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CA Biology Standards
Cell Biology
• Students know usable energy is captured from sunlight by chloroplasts and is stored through the synthesis of sugar from carbon dioxide.
Ecology
• Students know how water, carbon, and nitrogen cycle between abiotic resources and organic matter in the ecosystem and how oxygen cycles through photosynthesis and respiration.
PhotosynthesisChapter 8
PhotosynthesisChapter 8
1. Summarize how energy is captured from sunlight during the light dependent reactions of photosynthesis.
2. Analyze the function of electron transport chains during the light dependent reactions of photosynthesis.
3. Relate the Calvin cycle to carbon dioxide fixation in photosynthesis.
4. Identify three environmental factors that affect the rate of photosynthesis.
Using the Energy in Sunlight
• Plants, algae, and some bacteria capture 1% of the sunlight that reaches earth and convert it to chemical energy through the process of photosynthesis.
• Plants, algae, and some bacteria capture 1% of the sunlight that reaches earth and convert it to chemical energy through the process of photosynthesis.
History of the Discovery of Photosynthesis
The following people all contributed to the discovery of photosynthesis.
• Van Helmont (1600’s)
• Priestley (1700’s)
• Ingenhousz (1779)
• Mayer (1845)
• Ruben and Kamen (1941)
• Melvin Calvin (1948)
• Rudolph Marcus (1992)
The following people all contributed to the discovery of photosynthesis.
• Van Helmont (1600’s)
• Priestley (1700’s)
• Ingenhousz (1779)
• Mayer (1845)
• Ruben and Kamen (1941)
• Melvin Calvin (1948)
• Rudolph Marcus (1992)
Jan van Helmont• He wondered where the mass of
a tree came from- perhaps the soil?
• To find out, he did an experiment where he weighed a seedling and a pot of soil. After 5 years, he reweighed them both.
• The soil was the same mass but the tree had gained mass. Where did it come from?
• He concluded it came from the water!
Joseph Priestley (1700’s)
• He put a jar over a candle and found?
• The candle went out!
• But when he placed a living plant under the jar with the candle, it stayed lit longer. Why???
• The plant produced….OXYGEN!
Jan Ingenhousz
• He did the same experiment as Priestley, but in the dark and in the light.
• It only worked in the light, proving that plants need light to make oxygen!
Photosynthesis Equation
6 CO2 + 6 H2O C6H12O6 + 6O2
Carbon Dioxide
What we exhaleWater
Glucose
What we use for energy
Oxygen
What we breathe
Photosynthesis is…
• The process where plants, algae and some bacteria convert light energy into chemical energy (glucose), using water and carbon dioxide and releasing oxygen gas as a byproduct.
Usually in the leaves, but anywhere it is green!
Usually in the leaves, but anywhere it is green!
Where does photosynthesis
occur in a plant?
Photosynthesis
The raw materials of photosynthesis, water and carbon dioxide, enter the cells of the leaf, and the products of photosynthesis, sugar and oxygen, leave the leaf.
• Cross section of a leaf, showing the anatomical features important to the study of photosynthesis: stoma, guard cell, mesophyll cells, and vein.
• Water enters the root and is transported up to the leaves through specialized plant cells known as xylem (pronounced zigh-lem).
Land plants must guard against desiccation (drying out) and so have evolved specialized structures known as stomata to allow gas to enter and leave the leaf. (stoma = singular; stomata = plural; Greek for mouth)
• CO2 enters the leaf through the stomata.
• O2 exits the leaf through the stomata.
• H2O can also escape through the stomata, especially on hot, dry days. This is called transpiration, or the evaporation of water through plants. So when it’s hot, the stomata close.
CO2 What enters and exits the stomata?
• Carbon dioxide enter the leaf through the stoma flanked by two guard cells.
• Oxygen produced during photosynthesis can only pass out of the leaf through the opened stomata.
How would stomata closure
affect photosynthesis?
When the stomata close, CO2 levels drop rapidly within the leaf, inhibiting the light-independent reactions.
This then causes photosynthesis to stop.
Visible spectrum• Sunlight contains a
mixture of all the wavelengths (colors) of visible light.
• When sunlight passes through a prism, the prism separates the light into different colors.
PigmentsPigments Pigments are light-absorbing molecules which absorb only certain wavelengths and reflect all of the others.
Chlorophyll is the pigment in plants that makes them appear green.GREEN is reflected, while all other colors are absorbed.
