Closing the Cycle: Cellular Respiration

Back it up….a quick review: Remember that organisms are grouped into one of two categories based on how they get the energy they need to live: 1. Autotrophs: can produce their own a. “Producers”: Plants, algae, some bacteria 2. Heterotrophs: Cannot produce their own and must eat something else for energy. b. “Consumers”: Animals, fungi, most bacteria.

The Forms of Energy In living systems, there are four primary forms of energy. 1. Light Energy (from the sun) 2. Heat Energy (from the sun) 3. Chemical Energy (“glucose”) 4. The energy of “work” (“mechanical energy”)

AUTOTROPHS How do autotrophs do this? They take unusable sources of energy, like sunlight, and convert it to a source of energy that is usable by the organelles in our cells. 1. Mitochondria: These organelles are the “powerhouse” of all cells. a. Take glucose, break it apart to release energy for the cell.

Photosynthesis Definition : The process by which plants take unusable heat & light energy and convert it into chemical (food) energy. ◦ 1. This process occurs in plants, algae and some bacteria. ◦ 2. The energy is stored in the chemical bonds of the simple sugar, glucose. 3. Occurs in the special organelles found only in plant cells- Chloroplasts.

Summarizing Photosynthesis 6CO 2 + 6H 2 O + sunlight C 6 H 12 O 6 + 6O 2 Photosynthesis Occurs in 3 Stages: 1.Absorption of light energy by the cholorplasts. 2.Conversion of light energy into chemical energy (ATP) 3.Storage of chemical energy in the form of glucose. a. Glucose is a simple sugar and the primary cellular fuel.

Cellular Respiration Definition: A series of chemical reactions where the energy stored in simple sugars (glucose) is released in the form of ATP. 1. All organisms release energy thru this process a. Animals, plants, fungi, bacteria 2. This energy is used for: a. Metabolism b. Work/Activity c. Growth/Repair d. Reproduction

Cellular Respiration vs. Combustion The process of cellular respiration is very similar to the process of combustion. 1. Combustion requires a fuel source, oxygen, and a “spark” to release energy. 2. The waste products are carbon, carbon dioxide and sometimes water.

2 Types of cellular Respiration 1. Aerobic: A. Requires oxygen C 6 H 12 O 6 +6O 2  6CO 2 +6 H 2 O + 38 ATP B. This is why we have to breathe oxygen, without it, our cells would not be able to release the energy we need to live. 2. Anaerobic: A. Takes place in the absence of oxygen B. Less efficient = produces less ATP (only 2 ATP vs 38 ATP)

Where does Cellular Respiration Occur? Occurs in the mitochondria in the cells of all living organisms

3 Stages of Cellular Respiration Stage 1: Glycolysis A. This occurs outside of the mitochondria in the cytoplasm. B. Glucose is split into smaller molecules and transported to the mitochondria.

Stage 2 : Krebs Cycle * A. Occurs inside the mitochondria. B. Enzymes break the smaller molecules (this is when CO 2 is produced). C. Only 2 ATP produced. D. Most remaining energy is still in the hydrogen molecules. *aka: Citric Acid Cycle

Stage 3 : Electron Transport System A. Electrons removed and transferred to ATP. B. This produces 34 of the 38 ATP produced from one molecule of glucose

Why is ATP necessary? BECAUSE…. 1. The energy released must be able to be exported throughout the cell 2. Large chunks of energy (glucose) must be separated into smaller, more manageable amounts (ATP) SO, THINK OF IT LIKE THIS… ATP is like a rechargeable battery or like breaking a $100 bill into 400 quarters to use in a video game

Light/heat Energy Photosynthesis Chemical Energy Heat Work

Photosynthesis and Cellular Respiration as a Cycle Take a moment to compare the reactions of cellular respiration and photosynthesis: Photosynthesis: 6CO 2 + 6H 2 O + LIGHT C 6 H 12 O 6 + 6O 2 Cellular Respiration: C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O +38ATP What do you notice?

Photosynthesis and Cellular Respiration as a Cycle The reactions of photosynthesis and cellular respiration are “complimentary reactions”: A. The products of one become the reactants of the other. B. Both of these are metabolic processes where cellular respiration relies on photosynthesis. C. Cellular respiration produces the CO 2 needed in order for photosynthesis to occur.