2CA 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.EcologyStudents know how water, carbon, and nitrogen cycle between abiotic resources and organic matter in the ecosystem and how oxygen cycles through photosynthesis and respiration.
3Photosynthesis Chapter 8 Summarize how energy is captured from sunlight during the light dependent reactions of photosynthesis.Analyze the function of electron transport chains during the light dependent reactions of photosynthesis.Relate the Calvin cycle to carbon dioxide fixation in photosynthesis.Identify three environmental factors that affect the rate of photosynthesis.
5Using 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.
6History 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)
7Jan van HelmontHe 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!
8Joseph 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!
9Jan IngenhouszHe 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!
18Land 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)
19Stomata Consists of: Stomatal Opening and 2 Guard Cells
22What enters and exits the stomata? CO2CO2 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.
23Carbon 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.
24How 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.
27LIGHT AND PIGMENTS Light has different wavelengths. You can only see visible light.
28Visible spectrumSunlight 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.
29PigmentsPigments 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.Period 1 stopped here 10/19/10
30Absorbs mostly blue and red light and reflects green and yellow light. Thus, the plant looks green.Chlorophyll
31CarotenoidsPigments in plants that absorb blue and green light and reflect yellow and orange.
32Autumn ColorsIn 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.
33Pigments are located in the chloroplasts of leaf cells
42Photosynthesis Occurs in Two Stages: The Light-Dependent Reactions (occur in the thylakoid membranes)The Calvin Cycle(occurs in the stroma)
43Overview 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.
44Overview 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.
47Light strikes1. Light strikes chlorophyll in the thylakoid membrane and transfers solar energy to its electrons.
482. This energy transfer from light causes the electrons to become “excited”.3. These high-energy electrons are transferred to NADP+.
49NADP+ 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!
57ATP Synthase Animation Period 1 stopped here 10/21/10
586. Electron Transport Chain C. NADPH is made by adding H+ ions to NADP+
59Remember:NADPH is an electron carrier that provides the high-energy electrons needed to make carbon-hydrogen bonds in the third stage of photosynthesis.
60ATP is the molecule that provides energy for the plant to make glucose ATP is the molecule that provides energy for the plant to make glucose! NADPH provides hydrogen atoms for the plant to make glucose!
61Summary of Light dependent reaction Pigments in the thylakoids of chloroplasts absorb light energy.Electrons in the pigments are excited by light and move through electron transport chains in thylakoid membranes.These electrons are replaced by electrons from water molecules, which are split by an enzyme.Oxygen atoms from water molecules combine to form oxygen gas.Hydrogen ions accumulate inside thylakoids, setting up a concentration gradient that provides the energy to make ATP.
65Pigment molecules absorb energy at which stage of photosynthesis? The beginning of the Light-Dependent Reactions!
66At which stage of photosynthesis is light energy stored as ATP and NADPH? The end of the Light-Dependent Reactions!
67At which stage of photosynthesis are excited electrons passed along an electron transport chain? Light-Dependent Reactions!
68Where do the light-dependent reactions occur? The thylakoid membranes!
69What 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.
70What is produced in the light-dependent reactions? ATP and NADPH go into the Calvin Cycle.Oxygen gas is released into the atmosphere.
86Factors that Affect Photosynthesis Photosynthesis is directly affected by environmental factors such as:The intensity of lightThe concentration of carbon dioxideTemperature.Period 4 stopped here 10-7/10
87PHOTOSYNTHESIS QUIZ 15 points Where in a plant cell does photosynthesis occur?What are the 2 stages of photosynthesis and where do they occur?Why are plants green?What is the balanced equation for photosynthesis?What are the reactants and products of the light dependent reactions?What are the reactants and products of the Calvin Cycle?What are two reasons we depend on plants for our survival?
88ReviewSummarize how photosynthetic organisms capture the energy in sunlight.Compare the roles of water molecules and hydrogen ions in electron transport chains.Describe the role of the Calvin cycle in photosynthesis.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.
895. 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.
90What happens when a phosphate group is removed from an ATP molecule? Energy is released
91What happens to the electrons of a chlorophyll molecule that are raised to a higher energy level They enter the electron transport chain.
92Why does chlorophyll look green? Because it reflects green wavelengths of light.
93Because of photosynthesis the atmosphere is rich in which gas? oxygen
103At which stage of photosynthesis do the pigment molecules absorb energy?
104Light energy is converted to chemical energy by what process? Photosynthesis
105What is the major by-product of photosynthesis which goes into the atmosphere? Oxygen
106photosynthesis 6CO2 + 6H2O + light C6H12O6 + 6O2 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.
107photosynthesis ATP is used to power metabolism. All proteins, nucleic acids and other molecules are assembled from fragments of organic compounds being made into sugar.