Photosynthesis Life Is Solar Powered!

What Would Plants Look Like On Alien Planets?

Why Would They Look Different? Different Stars Give off Different types of light or Electromagnetic Waves The color of plants depends on the spectrum of the star’s light, which astronomers can easily observe. (Our Sun is a type “G” star.)

Anatomy of a Wave Wavelength Is the distance between the crests of waves Determines the type of electromagnetic energy

Electromagnetic Spectrum Is the entire range of electromagnetic energy, or radiation The longer the wavelength the lower the energy associated with the wave.

Visible Light Light is a form of electromagnetic energy, which travels in waves When white light passes through a prism the individual wavelengths are separated out.

Visible Light Spectrum Light travels in waves Light is a form of radiant energy Radiant energy is made of tiny packets of energy called photons The red end of the spectrum has the lowest energy (longer wavelength) while the blue end is the highest energy (shorter wavelength). The order of visible light is ROY-G-BIV This is the same order you will see in a rainbow b/c water droplets in the air act as tiny prisms

Chloroplast – Where the Magic Happens! + H2O CO2 Energy ATP and NADPH2 Which splits water Light is Adsorbed By Chlorophyll Calvin Cycle ADP NADP Chloroplast Used Energy and is recycled. O2 + C6H12O6 Light Reaction Dark Reaction 6 CO2 + 12 H2O + Light energy  C6H12O6 + 6 O2 + 6 H2 O

Light Options When It Strikes A Leaf Reflected Chloroplast Absorbed light Granum Transmitted Figure 10.7 Reflect – a small amount of light is reflected off of the leaf. Most leaves reflect the color green, which means that it absorbs all of the other colors or wavelengths. Absorbed – most of the light is absorbed by plants providing the energy needed for the production of Glucose (photosynthesis) Transmitted – some light passes through the leaf

Photosynthesis Overview Concept Map Photosynthesis includes Light dependent reactions Light independent reactions occurs in uses uses occur in Light Energy Thylakoid membranes Stroma ATP NADPH to produce of to produce ATP NADPH O2 Chloroplasts Glucose

Anatomy of a Leaf Figure 10.3 Leaf cross section Vein Mesophyll CO2 O2 Stomata

Chloroplast

Chloroplast Are located within the palisade layer of the leaf Stacks of membrane sacs called Thylakoids Contain pigments on the surface Pigments absorb certain wavelenghts of light A Stack of Thylakoids is called a Granum Chloroplast Mesophyll 5 µm Outer membrane Intermembrane space Inner Thylakoid Granum Stroma 1 µm

Pigments Are molecules that absorb light Chlorophyll, a green pigment, is the primary absorber for photosynthesis There are two types of cholorophyll Chlorophyll a Chlorophyll b Carotenoids, yellow & orange pigments, are those that produce fall colors. Lots of Vitamin A for your eyes! Chlorophyll is so abundant that the other pigments are not visible so the plant is green…Then why do leaves change color in the fall?

Color Change In the fall when the temperature drops plants stop making Chrlorophyll and the Carotenoids and other pigments are left over (that’s why leaves change color in the fall).

Wavelength of light (nm) The absorption spectra of three types of pigments in chloroplasts Three different experiments helped reveal which wavelengths of light are photosynthetically important. The results are shown below. EXPERIMENT RESULTS Absorption of light by chloroplast pigments Chlorophyll a (a) Absorption spectra. The three curves show the wavelengths of light best absorbed by three types of chloroplast pigments. Wavelength of light (nm) Chlorophyll b Carotenoids Figure 10.9

The action spectrum of a pigment Profiles the relative effectiveness of different wavelengths of radiation in driving photosynthesis (measured by O2 release) Rate of photosynthesis Action spectrum. This graph plots the rate of photosynthesis versus wavelength. The resulting action spectrum resembles the absorption spectrum for chlorophyll a but does not match exactly (see part a). This is partly due to the absorption of light by accessory pigments such as chlorophyll b and carotenoids. (b)

