteria, and blue green algae. They require the presence of chlorophyll, a specialized pigment that absorbs certain portions of the visible spectrum and can capture energy from sunlight.
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| Plants |
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| Blue Green Algae |
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| Cyanobacteria |
Photosynthesis uses carbon dioxide and water to assemble carbohydrate molecules and release oxygen as a waste product into the atmosphere. Eukaryotic autotrophs, such as plants and algae, have organelles called chloroplasts in which photosynthesis takes place, and starch accumulates. In prokaryotes, such as cyanobacteria, the process is less localized and occurs within folded membranes, extensions of the plasma membrane, and in the cytoplasm.
Photosynthesis is a multi-step process that requires sunlight, carbon dioxide (which is low in energy), and water as substrates (Figure 3). After the process is complete, it releases oxygen and produces glyceraldehyde-3-phosphate (GA3P), simple carbohydrate molecules (which are high in energy) that can subsequently be converted into glucose, sucrose, or any of dozens of other sugar molecules. These sugar molecules contain energy and the energized carbon that all living things need to survive.
To put it simply....
Although the equation looks simple, the many steps that take place during photosynthesis are actually quite complex. Before learning the details of how photo-autotrophs turn sunlight into food, it is important to become familiar with the structures involved.
In plants, photosynthesis generally takes place in the cells of the leaves inside an organelle called a chloroplast. Chloroplasts have a double membrane envelope (composed of an outer membrane and an inner membrane). Within the chloroplast are stacked, disc-shaped structures called thylakoids. Embedded in the thylakoid membrane is chlorophyll, a pigment (molecule that absorbs light) responsible for the initial interaction between light and plant material, and numerous proteins that make up the electron transport chain. The thylakoid membrane encloses an internal space called the thylakoid lumen. As shown in, a stack of thylakoids is called a granum, and the liquid-filled space surrounding the granum is called stroma.
Photosynthesis takes place in two sequential stages: the light-dependent reactions and the light independent-reactions.
LIGHT DEPENDENT REACTION: Energy from sunlight is absorbed by chlorophyll and that energy is converted into stored chemical energy. More specifically, energy from sunlight is captured in the bonds connection a Phosphate group to ADP while also exciting 2 electrons. These "high energy" electrons are then grabbed up by the carrier molecule NADP+ to be transported out of the thylakoid to be used in the light independent reaction. NADP+ also grabs a H+ ion from splitting a water molecule and carries it away also. The leftover O2 from the water molecule is released as a byproduct of photosynthesis.
LIGHT INDEPENDENT REACTION: The chemical energy harvested during the light-dependent reactions drive the assembly of sugar molecules from carbon dioxide in a cyclic process called the Calvin Cycle. Therefore, although the light-independent reactions do not use light as a reactant, they require the products of the light-dependent reactions to function.
The light-dependent reactions utilize certain molecules to temporarily store the energy. These energy carriers are NADP+ and ADP. After the energy is released, the “empty” energy carriers return to the light-dependent reaction to obtain more energy. Similarly, an oven mitt (carrier) is used to carry a hot potato (2e- and H+) and drop it off on a plate so the mitt can be used again and again.
... and to have a little fun...
For Class Powerpoint 8.2
Lesson 8.3
To view the 8.3 Powerpoint click the following link!
Photosynthesis: The "Light" and the "Dark" of it
Light Reaction: Energy from sunlight is used to produce O2 and convert ADP and NADP+ to energy carriers ATP and NADPH.
Light Dependent: Photosystem II and Photosystem I - Photosystems are clusters of chlorophyll and proteins.
PSII
In PSII Light energy absorbed by PSII produces high energy electrons. Water molecules are split to replace those electrons, releasing H+ ions and oxygen.=«
PSII: Electrons are reenergized in PSI. A second electron transport chain then transfers these electrons to NADP+, production NADPH!
As the thylakoid space fills up with positively charged H+ ions, the inside of the thylakoid membrane becomes positively charged relative to the outside of the membrane. H+ ions pass back across the thylakoid membrane through ATP synthase. As the ions pass through, the ATP synthase molecule rotates and the energy produced is used to convert ADP to ATP.
THE DARK SIDE
ATP and NADPH now move on to the "Dark Reaction" called this because it is light independent.
The Calvin Cycle
Named after Melvin Calvin who worked out the details of this remarkable cycle!
As 6 CO2 molecules from the atmosphere enter the Calvin cycle, they are combined with six 5-carbon molecules in the very first step of the cycle. This produces twelve 3-carbon compounds.
This produces 12 3-carbon molecules
Then ATP and NADPH add Energy to the compounds!
Now, two of the high energy compounds are broken off to make a 6 carbon molecule of
Glucose!! Yummy!!
The other ten 3-carbon molecules continue on through the cycle where they pick up some more E from ATP so that they can form bonds to make 5-carbon molecules again.
Factors Affecting Photosynthesis
The most important factors that affect photosynthesis are temperature,
light intensity,
and the availability of water!
- Reactions of photosynthesis work best between 0 and 35 degrees C
... above or below that may affect enzymes, slowing down the rate of rxn
- High light intensity increases the rate of photosynthesis and vise versa
- A shortage of water can slow or stop photosynthesis since H20 is essential to the process
.........Some plants like desert plants and conifers have waxy coatings to prevent water loss
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| The graph shows how the rate of photosynthesis changes in response to the light intensity |
Extreme Conditions
Most plants under bright, hot conditions close their small openings in their leaves that normally admit CO2. While preserving water, this causes photosynthesis to slow or stop.
C4 Plants: forms 4 carbon molecules instead of 3 carbon molecules
.....this enables photosynthesis to keep working under intense light and high temps
while keeping their stoma closed and taking in very small amts of CO2
.... these plants include corn, sugar cane, and sorghum
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| Corn |
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| Sugar Cane CAM Plants: Adapted to dry climates have to minimize water loss. CAM plants do this by only admitting air into their leaves only at night. In the cool darkness, CO2 is combined with existing molecules to produce organic acids, trapping Carbon within the leaves. Then, during the daytime, when leaf pores are sealed to prevent the loss of water, these compounds release CO2 into the Calvin Cycle. CAM stands for Crassulacean Acid Metabolism. CAM Plants include Pineapple Trees, Desert Cacti, and Ice Plants  .jpeg) |
ALL DONE!!!!
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