Chlorophyll is the pigment in plants that makes them appear green.GREEN is reflected, while all other colors are absorbed.
• Absorbs mostly blue and red light and reflects green and yellow light.
• Thus, the plant looks green.
• Absorbs mostly blue and red light and reflects green and yellow light.
• Thus, the plant looks green.
Chlorophyll
Autumn Colors
In the fall, as it gets colder, chlorophyll gets broken down because photosynthesis can’t occur in the winter. Why?
• Water freezes! • And if water freezes, it can’t do its part in photosynthesis.
Pigments are located in the chloroplasts of leaf cells
Pigments are located in the chloroplasts of leaf cells
Thylakoids• Are disk shaped structures
containing clusters of pigments embedded in their membranes.
• This is where the Light-Dependent Reactions occur.
• Are disk shaped structures containing clusters of pigments embedded in their membranes.
• This is where the Light-Dependent Reactions occur.
Fun Overview of Photosynthesis Animation
• http://www.pbs.org/wgbh/nova/methuselah/photosynthesis.html
Photosynthesis Occurs in Two Stages:
1. The Light-Dependent Reactions (occur in the thylakoid membranes)
2. The Calvin Cycle
(occurs in the stroma)
Overview of The Light-Dependent Reactions
• Where do they occur?
• What are they?
• The Thylakoid Membranes where there is chlorophyll!
• The light-dependent reactions use water, produce oxygen gas and convert ADP and NADP+ into the energy carriers ATP and NADPH.
Overview of The Light-Dependent Reactions
• What part of the photosynthesis equation is involved?
• Water (H2O) is broken apart for its electrons.
• Oxygen gas (O2) is given off as a waste product.
1. Light strikes chlorophyll in the thylakoid membrane and transfers solar energy to its electrons.
Light strikes
2. This energy transfer from light
causes the electrons to become “excited”.
3. These high-energy electrons are transferred to NADP+.
NADP+ is an energy carrier molecule.
• It can accept high-energy electrons (e-) from chlorophyll and become NADPH (the negative electrons attract a hydrogen ion).
• This is how the energy from sunlight is converted into chemical energy! COOL!
• But now chlorophyll is missing electrons…
• Where does it get more?
WATER!
4. Water molecules are split by
enzymes
to form electrons
(from the H atoms) which the chlorophyll takes to replace lost e-’s.
6. Electron Transport chain
A. Hydrogen ions move into the thylakoid and become concentrated inside.
6. Electron Transport chain
B. Hydrogen ions pass through ATP synthase (a protein in the thylakoid membrane) which catalyzes the reaction where a phosphate group is added to ADP to become ATP!
ATP Synthase Animation
• http://www.stolaf.edu/people/giannini/flashanimat/metabolism/photosynthesis.swf
Remember:NADPH is an electron carrier that provides the high-energy electrons needed to make carbon-hydrogen bonds in the third stage of photosynthesis.
NADPH is an electron carrier that provides the high-energy electrons needed to make carbon-hydrogen bonds in the third stage of photosynthesis.
ATP is the molecule that provides energy for the plant to make
glucose!
NADPH provides hydrogen atoms for the plant to make
glucose!
Summary of Light dependent reaction1. Pigments in the thylakoids of chloroplasts
absorb light energy.
2. Electrons in the pigments are excited by light and move through electron transport chains in thylakoid membranes.
3. These electrons are replaced by electrons from water molecules, which are split by an enzyme.
4. Oxygen atoms from water molecules combine to form oxygen gas.
5. Hydrogen ions accumulate inside thylakoids, setting up a concentration gradient that provides the energy to make ATP.
Pigment molecules absorb energy at which stage of photosynthesis?
The beginning of the Light-Dependent Reactions!
At which stage of photosynthesis is light energy stored as ATP and NADPH?
The end of the Light-Dependent Reactions!
At which stage of photosynthesis are excited electrons passed along an electron transport chain?
Light-Dependent Reactions!
What goes into the light-dependent reactions?What goes into the light-dependent reactions?
Light excites the electrons of chlorophyll.Water is split to replace lost e-’s in chlorophyll.ADP gets a phosphate group to become ATP.NADP+ gets hydrogen ions to become NADPH.
Light excites the electrons of chlorophyll.Water is split to replace lost e-’s in chlorophyll.ADP gets a phosphate group to become ATP.NADP+ gets hydrogen ions to become NADPH.
What is produced in the light-dependent reactions?
ATP and NADPH go into the Calvin Cycle.Oxygen gas is released into the atmosphere.
