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Photosynthesis and Cellular Respiration
+Energy
Energy that living things gain from eating comes indirectly from the sun.
Plants receive this energy directly, while we receive the energy indirectly.
This energy makes organic compounds found in our food.
+Flow of Energy
+Autotrophs
Organisms that use energy from sunlight to make organic compounds
Most are photosyntheticEx: Plants
Some do not have access to sunlight, and use chemical energy insteadEx: bacteria in extreme environments
+Photosynthesis
The process by which light energy is converted to chemical energy
+Heterotrophs
Organisms that must get energy from food
Humans and other animals
Go through cellular respiration processes for energy
+Cellular Respiration
Releases energy from food to make ATP
Energy released gradually through chemical reactions
ATP is a result of these reactions
ATP goes wherever it is needed in the cells
+ATP
ATP (Adenosine Triphosphate) goes to the areas that need energy in the cell
A phosphate group breaks off to release the energy needed and forms ADP.
ATP ADP + P + Energy
+
Let’s Look at Photosynthesis and
Cellular Respiration a little closer!
+Photosynthesis
All foods that we eat eventually lead back to plants.
These plants go through photosynthesis to get their energy.
Ex: Hamburger Beef comes from cow that ate grass.
+Photosynthesis
Photosynthesis occurs in chloroplasts of plant cells and cell membrane of bacteria.
3CO2 + 3H2O C3H6O3 + 3O2
+Three Stages of Photosynthesis
1.) Energy is captured from sunlight
2.) Light energy is converted to chemical energy (stored in ATP and NADPH)
3.) Chemical energy in ATP and NADPH power the formation of organic compounds
Steps 1 & 2 are light-dependent
NADPH is an energy carrier molecule
+Stage 1: Energy is Captured From Sunlight
When sun shines on us, there are several types of radiation hitting us at different wavelengths. We can only see visible light and sunlight contains all of the wavelengths of visible light.
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+Stage 1: Energy is Captured From Sunlight
How do we see light?
+Stage 1: Energy is Captured From Sunlight
We see light through light-absorbing substances called pigments. These absorb and reflect certain wavelengths.
These pigments are held in disk-shaped thylakoids in chloroplasts. These pigments are held in clusters.
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+Two Types of Pigments to Know
ChlorophyllReflects green and yellow light so we see leaves as green.
CarotenoidsReflects yellow and red light so we see leaves as yellow and orange in fall.
+Stage 1: Energy is Captured From Sunlight Light strikes thylakoid
Energy transferred to electrons in pigments
Electrons now “excited” and jump to higher energy level
These electrons used to power Stage 2
Electrons used now replaced through water molecules
This forms oxygen gas (O2)
+Stage 2: Light Energy is Converted to Chemical Energy
The excited electrons from Stage 1 jump through molecules along the thylakoid membrane.
Like a basketball being passed down a line of people
This is known as an electron transport chainOne chain helps make ATPOne chain helps make NADPH
+Electron Transport Chain: ATP
Excited electrons move through protein
Electrons lose energy, energy used to pump in H+ ions
Eventually these ions diffuse out of the thylakoid through a carrier protein
This protein causes ADP to add a phosphate group and it becomes ATP
+Electron Transport Chain: NADPH
Excited electrons combine with hydrogen ions and NADP+
Forms NADPH
+Stage 3: Energy Stored in Organic Compounds
Carbon dioxide fixation: transfer of carbon dioxide to organic compounds
“dark reaction” or light-independent
Most common method of carbon dioxide fixation is the Calvin Cycle
+Calvin Cycle
1.) Each carbon dioxide molecule is added to a five-carbon compound.
2.) Each of the three resulting six-carbon compounds is unstable and immediately splits, forming a total of six three-carbon compounds.
3.) One of the resulting three-carbon sugars is used to make organic compounds that the organism uses for energy.
4.) The five other three-carbon sugars are used to regenerate the five-carbon compound that began the cycle.
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+Factors that Affect Photosynthesis
Light Rate of Photosynthesis increases as light intensity increases
Carbon Dioxide Concentration Same as light
Temperature Enzymes assist reactions and have to stay within certain
temperature range