The action spectrum for photosynthesis Was first demonstrated by Theodor W. Engelmann 400 500 600 700 Aerobic bacteria Filament of alga Engelmann‘s experiment. In 1883, Theodor W. Engelmann illuminated a filamentous alga with light that had been passed through a prism, exposing different segments of the alga to different wavelengths. He used aerobic bacteria, which concentrate near an oxygen source, to determine which segments of the alga were releasing the most O2 and thus photosynthesizing most. Bacteria congregated in greatest numbers around the parts of the alga illuminated with violet-blue or red light. Notice the close match of the bacterial distribution to the action spectrum in part b. (c) Light in the violet-blue and red portions of the spectrum are most effective in driving photosynthesis. CONCLUSION

Absorption of chlorophylls a and b at various wavelengths in the visible light spectrum

Pigment Molecules that absorb specific wavelengths of light Chlorophyll absorbs reds & blues and reflects green Xanthophyll absorbs red, blues, greens & reflects yellow Carotenoids reflect orange

Chlorophyll Green pigment in plants Traps sun’s energy Sunlight energizes electron in chlorophyll

PHOTOSYNTHESIS Comes from Greek Word “photo” meaning “Light” and “syntithenai” meaning “to put together” Photosynthesis puts together sugar molecules using water, carbon dioxide, & energy from light.

Happens in two phases Light-Dependent Reaction Converts light energy into chemical energy Light-Independent Reaction Produces simple sugars (glucose) General Equation 6 CO2 + 6 H2O  C6H12O6 + 6 O2

First Phase Requires Light = Light Dependent Reaction Sun’s energy energizes an electron in chlorophyll molecule Electron is passed to nearby protein molecules in the thylakoid membrane of the chloroplast

Excitation of Chlorophyll by Light When a pigment absorbs light It goes from a ground state to an excited state, which is unstable Excited state Energy of election Heat Photon (fluorescence) Chlorophyll molecule Ground e– Figure 10.11 A

Two Photosystems Photosystem II: Clusters of pigments boost e- by absorbing light w/ wavelength of ~680 nm Photosystem I: Clusters boost e- by absorbing light w/ wavelength of ~760 nm. Reaction Center: Both PS have it. Energy is passed to a special Chlorophyll a molecule which boosts an e-

A mechanical analogy for the light reactions Mill makes ATP e– Photon Photosystem II Photosystem I NADPH Figure 10.14 

ATP Adenosine Triphosphate Stores energy in high energy bonds between phosphates

NADPH Made from NADP+; electrons and hydrogen ions Made during light reaction Stores high energy electrons for use during light-Independent reaction (Calvin Cycle)

Figure 10.5 H2O CO2 [CH2O] O2 (sugar) Light LIGHT REACTIONS CALVIN CYCLE Chloroplast [CH2O] (sugar) NADPH NADP  ADP + P O2 Figure 10.5 ATP

PART II LIGHT INDEPENDENT REACTION Also called the Calvin Cycle No Light Required Takes place in the stroma of the chloroplast Takes carbon dioxide & converts into sugar It is a cycle because it ends with a chemical used in the first step

Begins & Ends The Calvin Cycle begins with the products of the light reaction. (the Calvin Cycle uses ATP & NADPH) CO2 is added and ends in the production of sugar (GLUCOSE) Formula: C6H12O6

The Calvin cycle Figure 10.18 Input Light 3 CO2 CALVIN CYCLE (G3P) Input (Entering one at a time) CO2 3 Rubisco Short-lived intermediate 3 P P Ribulose bisphosphate (RuBP) 3-Phosphoglycerate 6 P 6 1,3-Bisphoglycerate 6 NADPH 6 NADPH+ Glyceraldehyde-3-phosphate 6 ATP 3 ATP 3 ADP CALVIN CYCLE 5 1 G3P (a sugar) Output Light H2O LIGHT REACTION ATP NADPH NADP+ ADP [CH2O] (sugar) CALVIN CYCLE Figure 10.18 O2 6 ADP Glucose and other organic compounds Phase 1: Carbon fixation Phase 3: Regeneration of the CO2 acceptor (RuBP) Phase 2: Reduction