Light Reactions Animation
• http://www.johnkyrk.com/photosynthesis.html
The Calvin Cycle!
The Calvin Cycle uses ATP and NADPH from the light-dependent reactions and CO2 from the air to make high-energy sugars (glucose)!
What is it?
Glucose
The Calvin Cycle occurs in the stroma of the chloroplast.The Calvin Cycle occurs in the stroma of the chloroplast.
Where does the Calvin Cycle occur?
What parts of the photosynthesis equation are involved in the Calvin Cycle?
CO2 is broken down to create glucose (C6H12O6)
CO2 is broken down to create glucose (C6H12O6)
C6H12O6
Calvin Cycle
1. Six CO2 molecules enter the leaf through the stoma and diffuse into the stroma. They are added to a 5 carbon compound by an enzyme.
1. Six CO2 molecules enter the leaf through the stoma and diffuse into the stroma. They are added to a 5 carbon compound by an enzyme.
2. They are split into twelve 3-carbon compounds.
3. Energy from ATP and electrons from NADPH are used to convert the 3-carbon compounds into 3-carbon sugars.
2. They are split into twelve 3-carbon compounds.
3. Energy from ATP and electrons from NADPH are used to convert the 3-carbon compounds into 3-carbon sugars.
Calvin Cycle
4. Two of the resulting 3-carbon sugars is used to make organic compounds – including GLUCOSE, starch and sucrose – in which energy is stored for later use by the organism.
4. Two of the resulting 3-carbon sugars is used to make organic compounds – including GLUCOSE, starch and sucrose – in which energy is stored for later use by the organism.
Calvin Cycle
5. The other ten 3-carbon sugars are used to regenerate the initial 5-carbon compound, thereby completing the cycle.
5. The other ten 3-carbon sugars are used to regenerate the initial 5-carbon compound, thereby completing the cycle.
Calvin Cycle
What goes into the Calvin Cycle?
• ATP and NADPH are used for energy
• CO2 is broken apart to create C6H12O6
Animation of Overview of Photosynthesis
• http://wps.prenhall.com/wps/media/objects/486/498596/CDA7_1/CDA7_1d/CDA7_1d.htm
Factors that Affect
Photosynthesis
Photosynthesis is directly affected by environmental factors such as:
1. The intensity of light
2. The concentration of carbon dioxide
3. Temperature.
PHOTOSYNTHESIS QUIZ15 points
1. Where in a plant cell does photosynthesis occur?
2. What are the 2 stages of photosynthesis and where do they occur?
3. Why are plants green?
4. What is the balanced equation for photosynthesis?
5. What are the reactants and products of the light dependent reactions?
6. What are the reactants and products of the Calvin Cycle?
7. What are two reasons we depend on plants for our survival?
Review1. Summarize how photosynthetic organisms
capture the energy in sunlight.2. Compare the roles of water molecules and
hydrogen ions in electron transport chains.3. Describe the role of the Calvin cycle in
photosynthesis.4. Critical Thinking Organizing Information
Make a table in which you identify the role of each of the following in photosynthesis: light, water, pigments. ATP. NADPH. and carbon dioxide.
5. Critical Thinking Inferring Relationships What combination of environmental factors affects the rate of photosynthesis?6. Standardized Test Prep During photosynthesis, plants store energy inA ADP.B carbon dioxide.C 3-carbon sugars.D water.
• What happens to the electrons of a chlorophyll molecule that are raised to a higher energy level
They enter the electron transport chain.
2. Light energy is converted to chemical energy, which is temporarily stored as ATP and the energy carrier molecule NADPH
2. Light energy is converted to chemical energy, which is temporarily stored as ATP and the energy carrier molecule NADPH
Photosynthesis
3. The chemical energy stored in ATP and NADPH powers the formation of organic compounds, using carbon dioxide, CO2.
Photosynthesis
photosynthesis
• Plants use the organic compounds to carry out their life processes.
• Starch is stored in the plant to be used later to be broken down into sugar and ATP.
• Plants use the organic compounds to carry out their life processes.
• Starch is stored in the plant to be used later to be broken down into sugar and ATP.
6CO2 + 6H2O + light C6H12O6 + 6O2
photosynthesis • ATP is used to power metabolism.
• All proteins, nucleic acids and other molecules are assembled from fragments of organic compounds being made into sugar.
• ATP is used to power metabolism.
• All proteins, nucleic acids and other molecules are assembled from fragments of organic compounds being made into sugar.