Where It Starts – Photosynthesis Chapter 6 Where It Starts – Photosynthesis

6.1 How Do Photosynthesizers Absorb Light? Energy flow through ecosystems begins when photosynthesizers intercept sunlight Autotrophs are producers Make food using energy from environment and carbon from inorganic molecules Heterotrophs are consumers Obtain carbon from organic compounds assembled by other organisms Insert label and caption for any figures here.

ultraviolet radiation near-infrared radiation Properties of Light visible light gamma rays x-rays ultraviolet radiation near-infrared radiation infrared radiation microwaves radio waves shortest wavelengths (highest energy) longest wavelengths (lowest energy) Figure 6.1 – Properties of light. 400 nm 500 nm 600 nm 700 nm A B

Capturing a Rainbow Photosynthesizers use pigments to capture light of specific wavelengths Chlorophyll α: most common photosynthetic pigment in plants and protists Absorbs violet, red, and orange light Reflects green light (appears as green) Accessory pigments harvest additional light wavelengths

6.2 Why Do Cells Use More Than One Photosynthetic Pigment? In 1882, Theodor Engelmann tested the hypothesis that the color of light affects the rate of photosynthesis Used motile, oxygen-requiring bacteria to identify where photosynthesis was taking place Directed a spectrum of light across individual strands of green algae

Why Do Cells Use More Than One Photosynthetic Pigment? In Engelmann’s experiment, oxygen- requiring bacteria gathered where blue and red light fell across the algal cells Conclusion: Blue and red light are best light for driving photosynthesis in these algal cells

Why Do Cells Use More Than One Photosynthetic Pigment? phycoerythrobilin phycocyanobilin chlorophyll b chlorophyll a bacteria β-carotene algae Figure 6.3 - {Animated} Discovery that photosynthesis is driven best by particular wavelengths of visible light. 400nm 500nm 600nm 700nm 400nm 500nm 600nm 700nm Wavelength B C

Why Do Cells Use More Than One Photosynthetic Pigment? The combination of pigments used for photosynthesis differs among species Photosynthetic species are adapted to the environment in which they evolved Light that reaches different environments varies in its proportions of wavelengths

6.3 What Happens During Photosynthesis? Photosynthesis converts the energy of light into the energy of chemical bonds Unlike light, chemical energy can power the reactions of life, and it can be stored for use at a later time

What Happens During Photosynthesis? In eukaryotes, photosynthesis takes place in chloroplasts Thylakoid membrane: a chloroplast’s continuous highly folded inner membrane system Stroma: cytoplasm-like fluid between the thylakoid membrane and the two outer membranes of a chloroplast

What Happens During Photosynthesis? Photosynthesis is often summarized as: CO2 + water sugars + O2 light energy

Adaptations to Climate Stomata are tiny gateways for gases Open stomata: Allow CO2 to diffuse from the air into photosynthetic tissues Allow O2 to diffuse out of these tissues into the air Closed stomata: Conserve water on hot, dry days Limit the availability of CO2 for the light- independent reactions; sugar synthesis slows

6.6 Application: Green Energy With fossil fuel prices soaring, there is an increasing demand for biofuels: Oils, gases, or alcohols made from organic matter that is not fossilized Most materials we use for biofuel production today consist of food crops: Mainly corn, soybeans, and sugarcane

Application: Green Energy Fossil fuels: Petroleum, coal, and natural gas Formed from the remains of ancient swamp forests that decayed and compacted over millions of years Consist of molecules originally assembled by ancient plants “Non-renewable”

Application: Green Energy The process of using fossil fuels or biofuels are fundamentally the same: Release energy by breaking the bonds of organic molecules Use oxygen to break those bonds Produce carbon dioxide

Application: Green Energy Biofuels are a renewable source of energy Growing more plants creates more sources of biofuels

Application: Green Energy Biofuels do not contribute to global climate change Growing plant matter for fuel recycles carbon that is already in the atmosphere

Application: Green Energy Corn and other food crops are rich in oils, starches, and sugars that can be easily converted to biofuels Starch from corn kernels can be broken down to glucose, which is converted to ethanol by bacteria or yeast

Application: Green Energy Making biofuels from some plants require additional steps, because these materials contain a higher proportion of cellulose Researchers are currently working on cost- effective ways to break down the abundant cellulose in fast-growing weeds

Application: Green Energy Figure 6.11 - Switchgrass growing wild in a North American prairie.

Application: Green Energy According to tropical forest scientist Willie Smits, the Arenga sugar palm has the potential to serve as the core of a waste- free system Produces premium organic sugar and ethanol for fuel Provides food products and jobs to villagers Helps preserve the existing native rain forest

How Cells Release Chemical Energy Chapter 7 How Cells Release Chemical Energy

7.1 How Do Cells Access the Chemical Energy in Sugars? In order to use the energy stored in sugars, cells must first transfer it to ATP The energy transfer occurs when the bonds of a sugar’s carbon backbone are broken, driving ATP synthesis Chemical Energy Usable Energy

How Do Cells Access the Chemical Energy in Sugars? There are two main mechanisms by which organisms break down sugars to make ATP: Aerobic respiration Fermentation (anaerobic respiration)

