Energy

ENERGY & LIFE Energy: the ability to do work. Energy comes in many forms: light, heat, electricity, etc. Without energy, living things could not exist. All energy in living systems originally comes from the SUN.

Autotrophs vs. Heterotrophs Autotrophic organisms Produce their own food from the sun. Also produce oxygen for the atmosphere. Examples: Plants Some Bacteria Heterotrophic organisms Cannot make their own food. Obtain energy from the food they consume. Examples: Herbivores: eat plants Carnivores: eat meat Omnivores: eat both plants and meat Decomposers: breakdown dead material

Chemical Energy Energy can be stored in chemical bonds Energy is released when high energy bonds are replaced by low energy bonds between atoms. Living things use chemical fuels. One of the main chemical compounds used to store energy in living things is ATP (adenosine triphosphate).

Adenosine Triphosphate (ATP) ATP is made of three main parts: Adenine: a nitrogen containing compound Ribose: a five carbon sugar Phosphates: energy is contained in each of the three phosphate bonds. ▫When the bonds are broken between the 2 nd and 3 rd phosphate groups, energy is released. ▫This produces ADP (Adenosine Diphosphate) and a single phosphate group.

AdenineRibose3 Phosphate groups Section 8-1 ATP

ADPATP Energy Adenosine diphosphate (ADP) + PhosphateAdenosine triphosphate (ATP) Partially charged battery Fully charged battery Section 8-1 Figure 8-3 Comparison of ADP and ATP to a Battery Video

Discovery of Photosynthesis

Question Where do plants get their mass when they grow?

Jan van Helmont’s Experiment Jan van Helmont: 1600s watched the growth of a plant for 5 years. He only watered the plant. The plant grew from a seedling to a 75 kg tree. The mass of the soil was almost identical. Conclusion: Most of the gain in mass had come from the water.

Joseph Priestley’s Experiment Joseph Priestley ▫1700s took a candle and placed a glass jar over it and the candle eventually went out. ▫Placed a mint plant in the jar with the candle and the candle would relight and burn for a short time. Conclusion: ▫The mint plant was producing something in the air required for the candle to burn. ▫The plant produced oxygen.

Jan Ingenhousz’ Experiment Jan Ingenhousz ▫In 1779 Ingenhousz extended Priestley’s experiment. ▫When the plant was in the dark, it did not produce the needed substance (oxygen) for the candle to burn. ▫When the plant was in the light, it did produce the substance (oxygen) needed for the candle to burn. Conclusion: ▫Light is necessary for plants to produce oxygen.

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Light and Pigments

Chlorophyll is required to carry out photosynthesis. Chlorophyll is a pigment found in chloroplasts that captures light energy and transfers it to electrons. ▫Pigments are molecules that absorb specific wavelengths (colors) of light There are two types, chlorophyll a and b. Each chlorophyll absorbs different wavelengths of light.

Absorption of Light by Chlorophyll a and Chlorophyll b VBGYOR Chlorophyll b Chlorophyll a Section 8-2 Figure 8-5 Chlorophyll Light Absorption

Chloroplasts The chloroplast is where photosynthesis takes place in plants. Within the chloroplast are: ▫Stroma: fluid inside the chloroplast ▫Thylakoids: membrane bound discs containing the pigment chlorophyll ▫Grana: stacks of thylakoids

Photosynthesis Overview

Light Energy Chloroplast CO 2 + H 2 OSugars + O 2 Section 8-2 Photosynthesis: Reactants and Products

The Chemical Equation for Photosynthesis Photosynthesis uses sunlight to convert water and carbon dioxide into high energy sugars and oxygen. 6CO2 + 6H2OC 6 H12O 6 + 6O2 SUNLIGHT

Overview of Photosynthesis Photosynthesis: organisms use the energy of sunlight to convert water and carbon dioxide into high-energy carbohydrates (sugars and starches) and oxygen. Purpose: store energy for later use Two Reactions: Light Dependent Light Independent (Calvin Cycle)

Chloroplast H2OH2O O2O2 Sugars CO 2 Light- Dependent Reactions Calvin Cycle NADPH ATP ADP + P NADP + Chloroplast Photosynthesis: An Overview Light

Reactions of Photosynthesis Light dependent reactions: ▫Chlorophyll captures light energy and uses it to produce ATP and NADPH ▫Occurs in the thylakoid. Light Independent reactions: ▫Transfer the energy from ATP and NADPH into chemical energy (glucose). ▫Does not need light only the ATP and NADPH from the light reactions. ▫Occurs in the stroma.

NADP+ and NADPH NADPH is an electron carrier ▫Carries high energy electrons from the light dependent reaction to the light independent reaction (Calvin Cycle) When NADPH loses its electrons, it becomes NADP + NADP + must return to the thylakoid to get more energized electrons and become NADPH again.

Light Dependent Reaction

Photosystem II This step requires the input of water and sunlight Sunlight is absorbed by electrons in PSII Water is broken down into 3 pieces ▫Oxygen (O2) – is released from the plant as a waste product ▫Hydrogen ions – (H+) – stays in luman ▫Electrons (e-) - replaces electrons on PS II

Photosystem I Light energy is absorbed by electrons (e-) in PS I These electrons eventually end up on NADP+ which forms NADPH

Formation of ATP Energy from the electrons is used to pump H+ into the thylakoid space (Active Transport). When they diffuse back through, ATP is made from ADP. The ATP and NADPH go on the to Calvin Cycle

Light Dependent Reactions

Light Independent Reaction

Calvin Cycle – AKA Light Independent Reactions- Requires the ATP and NADPH from the light dependant reactions as well as CO2 from the atmosphere. 6 CO2 are required to build one carbohydrate The ATP and NADPH are used for energy in this process

Calvin Cycle (Light Independent Reactions)

Factors Affecting Photosynthesis

Water availability. Temperature: ▫Too high or too low and photosynthesis cannot occur. Light intensity: ▫As light increases photosynthesis increases but will level out at higher intensities.