Popeye knew what he was doing! Photosynthesis & Cellular Respiration How does the spinach Popeye eats store energy from the sun? How does Popeye release the energy he finds in Spinach? It all starts at the cellular level….let’s take a look! Today’s reference: Sec 5.1

Popeye knew what he was doing! Photosynthesis & Cellular Respiration What We Know: Everything on earth needs energy. Energy is the fuel needed to do work (think gasoline for a car). Energy comes from two different sources in living organisms: 1. Autotrophic organisms: 2. Heterotrophic organisms: Organisms that make their own food. ONE EXAMPLE is photosynthetic organisms like plants, phytoplankton, & some bacteria, that convert solar energy into usable chemical energy. Organisms that eat autotrophs or other heterotrophs for food and release the chemical energy from them during cellular respiration.

Popeye knew what he was doing! Photosynthesis & Cellular Respiration What we may not know: What is “usable chemical energy” mean? The usable chemical energy needed for life is stored in the chemical bonds of molecules such as glucose. Reactions that build chemical bonds are called anabolic pathways and these require constant energy to occur (such as the solar energy needed to make glucose in photosynthesis). Reactions that break down chemical bonds to release the energy are called catabolic pathways and although they require an initial activation energy, will release a much larger amount of energy (such as the energy released during the breakdown of glucose during cellular respiration).

Popeye knew what he was doing! Photosynthesis & Cellular Respiration What We Know: Photosynthesis converts solar energy into chemical energy by storing it in the chemical bonds of glucose: 6H 2 O(l) + 6CO 2 (g) C 6 H 12 O 6 (aq)+ 6O 2 (g) Cellular respiration releases the chemical energy stored in glucose by breaking down the chemical bonds: Light, Chlorophyll C 6 H 12 O 6 (aq)+ 6O 2 (g) 6H 2 O(l) + 6CO 2 (g) + Energy

Popeye knew what he was doing! Photosynthesis & Cellular Respiration What We May Not Know: The reactions we just reviewed are actually overall reactions that summarize a large series of steps to end up with the final products. A closer look at the series of reactions (called metabolic pathways) will follow for the next week. The word “energy” was used in the cellular respiration equation: This represents another energy conversion. Cells cannot use glucose for energy to do work. However, they can take the energy out of the glucose bonds and convert it into a form our cells can use: adenosine triphosphate (ATP). C 6 H 12 O 6 (aq)+ 6O 2 (g) 6H 2 O(l) + 6CO 2 (g) + Energy

Popeye knew what he was doing! Photosynthesis & Cellular Respiration Adenosine Triphosphate (ATP) All cellular processes require ATP for energy (muscle contraction, moving chromosomes during cell division, moving cilia, active transport of waste products). ATP is an adenosine molecule with three phosphates attached: AdenosinePPP PP P Energy released for cellular processes P ADP ATP Energy gained in cellular respiration NOTE: Plants just don’t “do photosynthesis”. They need ATP too. So, after they produce glucose in photosynthesis, they break it down in cellular respiration to form ATP!

Popeye knew what he was doing! Photosynthesis & Cellular Respiration What We May Not Know: When we release energy in a catabolic reaction, the energy can be used to put a phosphate group on ADP to make ATP (this is called phosphorylation). The energy from a catabolic reaction is often released in steps rather than all at once because these reactions can be quite violent (think explosive) if done at once! The steps used to release energy from a catabolic reaction often occurs through an electron transport chain.

Popeye knew what he was doing! Photosynthesis & Cellular Respiration Electron transport chain An ETC is a series of redox reactions that slowly release the energy from a hydrogen’s electrons and traps the energy in the chemical bonds of ATP. This energy is used to make ATP!

Popeye knew what he was doing! Photosynthesis & Cellular Respiration Reduction and Oxidation (Redox) reactions If a compound or atom loses an electron to become more stable it is called oxidation. If a compound or atom gains an electron it is reduced. Oxidation and reduction occurs in pairs (as one is oxidized, another is reduced). To remember this, think OIL RIG. Oxidation Is Loss, Reduction Is Gain

Popeye knew what he was doing! Photosynthesis & Cellular Respiration Electron transport chain Compounds or atoms have more energy in their reduced form. When they become oxidized they release some energy that can be used to produce ATP. Glucose is in a reduced form.

Popeye knew what he was doing! Photosynthesis & Cellular Respiration Let’s try to recap what we just learned using images! To the SMARTBOARD!

Popeye knew what he was doing! Photosynthesis & Cellular Respiration Bringing it all together: There were a lot of new terms today! To make sense of it all, you will use your textbook sec 5.1 and your class notes to form a concept map (see next slide for example). Here are the terms you will use (you may add more if needed): PhotosynthesisCellular RespirationMetabolic Pathways Catabolic pathwaysAnabolic pathwaysEnergy ATPSolar energyChemical energy Chemical BondsETCReduction Oxidation If done early, can start homework questions

Popeye knew what he was doing! Photosynthesis & Cellular Respiration