Aerobic Respiration and Fermentation Compared Aerobic respiration: requires oxygen to break down sugars to make ATP Main energy-releasing pathway in nearly all eukaryotes and some bacteria

Aerobic Respiration and Fermentation Compared The three stages of aerobic respiration produce thirty-six ATP: Glycolysis Occurs in the cytoplasm; net yield is two ATP Krebs cycle Occurs in the mitochondria; net yield is two ATP Electron transfer phosphorylation Occurs in the mitochondria; net yield is thirty-two ATP

Aerobic Respiration and Fermentation Compared Fermentation: sugar breakdown pathway that does not require oxygen to make ATP Like aerobic respiration, fermentation begins with glycolysis in cytoplasm Unlike aerobic respiration, fermentation occurs entirely in cytoplasm, and does not include electron transfer chains Net yield is two ATP, which provides enough ATP to sustain many single-celled species

How Did Energy-Releasing Pathways Evolve?

What Is Fermentation? Two fermentation pathways: Alcoholic fermentation: anaerobic sugar breakdown pathway that produces ATP, CO2, and ethanol Lactate fermentation: anaerobic sugar breakdown pathway that produces ATP and lactate

Alcoholic Fermentation Alcoholic fermentation in a fungus, Saccharomyces cerevisiae, sustains these yeast cells as they grow and reproduce Used to produce beer, wine, and bread

Lactate Fermentation Animal muscle cells carry out aerobic respiration and/or lactate fermentation Red muscle fibers: many mitochondria and myoglobin; produce ATP mainly by aerobic respiration Sustains prolonged activity White muscle fibers: contain few mitochondria and no myoglobin; most ATP produced by lactate fermentation Useful for quick, strenuous activities

Lactate Fermentation B Figure 7.8 Lactate fermentation. C

7.7 Can the Body Use Any Organic Molecule for Energy? Energy from dietary molecules Aerobic respiration generates a lot of ATP by fully oxidizing glucose, completely dismantling it carbon by carbon Cells also dismantle other organic molecules by oxidizing them Complex carbohydrates, fats, and proteins in food can be converted to molecules that enter glycolysis or the Krebs cycle

Complex Carbohydrates Starches and other complex carbohydrates are broken down into monosaccharides Sugars are converted to glucose-6- phosphate for glycolysis A high concentration of ATP causes glucose- 6-phosphate to be diverted away from glycolysis and into the formation of glycogen stores

Fats Fats are dismantled by first breaking the bonds that connect the fatty acid tails to the glycerol head Free fatty acids are oxidized by splitting their backbones into two-carbon fragments These fragments are converted to acetyl– CoA, which can enter the Krebs cycle Glycerol gets converted to PGAL, an intermediate of glycolysis

Proteins Dietary proteins are split into their amino acid subunits Ammonia (NH3), formed as a waste product, is eliminated in urine The carbon backbone is split, and acetyl– CoA, pyruvate, or an intermediate of the Krebs cycle forms These molecules enter aerobic respiration’s second stage

7.7 Can the Body Use Any Organic Molecule for Energy? (cont’d.) Food a triglyceride (fat) glycerol head Fats Complex Carbohydrates Proteins fatty acids glycerol glucose, other simple sugars amino acids 2 3 1 4 acetyl–CoA PGAL acetyl–CoA fatty acid tails NADH pyruvate intermediate of Krebs cycle Figure 7.9 {Animated} A variety of organic compounds from food can enter the reactions of aerobic respiration. NADH, FADH2

Photosynthesis = Light Energy Chemical Energy Cell Respiration = Chemical Energy Usable Energy

In the setup shown below, which color light will cause the plant to produce the smallest number of gas bubbles? A) red B) orange C) blue D) green

In the setup shown below, which color light will cause the plant to produce the smallest number of gas bubbles? A) red B) orange C) blue D) green

An investigation was carried out and the results are shown below. Substance X resulted from a metabolic process that produces ATP in yeast (a single-celled fungus). Which statement best describes substance X? A) It is oxygen released by protein synthesis. B) It is glucose that was produced in photosynthesis. C) It is starch that was produced during digestion. D) It is carbon dioxide released by respiration.

An investigation was carried out and the results are shown below. Substance X resulted from a metabolic process that produces ATP in yeast (a single-celled fungus). Which statement best describes substance X? A) It is oxygen released by protein synthesis. B) It is glucose that was produced in photosynthesis. C) It is starch that was produced during digestion. D) It is carbon dioxide released by respiration.

The diagram represents a system in a space station that includes a tank containing algae. An astronaut from a spaceship boards the space station. A- State two changes in the chemical composition of the space station atmosphere that would result from turning on more lights. B- State two changes in the chemical composition of the space station atmosphere as a result of the astronaut coming on board the space station. C- Identify one process being controlled in the setup shown in the diagram.

The diagram represents a system in a space station that includes a tank containing algae. An astronaut from a spaceship boards the space station. A- State two changes in the chemical composition of the space station atmosphere that would result from turning on more lights. Less CO2 / More O2 B- State two changes in the chemical composition of the space station atmosphere as a result of the astronaut coming on board the space station. Less O2 / More CO2 / More water vapor C- Identify one process being controlled in the setup shown in the diagram. Photosynthesis