Chloroplast – Where the Magic Happens! + H2O CO2 Energy ATP and NADPH2 Which splits water Light is Adsorbed By Chlorophyll Calvin Cycle ADP NADP Chloroplast Used Energy and is recycled. O2 + C6H12O6 Light Reaction Dark Reaction 6 CO2 + 12 H2O + Light energy  C6H12O6 + 6 O2 + 6 H2 O

Cellular Respiration

How Cells Harvest Chemical Energy Introduction to Cell Metabolism Glycolysis Aerobic Cell Respiration Anaerobic Cell Respiration

BREATHING Breathing and Cell Respiration are related CO2 Lungs Muscle cells carrying out CO2 Bloodstream O2 CELLULAR RESPIRATION Sugar + O2  ATP + CO2 + H2O

Cellular Respiration uses oxygen and glucose to produce Carbon dioxide, water, and ATP. Glucose Oxygen gas Carbon dioxide Water Energy

How efficient is cell respiration? Energy released from glucose banked in ATP Energy released from glucose (as heat and light) Gasoline energy converted to movement 100% About 40% 25% Burning glucose in an experiment “Burning” glucose in cellular respiration Burning gasoline in an auto engine

Reduction and Oxidation OILRIG Oxidation is losing electrons Reduction is gaining electrons Loss of hydrogen atoms Energy Glucose Gain of hydrogen atoms Glucose gives off energy and is oxidized

Glycolysis Glucose General Outline No Oxygen Anaerobic Oxygen Aerobic Pyruvic Acid Transition Reaction Fermentation Krebs Cycle ETS 36 ATP

Glycolysis Where? The cytosol What? Breaks down glucose to pyruvic acid

Glycolysis Energy In: 2 ATP Energy Out: 4 ATP NET 2 ATP Steps – A fuel molecule is energized, using ATP. Glucose 1 3 Step Glycolysis 1 Glucose-6-phosphate 2 Fructose-6-phosphate Energy In: 2 ATP 3 Fructose-1,6-diphosphate Step A six-carbon intermediate splits into two three-carbon intermediates. 4 4 Glyceraldehyde-3-phosphate (G3P) 5 Step A redox reaction generates NADH. 5 1,3-Diphosphoglyceric acid (2 molecules) 6 Steps – ATP and pyruvic acid are produced. 3-Phosphoglyceric acid (2 molecules) Energy Out: 4 ATP 6 9 7 2-Phosphoglyceric acid (2 molecules) 8 2-Phosphoglyceric acid (2 molecules) NET 2 ATP 9 Pyruvic acid (2 molecules per glucose molecule)

General Outline of Aerobic Respiration Glycolysis Transition Reaction Krebs Cycle Electron Transport System

Transition Reaction Each pyruvic acid molecule is broken down to form CO2 and a two-carbon acetyl group, which enters the Krebs cycle Pyruvic Acid Acetyl CoA

General Outline of Aerobic Respiration Glycolysis Transition Reaction Krebs Cycle Electron Transport System

Krebs Cycle Where? In the Mitochondria What? Uses Acetyl Co-A to generate ATP, NADH, FADH2, and CO2.

Krebs Cycle

Krebs Cycle

General Outline of Aerobic Respiration Glycolysis Krebs Cycle Electron Transport System

ELECTRON TRANSPORT CHAIN Electron Transport System Protein complex Intermembrane space Electron carrier Inner mitochondrial membrane Electron flow Mitochondrial matrix ELECTRON TRANSPORT CHAIN ATP SYNTHASE Figure 6.12

Electron Transport System For each glucose molecule that enters cellular respiration, chemiosmosis produces up to 38 ATP molecules

Overview of Aerobic Respiration

Fermentation Requires NADH generated by glycolysis. Where do you suppose these reactions take place? Yeast produce carbon dioxide and ethanol Muscle cells produce lactic acid Only a few ATP are produced per glucose

Fermentation

Fermentation in the Absence of Oxygen Fermentation When oxygen is not present, fermentation follows glycolysis, regenerating NAD+ needed for glycolysis to continue. Lactic Acid Fermentation In lactic acid fermentation, pyruvate is converted to lactate.

Each molecule of glucose can generate 36-38 molecules of ATP in aerobic respiration but only 2 ATP molecules in respiration without oxygen (through glycolysis and fermentation).